IPAC2017 - List of Keywords (cavity)

Paper	Title	Other Keywords	Page
MOYBA1	The Future of Superconducting Technology for Accelerators	SRF, collider, superconducting-magnet, linear-collider	19
	A. Yamamoto KEK, Ibaraki, Japan
	Superconducting magnets and RF cavities are widely used in accelerators, and future accelerator projects heavily rely on this technology. There may be several questions on the future of the SC technology, concerning the feasibility of very high field dipoles (~15 T or more), possible technology evolution(s) with new materials, operation at higher temperature, and final sustainability of the technology in terms of helium procurement. The talk will cover a brief history/achievements and some interesting (future) developments, partly or fully answering these question.
	Slides MOYBA1 [25.792 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOYBA1
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MOOCA1	High Efficiency Klystrons Using the COM Bunching Technique	klystron, electron, simulation, bunching	37
	D.A. Constable Lancaster University, Lancaster, United Kingdom A.Yu. Baikov Moscow University of Finance & Law, Moscow, Russia G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom R.D. Kowalczyk L-3, Williamsport, Pennsylvania, USA I. Syratchev CERN, Geneva, Switzerland
	Future large-scale particle accelerators, for example, the Future Circular Collider (FCC), the Compact Linear Collider (CLIC) and the International Linear Collider (ILC), will require significant RF drive power on the order of 100 MW. Thus, an RF source with high efficiency is preferable to minimise the overall power required. Klystrons represent an attractive RF source, with the current state of the art operating at efficiencies of up to 70%. Such devices feature monotonic bunching, where at the output cavity, a number of electrons will not be in the main bunch, and instead will be present in the anti-bunch, and therefore not contributing to the output power. Therefore, novel bunching methods, such as the Core Oscillation Method (COM), are worthy of investigation. By allowing the core of the electron beam to bunch and de-bunch between successive cavities, the number of electrons contained in the final bunch can increase, and therefore improve the efficiency of the device. Numerical simulation of klystrons featuring COM will be presented, with efficiencies of up to 85% being predicted thus far.
	Slides MOOCA1 [12.765 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOOCA1
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MOOCA2	First Results From New Single-Cell Nb3Sn Cavities Coated at Cornell University	niobium, factory, radio-frequency, SRF	40
	D.L. Hall, J.J. Kaufman, M. Liepe, R.D. Porter, J. Sears Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Cavities coated with Nb3Sn at Cornell University demonstrate quality factors of >10¹⁰ at 4.2 K, outperforming equivalent niobium cavities by a factor of >30 at these bath temperatures. These quality factors have been maintained up to fields of 17-18 MV/m without significant Q-slope. Recently, new single-cell cavities have been added to the Cornell Nb3Sn programme in an effort to improve statistics and allow further exploration of the available parameter space. In this paper we report on the first results of these new cavities, as well as the latest performance from other cavities already in use on the programme. Furthermore, continuing work to optimise the coating procedure is reported on, and the latest understanding of the ideal coating profile is discussed.
	Slides MOOCA2 [10.366 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOOCA2
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MOPAB022	Fabrication Studies of a 650 MHz Superconducting RF Deflecting Mode Cavity for the ARIEL Electron Linac	niobium, electron, linac, impedance	120
	D.W. Storey, R.E. Laxdal, B. Matheson, N. Muller TRIUMF, Vancouver, Canada D.W. Storey Victoria University, Victoria, B.C., Canada
	A 650 MHz RF deflecting mode cavity is required for the ARIEL electron Linac to separate interleaved beams bound for either rare isotope production or a recirculation loop containing a Free Electron Laser. An RF separator will allow both modes to run simultaneously by imparting opposite transverse deflection to adjacent bunches at 1.3 GHz. The SRF cavity has been designed to provide up to 0.6 MV transverse voltage for operation with up to a 50 MeV CW electron beam. The design was optimised for compact geometry with high shunt impedance. Due to the low dissipated power, the cavity will operate at 4 K and allows for investigations into low cost fabrication techniques. The cavity is being machined from bulk reactor grade ingot Niobium and welds will be performed using TIG welding in an ultra-pure Argon chamber. Results of fabrication studies will be presented as well as measurements performed on a copper prototype cavity.
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MOPAB043	Very First Experience with the Standard Diagnostics at the European XFEL	diagnostics, operation, electron, electronics	180
	D. Lipka DESY, Hamburg, Germany
	The whole European XFEL becomes in operation this year. Dedicated standard diagnostics systems are installed and almost all types are tested at the injector before. Now the standard diagnostics are used to commission the facility. In this contribution the very first results and the operation experiences of the standard beam diagnostics of the entire European XFEL are reported.
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MOPAB044	X-Band TDS Project	electron, polarization, experiment, diagnostics	184
	B. Marchetti, R.W. Aßmann, B. Beutner, J. Branlard, F. Christie, R.T.P. D'Arcy, W. Decking, U. Dorda, J. Herrmann, M. Hoffmann, M. Hüning, O. Krebs, G. Kube, S. Lederer, F. Ludwig, F. Marutzky, D. Marx, J. Osterhoff, I. Peperkorn, S. Pfeiffer, F. Poblotzki, J. Rönsch-Schulenburg, J. Rothenburg, H. Schlarb, M. Scholz, S. Schreiber, M. Vogt, A. Wagner, T. Wilksen, K. Wittenburg DESY, Hamburg, Germany M. Bopp, H.-H. Braun, P. Craievich, M. Pedrozzi, E. Prat, S. Reiche, K. Rolli, R. Zennaro PSI, Villigen PSI, Switzerland N. Catalán Lasheras, A. Grudiev, G. McMonagle, W. Wuensch CERN, Geneva, Switzerland
	Based on the success of the X-Band Transverse Deflecting Structure (TDS) diagnostic at LCLS, a collaboration between DESY, PSI and CERN has formed with the aim of developing and building an advanced modular X-Band TDS system. The designed TDS has the new feature of providing variable polarization of the deflecting field. The possibility of changing the orientation of the streaking field of the TDS to an arbitrary azimuthal angle allows for 3D characterization of the phase space using tomographic methods. Moreover the complete 6D characterization of the beam phase space is possible by combining this technique with quadrupole scans and a dipole spectrometer. As this new cavity design requires very high manufacturing precision to guarantee highest azimuthal symmetry of the structure to avoid the deterioration of the polarization of the streaking field, the high precision tuning-free assembly procedures developed at PSI for the SwissFEL C-band accelerating structures will be used for the manufacturing*. The high-power rf system is based on the CERN-based X-band test stands. We summarize in this work the status of the projects and its main technical parameters. C. Behrens et al. , Nat. Comm. 4762 (2014). A. Grudiev, CLIC-note-1067 (2016). * D. Marx et al., contribution to this conference proceedings. **** U. Ellenberger et al., FEL 2013, TUPS017.
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MOPAB046	Lattice Considerations for the Use of an X-Band Transverse Deflecting Structure (TDS) at SINBAD	dipole, quadrupole, lattice, electron	192
	D. Marx, R.W. Aßmann, U. Dorda, U. Dorda, B. Marchetti, F. Mayet DESY, Hamburg, Germany F. Mayet University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	An X-band TDS is a well-known device for the characterization of the longitudinal properties of an electron bunch in a linear accelerator. It is planned that a novel X-band TDS with variable polarization* will be installed within the next few years at SINBAD, an upcoming accelerator R&D facility at DESY*. There are several measurements that can be performed with the TDS, each with specific optics requirements to reach the highest possible resolution and keep induced energy spread to a tolerable level. Quadrupoles will be installed between the TDS and the screen to help satisfy these conditions. In this paper, the requirements for the bunch length measurements, a novel 3D charge density reconstruction technique and slice energy measurements are discussed and some simulation results for the slice energy measurement using example lattices are presented. A. Grudiev, CLIC-note-1067 (2016). ** B. Marchetti et al. X-band TDS project contribution to these conference proceedings.
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MOPAB050	Reconstruction of Sub-Femtosecond Longitudinal Bunch Profile Measurement Data	laser, electron, diagnostics, undulator	207
	M.K. Weikum, R.W. Aßmann, U. Dorda DESY, Hamburg, Germany G. Andonian RadiaBeam, Santa Monica, California, USA G. Andonian UCLA, Los Angeles, California, USA Z.M. Sheng, M.K. Weikum USTRAT/SUPA, Glasgow, United Kingdom Z.M. Sheng Shanghai Jiao Tong University, Shanghai, People's Republic of China
	With a current trend towards shorter electron beams with lengths on the order of few femtoseconds (fs) to sub-femtoseconds both in conventional and novel accelerator communities, the need for diagnostics with equivalent attosecond resolution is increasing. The proposed design for a sub-femtosecond diagnostic by Andonian et al.* is one such example that combines a laser deflector with an RF deflecting cavity to streak the electron beam in the horizontal and vertical direction. In this paper, we present a tool for the reconstruction of the longitudinal beam profile from this diagnostic data, which can be used both for the analysis of planned experiments and testing of different beam scenarios with respect to their specific setup requirements. Applying this method, the usefulness of the device for measurements in a number of example scenarios, including plasma-accelerated and ultrashort RF-accelerated electron beams, is discussed. *G. Andonian, E. Hemsing, D. Xiang, P. Mumuseci, A. Murokh, S. Tochitsky, et al, Phys. Rev. Spec. Top-Ac. 14, 072802 (2011).
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MOPAB063	IFMIF EVEDA RFQ Local Control System: Power Tests	controls, rfq, EPICS, hardware	253
	M. Montis, L. Antoniazzi, A. Baldo, M.G. Giacchini INFN/LNL, Legnaro (PD), Italy
	In the IFMIF EVEDA project, normal conducting Radio Frequency Quadrupole (RFQ) is used to bunch and accelerate a 130 mA steady beam to 5 MeV. RFQ cavity is divided into three structures, named super-modules. Each super-module is divided into 6 modules for a total of 18 modules for the overall structure. The final three modules have to be tested at high power to test and validate the most critical RF components of RFQ cavity and, on the other hand, to test performances of the main ancillaries that will be used for IFMIF EVEDA project (vacuum manifold system, tuning system and control system). The choice of the last three modules is due to the fact that they will operate in the most demanding conditions in terms of power density (100 kW/m) and surface electric field (1.8*Ekp). The Experimental Physics and Industrial Control System (EPICS) environment [1] provides the framework for monitoring any equipment connected to it. This paper reports the usage of this framework to the RFQ power tests at Legnaro National Laboratories [2,3,4]. [1] http://www.aps.anl.gov/epics/ [2] http://www.lnl.infn.it/. [3] http://www.lnl.infn.it/~epics/joomla/ [4] M. Giacchini et al. LivEPICS: an EPICS Linux Live CD Nagios Equipped, TPPA32, ICALEPCS2007, Oak Ridge, USA
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MOPAB082	Design and Simulation of High Order Mode Cavity Bunch Length Monitor for Infrared Free Electron Laser	simulation, FEL, laser, electron	309
	Q. Wang, X.Y. Liu, P. Lu, Q. Luo, B.G. Sun, L.L. Tang, J.H. Wei, F.F. Wu, Y.L. Yang, T.Y. Zhou, Z.R. Zhou USTC/NSRL, Hefei, Anhui, People's Republic of China
	Funding: Supported by The National Key Research and Development Program of China (2016YFA0401900, 2016YFA0401903); NSFC (11375178, 11575181); the Fundamental Research Funds for the Central Universities (WK2310000046) A bunch length monitor using resonant cavity has been designed for the NSRL Infrared Free Electron Laser (IR-FEL) facility. To avoid the restriction of working fre-quency caused by the beam pipe radius, the high order modes of the harmonic cavities are utilized. The position and orientation of coaxial probes are optimized to avoid interference modes which come from the cavity and beam tube according to the analysis formula of electro-magnetic field distribution. Based on the parameters of IR-FEL, a simulation is performed to verify the feasibility of the bunch length monitor. The simulation result shows that the design meets the requirements of IR-FEL, and the resolution can be better than 50 fs.
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MOPAB092	Design and Performance of Digital BPM Processor for DCLS and SXFEL	FPGA, pick-up, controls, electronics	338
	L.W. Lai, F.Z. Chen, Y.B. Leng, Y.B. Yan, N. Zhang SSRF, Shanghai, People's Republic of China J. Chen SINAP, Shanghai, People's Republic of China
	Funding: Work supported by National Natural Science Foundation (No. 11305253, 11575282) A digital BPM processor has been developed in SINAP, which can be used on the signal processing of both stripline BPM and cavity BPM. The processor is a standalone system and providing 4 channels 120MS/s, 16 bits ADC and powerful Virtex-5 FPGA. The processor has been mas applied on Dalian Coherent Light Source and Shanghai X-ray FE. The processor specification and performance evaluations including lab and beam tests will be introduced.
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MOPAB095	Development of the Simulation Software Package for the CBPM System	simulation, network, FEL, experiment	349
	J. Chen, L.W. Lai, Y.B. Leng, L.Y. Yu SINAP, Shanghai, People's Republic of China N. Zhang SSRF, Shanghai, People's Republic of China
	In recent years, the development and construction of Free Electron Laser (FEL) facilities are in full swing. For FEL facilities, to generate coherent X-ray, cavity beam position monitor (CBPM) system which consist of cavity BPM, RF front-end and signal processor are employed to measure the transverse position in the undulator section. A generic simulation software package, with the S21 parameters of the real components, for the design of the RF front-end and the optimize of the CBPM system was developed. In this paper, the development of the generic simulation software package, and the experiment results with beam at Shanghai Deep ultraviolet (SDUV) FEL facility to verify the correctness of the simulation soft package will be introduced. The application in the design and optimize of the RF front-end for the Dalian Coherent Source (DCLS) will be addressed as well .
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MOPAB153	R&D of a Gas-Filled RF Beam Profile Monitor for Intense Neutrino Beam Experiments	plasma, electron, ion, experiment	491
	K. Yonehara, M. Backfish, A. Moretti, A.V. Tollestrup, A.C. Watts, R.M. Zwaska Fermilab, Batavia, Illinois, USA R.J. Abrams, M.A. Cummings, A. Dudas, R.P. Johnson, G.M. Kazakevich, M.L. Neubauer Muons, Inc, Illinois, USA Q. Liu Case Western Reserve University, Cleveland, USA
	Funding: Work supported by Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359 and DOE STTR Grant, No. DE-SC0013764. A MW-power beam facility is desired to produce an intense neutrino beam for study of fundamental particle physics. It is a critical challenge to measure beam profile in extreme radiation environments. To this end, a novel beam profile monitor based on a gas-filled multi-RF cavity is proposed. Charged particles through the gas-filled RF generate plasma that changes the gas permittivity. The modulated RF signal in the cavity due to the permittivity shift will be measured to reconstruct the flux of charged particles in the cavity. The demonstration is proposed to validate the concept of the monitor. We report the progress of the demonstration test.
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MOPAB155	Characterization of the Longitudinal Acceptance in a Storage Ring with RF Pinger	synchrotron, dynamic-aperture, storage-ring, damping	497
	G.M. Wang, B. Holub, Y. Li, J. Rose, T.V. Shaftan BNL, Upton, Long Island, New York, USA
	In modern generation light sources, it is desired to have SR performance at high beam current, low horizontal emittance with small coupling, resulting in intense Touschek scattering, which is the dominant limitation of beam lifetime. Touschek scattering strongly depends on momentum aperture. Understanding momentum aperture is extremely important. NSLS II storage ring RF system has the digital ramp control function, enabling rapid change of the cavity phase and amplitude. This makes the possibility to ping the beam in longitudinal phase space and directly measure the longitudinal acceptance, in contrast with traditional indirect way to understand it from other aspect of parameters. In this paper, we present the tool, longitudinal pinger, its application to characterize NSLS II longitudinal acceptance and localize the momentum aperture limit with SR BPMs.
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MOPIK003	Improvement of the Photoemission Efficiency of Magnesium Photocathodes	cathode, gun, SRF, laser	500
	R. Xiang, A. Arnold, P.N. Lu, P. Michel, P. Murcek, J. Teichert, H. Vennekate HZDR, Dresden, Germany P. Patra IUAC, New Delhi, India
	Funding: The work is supported by the European Community under the FP7 programme (EuCARD-2) and by the German Federal Ministry of Education and Research (BMBF) grant 05K12CR1. To improve the quality of photocathodes is one of the critical issues in enhancing the stability and reliability of photo-injector systems. Presently the primary choice is to use metallic photocathodes for the ELBE SRF Gun-II to reduce the risk of contamination of the superconducting cavity. Magnesium has a low work function (3.6 eV) and shows high quantum efficiency (QE) up to 0.3 % after laser cleaning. The SRF Gun II with an Mg photocathode has successfully provided electron beam for ELBE users. However, the present cleaning process with a high intensi-ty laser (activation) is time consuming and generates unwanted surface roughness. This paper presents the investigation of alternative surface cleaning procedures, such as thermal treatment. The QE and topography of Mg samples after treatment are reported.
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MOPIK005	Compact Electron Injectors Using Laser Driven THz Cavities	electron, gun, laser, acceleration	506
	M. Fakhari, A. Fallahi, F.X. Kärtner, N.H. Matlis, A. Yahaghi CFEL, Hamburg, Germany R.W. Aßmann, U. Dorda, K. Galaydych, B. Marchetti, G. Vashchenko, T. Vinatier, D. Zhang, C. Zhou DESY, Hamburg, Germany
	We present ultra-small electron injectors based on cascaded cavities excited by short multi-cycle THz signals. The designed structure is a 3.5 cell normal conducting cavity operating at 300 GHz. This cavity is able to generate pC electron bunches and accelerate them up to 250 keV using less than 1 mJ THz energy. Unlike conventional RF guns, the designed cavity operates in a transient state which, in combination with the high frequency of the driving field, makes it possible to apply accelerating gradients as high as 500 MV/m. Such high accelerating gradients are promising for the generation of high brightness electron beams with transverse emittances in the nm-rad range. The designed cavity can be used as the injector for a compact accelerator of low charge bunches.
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MOPIK009	Characterization of Cold Model Cavity for Cryocooled C-Band 2.6-Cell Photocathode RF Gun at 20 K	gun, experiment, cryogenics, simulation	518
	T. Tanaka, K. Hayakawa, Y. Hayakawa, K. Nakao, K. Nogami, T. Sakai, K. Takatsuka LEBRA, Funabashi, Japan M.K. Fukuda, D. Satoh, T. Takatomi, N. Terunuma, J. Urakawa, M. Yoshida KEK, Ibaraki, Japan
	Funding: This work was partly supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT). A cryocooled C-band 2.6-cell photocathode RF electron gun has been studied at Nihon University in cooperation with KEK. The cold model cavity with an input coupler was completed in spring 2016. The RF characteristics measured at room temperature were in agreement with the prediction by the CST Studio simulation. The RF characteristics at 20 K have been measured using a rather simple cavity-cooling vacuum system that was built by using existing components for tentative experiments. A thin-wall stainless-steel R48 waveguide with copper-plated inner walls has been used for the RF power transmission from the room-temperature input port to the 20-K cooled coupler waveguide. The unloaded Q-value of 73000 has been obtained by the reflection coefficient measurement at 20 K, which is in agreement with the result of the CST Studio simulation using the cavity surface resistance predicted by the theory of the anomalous skin effect.
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MOPIK013	Design and Simulation of a C-Band Photocathode RF Gun With a Coaxial Coupler for UEM	gun, electron, coupling, impedance	525
	T. Chen, Y.J. Pei, Y. Song USTC/NSRL, Hefei, Anhui, People's Republic of China
	A ultrafast electron microscope (UEM) has been become much more important research instrument and has been widely used in many fields. As a part of the UEM, a photocathode RF gun working at C-band frequency of 5712MHz is being developed, which provides electron beam with high qualities for UEM. This paper presents the physics and structure design, including optimization of cavity shape parameter for improving shunt impedance and Q factor. We adopt a novel coaxial coupler, which could decrease the multipole field and decrease the focusing coil size, build better accelerating field in the RF gun. In this paper, we discussed the simulation process and results of the RF gun, especially the design of the coaxial input coupler was described.
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MOPIK019	Upgrade Options Towards Higher Fields and Beam Energies for Continuous-Wave Room-Temperature VHF RF Guns	gun, brightness, electron, cathode	542
	F. Sannibale, J.M. Byrd, D. Filippetto, M.J. Johnson, D. Li, T.H. Luo, C.E. Mitchell, J.W. Staples, S.P. Virostek LBNL, Berkeley, California, USA
	Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231 Science demand for MHz-class repetition rate electron beam applications such as free electron lasers (FELs), inverse Compton scattering sources, and ultrafast electron diffraction and microscopy (UED/UEM), pushed the development of new gun schemes that could generate high brightness beams at such high rates. At the Lawrence Berkeley Lab (LBNL), we proposed a new concept room-temperature RF gun resonating in the VHF frequency range (30-300 MHz) capable of operating in continuous wave mode at the fields required for high-brightness performance. A first VHF-Gun was constructed and tested in the APEX facility at LBNL, which successfully demonstrated all design parameters and the generation of high brightness electron beams. A second version of the APEX VHF-Gun is being built at LBNL for the LCLS-II, the new SLAC X-ray FEL. Recent studies showed that a proposed LCLS-II upgrade and UED/UEM applications would greatly benefit from an increased gun brightness obtained by raising the electric field at the cathode and the beam energy at the gun exit. In this paper, we present and discuss possible upgrade options that would allow extension of the VHF-Gun performance towards these new goals.
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MOPIK040	Value Engineering of an Accelerator Design During Construction	linac, cryomodule, neutron, proton	592
	E. Bargalló, M. Eshraqi, M. Lindroos, S. Molloy, D.C. Plostinar, A. Sunesson ESS, Lund, Sweden F. Gerigk CERN, Geneva, Switzerland
	Value engineering is an important part of the process of designing and realising large-scale installations such as high power accelerators. This typically occurs during the later part of the design stage of the system, however such exercises may also be requested by funding bodies at later stages in order to manage project contingency. Naturally, the later this is done, the more challenging it becomes. In this paper we report on a recently concluded Value Engineering effort at the European Spallation Source. The challenges presented by the initiation of such an exercise during the construction phase are discussed. In addition, we present and discuss the various options that we examined, and indicate the philosophy and figures of merit used to narrow down these options. The final conclusion will be presented.
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MOPIK058	Beam Dynamic Studies for the SARAF MEBT and SC Linac	quadrupole, linac, rfq, simulation	655
	J. Dumas, N. Pichoff, D. Uriot CEA/IRFU, Gif-sur-Yvette, France P.A.P. Nghiem CEA/DSM/IRFU, France
	The SARAF MEBT and Super Conducting Linac (SCL) transport and accelerate deuterons or protons from the RFQ to the final energy. In this report, beam dynamics studies for this section are described. A rational distribution of the different roles of the MEBT leads to defining its necessary quadrupole/rebuncher composition. This allows easy beam re-tuning following changes from the RFQ or the SC Linac. After observing evidences of beam losses mainly due to phase unhooking, efforts have been dedicated to enlarge the SCL longitudinal acceptance. A combination of cavity field phases is found so that the required final beam energy is also fulfilled.
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MOPIK068	Beam Dynamics Design Parameters for KONUS Lattices	lattice, linac, acceleration, emittance	683
	R. Tiede, H. Hähnel, U. Ratzinger IAP, Frankfurt am Main, Germany
	The 'Combined Zero-Degree Structure' ('Kombinierte Null Grad Struktur - KONUS') beam dynamics concept has been successfully applied on several linacs, some of them in routine operation since decades. However, the KONUS lattice parameters optimization is often done in a results-oriented approach, depending on the designers' experience. This paper focuses on the description of the longitudinal beam motion along one KONUS lattice period. A test lattice is used for demonstrating the potential of KONUS lattices with respect to stable, periodic beam motion with emittance growth rates similar to those of conventional designs. The main objective of this ongoing work is to derive more general rules for the parametrization of KONUS lattices.
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MOPIK098	Techniques for Achieving High Reliability Operation of the Spallation Neutron Source High Power Radio-Frequency System	klystron, cathode, operation, neutron	756
	J. Moss, M.S. Champion ORNL, Oak Ridge, Tennessee, USA
	Funding: *ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. This research was supported by the DOE Office of Science, Basic Energy Science, Scientific User Facilities. The Spallation Neutron Source (SNS) high power radiofrequency (HPRF) system operates with high reliability to support the goals of the SNS user program. In recent operational periods the availability of the HPRF System has exceeded 97 percent while the neutron source availability overall is typically greater than 90 percent. SNS has a unique set of 92 HPRF stations that operate at either 402.5 MHz or 805 MHz with peak output power ranging from 550 kW to 5 MW and average power ranging from 49.5 kW to 450 kW. The HPRF transmitters consist of chassis-mounted power supplies, solid-state amplifiers and other equipment that support the operation of the klystrons that ultimately provide the RF power to the accelerating structures. Management of the operation and maintenance of the HPRF system has increasingly focused on reliability and sustainability in recent years. Techniques for klystron lifetime preservation and optimization of transmitter reliability have been developed and will be described.
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MOPIK117	On the Computation of Phase and Energy Gain for a Thin-Lens RF Gap Using a General Field Profile	simulation, linac, factory, acceleration	810
	C.K. Allen ORNL, Oak Ridge, Tennessee, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under contract number DE-AC05-00OR22725. The thin-lens representation for an RF accelerating gap has been well developed and is documented by Lapostolle [5], Weiss [6], Wangler [14], and others [9], [10]. These models assume that the axial electric field is both centered and symmetric so it has a cosine expansion. Presented here is a model that considers general axial fields. Both the cosine and sine transit time factors are required plus their Hilbert transforms. The combination yields a complex Hamiltonian rotating in the complex plane with the synchronous phase. The phase and energy gains are computed in the pre-gap and post-gap regions then aligned with asymptotic values of wave number. Derivations are outlined, examples are shown, and simulations presented.
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MOPVA005	Status of the Berlin Energy Recovery Linac Project BERLinPro	gun, SRF, linac, booster	855
	M. Abo-Bakr, W. Anders, K.B. Bürkmann-Gehrlein, A.B. Büchel, P. Echevarria, A. Frahm, H.-W. Glock, F. Glöckner, F. Göbel, B.D.S. Hall, S. Heling, H.-G. Hoberg, A. Jankowiak, C. Kalus, T. Kamps, G. Klemz, J. Knedel, J. Knobloch, J. Kolbe, G. Kourkafas, J. Kühn, B.C. Kuske, J. Kuszynski, D. Malyutin, A.N. Matveenko, M. McAteer, A. Meseck, C.J. Metzger-Kraus, R. Müller, A. Neumann, N. Ohm, K. Ott, E. Panofski, F. Pflocksch, J. Rahn, M. Schmeißer, O. Schüler, M. Schuster, J. Ullrich, A. Ushakov, J. Völker HZB, Berlin, Germany
	Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association. The Helmholtz-Zentrum Berlin is constructing the Energy Recovery Linac Prototype BERLinPro, a demonstration facility for the science and technology of ERLs for future light source applications. BERLinPro is designed to accelerate a high current (100 mA, 50 MeV), high brilliance (norm. emittance below 1 mm mrad) cw electron beam. We report on the project status. This includes the completion of the building and the installation of the first accelerator components as well as the assembly of the SRF gun and GunLab beam diagnostics, which are now ready for commissioning.
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MOPVA007	Simulations for Beam-Based Measurements in BERLinPro	simulation, diagnostics, gun, optics	859
	M. McAteer, M. Abo-Bakr, J. Knedel, G. Kourkafas, B.C. Kuske, J. Völker HZB, Berlin, Germany
	BERLinPro is an energy recovery linac project whose goal is to establish the accelerator physics knowledge and technology needed to produce 50 MeV beams with high current, low normalized emittance, and low losses. Precise measurements of beam parameters are essential for demonstrating the achievement of performance goals. In this paper we present simulations for measurements of energy, energy spread, and bunch length using the tracking code Astra.
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MOPVA018	Resonant Coherent Diffraction Radiation System at ERL Test Accelerator in KEK	radiation, resonance, experiment, emittance	887
	Y. Honda, A. Aryshev, R. Kato, T. Miyajima, T. Obina, M. Shimada, R. Takai, N. Yamamoto KEK, Ibaraki, Japan
	Funding: This work was supported by JSPS KAKENHI Grant Number 16H05991 An Energy Recovery Linac can produce a low emittance and short bunch beam at a high repetition rate. A test accelerator, compact-ERL, has been operating in KEK for development works of technologies related to ERL and CW-Superconducting accelerators. In a special beam operation mode of bunch compression, a short bunch beam of ~150 fs at the repetition rate of CW 1.3 GHz can be realized in the return-loop. One of the promising applications of such a short bunch beam is a high power THz radiation source produced by a coherent radiation. When a charged particle beam passes close to a conductive target, a radiation called diffraction radiation is produced. If the target mirrors form an optical cavity which fundamental frequency matches the repetition frequency of the beam, the radiation resonates in the cavity, resulting in extracting a huge radiation power determined by the loss of the cavity. We plan to perform an experiment of the resonant coherent diffraction mechanism in the return-loop of the compact-ERL to test the feasibility to be a wide band high power THz source. We report the design of the experimental setup to be installed in the summer of 2017.
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MOPVA019	60 pC Bunch Charge Operation of the Compact ERL at KEK	operation, emittance, laser, linac	890
	T. Miyajima, K. Harada, Y. Honda, E. Kako, R. Kato, T. Miura, N. Nakamura, T. Obina, M. Shimada, R. Takai, K. Umemori, M. Yamamoto KEK, Ibaraki, Japan R. Hajima, R. Nagai QST, Tokai, Japan T. Hotei Sokendai, Ibaraki, Japan N. Nishimori Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
	The compact ERL (cERL) at KEK was operated in March 2017 to demonstrate generation, acceleration and transportation of the target bunch charge of 60 pC without energy recovery. However, the maximum bunch charge was limited to 40 pC due to the limitation of the excitation laser power. For the bunch charge of 40 pC, the bunch length and the normalized emittance were measured in the injector diagnostic line. The results of the bunch length measurement gave good agreement with the values that had been obtained by model simulation. The measured normalized rms emittances for 40 pC were 0.9 to 2.4 mm mrad, and they were lager than the design value of 0.6 mm mrad. To achieve the design emittance, we have studied the source of the emittance growth for the bunch charge of 40 pC.
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MOPVA038	Manufacturing Status of the IFMIF LIPAc SRF Linac	cryomodule, vacuum, SRF, linac	939
	N. Bazin, P. Carbonnier, P. Contrepois, J. Plouin, B. Renard CEA/DSM/IRFU, France C. Boulch, A. Bruniquel, J.K. Chambrillon, G. Devanz, P. Hardy, H. Jenhani, N. N'Doye, O. Piquet, A. Riquelme, D. Roudier CEA/DRF/IRFU, Gif-sur-Yvette, France P. Charon, S. Chel, G. Disset, J. Relland CEA/IRFU, Gif-sur-Yvette, France D. Regidor, F. Toral CIEMAT, Madrid, Spain
	This paper gives the fabrication status of the IFMIF cryomodule. This cryomodule will be part of the Linear IFMIF Prototype Accelerator (LIPAc) whose construction is ongoing at Rokkasho, Japan. It is a full scale of one of the IFMIF accelerator, from the injector to the first cryomodule. The cryomodule contains all the necessary equipment to transport and accelerate a 125 mA deuteron beam from an input energy of 5 MeV up to the output energy of 9 MeV. It consists of a horizontal vacuum tank of around 6 m long, 3 m high and 2.0 m wide, which includes 8 superconducting HWRs for beam acceleration, working at 175 MHz and at 4.45 K, 8 Power Couplers to provide RF power to cavities up to 70 kW CW in LIPAc case and 200 kW CW in IFMIF case, and 8 Solenoid Packages as focusing elements.
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MOPVA039	Manufacturing and Validation Tests of IFMIF Low-Beta HWRs	cryomodule, SRF, operation, simulation	942
	G. Devanz, F. Éozénou, L. Maurice, P. Sahuquet, C. Servouin CEA/DSM/IRFU, France N. Bazin, P. Carbonnier, P. Charon, G. Disset, P. Hardy, E. Jacques, O. Piquet, D. Roudier CEA/IRFU, Gif-sur-Yvette, France J.K. Chambrillon, T. Percerou CEA/DRF/IRFU, Gif-sur-Yvette, France
	The IFMIF accelerator aims to provide an accelerator-based D-Li neutron source to produce high intensity high energy neutron flux to test samples as possible candidate materials to a full lifetime of fusion energy reactors. A prototype of the low energy part of the accelerator is under construction at Rokkasho in Japan. It includes one cryomodule containing 8 half-wave resonators (HWR) operating at 175 MHz .The first manufactured HWR has passed low power tests at 4.2K in vertical cryostat succesfully and exceeds the specifications. It has also been tested in the dedicated horizontal Sathori cryostat equiped with its cold tuning system. The serial production and qualification tests of the 8 cavities which will eventually equip the cryomodule are carried out in parallel. In this paper, we focus on the HWR preparation and test results and give a status of the manufacturing activities.
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MOPVA040	Status of the ESS Elliptical Cryomodules at CEA Saclay	cryomodule, cryogenics, vacuum, SRF	945
	P. Bosland, C. Arcambal, F. Ardellier, S. Berry, A. Bouygues, A. Bruniquel, E. Cenni, J.-P. Charrier, C. Cloué, G. Devanz, F. Éozénou, T. Hamelin, X. Hanus, P. Hardy, C. Marchand, O. Piquet, J. Plouin, J.P. Poupeau, T. Trublet CEA/DRF/IRFU, Gif-sur-Yvette, France G. Costanza Lund University, Lund, Sweden C. Darve ESS, Lund, Sweden P. Michelato INFN/LASA, Segrate (MI), Italy G. Olivier IPN, Orsay, France F. Peauger CEA/DSM/IRFU, France
	The first ESS prototype cryomodule with medium beta cavities named M-ECCTD is being assembled at CEA Saclay. The Q curves of the 4 cavities mounted inside the cryomodule are presented, and the four power couplers have been conditioned at high power before their assembly onto the cavity string. Completion of the M-ECCTD assembly outside clean room is in progress as well as the finalization of the RF power test stand preparation. RF power tests of the M-ECCTD will be performed during summer 2017. CEA is preparing the production of the ESS medium and high beta cryomodules of the series before the test of the M-ECCTD and the contracts for the procurement of the most critical components have already been signed
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MOPVA041	Vertical Test Results on ESS Medium and High Beta Elliptical Cavity Prototypes Equipped with Helium Tank	linac, radiation, cryomodule, background	948
	E. Cenni CEA/IRFU, Gif-sur-Yvette, France P. Bosland, G. Devanz, F. Éozénou, X. Hanus, L. Maurice, F. Peauger, J. Plouin, D. Roudier, C. Servouin CEA/DSM/IRFU, France G. Costanza Lund University, Lund, Sweden C. Darve ESS, Lund, Sweden
	The ESS elliptical superconducting Linac consists of two types of 704.42 MHz cavities, medium and high beta, to accelerate the beam from 216 MeV (spoke cavity Linac) up to the final energy at 2 GeV. The last Linac optimization, called Optimus+, has been carried out taking into account the limitations of SRF cavity performance (field emission). The medium and high-beta parts of the Linac are composed of 36 and 84 elliptical cavities, with geometrical beta values of 0.67 and 0.86 respectively. This work presents the latest vertical test results on ESS medium and high beta elliptical cavity prototypes equipped with helium tank. We describe the cavity preparation procedure from buffer chemical polishing to vertical test.
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MOPVA042	CEA Preliminary Design of the Cryomodules for SARAF Phase II Superconducting Linac	cryomodule, vacuum, simulation, alignment	951
	R. Cubizolles, P. Brédy, D. Chirpaz-Cerbat, P. Hardy, F. Leseigneur, C. Madec, J. Plouin CEA/IRFU, Gif-sur-Yvette, France N. Bazin CEA/DSM/IRFU, France R. Bruce, Th. Plaisant CEA/DRF/IRFU, Gif-sur-Yvette, France
	CEA is committed to deliver a Medium Energy Beam Transfer line and a superconducting linac (SCL) for SARAF accelerator in order to accelerate 5mA beam of either protons from 1.3 MeV to 35 MeV or deuterons from 2.6 MeV to 40.1 MeV. The SCL consists of 4 cryomodules and 4 warm sections with diagnostics at the end of each cryomodule. The first two identical cryomodules host 6 half-wave resonator (HWR) low-beta cavities (β = 0.091), 176 MHz, and 6 focusing superconducting solenoids. The last two identical cryomodule welcome 7 HWR high-beta cavities (β = 0.181), 176 MHz, and 4 solenoids. The paper will presents the preliminary design of the cryomodules.
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MOPVA043	Assembly Preparation of the IFMIF SRF Cryomodule	solenoid, cryomodule, SRF, vacuum	954
	J.K. Chambrillon, N. N'Doye CEA/DRF/IRFU, Gif-sur-Yvette, France N. Bazin, P. Charon, G. Devanz, P. Hardy, O. Piquet, J. Plouin CEA/IRFU, Gif-sur-Yvette, France P. Contrepois, C. Servouin CEA/DSM/IRFU, France
	This article presents the preparation work performed by CEA for the assembly of the IFMIF Cryomodule. Before the shipping of the components to Japan many tests and trial assemblies has been realized on the CEA site of Saclay, France. The cryomodule, which is part of the Linear IFMIF Prototype Accelerator (LIPAc) under construction at Rokkasho in Japan, will be assembled there under the responsibility of F4E (Fusion for Energy) with CEA assistance. To fulfill the assembly of the cavity string, a cleanroom will be built at Rokkasho under the responsibility of QST.
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MOPVA044	Conditioning of the Power Couplers for the ESS Elliptical Cavity Prototypes	coupling, vacuum, controls, pick-up	957
	C. Arcambal, P. Carbonnier, M. Desmons, G. Devanz, T. Hamelin, C. Marchand, C. Servouin CEA/DRF/IRFU, Gif-sur-Yvette, France C. Darve ESS, Lund, Sweden
	In the framework of the European Spallation Source (ESS), some power couplers have been designed and manufactured to supply, with RF power, the medium-beta (β=0.67) elliptical cavities of the cryomodule demonstrator. The power couplers work at 704.4 MHz and are tested up to 1.2 MW (repetition rate=14 Hz, RF pulse width close to 3.6 milliseconds). The CEA Saclay is in charge of the design, the manufacturing, the preparation and the conditioning of these power couplers. In this paper, after a general presentation of the power couplers used in the ESS LINAC and their characteristics, we give some détails about the manufacturing and then we describe the different steps of the preparation (cleaning), the assembly of the couplers on the coupling box in cleanroom, the baking of the couplers and the conditioning procedure. Finally, the experimental results obtained in travelling and standing waves on the first pairs of couplers will be shown.
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MOPVA046	120kW RF Power Input Couplers for BERLinPro	booster, coupling, SRF, linac	960
	B.D.S. Hall, V. Dürr, F. Göbel, J. Knobloch, A. Neumann HZB, Berlin, Germany
	The 50-MeV, 100-mA energy-recovery-linac (ERL) demonstration facility BERLinPro is currently undergoing construction at HZB. The high power injection system, that will deliver a beam at 6.5MeV, is split into a 1.4 cell SRF Photo injector and three Cornell-style 2-cell boosters. The injector and two of the booster cavities will provide about 2MeV each and must handle up to 220 kW of beam loading. New, cERL-based 115-kW high power couplers needed for the cavities' twin coupler system have begun manufacture. The design, optimization and manufacturing considerations of these couplers are presented.
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MOPVA048	Simulation of the Thermoelectrically Generated Magnetic Field in a SC Nine-Cell Cavity	simulation, SRF, operation, superconducting-RF	968
	J.M. Köszegi, J. Knobloch, O. Kugeler HZB, Berlin, Germany
	Several studies showed that thermocurrents generate a magnetic field in a horizontal cavity test assembly or cryomodul, which may get trapped during the supercon-ducting phase transition. The trapped flux causes additional dissipation in the order of 1 to 10 n' during operation and can therefore significantly degrade the quality factor in a TESLA cavity. We simulated the distribution of the generated magnetic field over the whole cavity-tank system for an asymmetric temperature distribution. The asymmetry allows the field to penetrate the RF surface which would be field free in the symmetric case. The calculated results complemented a direct measurement of trapped magnetic flux inside the cavity with a small number of field probes. Finally, the obtained data was combined with RF measurements in three passband modes to determine the overall distribution of trapped magnetic flux due to thermocurrents.
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MOPVA049	First Commissioning of an SRF Photo-Injector Module for BERLinPro	cathode, SRF, solenoid, linac	971
	A. Neumann, A. Burrill, D. Böhlick, A.B. Büchel, M. Bürger, P. Echevarria, A. Frahm, H.-W. Glock, F. Göbel, S. Heling, K. Janke, T. Kamps, S. Keckert, S. Klauke, G. Klemz, J. Knobloch, G. Kourkafas, J. Kühn, O. Kugeler, N. Ohm, E. Panofski, H. Plötz, S. Rotterdam, M. Schenk, M.A.H. Schmeißer, M. Schuster, H. Stein, Y. Tamashevich, J. Ullrich, A. Ushakov, J. Völker HZB, Berlin, Germany A. Matheisen, M. Schmökel DESY, Hamburg, Germany
	Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association. Helmholtz-Zentrum Berlin (HZB) is currently building an high average current superconducting ERL to demonstrate ERL operation with low normalized beam emittance of 1 mm·mrad at 100mA and short pulses of about 2 ps. For the injector section a series of SRF photoinjector cavities is being developed. The medium power prototype presented here features a 1.4 x λ/2 cell SRF cavity with a normal-conducting, high quantum efficiency CsK2Sb cathode, implementing a modified HZDR-style cathode insert. This injector potentially allows for 6 mA beam current at up to 3.5 MeV kinetic energy. In this contribution, the first RF commissioning results of the photo-injector module will be presented and compared to the level of performance during the cavity production and string assembly process.
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MOPVA050	Setup of a Spatially Resolving Vector Magnetometry System for the Investigation of Flux Trapping in Superconducting Cavities	SRF, niobium, experiment, radio-frequency	975
	B. Schmitz, K.Alomari. Alomari, J. Knobloch, O. Kugeler, J.M. Köszegi, Y. Tamashevich HZB, Berlin, Germany
	Flux trapping is the major contribution to the residual resistance of superconducting cavities. In order to gain a better understanding of the mechanisms involved and aiming at an eventual minimization of trapped flux, a measurement setup based on AMR sensors was devised that allows for monitoring the magnetic field vector at various positions near the cavity surface. First results of the efforts are presented.
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MOPVA051	Design of the High Power 1.5 GHz Input Couplers for BESSY VSR	coupling, operation, simulation, HOM	978
	E. Sharples, M. Dirsat, J. Knobloch, A.V. Vélez HZB, Berlin, Germany
	The Variable pulse length Storage Ring (BESSY VSR) upgrade to BESSY II at Helmholtz-Zentrum Berlin (HZB) requires an upgrade on the RF systems in the form of high-voltage longitudinally focusing super conducting RF cavities of 1.5 GHz ad 1.75 GHz. For operation, coaxial RF power couplers capable of handling 13 kW peak power at standing wave operation are required for both the 1.5 GHz and 1.75 GHz cavities. The coupler is based on a design by Cornell University with modifications to suit frequency and coupling requirements. The coupler is intended to provide variable coupling with a range of Qext from 6x10⁶ to 6x10⁷ to allow flexibility to adjust to operating conditions of BESSY VSR. Here we present the RF design of the high-power coaxial coupler for BESSY VSR along with the design of the test stand for conditioning a pair of couplers.
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MOPVA052	Study on HOM Power Levels in the BESSY VSR Module	HOM, SRF, operation, resonance	982
	A.V. Tsakanian, H.-W. Glock, J. Knobloch, A.V. Vélez HZB, Berlin, Germany
	The BESSY VSR upgrade of the BESSY II light source represents a novel approach to simultaneously store of long (ca. 15ps) and short (ca. 1.5ps) bunches in the storage ring with the 'standard' user optics. This challenging goal requires installation of four new SRF cavities (2x1.5GHz and 2x1.75GHz) in a single module to minimize space requirements. These cavities are equipped with strong waveguide and beam tube HOM dampers necessary for stable operation. The expected HOM power and spectrum has been analyzed for the complete module. This study is performed for various BESSY VSR bunch filling patterns with 300 mA beam current. In the module different cavity arrangements are analyzed to reach the optimal operation conditions with equally distributed power portions in warm HOM loads and tolerable beam coupling impedance.
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MOPVA053	The SRF Module Developments for BESSY VSR	HOM, synchrotron, damping, SRF	986
	A.V. Vélez, H.-W. Glock, F. Glöckner, B.D.S. Hall, J. Knobloch, A. Neumann, P. Schnizer, E. Sharples, A.V. Tsakanian HZB, Berlin, Germany
	Helmholtz-Zentrum Berlin is developing BESSY VSR, a novel upgrade of the BESSY II facility to provide highly flexible pulse lengths while maintaining the flux and brilliance. The project goal is to simultaneously circulate both standard (some 10 ps long) and short (ps and sub-ps long) pulses offering the BESSY user community picosecond dynamics and high-resolution experiments. The concept relies on the installation of high-voltage SRF cavities operating at the 3rd and 3.5th harmonic whereby the beating of the two frequencies provides RF buckets for long and short bunches. Since these cavities will operate in CW and with high beam current (Ib=300 mA), the cavity design represents a challenging goal. In addition the need to avoid coupled bunch instabilities (CBI's), the installation of the VSR Cryomodule must fit in one of the available 4-m long low beta straights. To address the technological and engineering challenges techniques such as waveguide-damped cavities have been developed. First prototypes have been produced. In this paper, the present SRF developments are presented, including the cavities, high power couplers, higher-order mode absorbers and the cryomodule design.
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MOPVA054	High Power RF Coupler for the CW-Linac Demonstrator at GSI	Windows, linac, simulation, ion	990
	M. Heilmann, W.A. Barth, S. Yaramyshev GSI, Darmstadt, Germany M. Amberg, M. Basten, R. Blank, M. Busch, F.D. Dziuba, H. Podlech, M. Schwarz IAP, Frankfurt am Main, Germany K. Aulenbacher IKP, Mainz, Germany K. Aulenbacher, W.A. Barth, V. Gettmann, M. Miski-Oglu HIM, Mainz, Germany W.A. Barth, S. Yaramyshev MEPhI, Moscow, Russia
	The planned super-heavy element (SHE) research project investigates heavy ions near the coulomb barrier in future experiments. A superconducting (sc) continuous wave (cw) CH-Linac Demonstrator was developed and installed behind the High Charge State Injector (HLI) at GSI Darmstadt, Germany. In future the advanced cw-LINAC setup, with several CH-cavities, will accelerates the heavy ion beam from HLI with an energy of 1.4 MeV/u up to 3.5 - 7.3 MeV/u. The RF power of several kW will be coupled capacitively into the CH-cavities with minimal reflection at an operation frequency of 217 MHz. Two ceramic windows (Al2O3) are installed inside the RF coupler, to reduce the premature contamination of the cavity and as an additional vacuum barrier. The CH-cavity will be operated at cryogenic temperature (4 K) and will be increased to room temperature along the RF coupler. The optimally adapted RF coupler design, providing minimal RF losses and simultaneously maximal performance, was optimized by electromagnetic simulations. An RF coupler design with a reflection-free RF adaptor as well as the temperature distribution along the coupler will be presented.
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MOPVA055	Upgrade of the Capture Section of the S-DALINAC Injector	SRF, electron, operation, accelerating-gradient	993
	D.B. Bazyl, H. De Gersem, W.F.O. Müller TEMF, TU Darmstadt, Darmstadt, Germany
	Funding: This work is supported by the DFG through GRK 2128. In order to reduce the energy spread of the recirculated beam, the injector of the S-DALINAC needs to be optimized, because the non-isochronous recirculation cannot correct for errors originating from the injector linac. For the S-DALINAC, spatial restrictions suggest the use of SRF technology for the capture section. In this work, we consider various SRF cavities with an operating frequency of 3 GHz for a possible upgrade of the capture section of the S-DALINAC. The first results of the RF and beam dynamics simulations for the proposed options are presented in this paper.
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MOPVA057	Structural Investigations of Nitrogen-Doped Niobium for Superconducting RF Cavities	niobium, SRF, vacuum, radio-frequency	996
	M. Major, L. Alff, M. Arnold, J. Conrad, S. Flege, R. Grewe, N. Pietralla TU Darmstadt, Darmstadt, Germany F. Hug IKP, Mainz, Germany
	Funding: Work supported by BMBF through 05H15RDRBA. Niobium is the standard material for superconducting RF (SRF) cavities. Superconducting materials with higher critical temperature or higher critical magnetic field allow cavities to work at higher operating temperatures or higher accelerating fields, respectively. Enhancing the surface properties of the superconducting material in the range of the penetration depth is also beneficial. One direction of search for new materials with better properties is the modification of bulk niobium by nitrogen doping. In the Nb-N phase diagram the cubic delta-phase of NbN has the highest critical temperature (16 K). Already slight nitrogen doping of the alpha-Nb phase results in higher quality factors.* Nb samples will be N-doped at the refurbished UHV furnace at IKP Darmstadt. The first results on the structural investigations of the processed Nb samples at the Materials Research Department of TU Darmstadt are presented. * Grassellino et al., Proc. SRF2015, MOBA06, 48.
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MOPVA058	Commissioning and Operation Experience of the 3.9 GHz System in the EXFEL Linac	operation, LLRF, linac, klystron	999
	C.G. Maiano, J. Branlard, M. Hüning, M. Omet, P. Pierini, E. Vogel DESY, Hamburg, Germany A. Bosotti, R. Paparella, P. Pierini, D. Sertore INFN/LASA, Segrate (MI), Italy
	The European X-ray Free Electron Laser (EXFEL) injector linac hosts a 3.9~GHz module (AH1) for beam longitudinal phase space manipulation after the first acceleration stage, in order for the linac to deliver the high current beams with sufficiently low emittance for the production of 1 Angstrom FEL light to the experimental users. The module was technically commissioned in December 2015 and operated well above its nominal performances during the Injector Run from January to July 2016. Its operation has restarted in January 2017 with the startup of the whole facility, and the system met the design beam specifications after the bunch compression stages. A brief review of the commissioning and first operation experience of the RF system are presented here.
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MOPVA060	Fabrication and Treatment of the ESS Medium Beta Prototype Cavities	controls, operation, feedback, vacuum	1003
	L. Monaco, A. Bellandi, M. Bertucci, A. Bignami, A. Bosotti, J.F. Chen, P. Michelato, R. Paparella, D. Sertore INFN/LASA, Segrate (MI), Italy C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy S. Pirani ESS, Lund, Sweden
	In view of the Medium Beta series cavities production at the industry for the European Spallation Source project, INFN Milano - LASA design prototypes have been fully produced at Ettore Zanon S.p.A. with our supervision. Based on our experience on the production of 1.3 GHz and 3.9 GHz E-XFEL series cavities, we set-up and applied an external quality control activity of the overall production of the prototype cavity, starting from the row materials to the ready to be tested cavity. In this paper, we report the strategy we have adopted on the overall production, mechanical and surface treatments, frequency measurement of subcomponents and cavities and the obtained results.
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MOPVA061	Quench and Field Emission Diagnostics for the ESS Medium-Beta Prototypes Vertical Tests at LASA	radiation, electron, detector, diagnostics	1007
	M. Bertucci, A. Bellandi, A. Bignami, A. Bosotti, J.F. Chen, P. Michelato, L. Monaco, R. Paparella, D. Sertore INFN/LASA, Segrate (MI), Italy C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy S. Pirani ESS, Lund, Sweden
	In order to investigate the possible causes of premature thermal breakdown and performance degradation, several diagnostic techniques have been employed during the vertical tests of the Fine and Large Grain ESS Medium Beta prototypes cavities. The whole equipment, which includes second sound, fast thermometry, photodiode x ray detectors and an external NaI scintillator, is here described and the results so far obtained during the vertical tests presented.
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MOPVA062	Test, Diagnostics and Computed Tomographic Inspection of a Large Grain 3.9 GHz Prototype Cavity	niobium, SRF, diagnostics, radio-frequency	1011
	M. Bertucci, A. Bignami, A. Bosotti, J.F. Chen, C.G. Maiano, P. Michelato, L. Monaco, R. Paparella, P. Pierini, D. Sertore INFN/LASA, Segrate (MI), Italy G. Ciovati, G.R. Myneni JLab, Newport News, Virginia, USA C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy
	A large grain 3.9 GHz prototype cavity made of RRR = 10⁵ ±10 has been tested at LASA. The cavity suffered of quench at moderate levels of accelerating field, for all nine fundamental pass-band modes. Several diagnostic techniques have been employed to determine the quench positions, which occur close to significant grain-boundary steps, visible from the external cavity surface. The cavity has been scanned with a high resolution X-ray tomographic machine, confirming the existence of remarkable topographic features on the inner RF surface at the suspected quench positions. A strategy for a future surface treatment for recover the cavity performances is here presented.
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MOPVA063	Vertical Tests of ESS Medium Beta Prototype Cavities at LASA	vacuum, operation, radiation, accelerating-gradient	1015
	A. Bosotti, A. Bellandi, M. Bertucci, A. Bignami, J.F. Chen, C.G. Maiano, P. Michelato, L. Monaco, R. Paparella, P. Pierini, D. Sertore INFN/LASA, Segrate (MI), Italy C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy S. Pirani ESS, Lund, Sweden
	In the framework of the INFN activity related to the European Spallation Source collaboration, the LASA infrastructure has been renewed to allow the qualification, in its vertical cryostat, of the 704 MHz medium beta cavity prototypes. A new cryogenic insert has been realized, fully equipped with dedicated mechanical supports, vacuum, thermal sensors and quench diagnostic systems. The RF test station has been upgraded as well with a new PLL electronics rack. The first beta 0.67 cavity prototype designed and produced by INFN Milano has been successfully cold tested at 2.0 K temperature, outperforming the ESS specifications. The technical features of LASA infrastructure, the design of novel components and the experimental results of cavities cold-tests are thoroughly described in this paper.
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MOPVA064	Multipacting Study in INFN-LASA ESS Medium-Beta Cavity	simulation, SRF, site, electron	1019
	J.F. Chen, M. Bertucci, A. Bosotti, P. Michelato, L. Monaco, C. Pagani, R. Paparella, D. Sertore INFN/LASA, Segrate (MI), Italy S. Pirani ESS, Lund, Sweden
	We present Multipacting studies in ESS Medium-Beta cavities of INFN-LASA design with both simulation and experimental results. The simulation on the ideal cavity shape with both FishPact and MultiPac2.1 codes shows that multipacting appears in a very small region near equator where the weld seam exists. A simulation with more realistic cavity shape considering the weld seam at cell equators has also been done out showing similar results for end cell but a remarkable mitigation for inner cell. During the vertical tests at LASA, Multipacting is frequently observed but with no limitation to the cavity performance, which well confirms the MP predicted by the simulations.
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MOPVA066	Limits for the Operation of the European XFEL 3.9 GHz System in CW Mode	operation, cryomodule, linac, laser	1023
	P. Pierini, A. Bosotti, R. Paparella, D. Sertore INFN/LASA, Segrate (MI), Italy J. Branlard, D. Kostin, C.G. Maiano, W.-D. Möller, P. Pierini, D. Reschke, J.K. Sekutowicz, E. Vogel DESY, Hamburg, Germany
	Future upgrades of the European XFEL (EXFEL) facility may require driving the linac at higher duty factor, possibly extending to CW mode at reduced gradients. A preliminary analysis for the accelerator modules has been presented in the EXFEL TDR, but no precise assessment has been performed so far for the present 3.9 GHz system design. By making use of data collected during the commissioning and operation phase of the EXFEL injector system, we discuss here an estimate for the limits of CW operation of the present system and a plan for its possible experimental verification with existing available cavities and the EXFEL spare module.
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MOPVA068	Experience on Design, Fabrication and Testing of a Large Grain ESS Medium Beta Prototype Cavity	radiation, niobium, operation, cryogenics	1027
	D. Sertore, A. Bellandi, M. Bertucci, A. Bignami, A. Bosotti, J.F. Chen, C.G. Maiano, P. Michelato, L. Monaco, R. Paparella, P. Pierini INFN/LASA, Segrate (MI), Italy C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy S. Pirani ESS, Lund, Sweden
	We report on the design, fabrication and testing of an ESS Medium Beta prototype cavity made with Large Grain Niobium sheets sliced from an ingot provided by CBMM. The peculiar choices during the fabrication process related to the Large Grain Niobium material are described. We present also the results of the cavity test at cryogenic temperature and the dedicated quench diagnostic.
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MOPVA071	Press Forming Tests of Superconducting Spoke Cavity for Laser Compton Scattered Photon Sources	laser, photon, niobium, resonance	1031
	M. Sawamura, R. Hajima QST, Tokai, Japan H. Hokonohara, Y. Iwashita, H. Tongu Kyoto ICR, Uji, Kyoto, Japan T. Kubo, T. Saeki KEK, Ibaraki, Japan
	We are developing the superconducting spoke cavity for laser Compton scattered (LCS) photon sources. We adopt the superconducting spoke cavity for electron beam drivers to realize a wide use of LCS X-ray and '-ray sources in academic and industrial applications. The spoke cavity can make the accelerator more compact than an elliptical cavity because the cavity size is small at the same frequency and the packing factor is good by installing couplers on outer conductor. Though our proposal design for the photon source consists of the 325 MHz spoke cavities in 4K operation, we are fabricating the half scale model of 650 MHz spoke cavity in order to accumulate our cavity production experience by effective utilization of our limited resources. Since the spoke has more complicated structure than an elliptical cavity, we performed press forming tests for the half spoke and estimated the formed shapes with 3-dimensional measurement.
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MOPVA074	Fabrication of Superconducting QWR at MHI-MS	SRF, linac, superconducting-RF, niobium	1037
	N. Shigeoka, H. Hara, A. Miyamoto, K. Sennyu, T. Yanagisawa MHI-MS, Kobe, Japan O. Kamigaito, K. Ozeki, N. Sakamoto, K. Suda, Y. Watanabe, K. Yamada RIKEN Nishina Center, Wako, Japan
	Mitsubishi Heavy Industries Mechatronics Systems, Ltd. (MHI-MS), a subsidiary campany of MHI, took over MHI's accelerator business on October 1, 2015, and has been developing the business. MHI-MS is manufacturing the prototype Superconducting QWR for RIKEN Superconducting linac project. MHI-MS has dedicated surface treatment facilities for superconducting cavities, the QWR will be treated using this facilities. In this presentation, recent progress will be reported.
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MOPVA075	Development of High Sensitive X-Ray Mapping for SC Cavities	survey, operation, interface, cryogenics	1040
	H. Tongu, H. Hokonohara, Y. Iwashita Kyoto ICR, Uji, Kyoto, Japan R.L. Geng, A.D. Palczewski JLab, Newport News, Virginia, USA H. Hayano, T. Kubo, T. Saeki, Y. Yamamoto KEK, Ibaraki, Japan H. Oikawa Utsunomiya University, Utsunomiya, Japan
	We developed an X-ray mapping system sX-map for superconducting cavities. The sensors are inserted under the stiffener rings between cavity cells, whose locations are close to the iris areas. The whole circuits are im-mersed in liquid He and the multiplexed signals reduces the number of cables to the room temperature region. sX-map has the advantages in its compact size, low cost and simple setup for nondestructive inspections. The sX-map system detected X-rays from field emissions in vertical RF tests of ILC 9-cell cavities at Jefferson Lab (JLab) and KEK. sX-map showed an excellent performance in the meas-urement test at JLab, it exhibited a high sensitivity com-pared with an the fixed diode rings colocated at irises and ion chamber located out side of the vertical test cryostat.
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MOPVA078	The Window Replacement and Q Recovery of BEPCII Storage Ring SCC	vacuum, operation, positron, radiation	1046
	T.M. Huang, J.P. Dai, R. Ge, S.P. Li, Z.Q. Li, H.Y. Lin, Q. Ma, W.M. Pan, Y. Sun, G.W. Wang IHEP, Beijing, People's Republic of China P. Sha Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
	The storage ring RF system for the upgrade of the Beijing Electron Positron Collider (BEPCII) adopted two 500 MHz superconducting cavities: west for the positron ring (BPR); east for the electron ring (BER). The excessive heating of the west window was observed in Nov.2013, and not cured thoroughly. After two years operation, the window cracked suddenly on Nov.18th, 2015. The replacement of the window was subsequently implemented in tunnel. However, the quality factor (Q) of the cavity decayed a lot after the window replacement. 90 degrees Celsius N2 gas baking of the outer surface of the cavity was carried out in situ and the Q recovered in a short time. This paper will present the process of the window replacement and the cavity Q recovery in detail. Tong-ming Huang et al., Chinese Physics C Vol. 40, No. 6 (2016) 067001
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MOPVA079	A 166.6 MHz Superconducting RF System for the HEPS Storage Ring	HOM, LLRF, SRF, injection	1049
	P. Zhang, H.X. Hao, T.M. Huang, Z.Q. Li, H.Y. Lin, F. Meng, Z.H. Mi, Y. Sun, G.W. Wang, Q.Y. Wang, X.Y. Zhang IHEP, Beijing, People's Republic of China
	Funding: This work has been supported by HEPS-TF project and partly by Pioneer 'Hundred Talents Program' of Chinese Academy of Science. A superconducting 166.6 MHz quarter-wave β=1 cavity was recently proposed for the High Energy Photon Source (HEPS), a 6 GeV kilometer-scale light source. Four 166.6 MHz cavities will be used for main acceleration in the newly planned on-axis beam injection scheme realized by a double-frequency RF system. The fundamental frequency, 166.6 MHz, was dictated by the fast injection kicker technology and the preference of using 499.8 MHz SC RF cavity as the third harmonic. Each 166.6 MHz cavity will be operated at 4.2 K providing 1.2 MV accelerating voltage and 150 kW of power to the electron beam. The input coupler will use single-window coaxial type graded up to 200 kW CW power. Each cavity will be equipped with a 200 kW solid-state amplifier and digital low-level RF system. This paper will describe the 166.6 MHz RF system with a focus on the design and optimization of the RF cavity and its ancillaries, the LLRF system and the status of the solid-state amplifiers.
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MOPVA080	HOM Simulations and Damping Scheme for CEPC Cavities	HOM, damping, collider, impedance	1052
	H.J. Zheng, J. Gao, F. Meng, P. Sha, J.Y. Zhai IHEP, Beijing, People's Republic of China
	In this paper, it will be presented that the higher order mode (HOM) analysis of the 650 MHz cavities for the Circular Electron-Positron Collider (CEPC). The higher order modes excited by the intense beam bunches must be damped to avoid additional cryogenic loss and multi-bunch instabilities. To keep the beam stable, the impedance budget and the HOM damping requirement are given. The conventional coaxial HOM coupler, which will be mounted on the beam pipe, is planned to extract the HOM power below the cut-off frequency of the beam pipe, and the propagating modes will be absorbed by the two HOM absorbers at room temperature outside the cryomodule.
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MOPVA082	PLASMA PROCESSING R&D OF THE 1.3 GHZ SINGLE-CELL SRF CAVITY AT IMP	plasma, SRF, accelerating-gradient, electromagnetic-fields	1055
	L. Yang, L. Chen, Y. He, S.C. Huang, C.X. Li, C.L. Li, Y.M. Li, L. Lu, A. Shi, L.P. Sun, A.D. Wu, S.H. Zhang IMP/CAS, Lanzhou, People's Republic of China
	The China-Accelerator Driven Sub-critical System (C-ADS) injector II has already commissioned with a CW 1 mA and a pulsed 10 mA proton beam. The beam energy achieved 10 MeV. The superconducting linac (SCL) is routinely operating at 4.7 MV/m average accelerating gradient in the low-beta cryomodules. Field emission and surface contaminants of the SCL limit the gradient in-crease in the beam commissioning. Hence, in order to increase the SCL accelerating gradient, reduce field emis-sion and remove surface pollutants, in-situ plasma pro-cessing R&D in a 1.3 GHz single-cell SRF cavity has being studied. In this paper, the current effort of plasma processing R&D in a 1.3 GHz single-cell SRF cavity will be presented in details and the future plan will be also reported.
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MOPVA087	Low Betta Superconducting Cavity for the New Injector Linac for Nuclotron-NICA	linac, simulation, multipactoring, accelerating-gradient	1058
	M. Gusarova, T.A. Bakhareva, M.V. Lalayan, S.V. Matsievskiy, N.P. Sobenin, D.V. Surkov, K.V. Taletskiy, V. Zvyagintsev MEPhI, Moscow, Russia A.A. Bakinowskaya, V.S. Petrakovsky, A.I. Pokrovsky, D.A. Shparla Physical-Technical Institute of the National Academy of Sciences of Belarus, Minsk, Belarus A.V. Butenko, G.V. Trubnikov JINR/VBLHEP, Dubna, Moscow region, Russia V. Zvyagintsev TRIUMF, Vancouver, Canada
	The results of the RF, mechanical and multipactor discharge simulations of the 162 MHz quarter wave resonator (QWR) for New Superconducting Injector Linac for Nuclotron-NICA are presented. Cavity design in conjunction with manufacturing features is discussed.
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MOPVA088	Medium Betta Superconducting Cavity for the New Injector Linac for Nuclotron-NICA	simulation, linac, multipactoring, accelerating-gradient	1061
	M. Gusarova, M.V. Lalayan, N.P. Sobenin, D.V. Surkov, K.V. Taletskiy MEPhI, Moscow, Russia A.A. Bakinowskaya, V.S. Petrakovsky, A.I. Pokrovsky, D.A. Shparla Physical-Technical Institute of the National Academy of Sciences of Belarus, Minsk, Belarus A.V. Butenko, G.V. Trubnikov JINR/VBLHEP, Dubna, Moscow region, Russia
	The results of the electrodynamical and multipactor discharge simulations of the medium betta superconducting cavity for New Superconducting Injector Linac for Nuclotron-NICA are presented. Different designs of CH and Spoke cavities are compared and the optimal one is chosen.
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MOPVA089	The Cryomodule Test Stands for the European Spallation Source	cryomodule, cryogenics, klystron, controls	1064
	E. Asensi Conejero, W. Hees ESS, Lund, Sweden K. Fransson, K.J. Gajewski, L. Hermansson, M. Jobs, H. Li, T. Lofnes, R.J.M.Y. Ruber, R. Santiago Kern, R. Wedberg Uppsala University, Uppsala, Sweden
	The European Spallation Source (ESS) is currently under construction in Lund, in southern Sweden. The superconducting section of the linear accelerator consists of three parts; 26 double-spoke cavities at 352.21 MHz gathered in 13 cryomodules, 36 medium beta elliptical cavities at 704.42 MHz gathered in 9 cryomodules and 84 high beta elliptical cavities also at 704.42 MHz gathered in 21 cryomodules. These cryomodules allow the acceleration of the beam from 90 MeV to 2.0 GeV. The cryomodules have to be tested in dedicated test facilities before installation in the ESS tunnel, the Test Stand 2 (TS2) in Lund and the FREIA Test Stand at Uppsala University, Sweden, which are dedicated to the tests of the medium and high beta elliptical cryomodules and the spoke cavity cryomodules, respectively, for the ESS linear accelerator. All cryomodules will go through their Site Acceptance Tests (SAT) on these dedicated test stands which will each consist of an RP bunker, a test stand cryoplant and RF power sources. Both test stands will allow the SAT of cryomodules with full cryogenic load at the final operating temperature and with full RF load on all cavities in parallel.
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MOPVA090	ESS Superconducting RF Collaboration	cryomodule, SRF, linac, proton	1068
	C. Darve, H. Danared, N. Elias, N.F. Hakansson, M. Lindroos, C.G. Maiano, F. Schlander ESS, Lund, Sweden F. Ardellier, P. Bosland CEA/DRF/IRFU, Gif-sur-Yvette, France S. Bousson, G. Olry IPN, Orsay, France M. Ellis, A.E. Wheelhouse STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom L. Hermansson, R.J.M.Y. Ruber Uppsala University, Uppsala, Sweden P. Michelato, D. Sertore INFN/LASA, Segrate (MI), Italy
	The European Spallation Source (ESS) project is a neutron-scattering facility, currently under construction by a partnership of at least 17 European countries, with Sweden and Denmark as host nations. The ESS was designated a European Research Infrastructure Consortium, or ERIC, by the European Commission in October of 2015. Scientists and engineers from 50 different countries are members of the workforce in Lund who participate in the design and construction of the European Spallation Source. In complement to the local workforce, the superconducting RF linear accelerator is being prototyped and will be constructed based on a collaboration with European institutions: CEA-Saclay, CNRS-IPN Orsay, INFN-LASA, STFC-Daresbury, Uppsala and Lund Universities. After a description of the ESS collaborative project and its in-kind model for the SRF linac, this article will introduce the linac component first results.
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MOPVA091	Investigation of HOM Frequency Shifts Induced by Mechanical Tolerances	HOM, simulation, operation, cryogenics	1071
	S. Pirani, M. Eshraqi, M. Lindroos ESS, Lund, Sweden A. Bosotti, J.F. Chen, P. Michelato, C. Pagani, R. Paparella, D. Sertore INFN/LASA, Segrate (MI), Italy T.P.Å. Åkesson Lund University, Department of Physics, Lund, Sweden
	We present Higher Order Mode (HOM) studies on ESS Medium-Beta cavity of INFN-LASA design, including both simulation and measurement results. Mechanical tolerances of the fabrication process might shift HOMs frequencies toward harmonics of the bunch frequency. Both simulation and measurements at room and cryogenic temperature show that INFN LASA cavity is fully compatible with ESS requirements.
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MOPVA094	ESS Spoke Cavity Conditioning at FREIA	vacuum, software, controls, feedback	1074
	H. Li, K.J. Gajewski, L. Hermansson, M. Jobs, R.J.M.Y. Ruber, R. Santiago Kern Uppsala University, Uppsala, Sweden
	The first ESS double spoke cavity installed with RF power coupler was tested in the HNOSS cryostat at the FREIA Laboratory. Power coupler and cavity conditioning have been optimized in order to reach high efficiency and high availability by reducing the time and effort of the overall conditioning process. Meanwhile, an optimal procedure for ESS conditioning is studied. This paper presents the study result and experience of the RF conditioning procedure for the first ESS double spoke cavity.
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MOPVA095	First RF Performance Results for the DQW Crab Cavities to be Tested in the CERN SPS	SRF, monitoring, operation, cryomodule	1077
	A. Castilla, R. Calaga, O. Capatina, K.M. Dr. Schirm, K.G. Hernández-Chahín, A. Macpherson, N.C. Shipman, K. Turaj CERN, Geneva, Switzerland I. Ben-Zvi BNL, Upton, Long Island, New York, USA G. Burt, J.A. Mitchell Lancaster University, Lancaster, United Kingdom K.G. Hernández-Chahín DCI-UG, León, Mexico N.C. Shipman Cockcroft Institute, Lancaster University, Lancaster, United Kingdom N.C. Shipman UMAN, Manchester, United Kingdom
	As part of the High Luminosity LHC (HL-LHC) project strategy, crab cavity correctors shall be installed around CMS and ATLAS experiments of the LHC. To accommodate the different crossing angle planes, two distinct cavity designs have been selected: the RF Dipole (RFD) and the Double Quarter Wave resonator (DQW). CERN has fabricated two double quarter wave resonators (DQW_SPS), for validation with a proton beam at the CERN SPS accelerator. Standard superconducting rf surface preparation protocols have been applied to the two bulk niobium cavities, followed by cryogenic testing in a vertical cryostat at CERN's SM18 facility. The performance results obtained after the first bare cavity tests for cavities DQW_SPS₀01 and DQW_SPS₀02 are shown in this paper, and include Q0 vs Vt curves, Lorentz Force Detuning (LFD) analyses and pressure sensitivity of a higher order mode.
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MOPVA096	The Crab Cavities Cryomodule for SPS Test	cryomodule, vacuum, HOM, monitoring	1081
	C. Zanoni, A. Amorim Carvalho, K. Artoos, S. Atieh, K. Brodzinski, R. Calaga, O. Capatina, T. Capelli, F. Carra, L. Dassa, T. Dijoud, K. Eiler, G. Favre, P. Freijedo Menendez, M. Garlaschè, L. Giordanino, S.A.E. Langeslag, R. Leuxe, H. Mainaud Durand, P. Minginette, M. Narduzzi, V. Rude, M. Sosin, J.S. Swieszek CERN, Geneva, Switzerland T.J. Jones, N. Templeton STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
	RF Crab Cavities are an essential part of the HL-LHC upgrade. Two concepts of such systems are being developed: the Double Quarter Wave (DQW) and the RF Dipole (RFD). A cryomodule with two DQW cavities is in advanced fabrication stage at CERN for their tests with protons in the SPS during the 2018 run. The cavities must be operated at 2 K, without excessive heat loads, in a low magnetic environment and in compliance with CERN safety guidelines on pressure and vacuum systems. A large set of components, such as a thermal shield, a two layers magnetic shield, RF lines, helium tank and tuner is required for the successful and safe operation of the cavities. The assembly of all these components with the cavities and their couplers forms the cryomodule. An overview of the design and fabrication strategy of this cryomodule is presented. The main components are described along with the present status of cavity fabrication and processing and cryomodule assembly. The lesson learned from the prototypes, the helium tank above all, and first manufactured systems is also included.
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MOPVA097	Finite Element Analysis on Helium Discharge from Superconducting RF in the Storage Ring Tunnel	simulation, cryogenics, SRF, distributed	1085
	J.-C. Chang, F. Z. Hsiao, J.C. Huang, S.P. Kao, H.C. Li, W.R. Liao, C.Y. Liu, H.H. Tsai, Z.-D. Tsai NSRRC, Hsinchu, Taiwan
	Liquid helium for transferring cooling power from the cryogenic plant to the magnets and SRF cavities had been widely applied on the advanced large superconducting particle accelerators. For requirements of high stable and reliable operation, many efforts have been put into the improvement and modification of the cryogenic system. However, personnel safety is another critical issue of the cryogenic system. Once large liquid helium was released on the atmospheric tunnel, the volume of helium will expand several hundred times and cause oxygen deficiency in short time due to sudden change of helium density. In this study, we applied numerical simulation to analyze helium discharge through a SRF cavity in the TPS tunnel.
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MOPVA098	Strategy Towards Non-Interrupted Operation of Superconducting Radio Frequency Modules at NSRRC	SRF, operation, vacuum, cryogenics	1088
	Ch. Wang, F.Y. Chang, L.-H. Chang, M.H. Chang, J. Chen, L.J. Chen, F.-T. Chung, M.-C. Lin, Z.K. Liu, C.H. Lo, C.L. Tsai, M.-S. Yeh, T.-C. Yu NSRRC, Hsinchu, Taiwan
	Two modern 3rd generation light sources, the well-developed 1.5-GeV Taiwan Light Source (TLS) and the new constructed 3-GeV Taiwan Photon Source (TPS), are now in routine operation. Both storage rings are powered by the superconducting RF (cavity) modules, one CESR-type SRF module for the TLS since 2005 and two KEKB-type SRF modules for the TPS since 2014. Thanks to continuous efforts, the operational reliability of SRF modules at NSRRC is now compatible or better in comparison with the best operation record of room temperature cavities ever achieved at TLS (1992-2004). How to improve the long term availability but hold the achieved reliability of SRF modules such as to maximize the available annual user beam time, especially, under requirements on high RF power operation, become a new operational challenge, especially for the SRF modules at TPS which is now routinely operated with a forward RF power around 150-kW individually and expected to push to 300-kW in the coming future. Here we report our strategy and achievement to minimize long term interrupt of SRF operation owing to regular full-thermal cycling and annual maintenance of cryogenic plant.
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MOPVA099	The Study of Electromagnet Compensated High Power Ferrite Circulator Operation With Superconducting RF Cavity	SRF, klystron, operation, vacuum	1091
	T.-C. Yu, F.Y. Chang, L.-H. Chang, M.H. Chang, L.J. Chen, F.-T. Chung, M.-C. Lin, Z.K. Liu, C.H. Lo, C.L. Tsai, M.H. Tsai, Ch. Wang, M.-S. Yeh NSRRC, Hsinchu, Taiwan
	In a high power RF system for accelerator application, the circulator is very important for protecting klystron or IOT from damage due to high reflection power from the cavity. When there is no beam current passing through the superconducting RF cavity of the accelerator, almost 100% RF power will be reflected from the cavity even the cavity is on resonance. The circulator shall be able to forward the reflected power to the load and remain good matching and isolation condition between ports at klystron and the cavity. However, for a ferrite material based circulator, the magnetic field within circulator would be temperature dependent which would cause the variation of input return loss and isolation between ports. Additional DC current driving electromagnet field is thus re-quired for compensating the temperature variation. Even with the compensating DC current, the circulator is still not ideal for practical operation especially when the performance of the circulator is strongly phase dependent. The phenomenon observed in actual operation with one set of SRF systems in NSRRC is thus reported in this article.
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MOPVA102	Modeling the Low Level RF Response on the Beam during Crab Cavity Quench	simulation, luminosity, SRF, klystron	1098
	R. Apsimon, G. Burt, A.C. Dexter Cockcroft Institute, Lancaster University, Lancaster, United Kingdom R.B. Appleby UMAN, Manchester, United Kingdom P. Baudrenghien, K.N. Sjobak CERN, Geneva, Switzerland
	The High Luminosity Upgrade for the LHC (HL-LHC) relies on crab cavities to compensate for the luminosity reduction due to the crossing angle of the colliding bunches at the interaction points. In this paper we present the simulation studies of cavity quenches and the impact on the beam. The cavity voltage and phase during the quench is determined from a simulation in Matlab and used to determine the impact on the beam from tracking simulations in SixTrack. The results of this study are important for determining the required machine protection and interlock systems for HL-LHC.
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MOPVA106	Experimental Studies of Asymmetric Dual Axis Cavity for Energy Recovery LINAC	electron, luminosity, linac, radiation	1105
	I.V. Konoplev, A.J. Lancaster, K. Metodiev, A. Seryi JAI, Oxford, United Kingdom R. Ainsworth Fermilab, Batavia, Illinois, USA G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
	Funding: The Leverhulme Trust via International Network Grant (IN-2015-012). Increasing the beam charge and repetition rate leads to appearance of beam break-up instabilities in conventional ERLs. At this stage the highest current, from the SRF ERL, is around 300mA. A single turn, dual axis, compact Asymmetric Energy Recovery LINAC (AERL) was proposed. The concept assumes the use of electron beams with energies up to 300 MeV and peak currents >1A, enabling the generation of high flux EUV/X-rays and THz radiation using conventional approaches. System allows beam to be transported through each stage i.e. the acceleration, interaction and deceleration only once partially removing the feedback thus increasing the instability start current. This further improved by tuning the individual cells allowing only operating mode to be uniform inside the cavity. We present the studies of 7 cells, aluminium alloy prototype of the cavity and discuss the experimental results. We show that HOMs excited on the different axis have different R/Q factors and show the field structures of operating mode and HOMs. The experimental results observed are in good agreement with theoretical predictions and the full scale copper prototype is demonstrated.
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MOPVA113	RF Quality Control of SRF Cavities for LCLS-II Cryo-Modules	HOM, controls, cryomodule, pick-up	1108
	M.H. Awida, P. Berrutti, T.N. Khabiboulline, A. Lunin, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	Funding: *Operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the U.S. DOE LCLS-II project is gearing up to build 36 cryo-modules of the 1.3 GHz TESLA style cavities. Half of those cryomodules are being built at Fermilab, while JLAB is carrying the production of the other half. In this paper, we present the process of quality controlling the RF performance of cavities until they are qualified for the final string assembly at Fermilab. The RF quality control process includes monitoring the frequency spectrum of each cavity and tuning/adjusting of the notch frequencies before testing at the Vertical Test Stand (VTS). Measured data during income QC is presented and in addition we show the notch frequencies before and after testing at the VTS. Moreover, we report some of the RF measurements taken while the cavity is cooled down to 2K temperature.
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MOPVA114	Materials Characterization for SRF Cavities: Gaining Insight Into Nb3Sn	ion, SRF, interface, electron	1111
	J. Tuggle Virginia Polytechnic Institute and State University, Blacksburg, USA G.V. Eremeev, A.D. Palczewski, C.E. Reece JLab, Newport News, Virginia, USA M.J. Kelley, U. Pudasaini The College of William and Mary, Williamsburg, Virginia, USA
	Funding: JLab work supported by U.S. DOE Contract No. DE-AC05-06OR23177. Work at William & Mary and Virginia Tech supported by the Office of High Energy Physics, U.S. Department of Energy grant DE-SC-0014475 Although SRF accelerators are an invaluable research tool they can be painfully expensive to construct and operate at the current level of SRF technology. This cost is significantly due to the necessity to operate at a temperature of only 2K. Considerable research is currently underway into next generation SRF cavity technologies such as Ndoping and Nb3Sn coating. Both of these technologies will lower the cryogenic load of accelerators, correspondingly lowering both construction and operating costs. However, current understanding of either technology is incomplete and in order to elucidate the underlying mechanisms there is a need to push current characterization methods forward. In this work, ion beam techniques (e.g. focused ion beam (FIB)), and electron backscatter diffraction (EBSD) were applied to help understand Nb3Sn coating mechanisms. This presentation will focus on characterization, providing examples of EBSD work, along with discussion of some of the issues encountered while trying to produce high quality EBSD data.
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MOPVA115	Status and Challenges of Vertical Electro-Polishing R&D at Cornell	cathode, niobium, SRF, linac	1115
	F. Furuta, M. Ge, T. Gruber, D.L. Hall, J.J. Kaufman, M. Liepe, R.D. Porter, J. Sears Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi MGH, Hyogo-ken, Japan T.D. Hall, M.E. Inman, R. Radhakrishnan, S.T. Snyder, E.J. Taylor Faraday Technology, Inc., Clayton, Ohio, USA H. Hayano, S. Kato, T. Saeki KEK, Ibaraki, Japan
	Advanced Vertical Electro-Polishing (VEP) R&D for SRF Niobium cavities continues at Cornell's SRF group. One focus of this work is new EP cathode development in collaboration with KEK and Marui Galvanizing Co. Ltd (Marui) in Japan, and another focus is on HF free or acid free VEP protocols in collaboration with Faraday Technology Inc. The outcomes of these activities could be a significant cost reduction and an environmentally-friendlier VEP, which would be a breakthrough for future large scale EP applications on SRF cavities. Here we give a status update and report latest results from these R&D activities.
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MOPVA116	Quench Studies in Single-Cell Nb3Sn Cavities Coated Using Vapour Diffusion	radio-frequency, accelerating-gradient, monitoring, niobium	1119
	D.L. Hall, M. Liepe, J.T. Maniscalco, R.D. Porter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA P. Cueva, D. Liarte, D.A. Muller, J.P. Sethna Cornell University, Ithaca, New York, USA
	The superconductor Nb3Sn is known to have a superheating field, Hsh, of approximately 400 mT. This critical field represents the ultimate achievable gradient in a superconducting cavity, and is equivalent to an accelerating gradient of 90 MV/m in an ILC single-cell cavity for this value of Hsh. However, the currently best performing Nb3Sn single-cell cavities remain limited to accelerating gradients of 17-18 MV/m, translating to a peak surface magnetic field of approx. 70 mT. In this paper, we consider theoretical models of candidate quench mechanisms, and compare them to experimental data from surface analysis and cavity tests.
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MOPVA117	Performance of a SRF Half-Wave-Resonator Tested at Cornell for the RAON Project	radiation, simulation, SRF, pick-up	1123
	M. Ge, F. Furuta, T. Gruber, D.L. Hall, S.W. Hartman, C. Henderson, M. Liepe, S. Lok, T.I. O'Connell, P.J. Pamel, J. Sears, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA B.H. Choi, J. Joo, J.W. Kim, W.K. Kim, J. Lee, I. Shin IBS, Daejeon, Republic of Korea
	A prototype half-wave-resonator (HWR) with frequency 162.5MHz and geometrical \beta=0.12 for the RAON project is currently undergoing testing at Cornell University. Detailed vertical performance testing includes (1) test of the bare cavity without the helium tank; (2) test of the dressed cavity with helium tank. In this paper, we report on the development of the test infrastructure, test results, and performance data analysis.
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MOPVA118	Impact of Trapped Magnetic Flux and Thermal Gradients on the Performance of Nb3Sn Cavities	niobium, site, target, operation	1127
	D.L. Hall, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA D. Liarte, J.P. Sethna Cornell University, Ithaca, New York, USA
	Trapped magnetic flux is known to degrade the quality factor of superconducting cavities by increasing the surface losses ascribed to the residual resistance. In Nb3Sn cavities, which consist of a thin layer of Nb3Sn coated on a bulk niobium substrate, the bimetallic interface results in a thermal current being generated in the presence of a thermal gradient, which will in turn generate flux that can be trapped. In this paper we quantify the impact of trapped flux, from either ambient fields or thermal gradients, on the performance of the cavity. We discover that the sensitivity to trapped flux, a measure of the increase in residual resistance as a function of the amount of flux trapped, is a function of the accelerating gradient. A theoretical framework to explain this phenomenon is proposed, and the impact on the requirements for operating a Nb3Sn cavity in a cryomodule are considered.
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MOPVA119	Surface Analysis of Features Seen on Nb3Sn Sample Coupons Grown by Vapour Diffusion	niobium, SRF, simulation, site	1130
	D.L. Hall, M. Liepe, J.T. Maniscalco, R.D. Porter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA T. Arias, P. Cueva, D.A. Muller, N. Sitaraman Cornell University, Ithaca, New York, USA
	As a high-kappa superconductor with a coherence length of 7 nm, the superconductor Nb3Sn is highly susceptible to material features at the sub-micron scale. For niobium surfaces coated with a thin layer of Nb3Sn using the vapour diffusion method, the polycrystalline nature of the film grown lends to the possibility that performance-degrading non-uniformities may develop. In particular, regions of insufficiently thick coating and tin-depletion have been seen to occur in sample coupons. In the interests of understanding how to control the presence and nature of such features, it is necessary to know how they form. In this paper we stop the coating at defined instances to gain a stop-motion image of the growth of the layer, and use SEM and TEM techniques to image the development of the features seen in previously coated samples. We demonstrate that surface pre-anodisation can suppress the formation of thin film regions, and apply this technique to a single-cell cavity. Contemporarily, we use TEM with EDS mapping to monitor grain boundaries and tin-depleted regions within the layer.
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MOPVA121	Frequency Tuner Development at Cornell for the RAON Half-Wave-Resonator	cryomodule, cryogenics, controls, simulation	1134
	M. Ge, F. Furuta, T. Gruber, D.L. Hall, S.W. Hartman, C. Henderson, M. Liepe, S. Lok, T.I. O'Connell, P.J. Pamel, P. Quigley, J. Sears, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA B.H. Choi, J. Joo, J.W. Kim, W.K. Kim, J. Lee, I. Shin IBS, Daejeon, Republic of Korea
	The half-wave-resonators (HWR) for the RAON pro-ject require a slow frequency tuner that can provide at least 80 kHz tuning range. Cornell University is currently in the process of designing, prototyping, and testing this HWR tuner. In this paper, we present the tuner design, prototype fabrication, and first test results.
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MOPVA122	Microphonics Studies of the CBETA Linac Cryomodules	cryomodule, operation, linac, SRF	1138
	N. Banerjee, J. Dobbins, F. Furuta, D.L. Hall, G.H. Hoffstaetter, M. Liepe, P. Quigley, E.N. Smith, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: This work was performed through the support of NYSERDA (New York State Energy Research and Development Agency). The Cornell BNL ERL Test Accelerator (CBETA) incorporates two SRF linacs; one for its injector and another for the energy recovery loop. Microphonics in both the cryomodules play a crucial role in determining the energy stability of the electron beam in high current operation. We have measured vibrations and frequency detuning of the SRF cavities and determined that the cryogenic system is the major source of microphonics in both cryomodules. In this paper we discuss these measurements and demonstrate an Active Microphonics Compensation system implemented using fast piezo-electric tuners which we incorporated in our Low Level RF control system to be used in routine operation.
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MOPVA123	Cornell Sample Host Cavity: Recent Results	niobium, SRF, electron, operation	1142
	J.T. Maniscalco, D.L. Hall, M. Liepe, R.D. Porter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA V.M. Arrieta, S.R. McNeal, W.E. Williams Ultramet, Pacoima, California, USA
	Funding: NSF-PHY 1416318 NSF-PHY 1549132 The Cornell sample host cavity is a 3.9~GHz testing system for RF analysis of novel superconducting surfaces. The cavity applies fields up to 100~mT on a removable and replaceable 5-inch sample plate in order to measure the surface resistance of the material under investigation. The cavity also includes a temperature-mapping system for localization of quench events and surface defects. In this paper, we present recent experimental results from the host cavity of niobium deposited onto molybdenum and copper substrates using chemical vapor deposition, in collaboration with industry partner Ultramet. The results indicate low BCS resistance and good adhesion but also areas of high residual resistance due to chemical and morphological defects.
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Paper

Title

Other Keywords

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MOYBA1

The Future of Superconducting Technology for Accelerators

SRF, collider, superconducting-magnet, linear-collider

19

A. Yamamoto
KEK, Ibaraki, Japan

Superconducting magnets and RF cavities are widely used in accelerators, and future accelerator projects heavily rely on this technology. There may be several questions on the future of the SC technology, concerning the feasibility of very high field dipoles (~15 T or more), possible technology evolution(s) with new materials, operation at higher temperature, and final sustainability of the technology in terms of helium procurement. The talk will cover a brief history/achievements and some interesting (future) developments, partly or fully answering these question.

Slides MOYBA1 [25.792 MB]

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MOOCA1

High Efficiency Klystrons Using the COM Bunching Technique

klystron, electron, simulation, bunching

37

D.A. Constable
Lancaster University, Lancaster, United Kingdom
A.Yu. Baikov
Moscow University of Finance & Law, Moscow, Russia
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
R.D. Kowalczyk
L-3, Williamsport, Pennsylvania, USA
I. Syratchev
CERN, Geneva, Switzerland

Future large-scale particle accelerators, for example, the Future Circular Collider (FCC), the Compact Linear Collider (CLIC) and the International Linear Collider (ILC), will require significant RF drive power on the order of 100 MW. Thus, an RF source with high efficiency is preferable to minimise the overall power required. Klystrons represent an attractive RF source, with the current state of the art operating at efficiencies of up to 70%. Such devices feature monotonic bunching, where at the output cavity, a number of electrons will not be in the main bunch, and instead will be present in the anti-bunch, and therefore not contributing to the output power. Therefore, novel bunching methods, such as the Core Oscillation Method (COM), are worthy of investigation. By allowing the core of the electron beam to bunch and de-bunch between successive cavities, the number of electrons contained in the final bunch can increase, and therefore improve the efficiency of the device. Numerical simulation of klystrons featuring COM will be presented, with efficiencies of up to 85% being predicted thus far.

Slides MOOCA1 [12.765 MB]

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MOOCA2

First Results From New Single-Cell Nb3Sn Cavities Coated at Cornell University

niobium, factory, radio-frequency, SRF

40

D.L. Hall, J.J. Kaufman, M. Liepe, R.D. Porter, J. Sears
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Cavities coated with Nb3Sn at Cornell University demonstrate quality factors of >10¹⁰ at 4.2 K, outperforming equivalent niobium cavities by a factor of >30 at these bath temperatures. These quality factors have been maintained up to fields of 17-18 MV/m without significant Q-slope. Recently, new single-cell cavities have been added to the Cornell Nb3Sn programme in an effort to improve statistics and allow further exploration of the available parameter space. In this paper we report on the first results of these new cavities, as well as the latest performance from other cavities already in use on the programme. Furthermore, continuing work to optimise the coating procedure is reported on, and the latest understanding of the ideal coating profile is discussed.

Slides MOOCA2 [10.366 MB]

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MOPAB022

Fabrication Studies of a 650 MHz Superconducting RF Deflecting Mode Cavity for the ARIEL Electron Linac

niobium, electron, linac, impedance

120

D.W. Storey, R.E. Laxdal, B. Matheson, N. Muller
TRIUMF, Vancouver, Canada
D.W. Storey
Victoria University, Victoria, B.C., Canada

A 650 MHz RF deflecting mode cavity is required for the ARIEL electron Linac to separate interleaved beams bound for either rare isotope production or a recirculation loop containing a Free Electron Laser. An RF separator will allow both modes to run simultaneously by imparting opposite transverse deflection to adjacent bunches at 1.3 GHz. The SRF cavity has been designed to provide up to 0.6 MV transverse voltage for operation with up to a 50 MeV CW electron beam. The design was optimised for compact geometry with high shunt impedance. Due to the low dissipated power, the cavity will operate at 4 K and allows for investigations into low cost fabrication techniques. The cavity is being machined from bulk reactor grade ingot Niobium and welds will be performed using TIG welding in an ultra-pure Argon chamber. Results of fabrication studies will be presented as well as measurements performed on a copper prototype cavity.

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MOPAB043

Very First Experience with the Standard Diagnostics at the European XFEL

diagnostics, operation, electron, electronics

180

D. Lipka
DESY, Hamburg, Germany

The whole European XFEL becomes in operation this year. Dedicated standard diagnostics systems are installed and almost all types are tested at the injector before. Now the standard diagnostics are used to commission the facility. In this contribution the very first results and the operation experiences of the standard beam diagnostics of the entire European XFEL are reported.

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MOPAB044

X-Band TDS Project

electron, polarization, experiment, diagnostics

184

B. Marchetti, R.W. Aßmann, B. Beutner, J. Branlard, F. Christie, R.T.P. D'Arcy, W. Decking, U. Dorda, J. Herrmann, M. Hoffmann, M. Hüning, O. Krebs, G. Kube, S. Lederer, F. Ludwig, F. Marutzky, D. Marx, J. Osterhoff, I. Peperkorn, S. Pfeiffer, F. Poblotzki, J. Rönsch-Schulenburg, J. Rothenburg, H. Schlarb, M. Scholz, S. Schreiber, M. Vogt, A. Wagner, T. Wilksen, K. Wittenburg
DESY, Hamburg, Germany
M. Bopp, H.-H. Braun, P. Craievich, M. Pedrozzi, E. Prat, S. Reiche, K. Rolli, R. Zennaro
PSI, Villigen PSI, Switzerland
N. Catalán Lasheras, A. Grudiev, G. McMonagle, W. Wuensch
CERN, Geneva, Switzerland

Based on the success of the X-Band Transverse Deflecting Structure (TDS) diagnostic at LCLS*, a collaboration between DESY, PSI and CERN has formed with the aim of developing and building an advanced modular X-Band TDS system. The designed TDS has the new feature of providing variable polarization of the deflecting field**. The possibility of changing the orientation of the streaking field of the TDS to an arbitrary azimuthal angle allows for 3D characterization of the phase space using tomographic methods***. Moreover the complete 6D characterization of the beam phase space is possible by combining this technique with quadrupole scans and a dipole spectrometer. As this new cavity design requires very high manufacturing precision to guarantee highest azimuthal symmetry of the structure to avoid the deterioration of the polarization of the streaking field, the high precision tuning-free assembly procedures developed at PSI for the SwissFEL C-band accelerating structures will be used for the manufacturing****. The high-power rf system is based on the CERN-based X-band test stands. We summarize in this work the status of the projects and its main technical parameters.
* C. Behrens et al. , Nat. Comm. 4762 (2014).
** A. Grudiev, CLIC-note-1067 (2016).
*** D. Marx et al., contribution to this conference proceedings.
**** U. Ellenberger et al., FEL 2013, TUPS017.

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MOPAB046

Lattice Considerations for the Use of an X-Band Transverse Deflecting Structure (TDS) at SINBAD

dipole, quadrupole, lattice, electron

192

D. Marx, R.W. Aßmann, U. Dorda, U. Dorda, B. Marchetti, F. Mayet
DESY, Hamburg, Germany
F. Mayet
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

An X-band TDS is a well-known device for the characterization of the longitudinal properties of an electron bunch in a linear accelerator. It is planned that a novel X-band TDS with variable polarization* will be installed within the next few years at SINBAD, an upcoming accelerator R&D facility at DESY**. There are several measurements that can be performed with the TDS, each with specific optics requirements to reach the highest possible resolution and keep induced energy spread to a tolerable level. Quadrupoles will be installed between the TDS and the screen to help satisfy these conditions. In this paper, the requirements for the bunch length measurements, a novel 3D charge density reconstruction technique and slice energy measurements are discussed and some simulation results for the slice energy measurement using example lattices are presented.
* A. Grudiev, CLIC-note-1067 (2016).
** B. Marchetti et al. X-band TDS project contribution to these conference proceedings.

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MOPAB050

Reconstruction of Sub-Femtosecond Longitudinal Bunch Profile Measurement Data

laser, electron, diagnostics, undulator

207

M.K. Weikum, R.W. Aßmann, U. Dorda
DESY, Hamburg, Germany
G. Andonian
RadiaBeam, Santa Monica, California, USA
G. Andonian
UCLA, Los Angeles, California, USA
Z.M. Sheng, M.K. Weikum
USTRAT/SUPA, Glasgow, United Kingdom
Z.M. Sheng
Shanghai Jiao Tong University, Shanghai, People's Republic of China

With a current trend towards shorter electron beams with lengths on the order of few femtoseconds (fs) to sub-femtoseconds both in conventional and novel accelerator communities, the need for diagnostics with equivalent attosecond resolution is increasing. The proposed design for a sub-femtosecond diagnostic by Andonian et al.* is one such example that combines a laser deflector with an RF deflecting cavity to streak the electron beam in the horizontal and vertical direction. In this paper, we present a tool for the reconstruction of the longitudinal beam profile from this diagnostic data, which can be used both for the analysis of planned experiments and testing of different beam scenarios with respect to their specific setup requirements. Applying this method, the usefulness of the device for measurements in a number of example scenarios, including plasma-accelerated and ultrashort RF-accelerated electron beams, is discussed.
*G. Andonian, E. Hemsing, D. Xiang, P. Mumuseci, A. Murokh, S. Tochitsky, et al, Phys. Rev. Spec. Top-Ac. 14, 072802 (2011).

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MOPAB063

IFMIF EVEDA RFQ Local Control System: Power Tests

controls, rfq, EPICS, hardware

253

M. Montis, L. Antoniazzi, A. Baldo, M.G. Giacchini
INFN/LNL, Legnaro (PD), Italy

In the IFMIF EVEDA project, normal conducting Radio Frequency Quadrupole (RFQ) is used to bunch and accelerate a 130 mA steady beam to 5 MeV. RFQ cavity is divided into three structures, named super-modules. Each super-module is divided into 6 modules for a total of 18 modules for the overall structure. The final three modules have to be tested at high power to test and validate the most critical RF components of RFQ cavity and, on the other hand, to test performances of the main ancillaries that will be used for IFMIF EVEDA project (vacuum manifold system, tuning system and control system). The choice of the last three modules is due to the fact that they will operate in the most demanding conditions in terms of power density (100 kW/m) and surface electric field (1.8*Ekp). The Experimental Physics and Industrial Control System (EPICS) environment [1] provides the framework for monitoring any equipment connected to it. This paper reports the usage of this framework to the RFQ power tests at Legnaro National Laboratories [2,3,4].
[1] http://www.aps.anl.gov/epics/
[2] http://www.lnl.infn.it/.
[3] http://www.lnl.infn.it/~epics/joomla/
[4] M. Giacchini et al. LivEPICS: an EPICS Linux Live CD Nagios Equipped, TPPA32, ICALEPCS2007, Oak Ridge, USA

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MOPAB082

Design and Simulation of High Order Mode Cavity Bunch Length Monitor for Infrared Free Electron Laser

simulation, FEL, laser, electron

309

Q. Wang, X.Y. Liu, P. Lu, Q. Luo, B.G. Sun, L.L. Tang, J.H. Wei, F.F. Wu, Y.L. Yang, T.Y. Zhou, Z.R. Zhou
USTC/NSRL, Hefei, Anhui, People's Republic of China

Funding: Supported by The National Key Research and Development Program of China (2016YFA0401900, 2016YFA0401903); NSFC (11375178, 11575181); the Fundamental Research Funds for the Central Universities (WK2310000046)
A bunch length monitor using resonant cavity has been designed for the NSRL Infrared Free Electron Laser (IR-FEL) facility. To avoid the restriction of working fre-quency caused by the beam pipe radius, the high order modes of the harmonic cavities are utilized. The position and orientation of coaxial probes are optimized to avoid interference modes which come from the cavity and beam tube according to the analysis formula of electro-magnetic field distribution. Based on the parameters of IR-FEL, a simulation is performed to verify the feasibility of the bunch length monitor. The simulation result shows that the design meets the requirements of IR-FEL, and the resolution can be better than 50 fs.

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MOPAB092

Design and Performance of Digital BPM Processor for DCLS and SXFEL

FPGA, pick-up, controls, electronics

338

L.W. Lai, F.Z. Chen, Y.B. Leng, Y.B. Yan, N. Zhang
SSRF, Shanghai, People's Republic of China
J. Chen
SINAP, Shanghai, People's Republic of China

Funding: Work supported by National Natural Science Foundation (No. 11305253, 11575282)
A digital BPM processor has been developed in SINAP, which can be used on the signal processing of both stripline BPM and cavity BPM. The processor is a standalone system and providing 4 channels 120MS/s, 16 bits ADC and powerful Virtex-5 FPGA. The processor has been mas applied on Dalian Coherent Light Source and Shanghai X-ray FE. The processor specification and performance evaluations including lab and beam tests will be introduced.

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MOPAB095

Development of the Simulation Software Package for the CBPM System

simulation, network, FEL, experiment

349

J. Chen, L.W. Lai, Y.B. Leng, L.Y. Yu
SINAP, Shanghai, People's Republic of China
N. Zhang
SSRF, Shanghai, People's Republic of China

In recent years, the development and construction of Free Electron Laser (FEL) facilities are in full swing. For FEL facilities, to generate coherent X-ray, cavity beam position monitor (CBPM) system which consist of cavity BPM, RF front-end and signal processor are employed to measure the transverse position in the undulator section. A generic simulation software package, with the S21 parameters of the real components, for the design of the RF front-end and the optimize of the CBPM system was developed. In this paper, the development of the generic simulation software package, and the experiment results with beam at Shanghai Deep ultraviolet (SDUV) FEL facility to verify the correctness of the simulation soft package will be introduced. The application in the design and optimize of the RF front-end for the Dalian Coherent Source (DCLS) will be addressed as well .

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MOPAB153

R&D of a Gas-Filled RF Beam Profile Monitor for Intense Neutrino Beam Experiments

plasma, electron, ion, experiment

491

K. Yonehara, M. Backfish, A. Moretti, A.V. Tollestrup, A.C. Watts, R.M. Zwaska
Fermilab, Batavia, Illinois, USA
R.J. Abrams, M.A. Cummings, A. Dudas, R.P. Johnson, G.M. Kazakevich, M.L. Neubauer
Muons, Inc, Illinois, USA
Q. Liu
Case Western Reserve University, Cleveland, USA

Funding: Work supported by Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359 and DOE STTR Grant, No. DE-SC0013764.
A MW-power beam facility is desired to produce an intense neutrino beam for study of fundamental particle physics. It is a critical challenge to measure beam profile in extreme radiation environments. To this end, a novel beam profile monitor based on a gas-filled multi-RF cavity is proposed. Charged particles through the gas-filled RF generate plasma that changes the gas permittivity. The modulated RF signal in the cavity due to the permittivity shift will be measured to reconstruct the flux of charged particles in the cavity. The demonstration is proposed to validate the concept of the monitor. We report the progress of the demonstration test.

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MOPAB155

Characterization of the Longitudinal Acceptance in a Storage Ring with RF Pinger

synchrotron, dynamic-aperture, storage-ring, damping

497

G.M. Wang, B. Holub, Y. Li, J. Rose, T.V. Shaftan
BNL, Upton, Long Island, New York, USA

In modern generation light sources, it is desired to have SR performance at high beam current, low horizontal emittance with small coupling, resulting in intense Touschek scattering, which is the dominant limitation of beam lifetime. Touschek scattering strongly depends on momentum aperture. Understanding momentum aperture is extremely important. NSLS II storage ring RF system has the digital ramp control function, enabling rapid change of the cavity phase and amplitude. This makes the possibility to ping the beam in longitudinal phase space and directly measure the longitudinal acceptance, in contrast with traditional indirect way to understand it from other aspect of parameters. In this paper, we present the tool, longitudinal pinger, its application to characterize NSLS II longitudinal acceptance and localize the momentum aperture limit with SR BPMs.

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MOPIK003

Improvement of the Photoemission Efficiency of Magnesium Photocathodes

cathode, gun, SRF, laser

500

R. Xiang, A. Arnold, P.N. Lu, P. Michel, P. Murcek, J. Teichert, H. Vennekate
HZDR, Dresden, Germany
P. Patra
IUAC, New Delhi, India

Funding: The work is supported by the European Community under the FP7 programme (EuCARD-2) and by the German Federal Ministry of Education and Research (BMBF) grant 05K12CR1.
To improve the quality of photocathodes is one of the critical issues in enhancing the stability and reliability of photo-injector systems. Presently the primary choice is to use metallic photocathodes for the ELBE SRF Gun-II to reduce the risk of contamination of the superconducting cavity. Magnesium has a low work function (3.6 eV) and shows high quantum efficiency (QE) up to 0.3 % after laser cleaning. The SRF Gun II with an Mg photocathode has successfully provided electron beam for ELBE users. However, the present cleaning process with a high intensi-ty laser (activation) is time consuming and generates unwanted surface roughness. This paper presents the investigation of alternative surface cleaning procedures, such as thermal treatment. The QE and topography of Mg samples after treatment are reported.

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MOPIK005

Compact Electron Injectors Using Laser Driven THz Cavities

electron, gun, laser, acceleration

506

M. Fakhari, A. Fallahi, F.X. Kärtner, N.H. Matlis, A. Yahaghi
CFEL, Hamburg, Germany
R.W. Aßmann, U. Dorda, K. Galaydych, B. Marchetti, G. Vashchenko, T. Vinatier, D. Zhang, C. Zhou
DESY, Hamburg, Germany

We present ultra-small electron injectors based on cascaded cavities excited by short multi-cycle THz signals. The designed structure is a 3.5 cell normal conducting cavity operating at 300 GHz. This cavity is able to generate pC electron bunches and accelerate them up to 250 keV using less than 1 mJ THz energy. Unlike conventional RF guns, the designed cavity operates in a transient state which, in combination with the high frequency of the driving field, makes it possible to apply accelerating gradients as high as 500 MV/m. Such high accelerating gradients are promising for the generation of high brightness electron beams with transverse emittances in the nm-rad range. The designed cavity can be used as the injector for a compact accelerator of low charge bunches.

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MOPIK009

Characterization of Cold Model Cavity for Cryocooled C-Band 2.6-Cell Photocathode RF Gun at 20 K

gun, experiment, cryogenics, simulation

518

T. Tanaka, K. Hayakawa, Y. Hayakawa, K. Nakao, K. Nogami, T. Sakai, K. Takatsuka
LEBRA, Funabashi, Japan
M.K. Fukuda, D. Satoh, T. Takatomi, N. Terunuma, J. Urakawa, M. Yoshida
KEK, Ibaraki, Japan

Funding: This work was partly supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT).
A cryocooled C-band 2.6-cell photocathode RF electron gun has been studied at Nihon University in cooperation with KEK. The cold model cavity with an input coupler was completed in spring 2016. The RF characteristics measured at room temperature were in agreement with the prediction by the CST Studio simulation. The RF characteristics at 20 K have been measured using a rather simple cavity-cooling vacuum system that was built by using existing components for tentative experiments. A thin-wall stainless-steel R48 waveguide with copper-plated inner walls has been used for the RF power transmission from the room-temperature input port to the 20-K cooled coupler waveguide. The unloaded Q-value of 73000 has been obtained by the reflection coefficient measurement at 20 K, which is in agreement with the result of the CST Studio simulation using the cavity surface resistance predicted by the theory of the anomalous skin effect.

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MOPIK013

Design and Simulation of a C-Band Photocathode RF Gun With a Coaxial Coupler for UEM

gun, electron, coupling, impedance

525

T. Chen, Y.J. Pei, Y. Song
USTC/NSRL, Hefei, Anhui, People's Republic of China

A ultrafast electron microscope (UEM) has been become much more important research instrument and has been widely used in many fields. As a part of the UEM, a photocathode RF gun working at C-band frequency of 5712MHz is being developed, which provides electron beam with high qualities for UEM. This paper presents the physics and structure design, including optimization of cavity shape parameter for improving shunt impedance and Q factor. We adopt a novel coaxial coupler, which could decrease the multipole field and decrease the focusing coil size, build better accelerating field in the RF gun. In this paper, we discussed the simulation process and results of the RF gun, especially the design of the coaxial input coupler was described.

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MOPIK019

Upgrade Options Towards Higher Fields and Beam Energies for Continuous-Wave Room-Temperature VHF RF Guns

gun, brightness, electron, cathode

542

F. Sannibale, J.M. Byrd, D. Filippetto, M.J. Johnson, D. Li, T.H. Luo, C.E. Mitchell, J.W. Staples, S.P. Virostek
LBNL, Berkeley, California, USA

Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231
Science demand for MHz-class repetition rate electron beam applications such as free electron lasers (FELs), inverse Compton scattering sources, and ultrafast electron diffraction and microscopy (UED/UEM), pushed the development of new gun schemes that could generate high brightness beams at such high rates. At the Lawrence Berkeley Lab (LBNL), we proposed a new concept room-temperature RF gun resonating in the VHF frequency range (30-300 MHz) capable of operating in continuous wave mode at the fields required for high-brightness performance. A first VHF-Gun was constructed and tested in the APEX facility at LBNL, which successfully demonstrated all design parameters and the generation of high brightness electron beams. A second version of the APEX VHF-Gun is being built at LBNL for the LCLS-II, the new SLAC X-ray FEL. Recent studies showed that a proposed LCLS-II upgrade and UED/UEM applications would greatly benefit from an increased gun brightness obtained by raising the electric field at the cathode and the beam energy at the gun exit. In this paper, we present and discuss possible upgrade options that would allow extension of the VHF-Gun performance towards these new goals.

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MOPIK040

Value Engineering of an Accelerator Design During Construction

linac, cryomodule, neutron, proton

592

E. Bargalló, M. Eshraqi, M. Lindroos, S. Molloy, D.C. Plostinar, A. Sunesson
ESS, Lund, Sweden
F. Gerigk
CERN, Geneva, Switzerland

Value engineering is an important part of the process of designing and realising large-scale installations such as high power accelerators. This typically occurs during the later part of the design stage of the system, however such exercises may also be requested by funding bodies at later stages in order to manage project contingency. Naturally, the later this is done, the more challenging it becomes. In this paper we report on a recently concluded Value Engineering effort at the European Spallation Source. The challenges presented by the initiation of such an exercise during the construction phase are discussed. In addition, we present and discuss the various options that we examined, and indicate the philosophy and figures of merit used to narrow down these options. The final conclusion will be presented.

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MOPIK058

Beam Dynamic Studies for the SARAF MEBT and SC Linac

quadrupole, linac, rfq, simulation

655

J. Dumas, N. Pichoff, D. Uriot
CEA/IRFU, Gif-sur-Yvette, France
P.A.P. Nghiem
CEA/DSM/IRFU, France

The SARAF MEBT and Super Conducting Linac (SCL) transport and accelerate deuterons or protons from the RFQ to the final energy. In this report, beam dynamics studies for this section are described. A rational distribution of the different roles of the MEBT leads to defining its necessary quadrupole/rebuncher composition. This allows easy beam re-tuning following changes from the RFQ or the SC Linac. After observing evidences of beam losses mainly due to phase unhooking, efforts have been dedicated to enlarge the SCL longitudinal acceptance. A combination of cavity field phases is found so that the required final beam energy is also fulfilled.

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MOPIK068

Beam Dynamics Design Parameters for KONUS Lattices

lattice, linac, acceleration, emittance

683

R. Tiede, H. Hähnel, U. Ratzinger
IAP, Frankfurt am Main, Germany

The 'Combined Zero-Degree Structure' ('Kombinierte Null Grad Struktur - KONUS') beam dynamics concept has been successfully applied on several linacs, some of them in routine operation since decades. However, the KONUS lattice parameters optimization is often done in a results-oriented approach, depending on the designers' experience. This paper focuses on the description of the longitudinal beam motion along one KONUS lattice period. A test lattice is used for demonstrating the potential of KONUS lattices with respect to stable, periodic beam motion with emittance growth rates similar to those of conventional designs. The main objective of this ongoing work is to derive more general rules for the parametrization of KONUS lattices.

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MOPIK098

Techniques for Achieving High Reliability Operation of the Spallation Neutron Source High Power Radio-Frequency System

klystron, cathode, operation, neutron

756

J. Moss, M.S. Champion
ORNL, Oak Ridge, Tennessee, USA

Funding: *ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. This research was supported by the DOE Office of Science, Basic Energy Science, Scientific User Facilities.
The Spallation Neutron Source (SNS) high power radiofrequency (HPRF) system operates with high reliability to support the goals of the SNS user program. In recent operational periods the availability of the HPRF System has exceeded 97 percent while the neutron source availability overall is typically greater than 90 percent. SNS has a unique set of 92 HPRF stations that operate at either 402.5 MHz or 805 MHz with peak output power ranging from 550 kW to 5 MW and average power ranging from 49.5 kW to 450 kW. The HPRF transmitters consist of chassis-mounted power supplies, solid-state amplifiers and other equipment that support the operation of the klystrons that ultimately provide the RF power to the accelerating structures. Management of the operation and maintenance of the HPRF system has increasingly focused on reliability and sustainability in recent years. Techniques for klystron lifetime preservation and optimization of transmitter reliability have been developed and will be described.

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MOPIK117

On the Computation of Phase and Energy Gain for a Thin-Lens RF Gap Using a General Field Profile

simulation, linac, factory, acceleration

810

C.K. Allen
ORNL, Oak Ridge, Tennessee, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under contract number DE-AC05-00OR22725.
The thin-lens representation for an RF accelerating gap has been well developed and is documented by Lapostolle [5], Weiss [6], Wangler [14], and others [9], [10]. These models assume that the axial electric field is both centered and symmetric so it has a cosine expansion. Presented here is a model that considers general axial fields. Both the cosine and sine transit time factors are required plus their Hilbert transforms. The combination yields a complex Hamiltonian rotating in the complex plane with the synchronous phase. The phase and energy gains are computed in the pre-gap and post-gap regions then aligned with asymptotic values of wave number. Derivations are outlined, examples are shown, and simulations presented.

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MOPVA005

Status of the Berlin Energy Recovery Linac Project BERLinPro

gun, SRF, linac, booster

855

M. Abo-Bakr, W. Anders, K.B. Bürkmann-Gehrlein, A.B. Büchel, P. Echevarria, A. Frahm, H.-W. Glock, F. Glöckner, F. Göbel, B.D.S. Hall, S. Heling, H.-G. Hoberg, A. Jankowiak, C. Kalus, T. Kamps, G. Klemz, J. Knedel, J. Knobloch, J. Kolbe, G. Kourkafas, J. Kühn, B.C. Kuske, J. Kuszynski, D. Malyutin, A.N. Matveenko, M. McAteer, A. Meseck, C.J. Metzger-Kraus, R. Müller, A. Neumann, N. Ohm, K. Ott, E. Panofski, F. Pflocksch, J. Rahn, M. Schmeißer, O. Schüler, M. Schuster, J. Ullrich, A. Ushakov, J. Völker
HZB, Berlin, Germany

Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association.
The Helmholtz-Zentrum Berlin is constructing the Energy Recovery Linac Prototype BERLinPro, a demonstration facility for the science and technology of ERLs for future light source applications. BERLinPro is designed to accelerate a high current (100 mA, 50 MeV), high brilliance (norm. emittance below 1 mm mrad) cw electron beam. We report on the project status. This includes the completion of the building and the installation of the first accelerator components as well as the assembly of the SRF gun and GunLab beam diagnostics, which are now ready for commissioning.

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MOPVA007

Simulations for Beam-Based Measurements in BERLinPro

simulation, diagnostics, gun, optics

859

M. McAteer, M. Abo-Bakr, J. Knedel, G. Kourkafas, B.C. Kuske, J. Völker
HZB, Berlin, Germany

BERLinPro is an energy recovery linac project whose goal is to establish the accelerator physics knowledge and technology needed to produce 50 MeV beams with high current, low normalized emittance, and low losses. Precise measurements of beam parameters are essential for demonstrating the achievement of performance goals. In this paper we present simulations for measurements of energy, energy spread, and bunch length using the tracking code Astra.

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MOPVA018

Resonant Coherent Diffraction Radiation System at ERL Test Accelerator in KEK

radiation, resonance, experiment, emittance

887

Y. Honda, A. Aryshev, R. Kato, T. Miyajima, T. Obina, M. Shimada, R. Takai, N. Yamamoto
KEK, Ibaraki, Japan

Funding: This work was supported by JSPS KAKENHI Grant Number 16H05991
An Energy Recovery Linac can produce a low emittance and short bunch beam at a high repetition rate. A test accelerator, compact-ERL, has been operating in KEK for development works of technologies related to ERL and CW-Superconducting accelerators. In a special beam operation mode of bunch compression, a short bunch beam of ~150 fs at the repetition rate of CW 1.3 GHz can be realized in the return-loop. One of the promising applications of such a short bunch beam is a high power THz radiation source produced by a coherent radiation. When a charged particle beam passes close to a conductive target, a radiation called diffraction radiation is produced. If the target mirrors form an optical cavity which fundamental frequency matches the repetition frequency of the beam, the radiation resonates in the cavity, resulting in extracting a huge radiation power determined by the loss of the cavity. We plan to perform an experiment of the resonant coherent diffraction mechanism in the return-loop of the compact-ERL to test the feasibility to be a wide band high power THz source. We report the design of the experimental setup to be installed in the summer of 2017.

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MOPVA019

60 pC Bunch Charge Operation of the Compact ERL at KEK

operation, emittance, laser, linac

890

T. Miyajima, K. Harada, Y. Honda, E. Kako, R. Kato, T. Miura, N. Nakamura, T. Obina, M. Shimada, R. Takai, K. Umemori, M. Yamamoto
KEK, Ibaraki, Japan
R. Hajima, R. Nagai
QST, Tokai, Japan
T. Hotei
Sokendai, Ibaraki, Japan
N. Nishimori
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan

The compact ERL (cERL) at KEK was operated in March 2017 to demonstrate generation, acceleration and transportation of the target bunch charge of 60 pC without energy recovery. However, the maximum bunch charge was limited to 40 pC due to the limitation of the excitation laser power. For the bunch charge of 40 pC, the bunch length and the normalized emittance were measured in the injector diagnostic line. The results of the bunch length measurement gave good agreement with the values that had been obtained by model simulation. The measured normalized rms emittances for 40 pC were 0.9 to 2.4 mm mrad, and they were lager than the design value of 0.6 mm mrad. To achieve the design emittance, we have studied the source of the emittance growth for the bunch charge of 40 pC.

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MOPVA038

Manufacturing Status of the IFMIF LIPAc SRF Linac

cryomodule, vacuum, SRF, linac

939

N. Bazin, P. Carbonnier, P. Contrepois, J. Plouin, B. Renard
CEA/DSM/IRFU, France
C. Boulch, A. Bruniquel, J.K. Chambrillon, G. Devanz, P. Hardy, H. Jenhani, N. N'Doye, O. Piquet, A. Riquelme, D. Roudier
CEA/DRF/IRFU, Gif-sur-Yvette, France
P. Charon, S. Chel, G. Disset, J. Relland
CEA/IRFU, Gif-sur-Yvette, France
D. Regidor, F. Toral
CIEMAT, Madrid, Spain

This paper gives the fabrication status of the IFMIF cryomodule. This cryomodule will be part of the Linear IFMIF Prototype Accelerator (LIPAc) whose construction is ongoing at Rokkasho, Japan. It is a full scale of one of the IFMIF accelerator, from the injector to the first cryomodule. The cryomodule contains all the necessary equipment to transport and accelerate a 125 mA deuteron beam from an input energy of 5 MeV up to the output energy of 9 MeV. It consists of a horizontal vacuum tank of around 6 m long, 3 m high and 2.0 m wide, which includes 8 superconducting HWRs for beam acceleration, working at 175 MHz and at 4.45 K, 8 Power Couplers to provide RF power to cavities up to 70 kW CW in LIPAc case and 200 kW CW in IFMIF case, and 8 Solenoid Packages as focusing elements.

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MOPVA039

Manufacturing and Validation Tests of IFMIF Low-Beta HWRs

cryomodule, SRF, operation, simulation

942

G. Devanz, F. Éozénou, L. Maurice, P. Sahuquet, C. Servouin
CEA/DSM/IRFU, France
N. Bazin, P. Carbonnier, P. Charon, G. Disset, P. Hardy, E. Jacques, O. Piquet, D. Roudier
CEA/IRFU, Gif-sur-Yvette, France
J.K. Chambrillon, T. Percerou
CEA/DRF/IRFU, Gif-sur-Yvette, France

The IFMIF accelerator aims to provide an accelerator-based D-Li neutron source to produce high intensity high energy neutron flux to test samples as possible candidate materials to a full lifetime of fusion energy reactors. A prototype of the low energy part of the accelerator is under construction at Rokkasho in Japan. It includes one cryomodule containing 8 half-wave resonators (HWR) operating at 175 MHz .The first manufactured HWR has passed low power tests at 4.2K in vertical cryostat succesfully and exceeds the specifications. It has also been tested in the dedicated horizontal Sathori cryostat equiped with its cold tuning system. The serial production and qualification tests of the 8 cavities which will eventually equip the cryomodule are carried out in parallel. In this paper, we focus on the HWR preparation and test results and give a status of the manufacturing activities.

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MOPVA040

Status of the ESS Elliptical Cryomodules at CEA Saclay

cryomodule, cryogenics, vacuum, SRF

945

P. Bosland, C. Arcambal, F. Ardellier, S. Berry, A. Bouygues, A. Bruniquel, E. Cenni, J.-P. Charrier, C. Cloué, G. Devanz, F. Éozénou, T. Hamelin, X. Hanus, P. Hardy, C. Marchand, O. Piquet, J. Plouin, J.P. Poupeau, T. Trublet
CEA/DRF/IRFU, Gif-sur-Yvette, France
G. Costanza
Lund University, Lund, Sweden
C. Darve
ESS, Lund, Sweden
P. Michelato
INFN/LASA, Segrate (MI), Italy
G. Olivier
IPN, Orsay, France
F. Peauger
CEA/DSM/IRFU, France

The first ESS prototype cryomodule with medium beta cavities named M-ECCTD is being assembled at CEA Saclay. The Q curves of the 4 cavities mounted inside the cryomodule are presented, and the four power couplers have been conditioned at high power before their assembly onto the cavity string. Completion of the M-ECCTD assembly outside clean room is in progress as well as the finalization of the RF power test stand preparation. RF power tests of the M-ECCTD will be performed during summer 2017. CEA is preparing the production of the ESS medium and high beta cryomodules of the series before the test of the M-ECCTD and the contracts for the procurement of the most critical components have already been signed

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MOPVA041

Vertical Test Results on ESS Medium and High Beta Elliptical Cavity Prototypes Equipped with Helium Tank

linac, radiation, cryomodule, background

948

E. Cenni
CEA/IRFU, Gif-sur-Yvette, France
P. Bosland, G. Devanz, F. Éozénou, X. Hanus, L. Maurice, F. Peauger, J. Plouin, D. Roudier, C. Servouin
CEA/DSM/IRFU, France
G. Costanza
Lund University, Lund, Sweden
C. Darve
ESS, Lund, Sweden

The ESS elliptical superconducting Linac consists of two types of 704.42 MHz cavities, medium and high beta, to accelerate the beam from 216 MeV (spoke cavity Linac) up to the final energy at 2 GeV. The last Linac optimization, called Optimus+, has been carried out taking into account the limitations of SRF cavity performance (field emission). The medium and high-beta parts of the Linac are composed of 36 and 84 elliptical cavities, with geometrical beta values of 0.67 and 0.86 respectively. This work presents the latest vertical test results on ESS medium and high beta elliptical cavity prototypes equipped with helium tank. We describe the cavity preparation procedure from buffer chemical polishing to vertical test.

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MOPVA042

CEA Preliminary Design of the Cryomodules for SARAF Phase II Superconducting Linac

cryomodule, vacuum, simulation, alignment

951

R. Cubizolles, P. Brédy, D. Chirpaz-Cerbat, P. Hardy, F. Leseigneur, C. Madec, J. Plouin
CEA/IRFU, Gif-sur-Yvette, France
N. Bazin
CEA/DSM/IRFU, France
R. Bruce, Th. Plaisant
CEA/DRF/IRFU, Gif-sur-Yvette, France

CEA is committed to deliver a Medium Energy Beam Transfer line and a superconducting linac (SCL) for SARAF accelerator in order to accelerate 5mA beam of either protons from 1.3 MeV to 35 MeV or deuterons from 2.6 MeV to 40.1 MeV. The SCL consists of 4 cryomodules and 4 warm sections with diagnostics at the end of each cryomodule. The first two identical cryomodules host 6 half-wave resonator (HWR) low-beta cavities (β = 0.091), 176 MHz, and 6 focusing superconducting solenoids. The last two identical cryomodule welcome 7 HWR high-beta cavities (β = 0.181), 176 MHz, and 4 solenoids. The paper will presents the preliminary design of the cryomodules.

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MOPVA043

Assembly Preparation of the IFMIF SRF Cryomodule

solenoid, cryomodule, SRF, vacuum

954

J.K. Chambrillon, N. N'Doye
CEA/DRF/IRFU, Gif-sur-Yvette, France
N. Bazin, P. Charon, G. Devanz, P. Hardy, O. Piquet, J. Plouin
CEA/IRFU, Gif-sur-Yvette, France
P. Contrepois, C. Servouin
CEA/DSM/IRFU, France

This article presents the preparation work performed by CEA for the assembly of the IFMIF Cryomodule. Before the shipping of the components to Japan many tests and trial assemblies has been realized on the CEA site of Saclay, France. The cryomodule, which is part of the Linear IFMIF Prototype Accelerator (LIPAc) under construction at Rokkasho in Japan, will be assembled there under the responsibility of F4E (Fusion for Energy) with CEA assistance. To fulfill the assembly of the cavity string, a cleanroom will be built at Rokkasho under the responsibility of QST.

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MOPVA044

Conditioning of the Power Couplers for the ESS Elliptical Cavity Prototypes

coupling, vacuum, controls, pick-up

957

C. Arcambal, P. Carbonnier, M. Desmons, G. Devanz, T. Hamelin, C. Marchand, C. Servouin
CEA/DRF/IRFU, Gif-sur-Yvette, France
C. Darve
ESS, Lund, Sweden

In the framework of the European Spallation Source (ESS), some power couplers have been designed and manufactured to supply, with RF power, the medium-beta (β=0.67) elliptical cavities of the cryomodule demonstrator. The power couplers work at 704.4 MHz and are tested up to 1.2 MW (repetition rate=14 Hz, RF pulse width close to 3.6 milliseconds). The CEA Saclay is in charge of the design, the manufacturing, the preparation and the conditioning of these power couplers. In this paper, after a general presentation of the power couplers used in the ESS LINAC and their characteristics, we give some détails about the manufacturing and then we describe the different steps of the preparation (cleaning), the assembly of the couplers on the coupling box in cleanroom, the baking of the couplers and the conditioning procedure. Finally, the experimental results obtained in travelling and standing waves on the first pairs of couplers will be shown.

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MOPVA046

120kW RF Power Input Couplers for BERLinPro

booster, coupling, SRF, linac

960

B.D.S. Hall, V. Dürr, F. Göbel, J. Knobloch, A. Neumann
HZB, Berlin, Germany

The 50-MeV, 100-mA energy-recovery-linac (ERL) demonstration facility BERLinPro is currently undergoing construction at HZB. The high power injection system, that will deliver a beam at 6.5MeV, is split into a 1.4 cell SRF Photo injector and three Cornell-style 2-cell boosters. The injector and two of the booster cavities will provide about 2MeV each and must handle up to 220 kW of beam loading. New, cERL-based 115-kW high power couplers needed for the cavities' twin coupler system have begun manufacture. The design, optimization and manufacturing considerations of these couplers are presented.

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MOPVA048

Simulation of the Thermoelectrically Generated Magnetic Field in a SC Nine-Cell Cavity

simulation, SRF, operation, superconducting-RF

968

J.M. Köszegi, J. Knobloch, O. Kugeler
HZB, Berlin, Germany

Several studies showed that thermocurrents generate a magnetic field in a horizontal cavity test assembly or cryomodul, which may get trapped during the supercon-ducting phase transition. The trapped flux causes additional dissipation in the order of 1 to 10 n' during operation and can therefore significantly degrade the quality factor in a TESLA cavity. We simulated the distribution of the generated magnetic field over the whole cavity-tank system for an asymmetric temperature distribution. The asymmetry allows the field to penetrate the RF surface which would be field free in the symmetric case. The calculated results complemented a direct measurement of trapped magnetic flux inside the cavity with a small number of field probes. Finally, the obtained data was combined with RF measurements in three passband modes to determine the overall distribution of trapped magnetic flux due to thermocurrents.

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MOPVA049

First Commissioning of an SRF Photo-Injector Module for BERLinPro

cathode, SRF, solenoid, linac

971

A. Neumann, A. Burrill, D. Böhlick, A.B. Büchel, M. Bürger, P. Echevarria, A. Frahm, H.-W. Glock, F. Göbel, S. Heling, K. Janke, T. Kamps, S. Keckert, S. Klauke, G. Klemz, J. Knobloch, G. Kourkafas, J. Kühn, O. Kugeler, N. Ohm, E. Panofski, H. Plötz, S. Rotterdam, M. Schenk, M.A.H. Schmeißer, M. Schuster, H. Stein, Y. Tamashevich, J. Ullrich, A. Ushakov, J. Völker
HZB, Berlin, Germany
A. Matheisen, M. Schmökel
DESY, Hamburg, Germany

Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association.
Helmholtz-Zentrum Berlin (HZB) is currently building an high average current superconducting ERL to demonstrate ERL operation with low normalized beam emittance of 1 mm·mrad at 100mA and short pulses of about 2 ps. For the injector section a series of SRF photoinjector cavities is being developed. The medium power prototype presented here features a 1.4 x λ/2 cell SRF cavity with a normal-conducting, high quantum efficiency CsK2Sb cathode, implementing a modified HZDR-style cathode insert. This injector potentially allows for 6 mA beam current at up to 3.5 MeV kinetic energy. In this contribution, the first RF commissioning results of the photo-injector module will be presented and compared to the level of performance during the cavity production and string assembly process.

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MOPVA050

Setup of a Spatially Resolving Vector Magnetometry System for the Investigation of Flux Trapping in Superconducting Cavities

SRF, niobium, experiment, radio-frequency

975

B. Schmitz, K.Alomari. Alomari, J. Knobloch, O. Kugeler, J.M. Köszegi, Y. Tamashevich
HZB, Berlin, Germany

Flux trapping is the major contribution to the residual resistance of superconducting cavities. In order to gain a better understanding of the mechanisms involved and aiming at an eventual minimization of trapped flux, a measurement setup based on AMR sensors was devised that allows for monitoring the magnetic field vector at various positions near the cavity surface. First results of the efforts are presented.

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MOPVA051

Design of the High Power 1.5 GHz Input Couplers for BESSY VSR

coupling, operation, simulation, HOM

978

E. Sharples, M. Dirsat, J. Knobloch, A.V. Vélez
HZB, Berlin, Germany

The Variable pulse length Storage Ring (BESSY VSR) upgrade to BESSY II at Helmholtz-Zentrum Berlin (HZB) requires an upgrade on the RF systems in the form of high-voltage longitudinally focusing super conducting RF cavities of 1.5 GHz ad 1.75 GHz. For operation, coaxial RF power couplers capable of handling 13 kW peak power at standing wave operation are required for both the 1.5 GHz and 1.75 GHz cavities. The coupler is based on a design by Cornell University with modifications to suit frequency and coupling requirements. The coupler is intended to provide variable coupling with a range of Qext from 6x10⁶ to 6x10⁷ to allow flexibility to adjust to operating conditions of BESSY VSR. Here we present the RF design of the high-power coaxial coupler for BESSY VSR along with the design of the test stand for conditioning a pair of couplers.

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MOPVA052

Study on HOM Power Levels in the BESSY VSR Module

HOM, SRF, operation, resonance

982

A.V. Tsakanian, H.-W. Glock, J. Knobloch, A.V. Vélez
HZB, Berlin, Germany

The BESSY VSR upgrade of the BESSY II light source represents a novel approach to simultaneously store of long (ca. 15ps) and short (ca. 1.5ps) bunches in the storage ring with the 'standard' user optics. This challenging goal requires installation of four new SRF cavities (2x1.5GHz and 2x1.75GHz) in a single module to minimize space requirements. These cavities are equipped with strong waveguide and beam tube HOM dampers necessary for stable operation. The expected HOM power and spectrum has been analyzed for the complete module. This study is performed for various BESSY VSR bunch filling patterns with 300 mA beam current. In the module different cavity arrangements are analyzed to reach the optimal operation conditions with equally distributed power portions in warm HOM loads and tolerable beam coupling impedance.

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MOPVA053

The SRF Module Developments for BESSY VSR

HOM, synchrotron, damping, SRF

986

A.V. Vélez, H.-W. Glock, F. Glöckner, B.D.S. Hall, J. Knobloch, A. Neumann, P. Schnizer, E. Sharples, A.V. Tsakanian
HZB, Berlin, Germany

Helmholtz-Zentrum Berlin is developing BESSY VSR, a novel upgrade of the BESSY II facility to provide highly flexible pulse lengths while maintaining the flux and brilliance. The project goal is to simultaneously circulate both standard (some 10 ps long) and short (ps and sub-ps long) pulses offering the BESSY user community picosecond dynamics and high-resolution experiments. The concept relies on the installation of high-voltage SRF cavities operating at the 3rd and 3.5th harmonic whereby the beating of the two frequencies provides RF buckets for long and short bunches. Since these cavities will operate in CW and with high beam current (Ib=300 mA), the cavity design represents a challenging goal. In addition the need to avoid coupled bunch instabilities (CBI's), the installation of the VSR Cryomodule must fit in one of the available 4-m long low beta straights. To address the technological and engineering challenges techniques such as waveguide-damped cavities have been developed. First prototypes have been produced. In this paper, the present SRF developments are presented, including the cavities, high power couplers, higher-order mode absorbers and the cryomodule design.

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MOPVA054

High Power RF Coupler for the CW-Linac Demonstrator at GSI

Windows, linac, simulation, ion

990

M. Heilmann, W.A. Barth, S. Yaramyshev
GSI, Darmstadt, Germany
M. Amberg, M. Basten, R. Blank, M. Busch, F.D. Dziuba, H. Podlech, M. Schwarz
IAP, Frankfurt am Main, Germany
K. Aulenbacher
IKP, Mainz, Germany
K. Aulenbacher, W.A. Barth, V. Gettmann, M. Miski-Oglu
HIM, Mainz, Germany
W.A. Barth, S. Yaramyshev
MEPhI, Moscow, Russia

The planned super-heavy element (SHE) research project investigates heavy ions near the coulomb barrier in future experiments. A superconducting (sc) continuous wave (cw) CH-Linac Demonstrator was developed and installed behind the High Charge State Injector (HLI) at GSI Darmstadt, Germany. In future the advanced cw-LINAC setup, with several CH-cavities, will accelerates the heavy ion beam from HLI with an energy of 1.4 MeV/u up to 3.5 - 7.3 MeV/u. The RF power of several kW will be coupled capacitively into the CH-cavities with minimal reflection at an operation frequency of 217 MHz. Two ceramic windows (Al2O3) are installed inside the RF coupler, to reduce the premature contamination of the cavity and as an additional vacuum barrier. The CH-cavity will be operated at cryogenic temperature (4 K) and will be increased to room temperature along the RF coupler. The optimally adapted RF coupler design, providing minimal RF losses and simultaneously maximal performance, was optimized by electromagnetic simulations. An RF coupler design with a reflection-free RF adaptor as well as the temperature distribution along the coupler will be presented.

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MOPVA055

Upgrade of the Capture Section of the S-DALINAC Injector

SRF, electron, operation, accelerating-gradient

993

D.B. Bazyl, H. De Gersem, W.F.O. Müller
TEMF, TU Darmstadt, Darmstadt, Germany

Funding: This work is supported by the DFG through GRK 2128.
In order to reduce the energy spread of the recirculated beam, the injector of the S-DALINAC needs to be optimized, because the non-isochronous recirculation cannot correct for errors originating from the injector linac. For the S-DALINAC, spatial restrictions suggest the use of SRF technology for the capture section. In this work, we consider various SRF cavities with an operating frequency of 3 GHz for a possible upgrade of the capture section of the S-DALINAC. The first results of the RF and beam dynamics simulations for the proposed options are presented in this paper.

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MOPVA057

Structural Investigations of Nitrogen-Doped Niobium for Superconducting RF Cavities

niobium, SRF, vacuum, radio-frequency

996

M. Major, L. Alff, M. Arnold, J. Conrad, S. Flege, R. Grewe, N. Pietralla
TU Darmstadt, Darmstadt, Germany
F. Hug
IKP, Mainz, Germany

Funding: Work supported by BMBF through 05H15RDRBA.
Niobium is the standard material for superconducting RF (SRF) cavities. Superconducting materials with higher critical temperature or higher critical magnetic field allow cavities to work at higher operating temperatures or higher accelerating fields, respectively. Enhancing the surface properties of the superconducting material in the range of the penetration depth is also beneficial. One direction of search for new materials with better properties is the modification of bulk niobium by nitrogen doping. In the Nb-N phase diagram the cubic delta-phase of NbN has the highest critical temperature (16 K). Already slight nitrogen doping of the alpha-Nb phase results in higher quality factors.* Nb samples will be N-doped at the refurbished UHV furnace at IKP Darmstadt. The first results on the structural investigations of the processed Nb samples at the Materials Research Department of TU Darmstadt are presented.
* Grassellino et al., Proc. SRF2015, MOBA06, 48.

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MOPVA058

Commissioning and Operation Experience of the 3.9 GHz System in the EXFEL Linac

operation, LLRF, linac, klystron

999

C.G. Maiano, J. Branlard, M. Hüning, M. Omet, P. Pierini, E. Vogel
DESY, Hamburg, Germany
A. Bosotti, R. Paparella, P. Pierini, D. Sertore
INFN/LASA, Segrate (MI), Italy

The European X-ray Free Electron Laser (EXFEL) injector linac hosts a 3.9~GHz module (AH1) for beam longitudinal phase space manipulation after the first acceleration stage, in order for the linac to deliver the high current beams with sufficiently low emittance for the production of 1 Angstrom FEL light to the experimental users. The module was technically commissioned in December 2015 and operated well above its nominal performances during the Injector Run from January to July 2016. Its operation has restarted in January 2017 with the startup of the whole facility, and the system met the design beam specifications after the bunch compression stages. A brief review of the commissioning and first operation experience of the RF system are presented here.

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MOPVA060

Fabrication and Treatment of the ESS Medium Beta Prototype Cavities

controls, operation, feedback, vacuum

1003

L. Monaco, A. Bellandi, M. Bertucci, A. Bignami, A. Bosotti, J.F. Chen, P. Michelato, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy
S. Pirani
ESS, Lund, Sweden

In view of the Medium Beta series cavities production at the industry for the European Spallation Source project, INFN Milano - LASA design prototypes have been fully produced at Ettore Zanon S.p.A. with our supervision. Based on our experience on the production of 1.3 GHz and 3.9 GHz E-XFEL series cavities, we set-up and applied an external quality control activity of the overall production of the prototype cavity, starting from the row materials to the ready to be tested cavity. In this paper, we report the strategy we have adopted on the overall production, mechanical and surface treatments, frequency measurement of subcomponents and cavities and the obtained results.

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MOPVA061

Quench and Field Emission Diagnostics for the ESS Medium-Beta Prototypes Vertical Tests at LASA

radiation, electron, detector, diagnostics

1007

M. Bertucci, A. Bellandi, A. Bignami, A. Bosotti, J.F. Chen, P. Michelato, L. Monaco, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy
S. Pirani
ESS, Lund, Sweden

In order to investigate the possible causes of premature thermal breakdown and performance degradation, several diagnostic techniques have been employed during the vertical tests of the Fine and Large Grain ESS Medium Beta prototypes cavities. The whole equipment, which includes second sound, fast thermometry, photodiode x ray detectors and an external NaI scintillator, is here described and the results so far obtained during the vertical tests presented.

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MOPVA062

Test, Diagnostics and Computed Tomographic Inspection of a Large Grain 3.9 GHz Prototype Cavity

niobium, SRF, diagnostics, radio-frequency

1011

M. Bertucci, A. Bignami, A. Bosotti, J.F. Chen, C.G. Maiano, P. Michelato, L. Monaco, R. Paparella, P. Pierini, D. Sertore
INFN/LASA, Segrate (MI), Italy
G. Ciovati, G.R. Myneni
JLab, Newport News, Virginia, USA
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy

A large grain 3.9 GHz prototype cavity made of RRR = 10⁵ ±10 has been tested at LASA. The cavity suffered of quench at moderate levels of accelerating field, for all nine fundamental pass-band modes. Several diagnostic techniques have been employed to determine the quench positions, which occur close to significant grain-boundary steps, visible from the external cavity surface. The cavity has been scanned with a high resolution X-ray tomographic machine, confirming the existence of remarkable topographic features on the inner RF surface at the suspected quench positions. A strategy for a future surface treatment for recover the cavity performances is here presented.

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MOPVA063

Vertical Tests of ESS Medium Beta Prototype Cavities at LASA

vacuum, operation, radiation, accelerating-gradient

1015

A. Bosotti, A. Bellandi, M. Bertucci, A. Bignami, J.F. Chen, C.G. Maiano, P. Michelato, L. Monaco, R. Paparella, P. Pierini, D. Sertore
INFN/LASA, Segrate (MI), Italy
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy
S. Pirani
ESS, Lund, Sweden

In the framework of the INFN activity related to the European Spallation Source collaboration, the LASA infrastructure has been renewed to allow the qualification, in its vertical cryostat, of the 704 MHz medium beta cavity prototypes. A new cryogenic insert has been realized, fully equipped with dedicated mechanical supports, vacuum, thermal sensors and quench diagnostic systems. The RF test station has been upgraded as well with a new PLL electronics rack. The first beta 0.67 cavity prototype designed and produced by INFN Milano has been successfully cold tested at 2.0 K temperature, outperforming the ESS specifications. The technical features of LASA infrastructure, the design of novel components and the experimental results of cavities cold-tests are thoroughly described in this paper.

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MOPVA064

Multipacting Study in INFN-LASA ESS Medium-Beta Cavity

simulation, SRF, site, electron

1019

J.F. Chen, M. Bertucci, A. Bosotti, P. Michelato, L. Monaco, C. Pagani, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
S. Pirani
ESS, Lund, Sweden

We present Multipacting studies in ESS Medium-Beta cavities of INFN-LASA design with both simulation and experimental results. The simulation on the ideal cavity shape with both FishPact and MultiPac2.1 codes shows that multipacting appears in a very small region near equator where the weld seam exists. A simulation with more realistic cavity shape considering the weld seam at cell equators has also been done out showing similar results for end cell but a remarkable mitigation for inner cell. During the vertical tests at LASA, Multipacting is frequently observed but with no limitation to the cavity performance, which well confirms the MP predicted by the simulations.

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MOPVA066

Limits for the Operation of the European XFEL 3.9 GHz System in CW Mode

operation, cryomodule, linac, laser

1023

P. Pierini, A. Bosotti, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
J. Branlard, D. Kostin, C.G. Maiano, W.-D. Möller, P. Pierini, D. Reschke, J.K. Sekutowicz, E. Vogel
DESY, Hamburg, Germany

Future upgrades of the European XFEL (EXFEL) facility may require driving the linac at higher duty factor, possibly extending to CW mode at reduced gradients. A preliminary analysis for the accelerator modules has been presented in the EXFEL TDR, but no precise assessment has been performed so far for the present 3.9 GHz system design. By making use of data collected during the commissioning and operation phase of the EXFEL injector system, we discuss here an estimate for the limits of CW operation of the present system and a plan for its possible experimental verification with existing available cavities and the EXFEL spare module.

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MOPVA068

Experience on Design, Fabrication and Testing of a Large Grain ESS Medium Beta Prototype Cavity

radiation, niobium, operation, cryogenics

1027

D. Sertore, A. Bellandi, M. Bertucci, A. Bignami, A. Bosotti, J.F. Chen, C.G. Maiano, P. Michelato, L. Monaco, R. Paparella, P. Pierini
INFN/LASA, Segrate (MI), Italy
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy
S. Pirani
ESS, Lund, Sweden

We report on the design, fabrication and testing of an ESS Medium Beta prototype cavity made with Large Grain Niobium sheets sliced from an ingot provided by CBMM. The peculiar choices during the fabrication process related to the Large Grain Niobium material are described. We present also the results of the cavity test at cryogenic temperature and the dedicated quench diagnostic.

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MOPVA071

Press Forming Tests of Superconducting Spoke Cavity for Laser Compton Scattered Photon Sources

laser, photon, niobium, resonance

1031

M. Sawamura, R. Hajima
QST, Tokai, Japan
H. Hokonohara, Y. Iwashita, H. Tongu
Kyoto ICR, Uji, Kyoto, Japan
T. Kubo, T. Saeki
KEK, Ibaraki, Japan

We are developing the superconducting spoke cavity for laser Compton scattered (LCS) photon sources. We adopt the superconducting spoke cavity for electron beam drivers to realize a wide use of LCS X-ray and '-ray sources in academic and industrial applications. The spoke cavity can make the accelerator more compact than an elliptical cavity because the cavity size is small at the same frequency and the packing factor is good by installing couplers on outer conductor. Though our proposal design for the photon source consists of the 325 MHz spoke cavities in 4K operation, we are fabricating the half scale model of 650 MHz spoke cavity in order to accumulate our cavity production experience by effective utilization of our limited resources. Since the spoke has more complicated structure than an elliptical cavity, we performed press forming tests for the half spoke and estimated the formed shapes with 3-dimensional measurement.

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MOPVA074

Fabrication of Superconducting QWR at MHI-MS

SRF, linac, superconducting-RF, niobium

1037

N. Shigeoka, H. Hara, A. Miyamoto, K. Sennyu, T. Yanagisawa
MHI-MS, Kobe, Japan
O. Kamigaito, K. Ozeki, N. Sakamoto, K. Suda, Y. Watanabe, K. Yamada
RIKEN Nishina Center, Wako, Japan

Mitsubishi Heavy Industries Mechatronics Systems, Ltd. (MHI-MS), a subsidiary campany of MHI, took over MHI's accelerator business on October 1, 2015, and has been developing the business. MHI-MS is manufacturing the prototype Superconducting QWR for RIKEN Superconducting linac project. MHI-MS has dedicated surface treatment facilities for superconducting cavities, the QWR will be treated using this facilities. In this presentation, recent progress will be reported.

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MOPVA075

Development of High Sensitive X-Ray Mapping for SC Cavities

survey, operation, interface, cryogenics

1040

H. Tongu, H. Hokonohara, Y. Iwashita
Kyoto ICR, Uji, Kyoto, Japan
R.L. Geng, A.D. Palczewski
JLab, Newport News, Virginia, USA
H. Hayano, T. Kubo, T. Saeki, Y. Yamamoto
KEK, Ibaraki, Japan
H. Oikawa
Utsunomiya University, Utsunomiya, Japan

We developed an X-ray mapping system sX-map for superconducting cavities. The sensors are inserted under the stiffener rings between cavity cells, whose locations are close to the iris areas. The whole circuits are im-mersed in liquid He and the multiplexed signals reduces the number of cables to the room temperature region. sX-map has the advantages in its compact size, low cost and simple setup for nondestructive inspections. The sX-map system detected X-rays from field emissions in vertical RF tests of ILC 9-cell cavities at Jefferson Lab (JLab) and KEK. sX-map showed an excellent performance in the meas-urement test at JLab, it exhibited a high sensitivity com-pared with an the fixed diode rings colocated at irises and ion chamber located out side of the vertical test cryostat.

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MOPVA078

The Window Replacement and Q Recovery of BEPCII Storage Ring SCC

vacuum, operation, positron, radiation

1046

T.M. Huang, J.P. Dai, R. Ge, S.P. Li, Z.Q. Li, H.Y. Lin, Q. Ma, W.M. Pan, Y. Sun, G.W. Wang
IHEP, Beijing, People's Republic of China
P. Sha
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China

The storage ring RF system for the upgrade of the Beijing Electron Positron Collider (BEPCII) adopted two 500 MHz superconducting cavities: west for the positron ring (BPR); east for the electron ring (BER). The excessive heating of the west window was observed in Nov.2013, and not cured thoroughly*. After two years operation, the window cracked suddenly on Nov.18th, 2015. The replacement of the window was subsequently implemented in tunnel. However, the quality factor (Q) of the cavity decayed a lot after the window replacement. 90 degrees Celsius N2 gas baking of the outer surface of the cavity was carried out in situ and the Q recovered in a short time. This paper will present the process of the window replacement and the cavity Q recovery in detail.
* Tong-ming Huang et al., Chinese Physics C Vol. 40, No. 6 (2016) 067001

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MOPVA079

A 166.6 MHz Superconducting RF System for the HEPS Storage Ring

HOM, LLRF, SRF, injection

1049

P. Zhang, H.X. Hao, T.M. Huang, Z.Q. Li, H.Y. Lin, F. Meng, Z.H. Mi, Y. Sun, G.W. Wang, Q.Y. Wang, X.Y. Zhang
IHEP, Beijing, People's Republic of China

Funding: This work has been supported by HEPS-TF project and partly by Pioneer 'Hundred Talents Program' of Chinese Academy of Science.
A superconducting 166.6 MHz quarter-wave β=1 cavity was recently proposed for the High Energy Photon Source (HEPS), a 6 GeV kilometer-scale light source. Four 166.6 MHz cavities will be used for main acceleration in the newly planned on-axis beam injection scheme realized by a double-frequency RF system. The fundamental frequency, 166.6 MHz, was dictated by the fast injection kicker technology and the preference of using 499.8 MHz SC RF cavity as the third harmonic. Each 166.6 MHz cavity will be operated at 4.2 K providing 1.2 MV accelerating voltage and 150 kW of power to the electron beam. The input coupler will use single-window coaxial type graded up to 200 kW CW power. Each cavity will be equipped with a 200 kW solid-state amplifier and digital low-level RF system. This paper will describe the 166.6 MHz RF system with a focus on the design and optimization of the RF cavity and its ancillaries, the LLRF system and the status of the solid-state amplifiers.

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MOPVA080

HOM Simulations and Damping Scheme for CEPC Cavities

HOM, damping, collider, impedance

1052

H.J. Zheng, J. Gao, F. Meng, P. Sha, J.Y. Zhai
IHEP, Beijing, People's Republic of China

In this paper, it will be presented that the higher order mode (HOM) analysis of the 650 MHz cavities for the Circular Electron-Positron Collider (CEPC). The higher order modes excited by the intense beam bunches must be damped to avoid additional cryogenic loss and multi-bunch instabilities. To keep the beam stable, the impedance budget and the HOM damping requirement are given. The conventional coaxial HOM coupler, which will be mounted on the beam pipe, is planned to extract the HOM power below the cut-off frequency of the beam pipe, and the propagating modes will be absorbed by the two HOM absorbers at room temperature outside the cryomodule.

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MOPVA082

PLASMA PROCESSING R&D OF THE 1.3 GHZ SINGLE-CELL SRF CAVITY AT IMP

plasma, SRF, accelerating-gradient, electromagnetic-fields

1055

L. Yang, L. Chen, Y. He, S.C. Huang, C.X. Li, C.L. Li, Y.M. Li, L. Lu, A. Shi, L.P. Sun, A.D. Wu, S.H. Zhang
IMP/CAS, Lanzhou, People's Republic of China

The China-Accelerator Driven Sub-critical System (C-ADS) injector II has already commissioned with a CW 1 mA and a pulsed 10 mA proton beam. The beam energy achieved 10 MeV. The superconducting linac (SCL) is routinely operating at 4.7 MV/m average accelerating gradient in the low-beta cryomodules. Field emission and surface contaminants of the SCL limit the gradient in-crease in the beam commissioning. Hence, in order to increase the SCL accelerating gradient, reduce field emis-sion and remove surface pollutants, in-situ plasma pro-cessing R&D in a 1.3 GHz single-cell SRF cavity has being studied. In this paper, the current effort of plasma processing R&D in a 1.3 GHz single-cell SRF cavity will be presented in details and the future plan will be also reported.

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MOPVA087

Low Betta Superconducting Cavity for the New Injector Linac for Nuclotron-NICA

linac, simulation, multipactoring, accelerating-gradient

1058

M. Gusarova, T.A. Bakhareva, M.V. Lalayan, S.V. Matsievskiy, N.P. Sobenin, D.V. Surkov, K.V. Taletskiy, V. Zvyagintsev
MEPhI, Moscow, Russia
A.A. Bakinowskaya, V.S. Petrakovsky, A.I. Pokrovsky, D.A. Shparla
Physical-Technical Institute of the National Academy of Sciences of Belarus, Minsk, Belarus
A.V. Butenko, G.V. Trubnikov
JINR/VBLHEP, Dubna, Moscow region, Russia
V. Zvyagintsev
TRIUMF, Vancouver, Canada

The results of the RF, mechanical and multipactor discharge simulations of the 162 MHz quarter wave resonator (QWR) for New Superconducting Injector Linac for Nuclotron-NICA are presented. Cavity design in conjunction with manufacturing features is discussed.

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MOPVA088

Medium Betta Superconducting Cavity for the New Injector Linac for Nuclotron-NICA

simulation, linac, multipactoring, accelerating-gradient

1061

M. Gusarova, M.V. Lalayan, N.P. Sobenin, D.V. Surkov, K.V. Taletskiy
MEPhI, Moscow, Russia
A.A. Bakinowskaya, V.S. Petrakovsky, A.I. Pokrovsky, D.A. Shparla
Physical-Technical Institute of the National Academy of Sciences of Belarus, Minsk, Belarus
A.V. Butenko, G.V. Trubnikov
JINR/VBLHEP, Dubna, Moscow region, Russia

The results of the electrodynamical and multipactor discharge simulations of the medium betta superconducting cavity for New Superconducting Injector Linac for Nuclotron-NICA are presented. Different designs of CH and Spoke cavities are compared and the optimal one is chosen.

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MOPVA089

The Cryomodule Test Stands for the European Spallation Source

cryomodule, cryogenics, klystron, controls

1064

E. Asensi Conejero, W. Hees
ESS, Lund, Sweden
K. Fransson, K.J. Gajewski, L. Hermansson, M. Jobs, H. Li, T. Lofnes, R.J.M.Y. Ruber, R. Santiago Kern, R. Wedberg
Uppsala University, Uppsala, Sweden

The European Spallation Source (ESS) is currently under construction in Lund, in southern Sweden. The superconducting section of the linear accelerator consists of three parts; 26 double-spoke cavities at 352.21 MHz gathered in 13 cryomodules, 36 medium beta elliptical cavities at 704.42 MHz gathered in 9 cryomodules and 84 high beta elliptical cavities also at 704.42 MHz gathered in 21 cryomodules. These cryomodules allow the acceleration of the beam from 90 MeV to 2.0 GeV. The cryomodules have to be tested in dedicated test facilities before installation in the ESS tunnel, the Test Stand 2 (TS2) in Lund and the FREIA Test Stand at Uppsala University, Sweden, which are dedicated to the tests of the medium and high beta elliptical cryomodules and the spoke cavity cryomodules, respectively, for the ESS linear accelerator. All cryomodules will go through their Site Acceptance Tests (SAT) on these dedicated test stands which will each consist of an RP bunker, a test stand cryoplant and RF power sources. Both test stands will allow the SAT of cryomodules with full cryogenic load at the final operating temperature and with full RF load on all cavities in parallel.

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MOPVA090

ESS Superconducting RF Collaboration

cryomodule, SRF, linac, proton

1068

C. Darve, H. Danared, N. Elias, N.F. Hakansson, M. Lindroos, C.G. Maiano, F. Schlander
ESS, Lund, Sweden
F. Ardellier, P. Bosland
CEA/DRF/IRFU, Gif-sur-Yvette, France
S. Bousson, G. Olry
IPN, Orsay, France
M. Ellis, A.E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
L. Hermansson, R.J.M.Y. Ruber
Uppsala University, Uppsala, Sweden
P. Michelato, D. Sertore
INFN/LASA, Segrate (MI), Italy

The European Spallation Source (ESS) project is a neutron-scattering facility, currently under construction by a partnership of at least 17 European countries, with Sweden and Denmark as host nations. The ESS was designated a European Research Infrastructure Consortium, or ERIC, by the European Commission in October of 2015. Scientists and engineers from 50 different countries are members of the workforce in Lund who participate in the design and construction of the European Spallation Source. In complement to the local workforce, the superconducting RF linear accelerator is being prototyped and will be constructed based on a collaboration with European institutions: CEA-Saclay, CNRS-IPN Orsay, INFN-LASA, STFC-Daresbury, Uppsala and Lund Universities. After a description of the ESS collaborative project and its in-kind model for the SRF linac, this article will introduce the linac component first results.

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MOPVA091

Investigation of HOM Frequency Shifts Induced by Mechanical Tolerances

HOM, simulation, operation, cryogenics

1071

S. Pirani, M. Eshraqi, M. Lindroos
ESS, Lund, Sweden
A. Bosotti, J.F. Chen, P. Michelato, C. Pagani, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
T.P.Å. Åkesson
Lund University, Department of Physics, Lund, Sweden

We present Higher Order Mode (HOM) studies on ESS Medium-Beta cavity of INFN-LASA design, including both simulation and measurement results. Mechanical tolerances of the fabrication process might shift HOMs frequencies toward harmonics of the bunch frequency. Both simulation and measurements at room and cryogenic temperature show that INFN LASA cavity is fully compatible with ESS requirements.

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MOPVA094

ESS Spoke Cavity Conditioning at FREIA

vacuum, software, controls, feedback

1074

H. Li, K.J. Gajewski, L. Hermansson, M. Jobs, R.J.M.Y. Ruber, R. Santiago Kern
Uppsala University, Uppsala, Sweden

The first ESS double spoke cavity installed with RF power coupler was tested in the HNOSS cryostat at the FREIA Laboratory. Power coupler and cavity conditioning have been optimized in order to reach high efficiency and high availability by reducing the time and effort of the overall conditioning process. Meanwhile, an optimal procedure for ESS conditioning is studied. This paper presents the study result and experience of the RF conditioning procedure for the first ESS double spoke cavity.

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MOPVA095

First RF Performance Results for the DQW Crab Cavities to be Tested in the CERN SPS

SRF, monitoring, operation, cryomodule

1077

A. Castilla, R. Calaga, O. Capatina, K.M. Dr. Schirm, K.G. Hernández-Chahín, A. Macpherson, N.C. Shipman, K. Turaj
CERN, Geneva, Switzerland
I. Ben-Zvi
BNL, Upton, Long Island, New York, USA
G. Burt, J.A. Mitchell
Lancaster University, Lancaster, United Kingdom
K.G. Hernández-Chahín
DCI-UG, León, Mexico
N.C. Shipman
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
N.C. Shipman
UMAN, Manchester, United Kingdom

As part of the High Luminosity LHC (HL-LHC) project strategy, crab cavity correctors shall be installed around CMS and ATLAS experiments of the LHC. To accommodate the different crossing angle planes, two distinct cavity designs have been selected: the RF Dipole (RFD) and the Double Quarter Wave resonator (DQW). CERN has fabricated two double quarter wave resonators (DQW_SPS), for validation with a proton beam at the CERN SPS accelerator. Standard superconducting rf surface preparation protocols have been applied to the two bulk niobium cavities, followed by cryogenic testing in a vertical cryostat at CERN's SM18 facility. The performance results obtained after the first bare cavity tests for cavities DQW_SPS₀01 and DQW_SPS₀02 are shown in this paper, and include Q0 vs Vt curves, Lorentz Force Detuning (LFD) analyses and pressure sensitivity of a higher order mode.

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MOPVA096

The Crab Cavities Cryomodule for SPS Test

cryomodule, vacuum, HOM, monitoring

1081

C. Zanoni, A. Amorim Carvalho, K. Artoos, S. Atieh, K. Brodzinski, R. Calaga, O. Capatina, T. Capelli, F. Carra, L. Dassa, T. Dijoud, K. Eiler, G. Favre, P. Freijedo Menendez, M. Garlaschè, L. Giordanino, S.A.E. Langeslag, R. Leuxe, H. Mainaud Durand, P. Minginette, M. Narduzzi, V. Rude, M. Sosin, J.S. Swieszek
CERN, Geneva, Switzerland
T.J. Jones, N. Templeton
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

RF Crab Cavities are an essential part of the HL-LHC upgrade. Two concepts of such systems are being developed: the Double Quarter Wave (DQW) and the RF Dipole (RFD). A cryomodule with two DQW cavities is in advanced fabrication stage at CERN for their tests with protons in the SPS during the 2018 run. The cavities must be operated at 2 K, without excessive heat loads, in a low magnetic environment and in compliance with CERN safety guidelines on pressure and vacuum systems. A large set of components, such as a thermal shield, a two layers magnetic shield, RF lines, helium tank and tuner is required for the successful and safe operation of the cavities. The assembly of all these components with the cavities and their couplers forms the cryomodule. An overview of the design and fabrication strategy of this cryomodule is presented. The main components are described along with the present status of cavity fabrication and processing and cryomodule assembly. The lesson learned from the prototypes, the helium tank above all, and first manufactured systems is also included.

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MOPVA097

Finite Element Analysis on Helium Discharge from Superconducting RF in the Storage Ring Tunnel

simulation, cryogenics, SRF, distributed

1085

J.-C. Chang, F. Z. Hsiao, J.C. Huang, S.P. Kao, H.C. Li, W.R. Liao, C.Y. Liu, H.H. Tsai, Z.-D. Tsai
NSRRC, Hsinchu, Taiwan

Liquid helium for transferring cooling power from the cryogenic plant to the magnets and SRF cavities had been widely applied on the advanced large superconducting particle accelerators. For requirements of high stable and reliable operation, many efforts have been put into the improvement and modification of the cryogenic system. However, personnel safety is another critical issue of the cryogenic system. Once large liquid helium was released on the atmospheric tunnel, the volume of helium will expand several hundred times and cause oxygen deficiency in short time due to sudden change of helium density. In this study, we applied numerical simulation to analyze helium discharge through a SRF cavity in the TPS tunnel.

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MOPVA098

Strategy Towards Non-Interrupted Operation of Superconducting Radio Frequency Modules at NSRRC

SRF, operation, vacuum, cryogenics

1088

Ch. Wang, F.Y. Chang, L.-H. Chang, M.H. Chang, J. Chen, L.J. Chen, F.-T. Chung, M.-C. Lin, Z.K. Liu, C.H. Lo, C.L. Tsai, M.-S. Yeh, T.-C. Yu
NSRRC, Hsinchu, Taiwan

Two modern 3rd generation light sources, the well-developed 1.5-GeV Taiwan Light Source (TLS) and the new constructed 3-GeV Taiwan Photon Source (TPS), are now in routine operation. Both storage rings are powered by the superconducting RF (cavity) modules, one CESR-type SRF module for the TLS since 2005 and two KEKB-type SRF modules for the TPS since 2014. Thanks to continuous efforts, the operational reliability of SRF modules at NSRRC is now compatible or better in comparison with the best operation record of room temperature cavities ever achieved at TLS (1992-2004). How to improve the long term availability but hold the achieved reliability of SRF modules such as to maximize the available annual user beam time, especially, under requirements on high RF power operation, become a new operational challenge, especially for the SRF modules at TPS which is now routinely operated with a forward RF power around 150-kW individually and expected to push to 300-kW in the coming future. Here we report our strategy and achievement to minimize long term interrupt of SRF operation owing to regular full-thermal cycling and annual maintenance of cryogenic plant.

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MOPVA099

The Study of Electromagnet Compensated High Power Ferrite Circulator Operation With Superconducting RF Cavity

SRF, klystron, operation, vacuum

1091

T.-C. Yu, F.Y. Chang, L.-H. Chang, M.H. Chang, L.J. Chen, F.-T. Chung, M.-C. Lin, Z.K. Liu, C.H. Lo, C.L. Tsai, M.H. Tsai, Ch. Wang, M.-S. Yeh
NSRRC, Hsinchu, Taiwan

In a high power RF system for accelerator application, the circulator is very important for protecting klystron or IOT from damage due to high reflection power from the cavity. When there is no beam current passing through the superconducting RF cavity of the accelerator, almost 100% RF power will be reflected from the cavity even the cavity is on resonance. The circulator shall be able to forward the reflected power to the load and remain good matching and isolation condition between ports at klystron and the cavity. However, for a ferrite material based circulator, the magnetic field within circulator would be temperature dependent which would cause the variation of input return loss and isolation between ports. Additional DC current driving electromagnet field is thus re-quired for compensating the temperature variation. Even with the compensating DC current, the circulator is still not ideal for practical operation especially when the performance of the circulator is strongly phase dependent. The phenomenon observed in actual operation with one set of SRF systems in NSRRC is thus reported in this article.

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MOPVA102

Modeling the Low Level RF Response on the Beam during Crab Cavity Quench

simulation, luminosity, SRF, klystron

1098

R. Apsimon, G. Burt, A.C. Dexter
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
R.B. Appleby
UMAN, Manchester, United Kingdom
P. Baudrenghien, K.N. Sjobak
CERN, Geneva, Switzerland

The High Luminosity Upgrade for the LHC (HL-LHC) relies on crab cavities to compensate for the luminosity reduction due to the crossing angle of the colliding bunches at the interaction points. In this paper we present the simulation studies of cavity quenches and the impact on the beam. The cavity voltage and phase during the quench is determined from a simulation in Matlab and used to determine the impact on the beam from tracking simulations in SixTrack. The results of this study are important for determining the required machine protection and interlock systems for HL-LHC.

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MOPVA106

Experimental Studies of Asymmetric Dual Axis Cavity for Energy Recovery LINAC

electron, luminosity, linac, radiation

1105

I.V. Konoplev, A.J. Lancaster, K. Metodiev, A. Seryi
JAI, Oxford, United Kingdom
R. Ainsworth
Fermilab, Batavia, Illinois, USA
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom

Funding: The Leverhulme Trust via International Network Grant (IN-2015-012).
Increasing the beam charge and repetition rate leads to appearance of beam break-up instabilities in conventional ERLs. At this stage the highest current, from the SRF ERL, is around 300mA. A single turn, dual axis, compact Asymmetric Energy Recovery LINAC (AERL) was proposed. The concept assumes the use of electron beams with energies up to 300 MeV and peak currents >1A, enabling the generation of high flux EUV/X-rays and THz radiation using conventional approaches. System allows beam to be transported through each stage i.e. the acceleration, interaction and deceleration only once partially removing the feedback thus increasing the instability start current. This further improved by tuning the individual cells allowing only operating mode to be uniform inside the cavity. We present the studies of 7 cells, aluminium alloy prototype of the cavity and discuss the experimental results. We show that HOMs excited on the different axis have different R/Q factors and show the field structures of operating mode and HOMs. The experimental results observed are in good agreement with theoretical predictions and the full scale copper prototype is demonstrated.

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MOPVA113

RF Quality Control of SRF Cavities for LCLS-II Cryo-Modules

HOM, controls, cryomodule, pick-up

1108

M.H. Awida, P. Berrutti, T.N. Khabiboulline, A. Lunin, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Funding: *Operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the U.S. DOE
LCLS-II project is gearing up to build 36 cryo-modules of the 1.3 GHz TESLA style cavities. Half of those cryomodules are being built at Fermilab, while JLAB is carrying the production of the other half. In this paper, we present the process of quality controlling the RF performance of cavities until they are qualified for the final string assembly at Fermilab. The RF quality control process includes monitoring the frequency spectrum of each cavity and tuning/adjusting of the notch frequencies before testing at the Vertical Test Stand (VTS). Measured data during income QC is presented and in addition we show the notch frequencies before and after testing at the VTS. Moreover, we report some of the RF measurements taken while the cavity is cooled down to 2K temperature.

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MOPVA114

Materials Characterization for SRF Cavities: Gaining Insight Into Nb3Sn

ion, SRF, interface, electron

1111

J. Tuggle
Virginia Polytechnic Institute and State University, Blacksburg, USA
G.V. Eremeev, A.D. Palczewski, C.E. Reece
JLab, Newport News, Virginia, USA
M.J. Kelley, U. Pudasaini
The College of William and Mary, Williamsburg, Virginia, USA

Funding: JLab work supported by U.S. DOE Contract No. DE-AC05-06OR23177. Work at William & Mary and Virginia Tech supported by the Office of High Energy Physics, U.S. Department of Energy grant DE-SC-0014475
Although SRF accelerators are an invaluable research tool they can be painfully expensive to construct and operate at the current level of SRF technology. This cost is significantly due to the necessity to operate at a temperature of only 2K. Considerable research is currently underway into next generation SRF cavity technologies such as Ndoping and Nb3Sn coating. Both of these technologies will lower the cryogenic load of accelerators, correspondingly lowering both construction and operating costs. However, current understanding of either technology is incomplete and in order to elucidate the underlying mechanisms there is a need to push current characterization methods forward. In this work, ion beam techniques (e.g. focused ion beam (FIB)), and electron backscatter diffraction (EBSD) were applied to help understand Nb3Sn coating mechanisms. This presentation will focus on characterization, providing examples of EBSD work, along with discussion of some of the issues encountered while trying to produce high quality EBSD data.

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MOPVA115

Status and Challenges of Vertical Electro-Polishing R&D at Cornell

cathode, niobium, SRF, linac

1115

F. Furuta, M. Ge, T. Gruber, D.L. Hall, J.J. Kaufman, M. Liepe, R.D. Porter, J. Sears
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi
MGH, Hyogo-ken, Japan
T.D. Hall, M.E. Inman, R. Radhakrishnan, S.T. Snyder, E.J. Taylor
Faraday Technology, Inc., Clayton, Ohio, USA
H. Hayano, S. Kato, T. Saeki
KEK, Ibaraki, Japan

Advanced Vertical Electro-Polishing (VEP) R&D for SRF Niobium cavities continues at Cornell's SRF group. One focus of this work is new EP cathode development in collaboration with KEK and Marui Galvanizing Co. Ltd (Marui) in Japan, and another focus is on HF free or acid free VEP protocols in collaboration with Faraday Technology Inc. The outcomes of these activities could be a significant cost reduction and an environmentally-friendlier VEP, which would be a breakthrough for future large scale EP applications on SRF cavities. Here we give a status update and report latest results from these R&D activities.

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MOPVA116

Quench Studies in Single-Cell Nb3Sn Cavities Coated Using Vapour Diffusion

radio-frequency, accelerating-gradient, monitoring, niobium

1119

D.L. Hall, M. Liepe, J.T. Maniscalco, R.D. Porter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
P. Cueva, D. Liarte, D.A. Muller, J.P. Sethna
Cornell University, Ithaca, New York, USA

The superconductor Nb3Sn is known to have a superheating field, Hsh, of approximately 400 mT. This critical field represents the ultimate achievable gradient in a superconducting cavity, and is equivalent to an accelerating gradient of 90 MV/m in an ILC single-cell cavity for this value of Hsh. However, the currently best performing Nb3Sn single-cell cavities remain limited to accelerating gradients of 17-18 MV/m, translating to a peak surface magnetic field of approx. 70 mT. In this paper, we consider theoretical models of candidate quench mechanisms, and compare them to experimental data from surface analysis and cavity tests.

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MOPVA117

Performance of a SRF Half-Wave-Resonator Tested at Cornell for the RAON Project

radiation, simulation, SRF, pick-up

1123

M. Ge, F. Furuta, T. Gruber, D.L. Hall, S.W. Hartman, C. Henderson, M. Liepe, S. Lok, T.I. O'Connell, P.J. Pamel, J. Sears, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
B.H. Choi, J. Joo, J.W. Kim, W.K. Kim, J. Lee, I. Shin
IBS, Daejeon, Republic of Korea

A prototype half-wave-resonator (HWR) with frequency 162.5MHz and geometrical \beta=0.12 for the RAON project is currently undergoing testing at Cornell University. Detailed vertical performance testing includes (1) test of the bare cavity without the helium tank; (2) test of the dressed cavity with helium tank. In this paper, we report on the development of the test infrastructure, test results, and performance data analysis.

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MOPVA118

Impact of Trapped Magnetic Flux and Thermal Gradients on the Performance of Nb3Sn Cavities

niobium, site, target, operation

1127

D.L. Hall, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
D. Liarte, J.P. Sethna
Cornell University, Ithaca, New York, USA

Trapped magnetic flux is known to degrade the quality factor of superconducting cavities by increasing the surface losses ascribed to the residual resistance. In Nb3Sn cavities, which consist of a thin layer of Nb3Sn coated on a bulk niobium substrate, the bimetallic interface results in a thermal current being generated in the presence of a thermal gradient, which will in turn generate flux that can be trapped. In this paper we quantify the impact of trapped flux, from either ambient fields or thermal gradients, on the performance of the cavity. We discover that the sensitivity to trapped flux, a measure of the increase in residual resistance as a function of the amount of flux trapped, is a function of the accelerating gradient. A theoretical framework to explain this phenomenon is proposed, and the impact on the requirements for operating a Nb3Sn cavity in a cryomodule are considered.

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MOPVA119

Surface Analysis of Features Seen on Nb3Sn Sample Coupons Grown by Vapour Diffusion

niobium, SRF, simulation, site

1130

D.L. Hall, M. Liepe, J.T. Maniscalco, R.D. Porter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
T. Arias, P. Cueva, D.A. Muller, N. Sitaraman
Cornell University, Ithaca, New York, USA

As a high-kappa superconductor with a coherence length of 7 nm, the superconductor Nb3Sn is highly susceptible to material features at the sub-micron scale. For niobium surfaces coated with a thin layer of Nb3Sn using the vapour diffusion method, the polycrystalline nature of the film grown lends to the possibility that performance-degrading non-uniformities may develop. In particular, regions of insufficiently thick coating and tin-depletion have been seen to occur in sample coupons. In the interests of understanding how to control the presence and nature of such features, it is necessary to know how they form. In this paper we stop the coating at defined instances to gain a stop-motion image of the growth of the layer, and use SEM and TEM techniques to image the development of the features seen in previously coated samples. We demonstrate that surface pre-anodisation can suppress the formation of thin film regions, and apply this technique to a single-cell cavity. Contemporarily, we use TEM with EDS mapping to monitor grain boundaries and tin-depleted regions within the layer.

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MOPVA121

Frequency Tuner Development at Cornell for the RAON Half-Wave-Resonator

cryomodule, cryogenics, controls, simulation

1134

M. Ge, F. Furuta, T. Gruber, D.L. Hall, S.W. Hartman, C. Henderson, M. Liepe, S. Lok, T.I. O'Connell, P.J. Pamel, P. Quigley, J. Sears, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
B.H. Choi, J. Joo, J.W. Kim, W.K. Kim, J. Lee, I. Shin
IBS, Daejeon, Republic of Korea

The half-wave-resonators (HWR) for the RAON pro-ject require a slow frequency tuner that can provide at least 80 kHz tuning range. Cornell University is currently in the process of designing, prototyping, and testing this HWR tuner. In this paper, we present the tuner design, prototype fabrication, and first test results.

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MOPVA122

Microphonics Studies of the CBETA Linac Cryomodules

cryomodule, operation, linac, SRF

1138

N. Banerjee, J. Dobbins, F. Furuta, D.L. Hall, G.H. Hoffstaetter, M. Liepe, P. Quigley, E.N. Smith, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: This work was performed through the support of NYSERDA (New York State Energy Research and Development Agency).
The Cornell BNL ERL Test Accelerator (CBETA) incorporates two SRF linacs; one for its injector and another for the energy recovery loop. Microphonics in both the cryomodules play a crucial role in determining the energy stability of the electron beam in high current operation. We have measured vibrations and frequency detuning of the SRF cavities and determined that the cryogenic system is the major source of microphonics in both cryomodules. In this paper we discuss these measurements and demonstrate an Active Microphonics Compensation system implemented using fast piezo-electric tuners which we incorporated in our Low Level RF control system to be used in routine operation.

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MOPVA123

Cornell Sample Host Cavity: Recent Results

niobium, SRF, electron, operation

1142

J.T. Maniscalco, D.L. Hall, M. Liepe, R.D. Porter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
V.M. Arrieta, S.R. McNeal, W.E. Williams
Ultramet, Pacoima, California, USA

Funding: NSF-PHY 1416318 NSF-PHY 1549132
The Cornell sample host cavity is a 3.9~GHz testing system for RF analysis of novel superconducting surfaces. The cavity applies fields up to 100~mT on a removable and replaceable 5-inch sample plate in order to measure the surface resistance of the material under investigation. The cavity also includes a temperature-mapping system for localization of quench events and surface defects. In this paper, we present recent experimental results from the host cavity of niobium deposited onto molybdenum and copper substrates using chemical vapor deposition, in collaboration with industry partner Ultramet. The results indicate low BCS resistance and good adhesion but also areas of high residual resistance due to chemical and morphological defects.

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MOPVA124

Effectiveness of Chemical Treatments for Reducing the Surface Roughness of Nb3Sn

niobium, SRF, linac, klystron

1145

R.D. Porter, F. Furuta, D.L. Hall, M. Liepe, J.T. Maniscalco
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: DOE DE-SC008431, NSF-PHY 1549132, NSF DMR-1120296
Current Niobium-3 Tin (Nb3Sn) superconducting radio-frequency (SRF) accelerator cavities have rougher surfaces than conventional electropolished Niobium accelerator cavities. The surface roughness can cause enhancement of the surface magnetic field, pushing it beyond the critical field. If this occurs over a large enough area it can cause the cavity to quench. The surface roughness may cause other effects that negatively impact cavity quality factor (Q) performance. Reducing surface roughness of Nb3Sn cavities may be necessary to achieve higher gradient with high Q. Current chemical treatments for reducing the surface roughness of Niobium are challenging for Nb3Sn: the Nb3Sn layer is only ~2 um thick while it is difficult to remove less than 1 mu uniformly with most chemical treatments. This paper presents measurements of the surface roughness before and after Buffered Chemical Polish, Electropolishing and oxipolishing.

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MOPVA126

Sample Host Cavity Design for Measuring Flux Entry and Quench

niobium, SRF, dipole, klystron

1149

R.D. Porter, M. Liepe, J.T. Maniscalco, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: NSF-PHY 1549132
Current state-of-the-art Niobium superconducting radio-frequency (SRF) accelerator cavities have reached surface magnetic field close to the theoretical maximum set by the superheating field. Further increasing accelerating gradients will require new superconducting materials for accelerator cavities that can support higher surface magnetic fields. This necessitates measuring the quench fields of new materials in high power RF fields. In this paper, we present designs and simulations of a sample host cavity. The cavity design is optimized to maximize the surface magnetic field achieved on the sample.

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MOPVA127

Vertical Test Results for the LCLS-II 1.3 GHz First Article Cavities

cryomodule, SRF, linac, FEL

1152

A. Burrill, D. Gonnella, M.C. Ross
SLAC, Menlo Park, California, USA
G.K. Davis, A.D. Palczewski, L. Zhao
JLab, Newport News, Virginia, USA
A. Grassellino, O.S. Melnychuk
Fermilab, Batavia, Illinois, USA

The LCLS-II project requires 35 1.3 GHz cryomodules to be installed in the accelerator in order to deliver a 4 GeV electron beam to the undulators hall. These 35 cryomodules will consist of 8 1.3 GHz TESLA style SRF cavities, a design most recently used for the XFEL project in Hamburg, Germany. The cavity design has remained largely unchanged, but the cavity treatment has been modified to utilize the nitrogen doping process to allow for Quality factors in excess of 3x10¹⁰ at 16 MV/m, the designed operating gradient of the cavities in the CM. Two industrialized vendors are producing most of the SRF cavities for these cryomodules; and the performance of the first article cavities, 16 from each vendor, will be reported on in this paper.

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MOPVA128

RF Performance of Nitrogen-Doped Production SRF Cavities for LCLS-II

SRF, niobium, operation, accelerating-gradient

1156

D. Gonnella, A. Burrill, M.C. Ross
SLAC, Menlo Park, California, USA
S. Aderhold, A. Grassellino, C.J. Grimm, T.N. Khabiboulline, O.S. Melnychuk, S. Posen, D.A. Sergatskov
Fermilab, Batavia, Illinois, USA
E. Daly, G.K. Davis, F. Marhauser, K.M. Wilson
JLab, Newport News, Virginia, USA

Funding: DOE and the LCLS-II Project
The Linac Coherent Light Source II (LCLS-II) requires 280 9-cell superconducting RF cavities for operation in continuous wave mode. Two vendors have previously been selected to produce the cavities, Research Instruments GmbH and Ettore Zanon S.p.a. Here we present results from manufacturing and cavity preparation for the cavities constructed at these two vendors for LCLS-II. We show how the cavity preparation method has been changed mid-production in order to improve flux expulsion in the cavities and maintain high performance in realistic magnetic field environments (~5 mG). Additionally, we show that the nitrogen-doping process has been carried out successfully and repeatedly on over 70 cavities.

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MOPVA130

Development of Waveguide HOM Loads for BERLinPro and BESSY-VSR SRF Cavities

HOM, simulation, SRF, network

1160

J. Guo, F. Fors, J. Henry, R.A. Rimmer, H. Wang
JLab, Newport News, Virginia, USA
H.-W. Glock, A. Neumann, A.V. Tsakanian, A.V. Vélez
HZB, Berlin, Germany

Two ongoing accelerator projects at Helmholtz-Zentrum Berlin (HZB), BERLinPro and BESSY-VSR, need to design three different SRF cavities, a 1.3GHz cavity in BERLinPro and 1.5GHz/1.75GHz cavities in BESSY-VSR. These cavities have adopted waveguide HOM dampers in their design, with a few tens of watts HOM power in each load for BERLinPro and a few hundred watts for BESSY-VSR. JLab is collaborating with HZB prototyping these HOM loads. In this paper, we will report on the integrated RF-thermal-mechanical design of the loads, as well as the fabrication and testing results.

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MOPVA131

Status of the LCLS-II Accelerating Cavity Production

status, controls, linac, target

1164

F. Marhauser, E. Daly, J.A. Fitzpatrick, A.D. Palczewski, J.P. Preble, K.M. Wilson
JLab, Newport News, Virginia, USA
A. Burrill, D. Gonnella
SLAC, Menlo Park, California, USA
C.J. Grimm
Fermilab, Batavia, Illinois, USA

Funding: Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 with supplemental funding from the LCLS-II Project U.S. DOE Contract No. DE-AC02-76SF00515.
Cavity serial production for the LCLS-II 4 GeV CM SRF linac has started. A quantity of 266 accelerating cavities has been ordered from two industrial vendors. Jefferson Laboratory leads the cavity procurement activities for the project and has successfully transferred the Nitrogen-Doping process to the industrial partners in the initial phase, which is now being applied for the production cavities. We report on the results from vendor qualification and the status of the cavity production for LCLS-II.

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MOPVA132

Production of Copper-Plated Beamline Bellows and Spools for LCLS-II

cryomodule, controls, vacuum, simulation

1167

K.M. Wilson, B. Carpenter, E. Daly, N.A. Huque, T. Peshehonoff
JLab, Newport News, Virginia, USA
T.T. Arkan, A. Lunin, K.S. Premo
Fermilab, Batavia, Illinois, USA

Funding: This work was supported by the LCLS-II Project and the U.S. Department of Energy, Contract DE-AC02-76SF00515
The SLAC National Accelerator Laboratory is currently constructing a major upgrade to its accelerator, the Linac Coherent Light Source II (LCLS-II). Several Department of Energy national laboratories, including the Thomas Jefferson National Accelerator Facility (JLab) and Fermi National Accelerator Laboratory (FNAL), are participating in this project. The 1.3-GHz cryomodules for this project consist of eight cavities separated by bellows (expansion joints) and spools (tube sections), which are copper plated for RF conduction. JLab is responsible for procurement of these bellows and spools, which are delivered to JLab and FNAL for assembly into cryomodules. Achieving accelerator-grade copper plating is always a challenge and requires careful specification of requirements and application of quality control processes. Due to the demanding technical requirements of this part, JLab implemented procurement strategies to make the process more efficient as well as provide process redundancy. This paper discusses the manufacturing challenges that were encountered and resolved, as well as the strategies that were employed to minimize the impact of any technical issues.

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MOPVA133

Optimization of the RF Cavity Heat Load and Trip Rates for CEBAF at 12 GeV

linac, operation, electron, SRF

1170

H. Zhang, A. Freyberger, G.A. Krafft, Y. Roblin
JLab, Newport News, Virginia, USA
B. Terzić
ODU, Norfolk, Virginia, USA

Funding: Work supported by the Department of Energy under Contract No. DE-AC05-06OR23177
The Continuous Electron Beam Accelerator Facility at JLab has 200 RF cavities in the north linac and the south linac respectively after the 12 GeV upgrade. The purpose of this work is to simultaneously optimize the heat load and the trip rate for the cavities and to reconstruct the pareto-optimal front in a timely manner when some of the cavities are turned down. By choosing an efficient optimizer and strategically creating the initial gradients, the pareto-optimal front for no more than 15 cavities down can be re-established within 20 seconds.

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MOPVA135

Fabrication, Processing and RF Test of RF-Dipole Prototype Crabbing Cavity for LHC High Luminosity Upgrade

dipole, HOM, luminosity, cryogenics

1174

S.U. De Silva, J.R. Delayen
ODU, Norfolk, Virginia, USA
H. Park
JLab, Newport News, Virginia, USA

The superconducting rf-dipole crabbing cavity is one of two crabbing cavity designs proposed for the LHC high luminosity upgrade. The proof-of-principle rf-dipole cavity operating at 400 MHz has demonstrated excellent performance exceeding the design specifications. The prototype cavity for SPS beam test has been designed to include the fundamental power coupler, HOM couplers, and all the ancillary components intended to meet the design requirements. A crabbing cavity system is expected to be installed in the SPS beam line and tested prior to the installation in LHC; this will be the first crabbing cavity operation on a proton beam. The fabrication of two prototype rf-dipole cavities is currently being completed at Jefferson Lab. This paper presents the details on cavity processing and cryogenic test results of the rf-dipole cavities.

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MOPVA136

Higher Order Multipole Analysis for 952.6 Mhz Superconducting Crabbing Cavities for Jefferson Lab Electron-Ion Collider

multipole, dipole, electron, proton

1177

S.U. De Silva, J.R. Delayen
ODU, Norfolk, Virginia, USA
H. Park
JLab, Newport News, Virginia, USA

The proposed electron ion collider at Jefferson Lab requires a crabbing cavity system to increase the luminosity in the colliding beams. Currently several superconducting crabbing cavity designs are being reviewed as the design option for the crabbing cavity. Knowledge of higher order mode multipole field effects is important for accurate beam dynamics study for the crabbing system, in selecting the design that meets the design specifications. The multipole components can be accurately determined numerically using the electromagnetic field data in the rf structure. This paper discusses the detailed analysis of higher order multipole components for the operating crabbing mode and design modifications in reducing those components.

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MOPVA140

Multipacting Behavior Study for the 112 MHz Superconducting Photo-Electron Gun

gun, electron, SRF, cathode

1180

I. Petrushina
SUNY SB, Stony Brook, New York, USA
V. Litvinenko, G. Narayan, I. Pinayev, F. Severino, K.S. Smith
BNL, Upton, Long Island, New York, USA
V. Litvinenko
Stony Brook University, Stony Brook, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Superconducting 1.2 MV 112 MHz quarter-wave photo-electron gun (SRF gun) is used as a source of electron beam for the Coherent electron Cooling experiment (CeC) at BNL. During the CeC commissioning we encountered a number of multipacting zones in the gun. It was also observed that introduction of CsK2Sb photocathode creates additional multipacting zone. This paper presents numerical and experimental study of the multipactor discharge in the SRF gun. We also discuss ways of crossing the multipacting levels to the operational voltage. Finally, we compare the results of our numerical simulations of the multipactor discharge using ACE3P with experimental data.

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MOPVA141

Input RF Coupler Design for Energy Compensator Cavity in eRHIC

simulation, radiation, impedance, synchrotron

1184

C. Xu, S. Bellavia, I. Ben-Zvi, M. Blaskiewicz, Y. Hao, K.S. Smith, R. Than, A. Zaltsman
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
This report gives a detail design of a 1.3 GHz input coupler for second harmonic cavity for eRHIC project. This coupler is designed to transmit 200KW CW RF to the cavity to compensate the synchrotron radiation loss. This report include RF and thermal simulation for this design.

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MOPVA143

Trim Tuning of SPS-Series DQW Crab Cavity Prototypes

target, operation, simulation, controls

1187

S. Verdú-Andrés, J. Skaritka, Q. Wu
BNL, Upton, Long Island, New York, USA
S. Baurac, C.H. Boulware, T.L. Grimm, J.A. Yancey
Niowave, Inc., Lansing, Michigan, USA
W.A. Clemens, E.A. McEwen, H. Park
JLab, Newport News, Virginia, USA
H. Park
ODU, Norfolk, Virginia, USA
A. Ratti
LBNL, Berkeley, California, USA
A. Ratti
SLAC, Menlo Park, California, USA

Funding: Work partially supported by US DOE via BSA LLC contract No.DE-AC02-98CH10886 and by the US LARP program.
The final steps in the manufacturing of a superconducting RF cavity involve careful tuning before the final welds to match the target frequency as fabrication tolerances may introduce some frequency deviations. The target frequency is chosen based on analysis of the shifts induced by remaining processing steps including acid etching and cool down. The baseline fabrication of a DQW crab cavity for the High Luminosity LHC (HL-LHC) envisages a first tuning before the cavity subassemblies are welded together. To produce a very accurate final result, subassemblies are trimmed to frequency in the last machining steps, using a clamped cavity assembly for RF measurements. This paper will describe the trim tuning of one of the SPS prototype DQW crab cavities fabricated by Niowave.

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MOPVA144

Post-Processing of Nb3Sn Coated Nb

niobium, SRF, superconductivity, experiment

1190

U. Pudasaini, M.J. Kelley
The College of William and Mary, Williamsburg, Virginia, USA
G.V. Eremeev, M.J. Kelley, C.E. Reece
JLab, Newport News, Virginia, USA
M.J. Kelley, J. Tuggle
Virginia Polytechnic Institute and State University, Blacksburg, USA

Funding: Supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DEÂAC05Â06OR23177 and Office of High Energy Physics under grant SC00144475.
Practical SRF cavities may be subjected to one or more processes after nominally complete preparation. Successful implementation of such processes in Nb3Sn coated cavities requires the understanding of material's response to these treatments. SRF-grade Nb samples, coated with Nb3Sn by the widely used tin vapor diffusion process were subjected to one or more of the following: hydrofluoric acid (HF) rinsing, oxypolishing, buffered chemical polishing (BCP) or electrochemical treatment. They were examined by materials characterization tech-niques including scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), and X-ray photoelectron spec-troscopy (XPS). The effects compared to niobium are different enough in most cases that further development is desirable to routinely obtain a favorable result.

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TUOBA1

Beam Commissioning Results of the CSNS Linac

DTL, linac, rfq, quadrupole

1223

J. Peng, Y.W. An, S. Fu, L. Huang, M.Y. Huang, Y. Li, Z.P. Li, S. Wang, S.Y. Xu, Y. Yuan
IHEP, Beijing, People's Republic of China
M.T. Li, Y.D. Liu
CSNS, Guangdong Province, People's Republic of China

The China Spallation Neutron Source(CSNS) accelera-tor systems is designed to deliver a 1.6GeV, 100kW pro-ton beam to a solid metal target for neutron scattering research. It consists of a 50keV H⁻ Ion Source, a 3MeV Radio Frequency Quadrupole (RFQ), an 80MeV Drift Tube Linac (DTL), and a 1.6GeV Rapid-cycling Synchro-tron (RCS). The beam commissioning has been started since April 2015. The Front End and three of the four DTL tanks have been commissioned, while the last tank and the RCS will be commissioned at the autumn this year. At the end of the DTL3, beam has been accelerated to 61MeV with nearly 100% transmission, other parame-ters such as peak current, transverse emittance and beam orbit have reached the design goal. Results and status of the beam commissioning program will be presented.
*This work is supported by National Natural Science Foundation of China (11505101).
**E-mail:pengjun@ihep.ac.cn

Slides TUOBA1 [4.272 MB]

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TUPAB006

Achievement of Stable Pulsed Operation at 31 MV/m in the STF-2 Cryomodule for the ILC

cryomodule, operation, radiation, accelerating-gradient

1308

Y. Yamamoto, T. Dohmae, M. Egi, K. Hara, T. Honma, E. Kako, Y. Kojima, T. Konomi, N. Kota, T. Kubo, T. Matsumoto, T. Miura, H. Nakai, K. Nakanishi, G.-T. Park, T. Saeki, H. Shimizu, T. Shishido, T. Takenaka, K. Umemori
KEK, Ibaraki, Japan

In the Superconducting RF Test Facility (STF) in KEK, the cooldown test for the STF-2 cryomodule with 12 cavities has been done totally three times since 2014. In 2016, the 3rd cooldown test for the STF-2 cryomodule including the capture cryomodule with 2 cavities, which was used for Quantum Beam Project in 2012, was successfully done. The main purpose is the vector-sum operation with 8 cavities at average accelerating gradient of 31 MV/m as the ILC specification, and the others are the measurement for Lorenz Force Detuning (LFD) and unloaded Q value, and Low Level RF (LLRF) study, etc. During 8 cavities operation, piezo actuators were used for the compensation of LFD, and the feed-forward and vector-sum control system by LLRF worked perfectly for keeping the lowest forward power and the stable flat-top of accelerating gradient. In this paper, the result for the STF-2 cryomodule in the 3rd cooldown test will be presented in detail.

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TUPAB010

High-Gradient Breakdown Studies of X-Band Choke-Mode Structures

linac, operation, collider, linear-collider

1322

X.W. Wu, H.B. Chen, J. Shi, H. Zha
TUB, Beijing, People's Republic of China
T. Abe, T. Higo, S. Matsumoto
KEK, Ibaraki, Japan

As an alternative design for Compact Linear Collider (CLIC) main accelerating structures, X-band choke-mode damped structures had been studied for several years. However, the performance of choke-mode cavity under high power is still in lack of research. Two standing-wave single-cell choke-mode damped accelerating structures working at 11.424 GHz and one reference structure without choke were designed, manufactured, low-power measured, and tuned by accelerator group at Tsinghua University. High-power test had been done on them to study the breakdown phenomenon in high gradient and how the choke affects high-gradient properties. A max gradient of 75 MV/m were achieved by the choke-mode structure and the choke breakdown limited further increasing of the gradient. Inner surface inspection of the choke-mode structures indicates that the axial part of the choke limits the performance of the structure. Based on this observation, three new choke-mode structures were designed and being manufactured.

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TUPAB013

Beam Dynamics Study and Electrodynamics Simulations for the CW RFQ

rfq, simulation, linac, Windows

1333

S.M. Polozov, W.A. Barth, T. Kulevoy, Y. Lozeev, S. Yaramyshev
MEPhI, Moscow, Russia
W.A. Barth, S. Yaramyshev
GSI, Darmstadt, Germany
W.A. Barth
HIM, Mainz, Germany
T. Kulevoy, S.M. Polozov
ITEP, Moscow, Russia

A compact university scale CW research proton accelerator, as well as driver linac with three branches of experimental beam lines, delivering beam energy of 3, 30 and 100 MeV for experiments, are recently under development in Russia. First results of the beam dynamics simulations for such a linac were already shown in *. The recently developed advanced RFQ cavity design is presented. The low energy beam transport line (LEBT), dedicated to transport proton beam from an ECR ion source, as well as to match beam emittance to the RFQ acceptance, was investigated. The results of beam dynamics simulations for LEBT are discussed.
* W.Barth, T.Kulevoy, S.Polozov, S.Yaramyshev, Proc. of HB-2016, 188-190.

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TUPAB015

Pulsed Beam Tests at the SANAEM RFQ Beamline

rfq, proton, plasma, emittance

1341

G. Turemen, Y. Akgun, A. Alacakir, I. Kilic, B. Yasatekin
TAEK - SANAEM, Ankara, Turkey
F. Ahiska
EPROM Electronic Project & Microwave Ind. and Trade Ltd. Co., Ankara, Turkey
E. Cicek
Gazi University, Faculty of Arts and Sciences, Teknikokullar, Ankara, Turkey
E. Ergenlik, S. Ogur, E. Sunar, V. Yildiz
Bogazici University, Bebek / Istanbul, Turkey
G. Unel
UCI, Irvine, California, USA

Funding: Turkish Atomic Energy Authority
A proton beamline consisting of an inductively coupled plasma (ICP) source, two solenoid magnets, two steerer magnets and a radio frequency quadrupole (RFQ) is developed at the Turkish Atomic Energy Authority's (TAEA) Saraykoy Nuclear Research and Training Center (SNRTC-SANAEM) in Ankara. In Q4 of the 2016 the RFQ was installed in the beamline. The high power tests of the RF power supply and the RF transmission line were done successfully. The high power RF conditioning of the RFQ was performed recently. The 13.56 MHz ICP source was tested in two different conditions, CW and pulsed. The characterization of the proton beam was done with ACCTs, Faraday cups and a pepper-pot emittance meter. Beam transverse emittance was measured in between the two solenoids of the LEBT. The measured beam is then reconstructed at the entrance of the RFQ by using computer simulations to determine the optimum solenoid currents for acceptance matching of the beam. This paper will introduce the pulsed beam test results at the SANAEM RFQ beamline. In addition, the high power RF conditioning of the RFQ will be discussed.

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TUPAB022

TRIUMF ARIEL e-Linac Ready for 30 MeV

linac, cryomodule, TRIUMF, electron

1361

S.R. Koscielniak, Z.T. Ang, K. Fong, J.J. Keir, O.K. Kester, M.P. Laverty, R.E. Laxdal, Y. Ma, A.K. Mitra, T. Planche, D.W. Storey, E. Thoeng, B.S. Waraich, Z.Y. Yao, V. Zvyagintsev
TRIUMF, Vancouver, Canada

Funding: TRIUMF is funded under a contribution agreement with the National Research Council of Canada.
The ARIEL electron linac (e-linac) in its present configuration has a 10 mA electron gun and a single-cavity 10 MeV injector cryomodule followed by the accelerator cryomodule intended to house two 10-MeV-capable SRF cavities. There are momentum analysis stations at 10 MeV and 30 MeV. In October 2014, using a total of two cavities, the e-linac demonstrated 22.9 MeV acceleration. In 2017 an additional SRF cavity was installed in the accelerator cryomodule, thereby completing its design specification; and leading to 30 MeV acceleration capability. The 9-cell 1.3 GHz cavities are a variant of the TESLA type, modified for c.w. operation and recirculation. An unusual feature of the module is the power feed of two cavities by one klystron through a wave-guide type power divider, and closed loop control of the combined voltage from the cavities. Initial operation of the two-cavity control, including power and phase balancing, is reported.

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TUPAB023

Commissioning of the 10MeV Electron Injector Cryomodule for VECC at TRIUMF

cryomodule, TRIUMF, linac, electron

1365

R.E. Laxdal, Y. Ma, R.R. Nagimov, D.W. Storey, E. Thoeng, Z.Y. Yao, V. Zvyagintsev
TRIUMF, Vancouver, Canada
U. Bhunia, A. Chakrabarti, S. Dechoudhury, V. Naik
VECC, Kolkata, India

TRIUMF (Vancouver) and VECC (Kolkata) have been engaged in a collaboration on superconducting electron linacs since 2008. The motivation for the collaboration was to support initiatives at both labs, ARIEL at TRIUMF and ANURIB at VECC, to augment the respective radioactive ion beam (RIB) programs with the addition of a high intensity electron linac driver to produce RIBs through photo-fission. The common linac architecture is based on five 1.3GHz nine-cell SRF cavities housed in three cryomodules; a single cavity injector (ICM) and a pair of two cavity accelerating modules (ACM). Final design goals are 50MeV and 10mA/3mA at TRIUMF/VECC respectively. A ARIEL e-linac demonstrator with two cold cavities in two modules successfully accelerated beam to 20MeV. Recently the VECC 10MeV injector cryomodule was commissioned with beam. A summary of the ICM design and results of the commissioning will be presented.

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TUPAB027

Production, Tuning and Processing Challenges of the BERLinPro Gun1.1 Cavity

gun, cathode, niobium, SRF

1375

H.-W. Glock, A. Frahm, J. Knobloch, A. Neumann
HZB, Berlin, Germany
B. Rosin, D. Trompetter
RI Research Instruments GmbH, Bergisch Gladbach, Germany

Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of the Helmholtz Association
For the BERLinPro energy recovery LINAC, HZB is developing a superconducting 1.4-cell electron gun, which, in its final version, is planned to be capable of CW 1.3 GHz operation with 77 pC/bunch. For this purpose a series of three superconducting cavities, denoted as Gun 1.0, Gun 1.1 (both designed for 6 mA) and Gun 2.0 (100 mA) are foreseen. Gun 1.0 now reached operational status and the Gun 1.1 cavity is completely manufactured. In the paper the chronology of manufacturing, tuning and processing of the Gun 1.1-cavity is described, also giving details about combined mechanical/electrodynamic simulations, which were performed in order to gain deeper understanding of the cavity's unexpected tuning behavior.

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TUPAB029

UHV Photocathode Plug Transfer Chain for the BERLinPro SRF-Photoinjector

SRF, vacuum, cathode, laser

1381

J. Kühn, J. Borninkhof, M. Bürger, A. Frahm, A. Jankowiak, T. Kamps, M.A.H. Schmeißer, M. Schuster
HZB, Berlin, Germany
P. Murcek, J. Teichert, R. Xiang
HZDR, Dresden, Germany

A dedicated particle free UHV photocathode plug transfer chain from the preparation system to the SRF-Photoinjector was set up and commissioned at HZB for the BERLinPro project. The plug handling system was designed in collaboration with the ELBE team at HZDR, where the same transfer chain is in commissioning phase. In the future the exchange of photocathodes between the laboratories offers the possibility to test different types of photocathodes in different SRF-photoinjectors.

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TUPAB044

SIMULATION, MEASUREMENT AND TUNING OF A PROTOTYPE DISK LOADED RF CAVITY

electron, simulation, linac, operation

1424

S. Ahmadiannamin
ILSF, Tehran, Iran
F. Abbasi, F. Ghasemi
Shahid Beheshti University, Tehran, Iran
M. Lamehi, M. Shirshekan
IPM, Tehran, Iran

Constant impedance accelerator RF cavities are constructed from similar resonator cells that stacked to each other. Best operation condition is achieved when all of cells resonate in one resonance frequency with similar quality factors. So, measurement and tuning of RF cavities is the critical step for final best operation of linear accelerators. In this paper, the electromagnetic computer simulations, RF measurement and final tuning of a nine cell periodic accelerator structure was represented. All of cavities tuned in one resonant frequency and according to theoretical concepts we obtain nine resonant modes from RF measurements by vector network analyzer.

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TUPAB045

Design and Construction of a Pre-Buncher for Iranian Low Energy Linear Accelerator

electron, linac, simulation, coupling

1428

S. Ahmadiannamin
ILSF, Tehran, Iran
M. Bahrami, M.R. Khalvati, M. Lamehi, H. Shaker, M. Shirshekan
IPM, Tehran, Iran

Iranian IPM low energy linear accelerator project (e-Linac) is in its final steps for commissioning. Beam dynamic simulations with and without Pre-buncher prior to buncher was done. The results represent improvement in capturing efficiency better than 25% by application of Pre-buncher cavity. In this paper, we present the simulation, construction, RF measurements and vacuum test results. After construction, we measured RF reflection coefficient better than -33 dB in the nominal frequency of 2997.9 MHz with quality factor of 4500.

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TUPAB047

Design of a Low Emittance High Current Photocathode RF Gun for the IPM Linear Accelerator

gun, emittance, focusing, simulation

1431

M. Dayyani Kelisani, H. Shaker
CERN, Geneva, Switzerland
H. Shaker
IPM, Tehran, Iran

The IPM accelerator project is developing a 50 MeV linear accelerator as an injector for a terahertz source or an IR FEL. The design specifications require a laser driven photocathode located in one end of a high gradient RF cavity operated at 3 GHz frequency and a solenoid channel for the beam transport. In this work, we report on the RF design of an special photocathode RF gun and its associated focusing channel for the emittance compensation process along the whole injector.

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TUPAB059

Study on CsKSb Photocathode for the RF Electron Gun

cathode, gun, electron, laser

1456

H. Ono, J. Miyamatsu, M. Washio
Waseda University, Tokyo, Japan
H. Iijima
Tokyo University of Science, Tokyo, Japan
K. Sakaue
Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan

At Waseda University, we have been developing a Cs-Te photocathode S-band RF electron gun and application experiments of the electron beam. On the experiments, charge amount is important factor, which strongly depends on laser power and photocathode quality. At present, we are studying CsKSb photocathode to increase the charge amount of an electron beam generated from the RF-Gun. As a result of using CsKSb photocathode in the RF-cavity, we obtained as much charge as using Cs-Te photocathode but the lifetime was shorter than that of Cs-Te. In order to lengthen the photocathode lifetime, we tried to coat a protective film on CsKSb photocathode surface and investigated its robustness for poor vacuum condition that simulates cathode transportation and usage in the RF-Gun. In this conference, we report current status of fabricating coated photocathode and future prospects.
A. Buzulutskov et al. The protection of K-Cs-Sb photocathodes with CsBr films Nuclear Instruments and Methods in Physics Research A 400 (1997) 173-176

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TUPAB082

Research of L-Band Disk-Loaded Waveguides Travelling Wave Accelerating Structures for a High Power Linac

bunching, electron, network, impedance

1506

Y.M. Zhang
USTC, SNST, Anhui, People's Republic of China
Y.J. Pei, L.S. Sheng, Y. Song
USTC/NSRL, Hefei, Anhui, People's Republic of China

L-band Electron Accelerator is widely used for industrial irradiation. This paper describes a constant-impedance, disk-loaded structure operating on the 2Pi/3 mode. The design details of L-band travelling wave accelerating structures are presented. All RF parameters in metal disk-loaded waveguides and fields were calculated. The SUPERFISH code was used to design the bunching and accelerating cavities. At the same time, we also calculated the beam dynamics. Some model cavities have been fabricated and experimental studies were carried on. In this study, some valuable results were obtained, which can provide a beneficial datum for the design and manufacture of L-band travelling-wave accelerating structures of 50MeV LINAC.

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TUPAB126

Multi-objective Genetic Optimization of Single Shot Ultrafast Electron Diffraction Beamlines

gun, emittance, electron, cathode

1615

C.M. Gulliford, A.C. Bartnik, I.V. Bazarov
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
J.M. Maxson
UCLA, Los Angeles, California, USA

We present the results of multi-objective genetic algorithm optimizations of two single-shot ultrafast electron diffraction (UED) beam lines. The first is based on a 225 kV dc gun featuring a novel cryocooled photocathode system and buncher cavity. The second uses a 100 MV/m 1.6 cell normal conducting rf (NCRF) gun, as well as a 9 cell 2 Pi/3 bunching cavity placed between two solenoids. Optimizations of the transverse projected emittance as a function of bunch charge are presented and discussed in terms of the scaling laws derived in the charge saturation limit. Additionally, optimization of the transverse coherence length as a function of final rms bunch length at the sample location have been performed. These results demonstrate the viability of the approaches taken for both beamlines studied as well as the use of using genetic algorithms in the design and operation of UED beamlines.

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TUPAB130

Status of the LCLS-II Superconducting RF Linac

cryomodule, linac, operation, FEL

1630

A. Burrill
SLAC, Menlo Park, California, USA

The LCLS-II project requires the assembly and installation of 37 cryomodules in order to deliver a 4 GeV electron beam to the undulators to produce both soft and hard x-ray pulses at a repetition rate up to 1 MHz. All of the cryomodules will operate in continuous wave mode, with 35 operating at 1.3 GHz for acceleration and 2 operating at 3.9 GHz to linearize the longitudinal beam profile. The assembly and testing of the 1.3 GHz cryomodules is well underway and the 3.9 GHz cryomodule work is entering into the pre-cryomodule testing and component validation phase. Both of these efforts will be reported on in this paper.

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TUPAB132

A Novel Dual-Mode Dual-Frequency Linac Design

impedance, operation, network, distributed

1634

M.H. Nasr, S.G. Tantawi
SLAC, Menlo Park, California, USA

In this paper we will present a new type of accelerator structure that operates simultaneously at two accelerating modes with two frequencies. The frequencies are not harmonically related, but rather have a common sub-harmonic. This design will use a recently developed parallel-feeding network that feeds every cavity cell independently using a distributed feeding network. This will overcome many of the practical complications of coupled cell structure. We will provide the theoretical background for our dual-mode design as well as present our optimized design that operates at C and X bands simultaneously and provides enhanced gradient and efficiency compared to single-mode designs.

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TUPAB135

A 1.75 mm Period RF-Driven Undulator

undulator, laser, electron, FEL

1643

F. Toufexis, S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515, and the National Science Foundation under Contract No. PHY-1415437.
To reduce the linac energy, and hence the size required for a Free Electron Laser radiating at a given wavelength, a smaller undulator period with sufficient field strength is needed. Previous work from our group successfully demonstrated a microwave undulator at 11.424 GHz using a corrugated cylindrical waveguide operating in the HE11 mode. Scaling down the undulator period using this technology poses the challenge of confining and coupling* the electromagnetic fields while maintaining over-moded features for power handling capability and electron beam wakefield mitigation. In this work, we present a novel end section of an RF undulator at 91.392 GHz. To confine the fields inside the undulator, a corrugated waveguide is connected through a matching section to a linear taper and a mirror. After the mirror, a Bragg reflector and a matching section are used to reflect back all the fields leaking out of the mirror opening.
* F. Toufexis, J. Neilson, and S.G. Tantawi, Coupling and Polarization Control in a mm-wave Undulator, these proceedings.

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TUPAB138

LCLS-II Injector Physics Design and Beam Tuning

laser, emittance, gun, solenoid

1655

F. Zhou, D. Dowell, P. Emma, J.F. Schmerge
SLAC, Menlo Park, California, USA
C.E. Mitchell, F. Sannibale
LBNL, Berkeley, California, USA

Funding: US DOE under grant No. DE-AC02-76SF00515.
LCLS-II is a proposed high-repetition rate (up to 1 MHz) Free Electron Laser X-ray light source, based on a CW normal conducting (NC) RF gun injector and a CW 4-GeV superconducting (SC) linac, under construction at SLAC. LCLS-II CW injector consists of a 186 MHz NC RF gun, two solenoids, two BPMs, 1.3 GHz NC RF buncher, and 1.3 GHz SC standard 8-cavity cryomodule to boost the beam energy >95 MeV, and 5 pairs of steering correctors. In this paper, we describe the injector physics design including the beam optimization and low level RF requirement, and also present the studies of beam performance with any one SC cavity failure. The beam tuning procedure is developed with the correctors and two BPMs. The simulations of the phase/amplitude calibration for the gun and buncher and beam based alignment for cathode, two solenoids, and RF buncher with the limited diagnostics, will be presented.

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TUPAB139

Design of an X-Band Photoinjector Operating at 1 kHz

gun, cathode, solenoid, power-supply

1659

W.S. Graves, A.C. Goodrich, M.R. Holl, N.J. O'Brien
Arizona State University, Tempe, USA
V. Bharadwaj, P. Borchard
Tibaray Inc., Stanford, USA
V.A. Dolgashev, E.A. Nanni
SLAC, Menlo Park, California, USA

A kHz repetition rate RF photoinjector with novel features has been designed for the ASU CXLS project. The photoinjector consists of a 9.3 GHz 4.5 cell standing-wave RF cavity that is constructed from 2 halves. The halves are brazed together, with the braze joint bisecting the irises and cells, greatly simplifying its construction. The cathode is brazed onto this assembly. RF power is coupled into the cavity through inline circular waveguide using a demountable TM01 mode launcher. The mode launcher feeds the power through 4 ports distributed azimuthally to eliminate both dipole and quadrupole field distortions. The brazed-in cathode and absence of complex power coupler result in a very inexpensive yet high performance device. The clean design allows the RF cavity to sit entirely within the solenoid assembly. The cathode gradient is 120 MV/m at 3 MW of input power. The cathode cell is just 0.17 RF wavelength so that laser arrival phase for peak acceleration is 70 degrees from zero crossing resulting in exit energy of 4 MeV. The photoinjector will operate with 1μs pulses at 1 kHz, dissipating 3 kW of heat. Details of the design are presented.

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TUPAB142

Tracking of Electrons Created at Wrong RF Phases in the RHIC Low Energy Cooler

electron, cathode, space-charge, laser

1666

J. Kewisch, A.V. Fedotov, D. Kayran, S. Seletskiy
BNL, Upton, Long Island, New York, USA

Funding: Work supported by the US Department of Energy under contract No. DE-SC0012704.
The RHIC Low Energy Cooler will be based on a 400 keV DC electron gun with a photo-cathode and a 2.2 MeV SRF booster cavity. Electron that leave the cathode at the wrong time may be decelerated and turned around in the booster and return to the cathode with energies up to 1 MeV. On the way back these electron will encounter the defocussing EM fields up to nine following electron bunches. Such electrons may be created for various reasons: Cosmic rays, stray laser light including a catastrophic failure of the laser timing system or as secondaries of returning electrons. We present tracking results from the GPT program* and discuss the consequences for the machine protection system.
* www.pulsar.nl

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TUPIK052

Fast Automatic Ramping of High Average Power Guns

gun, resonance, operation, feedback

1809

Y. Renier
DESY Zeuthen, Zeuthen, Germany
M.K. Grecki, O. Hensler, S. Pfeiffer
DESY, Hamburg, Germany

The electron guns at PITZ, FLASH and European XFEL are standing wave structures which operate at high average power (>40 kW) to produce long trains of high quality beams. This amount of power heats the cavity surface enough to change signi'cantly the gun resonance frequency. As consequence, to keep the re'ection low, the RF power ramp must be enough slow to permit the water cooling system to keep the gun temperature close to the set-point. Also, as the temperature probe sits close to the surface of the iris, the required gun temperature set-point to maintain the gun on resonance is a function of the average power. The RF power ramping is a difficult process in which temperature and re'ection must be monitored to adjust accordingly the temperature set-point and the ramping speed of the RF power. An automatic software to adjust the RF frequency and the temperature set-point of the PITZ gun in parallel to the RF power ramping has been developed. The use of this software has signi'cantly reduced the time spent to start up the gun or to recover from interlocks, increasing the time spent at nominal parameters which would also be very important for user facilities.

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TUPIK068

Parameters Calibration and Compensation-Rematch of Failure Cavities in CADS Injector

simulation, experiment, brightness, rfq

1852

Y.Z. Jia, W.L. Chen, W.P. Dou, P.H. Gao, H. Jia, S.H. Liu, Y.S. Qin, C. Wang, W.S. Wang, Z.J. Wang
IMP/CAS, Lanzhou, People's Republic of China

Now when a failure on the China Accelerator Driven System (CADS) is detected, the beam will be stopped by the machine protection system (MPS) immediately. But because of the demand of the beam trip (more than 5 min) rate which should be less than 50 times per year [1], it is important to avoid cutting beam down or recover the beam in a short time. The compensation and rematch is of great importance. If the failure is on a cavity, the other cavities should retune to compensate the beam energy, position and phase in order to recover the beam in short time depending on the time of online calculation.

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TUPIK108

Beam Based Alignment Studies for the CLARA FEL Test Facility

FEL, quadrupole, alignment, undulator

1971

J.K. Jones, N. Thompson
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

The CLARA (Compact Linear Accelerator for Research and Applications) test facility is designed to experimentally demonstrate innovative FEL schemes for future light source applications. Such schemes can place strict requirements on the accelerator beam properties as well as the relative alignment of the beam in the FEL radiators and modulators. Beam-based alignment (BBA) of the FEL section is therefore an operational requirement for all advanced FEL facilities. In this paper we demonstrate results of CLARA BBA simulations, and also report initial simulation results from the use of non-linear algorithms to optimise the FEL performance directly.

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TUPIK110

Optimisation of a High-Resolution, Low-Latency Stripline Beam Position Monitor System for Use in Intra-Train Feedback

feedback, electron, extraction, collider

1979

N. Blaskovic Kraljevic, R.M. Bodenstein, T. Bromwich, P. Burrows, G.B. Christian, C. Perry, R.L. Ramjiawan
JAI, Oxford, United Kingdom
D.R. Bett
CERN, Geneva, Switzerland

A high-resolution, low-latency beam position monitor (BPM) system has been developed for use in feedback systems at particle accelerators and beamlines that operate with trains of particle bunches with bunch separations as low as several tens of nanoseconds, such as future linear electron-positron colliders and free-electron lasers. The system was tested with electron beams in the extraction line of the Accelerator Test Facility at the High Energy Accelerator Research Organization (KEK) in Japan. The fast analogue front-end signal processor is based on a single-stage RF down-mixer, with a measured latency of 15.6 ± 0.1 ns. The processor has been optimised, doubling the maximum operating beam intensity up to 1.6 nC, and the signal processing in the custom digital acquisition board has been upgraded in order to improve the resolution beyond the 300 nm level measured previously. The latest results, demonstrating a position resolution of order 150 nm with single-pass beam, will be presented.

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TUPIK112

Progress Towards Nanometre-Level Beam Stabilisation Using a Cavity BPM System at ATF2

feedback, dipole, kicker, electronics

1986

T. Bromwich, N. Blaskovic Kraljevic, R.M. Bodenstein, P. Burrows, G.B. Christian, C. Perry, R.L. Ramjiawan
JAI, Oxford, United Kingdom

A low-latency feedback system has been designed and tested to achieve inter-bunch position stabilisation at the final focus of the Accelerator Test Facility (ATF2) at KEK. This system has now been enhanced through the use of position information from two cavity beam position monitors (BPMs) to enable beam stabilisation at a third, intermediate location where a witness BPM measures the correction. Low-Q cavity BPMs were used, along with custom signal processing electronics designed for low latency and optimal position resolution. A custom stripline kicker, power amplifier and digital feedback board were used to provide beam correction and feedback control. The system was tested in single-pass, multi-bunch mode with the aim of providing inter-bunch beam stabilisation on electron bunches of charge ~1 nC separated in time by 280 ns. In 2015 a single BPM feedback system demonstrated beam stabilisation to below 75 nm. To date the two BPM input feedback system has demonstrated beam stabilisation to 83 ± 6 nm. This performance is limited by the current understanding of the cavity BPM resolution. Work will be described with the aim of improving this result.

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TUPIK114

First Experiences with the Longitudinal Feedback System at Diamond Light Source

feedback, kicker, simulation, hardware

1992

A.F.D. Morgan, M.G. Abbott, G. Rehm
DLS, Oxfordshire, United Kingdom

In order to avoid longitudinal multibunch instabilities potentially caused by the addition of normal conducting RF cavities into the Diamond storage ring, a longitudinal feedback was installed. The main components are newly developed feedback electronics, in-house built modulator and amplifier, and a low Q kicker cavity. This paper describes the performance of the cavity as well as the full longitudinal feedback system as it is installed on the machine and tested before the installation of the normal conducting RF cavities.

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TUPVA008

Assessment of Thermal Loads in the CERN SPS Crab Cavities Cryomodule

cryomodule, HOM, radiation, pick-up

2047

F. Carra, J. Apeland, R. Calaga, O. Capatina, T. Capelli, C. Zanoni
CERN, Geneva, Switzerland
S. Verdú-Andrés
BNL, Upton, Long Island, New York, USA

Funding: *Work supported by the European Union HL-LHC Project and by US DOE through Brookhaven Science Associates LLC under contract No. DE-AC02-98CH10886 and the US LHC Accelerator Research Program (LARP). Research supported by the HL-LHC project.
As a part of the HL-LHC upgrade, a cryomodule is designed to host two crab cavities for a first test with protons in the SPS machine. The evaluation of the cryomodule heat loads is essential to dimension the cryogenic infrastructure of the system. The current design features two cryogenic circuits. The first circuit adopts superfluid helium at 2 K to maintain the cavities in the superconducting state. The second circuit, based on helium gas at a temperature between 50 K and 70 K, is connected to the thermal screen, also serving as heat intercept for all the interfaces between the cold mass and the external environment. An overview of the heat loads to both circuits, and the combined numerical and analytical estimations, is presented. The heat load of each element is detailed for the static and dynamic scenarios, with considerations on the design choices for the thermal optimization of the most critical components.
#Federico.carra@cern.ch

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TUPVA022

Requirements for Crab Cavity System Availability in HL-LHC

luminosity, optics, operation, proton

2097

M. Valette, A. Apollonio, J.A. Uythoven, D. Wollmann
CERN, Geneva, Switzerland

Funding: Research supported by the HL-LHC project.
Crab Cavities will be installed in the High Luminosity LHC in order to increase the effective peak luminosity through a partial compensation of the geometric factor. This will allow extending the levelling time resulting in an increased production of integrated luminosity. Based on the availability of the LHC during 2016 operation, the expected yearly-integrated luminosity of the future HL-LHC was estimated using a Monte Carlo model. Crab cavity faults were added to the observed failure distribu-tions and their impact on integrated luminosity produc-tion as a function of fault time and fault frequency was studied. This allows identifying a breakeven point in luminosity production and defining minimum system availability requirements for the crab cavities to reach the design goal of 250 fb-1 of integrated luminosity per year.

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TUPVA034

SPS Studies in Preparation for the Crab Cavity Experiment

emittance, experiment, luminosity, simulation

2133

A. Alekou, A. Alekou, F. Antoniou, F. Antoniou, G. Arduini, G. Arduini, H. Bartosik, H. Bartosik, R. Calaga, R. Calaga, Y. Papaphilippou, Y. Papaphilippou, Y. Papaphilippou
CERN, Geneva, Switzerland
A. Alekou, R.B. Appleby, R.B. Appleby
UMAN, Manchester, United Kingdom
R.B. Appleby, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom

A local Crab Cavity (CC) scheme will recover head-on collisions at the Interaction Points (IPs) of the High Luminosity LHC (HL-LHC), which aims to increase the LHC luminosity by a factor of 3-10. The first time that CC will ever be tested with proton beams will be in 2018 in the SPS machine. The available dedicated Machine Development (MD) time after the installation of the cavities will be limited and therefore good preparation is essential in order to ensure that the MDs are as efficient as possible. This paper presents the simulations and experimental studies performed in preparation for the future MDs and discusses the next steps.

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TUPVA046

Beam Energy Scan With Asymmetric Collision at RHIC

operation, emittance, booster, kicker

2175

C. Liu, J.G. Alessi, E.N. Beebe, M. Blaskiewicz, J.M. Brennan, K.A. Brown, D. Bruno, J.J. Butler, R. Connolly, T. D'Ottavio, K.A. Drees, W. Fischer, C.J. Gardner, D.M. Gassner, X. Gu, Y. Hao, M. Harvey, T. Hayes, H. Huang, R.L. Hulsart, P.F. Ingrassia, J.P. Jamilkowski, J.S. Laster, V. Litvinenko, Y. Luo, M. Mapes, G.J. Marr, A. Marusic, G.T. McIntyre, K. Mernick, R.J. Michnoff, M.G. Minty, C. Montag, J. Morris, C. Naylor, S. Nemesure, I. Pinayev, V.H. Ranjbar, D. Raparia, G. Robert-Demolaize, T. Roser, P. Sampson, J. Sandberg, V. Schoefer, F. Severino, T.C. Shrey, K.S. Smith, S. Tepikian, R. Than, P. Thieberger, J.E. Tuozzolo, G. Wang, Q. Wu, A. Zaltsman, K. Zeno, S.Y. Zhang, W. Zhang
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
A beam energy scan of deuteron-gold collision, with center-of-mass energy at 19.6, 39, 62.4 and 200.7 GeV/n, was performed at the Relativistic Heavy Ion Collider in 2016 to study the threshold for quark-gluon plasma (QGP) production. The lattice, RF, stochastic cooling and other subsystems were in different configurations for the various energies. The operational challenges changed with every new energy. The operational experience at each energy, the operation performance, highlights and lessons of the beam energy scan are reviewed in this report.

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TUPVA047

IBS Simulation with Different RF Configurations in RHIC

emittance, simulation, proton, injection

2178

C. Liu, A.V. Fedotov, M.G. Minty, V. Ptitsyn
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
This report focuses on three dimensional emittance growth of polarized proton beam due to Intra-Beam Scattering (IBS) at RHIC. Simulations are presented which give guidance on the configuration of the RF systems to mitigate IBS-induced emittance growth. In addition, simulated growth rates are compared with measured emittance evolution at injection, which shows better agreement in longitudinal than transverse dimension. The results in this report will help us better understand the emittance evolution for current RHIC operations and for future operations (eRHIC).

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TUPVA055

Further Investigations for a Superconducting cw-LINAC at GSI

linac, ion, heavy-ion, solenoid

2197

W.A. Barth, M. Heilmann, S. Yaramyshev
GSI, Darmstadt, Germany
K. Aulenbacher
IKP, Mainz, Germany
K. Aulenbacher, F.D. Dziuba, V. Gettmann, M. Miski-Oglu
HIM, Mainz, Germany
M. Basten, H. Podlech, M. Schwarz
IAP, Frankfurt am Main, Germany
S. Yaramyshev
MEPhI, Moscow, Russia

For superconducting (sc) accelerator sections operating at low and medium beam energies very compact accelerating-focusing structures are strongly required, as well as short focusing periods, high accelerating gradients and very short drift spaces. The Facility for Antiproton and Ion Research (FAIR) is going to use heavy ion beams with extremely high peak current from UNiversal Linear ACcelerator (UNILAC) and the synchrotron SIS18 as an injector for the SIS100. To keep the GSI-Super Heavy Element program competitive on a high level and even beyond, a standalone sc continuous wave LINAC in combination with the upgraded GSI High Charge State injector is envisaged. In preparation for this, testing of the first LINAC section (financed by HIM and GSI) as a demonstration of the capability of 216 MHz multi gap Crossbar H-structures (CH) is still ongoing, while an accelerating gradient of 9.6 MV/m (4K) at a sufficient quality factor has been already reached in a horizontal cryostat. As a final R&D step towards an entire LINAC three advanced cryo modules, each comprising two short CH cavities, should be built until 2019, serving for first user experiments at the coulomb barrier.

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TUPVA057

Design Study for a Prototype Alvarez-Cavity for the Upgraded Unilac

DTL, operation, ion, quadrupole

2205

M. Heilmann, X. Du, P. Gerhard, L. Groening, M. Kaiser, S. Mickat, A. Rubin
GSI, Darmstadt, Germany
A. Seibel
IAP, Frankfurt am Main, Germany

The design study describes the prototype Alvarez-tank of the new post-stripper of the UNILAC. A prototype with 17 drift tubes (including quadrupole singulets) of 3 m of total length and 2 m of diameter will be manufactured. This cavity features new drift tube shape profiles to provide for high shunt impedance at a maximum electric surface field of 1 Ek. Additionally, it allows realization and high power testing of an optimized stem configuration for field stabilization. In case of successful tuning and long-term operation at high power level, it shall be used as a first of series cavity of the new UNILAC post-stripper DTL.

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TUPVA058

Status of the FAIR pLinac

proton, rfq, diagnostics, linac

2208

C.M. Kleffner, R. Berezov, D. Daehn, J. Fils, P. Forck, L. Groening, M. Kaiser, K. Knie, C. Mühle, S. Puetz, A. Schnase, G. Schreiber, T. Sieber, J. Trüller, W. Vinzenz, C. Will
GSI, Darmstadt, Germany
U. Ratzinger
IAP, Frankfurt am Main, Germany

This paper describes the development progress of the 70 MeV, 70 mA proton injector for the FAIR facility. The injector comprises an ECR-type high current proton source followed by a ladder 4-rod RFQ and six normal conduction CH-DTL accelerating cavities. This unique design allows for a compact structure. The design work of the cavities has been mostly completed by our collaberation partners at IAP Frankfurt. The design of the buncher cavities, the mechanical integration as well as beam diagnostic devices are currently under development. The construction of a new modulator for the pLinac rf-system has been started on site. The proton source and the LEBT as well as the subsequent chopper are currently assembled at CEA/Saclay. Beam commissioning of the source at Saclay will start at the beginning of 2017. An overview of the pLinac main parameters and design choices is given, and the overall status reported.

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TUPVA061

Beam Dynamics Study for the HIM&GSI Heavy Ion SC CW-LINAC

linac, ion, acceleration, simulation

2217

S. Yaramyshev, W.A. Barth, M. Heilmann
GSI, Darmstadt, Germany
K. Aulenbacher
IKP, Mainz, Germany
K. Aulenbacher, W.A. Barth, V. Gettmann, M. Miski-Oglu
HIM, Mainz, Germany
W.A. Barth, S. Yaramyshev
MEPhI, Moscow, Russia
M. Basten, M. Busch, F.D. Dziuba, H. Podlech, M. Schwarz
IAP, Frankfurt am Main, Germany

A sc cw-linac with variable output energy from 3.7 to 7.5 MeV/u for ions with mass to charge ratio of A/Z<6 is recently under development at HIM and GSI. Following the results of the latest RF-tests with the newly constructed sc CH-DTL cavity, even heavier ions up to Uranium 28+ could be potentially accelerated with the already reached higher RF-voltage. Also the possibility for an up to 10 MeV/u increased output energy, using the same 13 independent cavities, is under consideration. All these options require an advanced beam dynamics layout, as well as a versatile procedure for transverse and longitudinal beam matching along the entire linac. The proposed algorithms are discussed and the obtained simulation results are presented.

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TUPVA062

Construction of the MYRRHA Injector

quadrupole, diagnostics, beam-diagnostic, linac

2221

D. Mäder, H. Höltermann, H. Hähnel, D. Koser, K. Kümpel, U. Ratzinger, W. Schweizer
BEVATECH, Frankfurt, Germany
C. Angulo, J. Belmans, L. Medeiros Romão, D. Vandeplassche
Studiecentrum voor Kernenergie - Centre d'Étude de l'énergie Nucléaire (SCK•CEN), Mol, Belgium
M. Busch, H. Podlech
IAP, Frankfurt am Main, Germany

A collaboration of SCK•CEN, IAP and BEVATECH GmbH is currently constructing the room temperature CH section of the 16.6 MeV CW proton injector for the MYRRHA project. The elaboration of all the construction readiness files for the construction of the accelerating cavities of the first CH section (1.5 to 5.9 MeV) is ongoing. In parallel, the planning, development and fabrication of all further components of this accelerator section is in progress, while the full study for the remaining section is under preparation. This contribution is documenting the most recent status.

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TUPVA063

RF Tuning Tests on the Coupled FRANZ RFQ-IH-DTL

rfq, DTL, coupling, resonance

2224

A. Almomani, U. Ratzinger
IAP, Frankfurt am Main, Germany
M. Heilmann
GSI, Darmstadt, Germany

The neutron beam at the FRANZ facility will be produced by the 7Li(p, n)7Be reaction using an intense 2 MeV proton beam. These protons will be accelerated from 120 keV to 2 MeV by a coupled 4-Rod-type RFQ and a 8 gap interdigital H-type structure (IH-DTL). This coupled RFQ-IH-cavity will be operated at 175 MHz in cw mode and it has a total length of about 2.3 m. The two structures (RFQ, IH-DTL) are internally coupled inductively, and consequently only one RF-amplifier providing a total power up to 250 kW is needed for operation. The IH-DTL is RF tuned together with an Al-RFQ model, before final IH-DTL installation in the FRANZ cave, while the original RFQ was already installed in the beam line. After RF power and beam tests the coupled structure will be installed and continued with RF and beam. This paper will be focused on the RF tuning process and the main results will be presented.

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TUPVA064

Updated Cavities Design for the FAIR p-Linac

linac, proton, quadrupole, coupling

2227

A. Almomani, M. Busch, F.D. Dziuba, U. Ratzinger, R. Tiede
IAP, Frankfurt am Main, Germany
F.D. Dziuba, C.M. Kleffner
GSI, Darmstadt, Germany

The research program of antiproton beams for the FAIR facility requires a dedicated 68 MeV, 70 mA proton injector. This injector will consist of an RFQ followed by six room temperature Crossbar H-type CH-cavities operated at 325 MHz. The beam dynamics had been revised by IAP Frankfurt in collaboration with GSI-FAIR in Darmstadt to further optimize the design. This step was followed by cavity RF design. The detailed mechanical cavity design will begin in 2017, while the quadrupole lenses are under production already. In this paper, besides an overview the RF design of the coupled cavities with integrated focusing triplets will be a main focus.

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TUPVA068

The New Injector Design for MYRRHA

simulation, emittance, impedance, rfq

2234

K. Kümpel, P. Müller, D. Mäder, N.F. Petry, H. Podlech
IAP, Frankfurt am Main, Germany

The MYRRHA (Multi-purpose hYbrid Research Reactor for High-tech Applications) Project is a planned accelerator driven system (ADS) for the transmutation of long-living radioactive waste. A critical passage for the beam quality and especially for the emittance is the injector. Therefore, a new injector design with improved beam dynamics has been developed, featuring low emittance growth rates while using only room temperature structures. The previous design consisted of a 4-Rod RFQ, 7 room temperature and 5 superconducting CH-DTL cavities and 2 rebuncher cavities, whereas the superconducting cavities in the new design have been replaced by 8 room temperature CHs and an additional rebuncher. The main challenge during the development is achieving the required reliability to reduce the thermal stress inside the planned reactor. Therefore, simulations with CST MICROWAVE STUDIO have been made to compare several cooling concepts and to optimize the cavities, especially in terms of the shunt impedance.

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TUPVA069

Test of a High Power Room Temperature CH DTL Cavity

operation, coupling, impedance, DTL

2237

N.F. Petry, S. Huneck, K. Kümpel, H. Podlech, U. Ratzinger, M. Schwarz
IAP, Frankfurt am Main, Germany

The Frankfurt Neutron Source at the Stern-Gerlach-Zentrum (FRANZ) is planned to deliver ultra-short neutron pulses at high intensities and repetition rates. As part of FRANZ a 175 MHz room temperature 5-gap CH DTL cavity was designed and built. Its main task will be focusing the particle bunch longitudinally at 2 MeV particle energy. Furthermore the CH cavity can also be used to increase the energy as well as decrease it by 0.2 MeV. The rebuncher and its cooling system is optimized to work with a 5 kW amplifier. The amplification system is intended to provide continuous power (cw mode). Due to its operating parameters being nearly identical to the requirements of the MYRRHA (Multi-purpose hYbrid Research Reactor for High-tech Applications) Project, experience for future cavity designs was gained. This includes considerations concerning cooling with use of a 12 kW amplifier. The recent results of conditioning and high power tests will be presented.

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TUPVA072

Conceptual Injector Design for an Electron-Ion-Collider Front-End

ion, rfq, linac, heavy-ion

2246

H. Podlech, M. Busch, M. Schwarz
IAP, Frankfurt am Main, Germany
R.C. York
NSCL, East Lansing, Michigan, USA
C. Zhang
GSI, Darmstadt, Germany

An electron-hadron collider (EIC) could be the next large-scale nuclear physics facility in the United States. A hadron linac with a final energy of 40 AMeV (heavy ions) and up to 130 MeV for protons with an upgrade path to higher energies is required as the first step of the hadron accelerator chain. From a cost point of view superconducting technology seems to be the better choice above an energy of about 5 AMeV compared to a room temperature (rt) solution. This paper describes the conceptual design of a rt front-end up to an energy of 5 AMeV appropriate as initial element of the EIC hadron linac. It consists of two separate injectors based on efficient H-mode cavities, one optimized for heavy ions (Pb³⁰⁺) and the other optimized for protons and deuterons. Beam dynamics and first RF simulations are presented.

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TUPVA084

Quasi-Frozen Spin Concept of Deuteron Storage Ring as an Instrument to Search for the Electric Dipole Moment

lattice, dipole, sextupole, experiment

2275

V. Senichev, A.E. Aksentyev
FZJ, Jülich, Germany
A.E. Aksentyev
MEPhI, Moscow, Russia
S.N. Andrianov, A.N. Ivanov
St. Petersburg State University, St. Petersburg, Russia
M. Berz, E. Valetov
MSU, East Lansing, Michigan, USA
S. Chekmenev, J. Pretz
RWTH, Aachen, Germany

One of the possible arguments for the breaking of CP invariance is the existence of non-vanishing electric dipole moments (EDM) of elementary particles. Currently, the Jülich Electric Dipole Moment Investigation (JEDI) collaboration works under the conceptual design of the ring specifically for search of the deuteron electrical dipole moment (dEDM). The proposed Quasi-Frozen Spin concept differs from the Frozen Spin concept in that the spin of the reference particle is alternately deflected by a few degrees in different directions relative to momentum in the electric and magnetic parts of the ring. The QFS concept will allow using the existing COSY ring as pilot facility. The paper presents conceptual approach to ring design based on results of a study of spin decoherence and systematic errors, as well as the sensitivity estimation of the method to the determination of EDM.

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TUPVA088

Observing Suppression of Syncrotron Oscillation Amplitudes

synchrotron, acceleration, betatron, dipole

2284

K. Jimbo
Kyoto University, Kyoto, Japan

We proposed a method to reduce loosing particles in acceleration stage of synchrotrons. A slowly varying horizontal electrostatic field may be useful to de-excite synchrotron oscillations. Then we have to somehow observe the damping of amplitudes of synchrotron oscillations to confirm the effect. We assume that the synchrotron component of rationalized Hamiltonian in acceleration stage is kept constant. Our experimental results did not contradict with this assumption. Taking advantage of this assumption, we can easily confirm the damping of synchrotron oscillation amplitudes experimentally through the increase of synchrotron frequencies.
jimbo@iae.kyoto-u.ac.jp

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TUPVA091

Batch Compression Scheme for Multi-MW J-PARC

injection, booster, beam-loading, proton

2294

C. Ohmori, M. Furusawa, K. Hara, K. Hasegawa, Y. Sugiyama, M. Yoshii
KEK, Tokai, Ibaraki, Japan
M. Nomura, T. Shimada, F. Tamura, M. Yamamoto
JAEA/J-PARC, Tokai-mura, Japan

Replacement of all J-PARC MR cavities has completed in this summer to increase the RF voltage. Nine sets of new high-gradient FT3L cavities will generate the required RF voltage for the 1.16 second cycle operation. Upgrade of magnet power supplies is planned and the cycle time becomes 1.3 seconds from the present 2.48 seconds in FY2018 to achieve the beam power of 750 kW-1 MW. For the further improvement of beam power, a new rapid-cycling booster is considered to increase the injection energy of the MR from 3 GeV to 6-8 GeV. By the reduction of the space charge effects, the injection time can be extended and a batch compression scheme becomes possible. It will increase the number of bunches from 8 to 11 or 12 during the beam injection. And, recent beam study of the 3 GeV RCS shows the potential capability of 6.6·10¹³ proton per bunch. Combining these improvements with the booster, the beam power of 3 MW will be manageable.

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TUPVA092

An Upgrade Scenario of RF System to Achieve 1.6 MW Beam Acceleration in J-PARC RCS

power-supply, resonance, acceleration, impedance

2297

M. Yamamoto, M. Nomura, T. Shimada, F. Tamura
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
K. Hara, K. Hasegawa, C. Ohmori, Y. Sugiyama, M. Yoshii
KEK, Tokai, Ibaraki, Japan

The J-PARC RCS has successfully accelerated 1 MW equivalent proton beam. However, the beam commissioning results and the particle tracking simulation suggest that the RCS has possibility to accelerate up to 1.6 MW beam. Since the power supply of the rf system almost reaches the limit under the condition of 1 MW beam, we consider the possible upgrade scenario of the rf system to accelerate 1.6 MW beam.

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TUPVA098

Beam Commissioning of Transport Line LRBT of CSNS

linac, emittance, DTL, beam-transport

2314

Z.P. Li, Y. Li, J. Peng, S. Wang
IHEP, Beijing, People's Republic of China

The linac to ring beam transport line (LRBT) connects the 80 MeV linac and the 1.6 GeV rapid cycling synchrotron (RCS) of the China spallation neutron source (CSNS). The linac and LRBT commissioning have been in progress in the past months and the H⁻ beam has been accelerated to the kinetic energy of 60MeV this April. The H⁻ beam in LRBT which was measured and commissioned transported through the long beam line with low loss. The beam commissioning process and results of LRBT are presented and discussed.

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TUPVA100

High Power Conditioning and First Beam Acceleration of the CSNS DTL-1

DTL, vacuum, acceleration, linac

2320

Y. Wang, A.H. Li, B. Li, J. Peng, P.H. Qu, X.L. Wu
CSNS, Guangdong Province, People's Republic of China
Q. Chen, M.X. Fan, K.Y. Gong, H.C. Liu
IHEP, Beijing, People's Republic of China

The CSNS DTLs are divided into 4 cavities. The DTL-1 was transferred and installed in the CSNS Linac tunnel in August of 2015. The RF high power conditioning of DTL-1 started in December 2015 and ended in February 2016. At the end, we finished DTL-1 high power conditioning mission with peak power 1.5MW (1.1 times design value), 1.625% duty factor (650us, 25Hz). And the first beam has been successfully accelerated to the design value 21.6MeV with nearly 100% transmission efficiency. In this paper, the details of conditioning process were presented and one severe RF discharge breakdown was described specifically, which occurred during high power conditioning.

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TUPVA104

RF and Primary Beam Dynamics Design of a 325 MHz IH-DTL

DTL, proton, linac, simulation

2332

Y. Lei, X. Guan, C.-X. Tang, R. Tang, X.W. Wang, Q.Z. Xing, S.X. Zheng
TUB, Beijing, People's Republic of China

An interdigital H-mode drift tube linac (IH-DTL), which is aimed at proton medical facilities, has been proposed and developing at Tsinghua University. Considering following 3 MeV RFQ in the platform of CPHS (Compact Pulse Hadron Source at Tsinghua University) and XiPAF (Xi‘an Proton Application Facility) project, the input energy of IH-DTL is 3 MeV and the RF frequency is 325 MHz. The proton beam can be accelerated from 3 MeV to 7 MeV and the peak current of the beam at the exit of the cavity is about 15 mA. In order to simplify the fabrication, A KONUS structure without focusing element in the cavity is chosen. The RF design of single CELL and the primary dynamics design is done. The co-iteration of dynamics simulation and RF calculation of whole cavity is undergoing.

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TUPVA108

Development of 1 MeV/n RFQ for Ion Beam Irradiation

rfq, ion, ion-source, vacuum

2343

H.S. Kim
KAERI, Daejon, Republic of Korea
Y.-S. Cho, H.-J. Kwon, Y.G. Song, S.P. Yun
Korea Atomic Energy Research Institute (KAERI), Gyeongbuk, Republic of Korea

Funding: This work has been supported through KOMAC (Korea Multi-purpose Accelerator Complex) operation fund of KAERI by MSIP (Ministry of Science, ICT and Future Planning).
For the purpose of the ion beam irradiation, especially for helium beam application to semiconductor industry, an ion beam RFQ is under development at KOMAC (Korea Multi-purpose Accelerator Complex). The output energy of the RFQ is determined to be 1 MeV/n, which corresponds to 4 MeV in helium beam case, in consideration of the penetration depth in the silicon substrate. The RFQ is a four-vane type and will be fabricated through vacuum brazing technique. The RF power of 130 kW at 200 MHz will be provided to the RFQ by using a solid-state RF amplifier through two coaxial RF couplers with coaxial RF windows. The details of the RFQ development including some design features and fabrication methods will be given in this paper.

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TUPVA120

Design and Fabrication of ESS-Bilbao RFQ Linac

rfq, vacuum, proton, simulation

2373

J.L. Muñoz, I. Bustinduy, I. Rueda, D. de Cos
ESS Bilbao, Zamudio, Spain

The RFQ accelerator for ESS-Bilbao is presented. This device will complete ESS-Bilbao injection chain after the ion source and LEBT. Design, carried out by ESS-Bilbao team, was finished in 2015. Machining has started in 2016. The RFQ is a 4-vane structure, aimed to accelerate protons from 45 keV to 3.0 MeV and operating at 352.2 MHz. It has a total length of about 3.1 meters, divided in 4 segments. Segments themselves are formed by 2 major and 2 minor vanes, assembled together by using polymeric vacuum gaskets instead of brazing or other welding system. In this paper the design is presented, including the beam dynamics, RF cavity design, field flatness and frequency tuning. Cooling and thermo-mechanical design is also described. Mechanical design, including vacuum strategy and test models, is also briefly described (there is a dedicated poster on this). The first segment fabrication is scheduled to finish before the end of 2016, so vacuum and low power RF tests results would also be included in the presented paper.

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TUPVA129

Energy Efficiency and Saving Potential Analysis of the High Intensity Proton Accelerator HIPA at PSI

cyclotron, proton, neutron, cryogenics

2399

A. Kovach, J. Grillenberger, A.S. Parfenova, M. Seidel
PSI, Villigen PSI, Switzerland

High power proton machines consume a large amount of energy. Thus, the energy efficiency of grid to beam power conversion is particularly important for the overall power consumption of such facilities. In this study, we analyse the energy efficiency of PSI's cyclotron-based HIPA facility, which presently delivers a maximum of 1.4 MW beam power. The total power consumption of the entire facility is 12.5 MW at 2.2 mA beam current (1.3 MW). Main power consumers are: RF systems, electromagnets, water cooling and auxiliary systems including infrastructure, each consuming 5.3 MW, 3.6 MW, 1.65 MW and 1.95 MW, respectively. HIPA's grid to beam efficiency is 18.3% when considering only those parts of any subsystems (RF components, magnets, cooling, and auxiliary systems), which are minimally required to produce a full 1.3 MW beam. The dependency of individual subsystems on beam power was also studied. These findings serve as a basis for further optimizations of the HIPA facility and give a reference of the efficiency estimate for the cyclotron-based high power machines.
* https://www.psi.ch/enefficient/

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TUPVA140

Space charge effects of catch-up collision in a CW double-pass proton linac

simulation, linac, proton, space-charge

2429

Y. Tao, K. Hwang, J. Qiang
LBNL, Berkeley, California, USA

Recirculating superconducting proton linac has an advantage to reduce the number of cavities and the resulting accelerator construction/operation costs. Beam dynamics simulations were done recently in a double pass recirculating proton linac using a single bunch. For continuous wave (CW) operation, the high energy proton beam bunch during the second pass will catch up and collide with the low energy proton bunch at a number of locations inside the superconducting linac. In this paper, we report on the study of the space-charge effects during a collision on both beams through the rest of the linac.

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TUPVA154

Project-Based Cooperative Learning in Accelerator Science and Technology Education

dipole, feedback, FEL, quadrupole

2458

G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
R.B. Appleby, G.X. Xia
UMAN, Manchester, United Kingdom
I.R. Bailey
Lancaster University, Lancaster, United Kingdom
J.A. Clarke, O.B. Malyshev, N. Marks, B.D. Muratori, M.W. Poole, Y.M. Saveliev, B.J.A. Shepherd
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
C.P. Welsch, A. Wolski
The University of Liverpool, Liverpool, United Kingdom

Funding: The work is funded by STFC via the Cockcroft Institute core grant.
The next generation of particle accelerators will require the training of greater numbers of specialist accelerator physicists and engineers . These physicists and engineers should have a broad understanding of accelerator physics as well as the technology used in particle accelerators as well as a specialist in some area of accelerator science and technology . Such specialists can be trained by combining a University based PhD, in collaboration with national laboratory training with a broad taught accelerator lecture program. In order to have a faster start we decided to run an intensive two week school to replace the basic course at the Cockcroft Institute. At the same time we decided to investigate the use of problem based learning to simulate the way accelerator science tends to work in practice. In this exercise he students worked in groups of 5 to design a 3rd generation light source from scratch based on photon light specifications. In comparison to similar design exercises we stipulate that all students must do all parts and students are not allowed to specialise. A comparison with a standard lecture based education programme is discussed in this paper.

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WEYA1

Crab Cavity Systems for Future Colliders

collider, luminosity, electron, proton

2474

S. Verdú-Andrés, I. Ben-Zvi, Q. Wu
BNL, Upton, Long Island, New York, USA
I. Ben-Zvi
Stony Brook University, Stony Brook, USA
R. Calaga
CERN, Geneva, Switzerland

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy, by the US LARP program and by the HL-LHC project.
KEKB was the first facility to implement the crab crossing technique in 2007, for the interaction of electron and positron beams. The High Luminosity Large Hadron Collider (HL-LHC) project envisages the use of crab cavities for increasing and levelling the luminosity of proton-proton collisions in LHC. Crab cavities have also been proposed and studied for future colliders like CLIC, ILC and eRHIC. This contribution will focus on the near and far future of crab cavities for particle colliders.

Slides WEYA1 [6.571 MB]

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WEZB1

Review and Prospects of RF Solid State Amplifiers for Particle Accelerators

coupling, power-supply, booster, vacuum

2537

P. Marchand
SOLEIL, Gif-sur-Yvette, France

Thanks to the growth of high power semiconductor technology, solid state power amplifier (SSPA) systems with several hundred kW RF power are now available for various accelerator fields. Following the successful development at 352 MHz that took place at SOLEIL in the 2000s, the technology was transferred to industry and SSPAs at different frequencies, power levels, and pulse lengths have been widely adopted. In this paper we report about the SOLEIL experience with SSPAs and review the used or planned SSPAs in other accelerator facilities.

Slides WEZB1 [13.860 MB]

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WEPAB003

The Danish Synchrotron Radiation Light Source ASTRID2

quadrupole, synchrotron, dipole, operation

2561

J.S. Nielsen, N. Hertel, S.P. Møller
ISA, Aarhus, Denmark

The ASTRID2 synchrotron light source has now been in user operation for more than 3 years, and most of the initially unresolved minor issues have been dealt with. This paper will report on the solutions, and give an over-view of the current status. The problem of the fast injection bumpers, which overheated at high currents, has been solved. The 3rd harmonic Landau cavity has been installed, and it has resulted in a much better lifetime and a more stable beam. We observe vertically unstable beams above a given threshold beam current. Initially this threshold was quite low, but with time, as the vacuum chambers have been conditioned more and more, the threshold has increased steadily, and is now close to the design current of 200 mA. It is planned to add 3 more power supplies to each of the pole-face windings, which are found in all 12 dipoles. These three supplies will in addition to the original quadrupole correctors give a vertical corrector, a horizontal corrector and a skew quadrupole corrector. Furthermore we are presently producing a new timing system, which will allow us to run single-bunch operation, and a fast orbit feedback system.

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WEPAB047

Concept of a New Generation Synchrotron Radiation Facility KEK Light Source

lattice, undulator, emittance, brightness

2687

T. Honda
KEK, Ibaraki, Japan

KEK has proposed a new SR facility: KEK Light Source (KEK-LS) towards the completion of the first half of the 2020s. The energy and the natural horizontal emittance are 3 GeV and 0.13 nm rad, respectively. To mitigate the intra-beam scattering effect, we are planning to install third harmonic RF cavities. The extremely low emittance ring has been designed based on the Hybrid Multi-Bend Achromatic (HMBA) lattice, which was originally developed at the ESRF upgrade project. We have modified it to insert a short straight section at the center of the unit cell. The number of unit cells is 20, and the circumference is about 570 m. Except for an RF section and an injection section, the ring can accommodate 18 undulators in the long straight sections of 5.6 m, and the additional 20 short straight section of 1.2 m will be used for short-period narrow-gap undulators. If we assume an undulator of the magnetic period 20 mm, total length 5.0 m, and the smallest gap 4 mm, the SR brightness approaches 10²² Photons/mrad²/mm²/s/0.1%B.W. at the X-ray range. It has a high coherent fraction of about 20% at the diffraction limit wavelength 0.32 keV.

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WEPAB087

TARLA: The First Facility of Turkish Accelerator Center (TAC)

electron, FEL, laser, linac

2776

A.A. Aksoy, A.A. Aydin, C. Kaya
Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey
B. Ketenoğlu, O. Yavaş
Ankara University, Faculty of Engineering, Tandogan, Ankara, Turkey

Funding: Work supported by Ministry of Development of Turkey
Turkish Accelerator and Radiation Laboratory in Ankara (TARLA) is proposed as first accelerator based infrastructure in Turkey as a first step Turkish Accelerator Center (TAC). The facility under construction at Institute of Accelerator Technologies of Ankara University since 2012. Based superconducting technology, TARLA accelerator will offer a multi-experiment facility providing various accelerator-based radiation sources for the users coming from different fields like physics, chemistry, biology, material sciences, medicine and nanotechnology. Two of the planed free-electron laser (FEL) beamlines of TARLA will provide Continuous Wave (CW) tunable radiation of high brightness in the mid- and far-infrared regime. In addition a Bremmstrahlung radiation station is proposed within current scope of TARLA. In this paper current status of facility is presented.

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WEPAB094

Diamond: Ten Years of Operation

operation, vacuum, storage-ring, controls

2797

V.C. Kempson
DLS, Oxfordshire, United Kingdom

In January 2017 Diamond Light Source reached ten years of operation, providing beam to beam lines and users. At the start of operations there was an initial suite of 7 beam lines, phase 1. We are now in the later part of a phase 3 beam line upgrade bringing the total number of beam lines up to 29+ which is close to maximum capacity. The 3GeV storage ring has had a number of modifications and improvements across the last 10 years culminating in the recent (Autumn 2016) addition of a major local lattice modification, DDBA , reported elsewhere at this conference. This review paper will look at machine improvements operationally and machine developments that improved overall performance.

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WEPAB096

Diamond Light Source: A 10-year View of the Past and Vision of the Future

vacuum, operation, feedback, emittance

2804

R.P. Walker, R. Bartolini, C. Christou, P. Coll, M.P. Cox, M.T. Heron, J. Kay, V.C. Kempson, S. Milward, G. Rehm
DLS, Oxfordshire, United Kingdom
R. Bartolini
JAI, Oxford, United Kingdom

Diamond Light Source has been in regular operation for users for 10 years and so it is an appropriate moment to review the successes and challenges of the past, and also consider the vision for the next 10 years.

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WEPAB099

Development of the Manufacturing and QA Processes for the LCLS-II Injector Source VHF Electron Gun

gun, operation, site, electron

2815

J.A. Doyle, J.N. Corlett, M.J. Johnson, R. Kraft, T.D. Kramasz, D. Leitner, S.P. Virostek
LBNL, Berkeley, California, USA

Funding: * This work is supported by the Office of Science, United States Department of Energy under DOE contract DE-AC02-05CH11231.
The Linear Coherent Light Source-II (LCLS-II), a new free electron laser currently under construction at SLAC, requires a high repetition rate, high brightness, continuous wave electron source. Lawrence Berkeley National Laboratory (LBNL) has developed a design for a normal conducting VHF gun in response to that need and is responsible for its production and that of the associated beamline, with much of the fabrication done in-house. The 186 MHz copper cavity dissipates approximately 90 kW of RF power while maintaining a vacuum pressure on the order of 10^-10 Torr. The gun is a critical component that requires a very high level of operational reliability to ensure uninterrupted availability for future system users. A quality assurance system to instruct manufacturing and change control is vital to ensure production of a gun that reliably meets physics requirements over an extended period of usage. This paper describes the QA processes developed for fabrication and assembly of the Injector Source electron gun along with results and lessons learned from their current implementation.

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WEPAB115

Normal Conducting CW Transverse Crab Cavity For Producing Short Pulses In SPEAR3

HOM, impedance, damping, photon

2840

Z. Li, V.A. Dolgashev, M. Dunham, K.J. Gaffney, R.O. Hettel, X. Huang, N. Kurita, J.A. Safranek, J.J. Sebek, K. Tian
SLAC, Menlo Park, California, USA

Funding: This work was supported by DOE Contract No. DE-AC02-76SF00515.
The ability to produce short pulse X-rays on the scale of 1-10 ps fwhm in the SPEAR3 storage ring light source would enable enhanced timing mode studies of dynamic processes in materials as they occur. The crab cavity approach appears to be optimal for SPEAR3 to produce short pulse X-rays. Furthermore, by using a two-frequency crabbing scheme, SPEAR3 would be able to produce short-pulse bunches while supplying the high average flux needed for regular users. While supercon-ducting RF (SCRF) technology could be a natural choice for the CW crab cavity, the deflecting voltage for SPEAR3 crabbing appears to be within reach of more affordable normal conducting RF (NCRF). In this paper, we present a preliminary NCRF CW crab cavity design for SPEAR3.

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WEPAB125

Crossbar H-Mode Drift-Tube Linac Design With Alternative Phase Focusing for Muon Linac

linac, emittance, acceleration, dipole

2868

M. Otani, K. Futatsukawa
KEK, Tsukuba, Japan
K. Hasegawa, Y. Kondo
JAEA/J-PARC, Tokai-mura, Japan
R. Kitamura
University of Tokyo, Tokyo, Japan
S.S. Kurennoy
LANL, Los Alamos, New Mexico, USA

Funding: This work was supported by JSPS KAKENHI Grant Number 15H03666.
A crossbar H-mode (CH) drift-tube linac (DTL) is one of alternatives for a low velocity part in a muon linac at the J-PARC E34 experiment. It will accelerate muons from v/c = 0.08 to 0.28 at an operational frequency of 324 MHz. In order to achieve higher acceleration efficiency and make cost lower, an alternative phase focusing (APF) scheme is adopted. In this poster, dynamics and cavity designs with computer calculations will be presented.

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WEPAB138

Prototyping High-Gradient mm-Wave Accelerating Structures

accelerating-gradient, interface, experiment, RF-structure

2902

E.A. Nanni, V.A. Dolgashev, A.A. Haase, J. Neilson, S.G. Tantawi
SLAC, Menlo Park, California, USA
S.C. Schaub
MIT, Cambridge, Massachusetts, USA
B. Spataro
INFN/LNF, Frascati (Roma), Italy
R.J. Temkin
MIT/PSFC, Cambridge, Massachusetts, USA

We present single-cell accelerating structures designed for high-gradient testing at 110 GHz. The purpose of this work is to study the basic physics of ultrahigh vacuum RF breakdown in high-gradient RF accelerators. The accelerating structures are pi-mode standing-wave cavities fed with a TM01 circular waveguide. The structures are fabricated using precision milling out of two metal blocks, and the blocks are joined with diffusion bonding and brazing. The impact of fabrication and joining techniques on the cell geometry and RF performance will be discussed. First prototypes had a measured Qo of 2800, approaching the theoretical design value of 3300. The geometry of these accelerating structures are as close as practical to single-cell standing-wave X-band accelerating structures more than 40 of which were tested at SLAC. This wealth of X-band data will serve as a baseline for these 110 GHz tests. The structures will be powered with short pulses from a MW gyrotron oscillator. RF power of 1 MW may allow us to reach an accelerating gradient of 400 MeV/m.

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WEPIK036

ERL Cryomodule Testing and Beam Capabilities

linac, cryomodule, SRF, operation

3010

F. Furuta, N. Banerjee, J. Dobbins, R.G. Eichhorn, M. Ge, D.L. Hall, G.H. Hoffstaetter, M. Liepe, R.D. Porter, P. Quigley, D.M. Sabol, J. Sears, E.N. Smith, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

The main linac cryomodule (MLC) prototype is a key component for the Cornell-BNL ERL Test Accelerator (CBETA) project, which is a 4-turn FFAG ERL under construction at Cornell University. This novel cryomodule is the first SRF module ever to be fully optimized simul-taneously for high efficient SRF cavity operation and for supporting very high CW beam currents. Initial MLC testing has demonstrated that cavity performance and HOMs damping meet specification values. Recent, addi-tional tests have focused on RF field stability, and cavity microphonics. In this paper, we summarize the perfor-mance of this novel ERL cryomodule and evaluate its beam capabilities based on the measured performance.

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WEPIK043

Modeling Local Crabbing Dynamics in the JLEIC Ion Collider Ring

ion, lattice, emittance, luminosity

3022

S.I. Sosa Guitron, J.R. Delayen
ODU, Norfolk, Virginia, USA
V.S. Morozov
JLab, Newport News, Virginia, USA

The Jefferson Lab Electron-Ion Collider (JLEIC) design considers a 50 mrad crossing angle at the Interaction Point. Without appropriate compensation, this could geometrically reduce the luminosity by an order of magnitude. A local crabbing scheme is implemented to avoid the luminosity loss: crab cavities are placed at both sides of the interaction region to restore a head-on collision scenario. In this contribution, we report on the implementation of a local crabbing scheme in the JLEIC ion ring. The effects of this correction scheme on the stability of proton bunches are analyzed using the particle tracking software elegant.

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WEPIK044

Effects of Crab Cavitiy Multipoles on JLEIC Ion Ring Dynamic Aperture

multipole, ion, dynamic-aperture, dipole

3025

S.I. Sosa Guitron, S.U. De Silva, J.R. Delayen
ODU, Norfolk, Virginia, USA
V.S. Morozov
JLab, Newport News, Virginia, USA

We study the effects of crab cavity multipole fields on the beam dynamic aperture of the Jefferson Lab Electron-Ion Collider (JLEIC) ion ring. Crab cavities are needed to compensate for luminosity loss due to a 50 mrad crossing angle at the interaction point. New compact crab cavity designs are interesting as they do not require considerable space in the ring but their non-linear field needs to be well understood. In this contribution, we study the impact of field multipoles on the beam dynamic aperture and report tolerance values for crab cavity multipoles.

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WEPIK047

Frequency Choice Studies of eRHIC Crab Cavity

luminosity, ion, electron, simulation

3028

Y. Hao, Y. Luo, V. Ptitsyn
BNL, Upton, Long Island, New York, USA
J. Qiang
LBNL, Berkeley, California, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Crab crossing scheme is essential collision scheme to achieve high luminosity for the future electron-ion collider (EIC). Since the ion beam is long when cooling is not present, the nonlinear dependence of the crabbing kick may present a challenge to the beam dynamics of the ion beam, hence a impact to the luminosity lifetime. In this paper, we present the initial result of the weak-strong and strong-strong beam-beam tracking with the crab crossing scheme. The result provides beam dynamics guidance in choosing the proper frequency the crab cavity for the future EIC.

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WEPIK056

Compensation of Transient Beam Loading with Detuned Cavities at BESSY II

operation, experiment, beam-loading, synchrotron

3056

M. Ruprecht, P. Goslawski, F. Kramer, M. Ries
HZB, Berlin, Germany

This paper presents operational experience and use cases of cavity operation in the synchrotron light source BESSY II, where an active or passive cavity is detuned by a small fraction of the harmonic number. If the detuning is an integer multiple of the fundamental RF harmonic, the distortion of the longitudinal phase space is periodic with the revolution, which allows for the compensation of fill pattern induced transients. Measurements at BESSY II are presented, where a fundamental cavity is detuned to decrease the effects of transient beam loading. Thus, reducing the phase transient and increasing the beam life time. Calculations depicting the application of this scheme for the future project BESSY VSR[*] are presented.
* A. Jankowiak, J. Knobloch, P. Goslawski, and N. Neumann, eds., BESSY VSR - Technical Design Study, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 2015.

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WEPIK064

Eigenvalue Calculations Based on the Finite Element Method With Physically Motivated Field Smoothing Using the Kirchhoff Integral

electromagnetic-fields, simulation, extraction, radio-frequency

3074

W. Ackermann, H. De Gersem, T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany

In current linear particle accelerators, the actual acceleration of the charged particles is realized with the help of the electric field strength within driven radio frequency resonators. The characterization and optimization of the applied resonating structures can be reliably performed based on numerical simulation techniques. Efficient numerical methods have been introduced in the last decades to determine the electromagnetic fields while special care has been put in the correct description of the geometry and the material distribution of the structures. Although the resonators are operated in a driven setup, one of the advantageous numerical strategies here is given by an eigendecomposition of the fields which is realized by the application of accurate eigenmode calculations together with suitable postprocessing steps. In particular, the extraction of representative field maps used for particle tracking for example requires an accurate numerical modeling of the field at any position inside the structure. In order to avoid numerically motivated discontinuities of the fields a proper smoothing algorithm based on the vector equivalents of the Kirchhoff integral is proposed.

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WEPIK106

Impedance and Collective Effects for the Advanced Light Source Upgrade at LBNL

impedance, simulation, wakefield, vacuum

3192

S. Persichelli, J.M. Byrd, S. De Santis, D. Li, T.H. Luo, C. Steier, M. Venturini
LBNL, Berkeley, California, USA

Funding: Work supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
The upgrade of the Advanced Light Source (ALS-U) consists of a multiband achromat ultralow emittance lattice for the production of diffraction-limited soft x-rays. A very important issue for ALS-U is represented by instabilities induced by wakefields, that may limit the peak current of individual bunches and the total beam current. In addition, vacuum chamber apertures of few millimeters, that are a key feature of low-emittance machines, can result in a significant increase in the Resistive Wall (RW) impedance. In this paper we present progress on establishing short range wakefield model for ALS-U and evaluating the impact on the longitudinal and transverse single-bunch dynamics.

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WEPIK112

A 2D Finite Element Solver for Electromagnetic Fields with m-fold Azimuthal Symmetry

operation, simulation, interface, gun

3211

A.R. Vrielink, M.H. Nasr, S.G. Tantawi
SLAC, Menlo Park, California, USA

Radiofrequency (RF) cavities for use in accelerators, from RF sources to accelerating and transverse cavities, often exhibit m-fold azimuthal symmetry. For cases where m>0, commercially available finite element codes used to simulate the beam-wave interaction typically require a full 3D simulation. We have derived a finite element formulation which accounts for the known azimuthal dependence of the electromagnetic fields, allowing us to solve for these problems on a 2D mesh and reducing simulation times significantly. The theory, including the construction of the local finite element matrices and the selection of appropriate basis functions, will be presented in addition to numerical results.

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WEPIK118

Synchronous Phase Shift from Beam Loading Analysis

beam-loading, storage-ring, operation, resonance

3227

G. Bassi, A. Blednykh, J. Rose, V.V. Smaluk, J. Tagger
BNL, Upton, Long Island, New York, USA

We discuss measurements, performed in the NSLS-II storage ring, of the synchronous phase shift as a function of single bunch current from beam loading parameters. The synchronous phase is calculated from the forward and reflected power measured in the RF cavities. The comparison with direct synchronous phase measurements shows good agreement.

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WEPVA002

Simulations of DLA Grating Structures in the Frequency Domain

laser, simulation, electron, acceleration

3247

T. Egenolf, O. Boine-Frankenheim, U. Niedermayer
TEMF, TU Darmstadt, Darmstadt, Germany
O. Boine-Frankenheim
GSI, Darmstadt, Germany

Dielectric laser accelerators (DLA) driven by ultrashort laser pulses can reach orders of magnitude larger gradients than contemporary RF electron accelerators. A new implemented field solver based on the finite element method in the frequency domain allows the calculation of the structure constant, i.e. the ratio of energy gain to laser peak amplitude. We present the maximization of this ratio as a parameter study looking at a single grating period only. Based on this optimized shape the entire design of a beta-matched grating is completed in an iterative process. The period length of a beta-matched grating increases due to the increasing velocity of the electron when a subrelativistic beam is accelerated. The determination of the optimal length of each grating period thus requires the knowledge of the energy gain within all so far crossed periods. Furthermore, we outline to reverse the excitation in the presented solver for beam coupling impedance calculations and an estimation of the beam loading intensity limit.

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WEPVA036

The LHC Injectors Upgrade (LIU) Project at CERN: Proton Injector Chain

linac, injection, impedance, proton

3335

K. Hanke, J. Coupard, H. Damerau, A. Funken, B. Goddard, A.M. Lombardi, D. Manglunki, S. Mataguez, M. Meddahi, B. Mikulec, G. Rumolo, R. Scrivens, E.N. Shaposhnikova, M. Vretenar
CERN, Geneva, Switzerland

The LHC Injectors Upgrade (LIU) project at CERN aims at delivering high brightness beams required by the LHC in the high-luminosity LHC (HLLHC) era. The project comprises a new H⁻ Linac (Linac4) as well as a massive upgrade of the PS Booster, PS and SPS synchrotrons. This paper gives an update of the activities regarding the proton injector chain. We present the target beam parameters, a brief status of the upgrade work per machine and the outcome of the recent reviews. The planning for the implementation of the hardware upgrades and the re-commissioning of the complex will also be discussed.

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WEPVA047

Input Signal Generation for Barrier Bucket RF Systems at GSI

synchrotron, storage-ring, operation, impedance

3359

J. Harzheim, D. Domont-Yankulova, K. Groß, H. Klingbeil
TEMF, TU Darmstadt, Darmstadt, Germany
M. Frey, H. Klingbeil
GSI, Darmstadt, Germany

At the GSI facility in Darmstadt, Germany, Barrier Bucket RF systems are currently designed for the SIS 100 synchrotron (part of the future FAIR facility) and the Experimental Storage Ring (ESR). The purpose of these systems is to provide single sine voltage pulses at the cavity gap. Due to the high requirements regarding the gap signal quality, the calculation of the pre-distorted input signal plays a major role in the system development. A procedure to generate the input signal based on the dynamic properties in the linear region of the system has been developed and tested at a prototype system. It was shown that this method is able to generate single sine gap signals of high quality in a wide voltage range. As linearity can only be assumed up to a certain magnitude, nonlinear effects limit the quality of the output signal at very high input levels. An approach to overcome this limit is to extend the input signal calculation to a nonlinear model of the system. In this contribution, the current method to calculate the required input signal is presented and experimental results at a prototype system are shown. Additionally, first results in the nonlinear region are presented.

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WEPVA062

Improvements of Vacuum System in J-PARC 3 GeV Synchrotron

vacuum, injection, kicker, operation

3408

J. Kamiya, Y. Hikichi, M. Kinsho, Y. Namekawa, K. Takeishi, T. Yanagibashi
JAEA/J-PARC, Tokai-mura, Japan
A. Sato
Nippon Advanced Technology Co., Ltd., Tokai, Japan

The RCS vacuum system has been upgraded since the completion of its construction towards the objectives of both better vacuum quality and higher reliability of the components. For the better vacuum quality, (1) pressure of the injection beam line was improved to prevent the H⁻ beam from converting to H0; (2) leakage in the beam injection area due to the thermal expansion was eliminated by applying the adequate torque amount for the clamps; (3) new in-situ degassing method of the kicker magnet was developed. For the reliability increase of the components, (1) A considerable number of fluoroelastmer seal was exchanged to metal seal with the low spring constant bellows and the light clamps; (2) TMP controller for the long cable was developed to prevent the controller failure by the severe electrical noise; (3) A number of TMP were installed instead of ion pumps in the RF cavity section as an insurance for the case of pump trouble.

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WEPVA121

Thermal Experimet Results on TPS Beam Position Monitors

impedance, simulation, storage-ring, vacuum

3554

Y.T. Huang, C.K. Chan, J. -Y. Chuang, I.C. Sheng, Y.C. Yang
NSRRC, Hsinchu, Taiwan

Beam position monitors mounted in straight sections exhibit an unusual temperature rise which is attributed to poor thermal and electrical conductivity of the stainless steel BPM chamber, to the vicinity to RF-bellows, and the large button electrode size to get superior signal levels. Thermocouples tied to BPM flanges and RF bellows show that the temperature could reach 50 oC when storing a beam current of 400 mA and BPMs located between two RF-bellows in RF cavity sections responds by even 5-10 oC higher values than average. To resolve this issue, off site experiments and simulations were conducted to further understand the heat flow in the whole structure. In this paper we discuss more details of these studies.

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WEPVA134

Impedance Measurement of Vacuum Chamber Components for the Advance Photon Source (APS) Upgrade

impedance, simulation, vacuum, photon

3583

M.P. Sangroula
IIT, Chicago, Illinois, USA
R.M. Lill, R.R. Lindberg, X. Sun
ANL, Argonne, Illinois, USA

Funding: U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC0206CH11357.
The proposed Advance Photon Source Upgrade (APS-U) employs a multi-bend achromat (MBA) lattice to increase the photon brightness by two to three orders of magnitude. One of the main design challenges of the upgrade is to minimize rf heating and collective instabilities associated with the impedance of small-aperture vacuum components. As part of this effort, my research focuses on impedance measurement and simulation of various MBA vacuum components. Here, we present the summary of the impedance contributions for the APS-U and describe our planned impedance measurement technique, including some measurement results for the non-evaporative getter (NEG)-coated copper chamber and simulation results for other critical components using a novel Goubau line (G-line) set up.

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WEPVA145

Analysis of Mean Free Path and Field Dependent Surface Resistance

niobium, SRF, electron, radio-frequency

3609

J.T. Maniscalco, F. Furuta, D.L. Hall, P.N. Koufalis, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: NSF-PHY 1416318
Work from Cornell in 2016 built on recent theoretical research in the field of SRF to link the electron mean free path to the field-dependent BCS surface resistance. This research relates the magnitude of the ‘‘anti-Q-slope'', the puzzling reduction of surface resistance with increasing RF field intensity observed in certain cavities, to the doping level of nitrogen-doped niobium, quantified by the mean free path: shorter mean free paths correspond directly with stronger anti-Q-slopes. The theoretical connection comes through the overheating of the quasiparticles, which more effectively transfer their energy to the lattice at short mean free paths. In this report, we present an update of this analysis, investigating recent test results of low-temperature-doped single-cell and nine-cell cavities. We also study the theoretical implications for cavities at frequencies higher and lower than the often-studied 1.3~GHz.

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THOAA1

Development of a DLLRF Using Commercial uTCA Platform

LLRF, FPGA, controls, synchrotron

3631

A. Salom, E. Morales, F. Pérez
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

The Digital LLRF of ALBA has been implemented using commercial cPCI boards with Virtex-4 FPGA, fast ADCs and fast DACs. The firmware of the FPGA is based on IQ demodulation technique and the main feed-back loops adjust the phase and amplitude of the cavity voltage and also the resonance frequency of the cavity. But the evolution of the market is moving towards uTCA technology and due to the interest of this technology by several labs, we have developed at ALBA a DLLRF using a HW platform based on uTCA commercial boards and Virtex-6 FPGA. The paper will present the development done and will compare it with respect the cPCI one.

Slides THOAA1 [1.381 MB]

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THOAA2

Research on Compensation of Superconducting Cavity Failures in C-ADS Injector-I

FPGA, hardware, space-charge, linac

3635

J.P. Dai, C. Meng, Y. Shao, Z. Xue, F. Yan
IHEP, Beijing, People's Republic of China

Funding: Work supported by Natural Science Foundation of China (11575216)
For the proton accelerators such as the China Accelerator Driven subcritical System(C-ADS), it is essential and difficult to achieve extremely high performance reliability requirement. In order to achieve this performance reliability requirement, in addition to hardware improvement, a failure tolerant design is mandatory. A compensation mechanism to cope with hardware failure, mainly RF failures of superconducting cavities, will be in place in order to maintain the high uptime, short recovery time and extremely low frequency of beam loss. This paper proposes an innovative and challenging way for compensation and rematch of cavity failure with the hardware implementation of the scheme using fast electronic devices and Field Programmable Gate Arrays (FPGAs). A method combined building an equivalent model for the FPGA with an improved genetic algorithm has been developed. Results based on the model and algorithm are compared with TRACEWIN simulation to show the precision and correctness of the mechanism.

Slides THOAA2 [2.414 MB]

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THOAA3

Installation and First Commissioning of the LLRF System for the European XFEL

LLRF, linac, operation, cryomodule

3638

J. Branlard, G. Ayvazyan, V. Ayvazyan, L. Butkowski, M. Fenner, M.K. Grecki, M. Hierholzer, M. Hoffmann, M. Killenberg, D. Kostin, D. Kühn, F. Ludwig, D.R. Makowski, U. Mavrič, M. Omet, S. Pfeiffer, H. Pryschelski, K.P. Przygoda, A.T. Rosner, R. Rybaniec, H. Schlarb, Ch. Schmidt, N. Shehzad, B. Szczepanski, G. Varghese, H.C. Weddig, R. Wedel, M. Wiencek, B.Y. Yang
DESY, Hamburg, Germany
W. Cichalewski, F. Makowski, A. Mielczarek, P. Perek
TUL-DMCS, Łódź, Poland
K. Czuba, P.K. Jatczak, T.P. Leśniak, K. Oliwa, D. Sikora, M. Urbański, W. Wierba
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
A.S. Nawaz
TUHH, Hamburg, Germany

The installation phase of the European X-ray free laser electron laser (XFEL) is finished, leaving place for its commissioning phase. This contribution summarizes the low-level radio frequency (LLRF) installation steps, illustrated with examples of its challenges and how they were addressed. The commissioning phase is also presented, with a special emphasis on the effort placed into developing LLRF automation tools to support the commissioning of such a large scale accelerator. The first results of the LLRF commissioning of the XFEL injector and first RF stations in the main linac are also given.

Slides THOAA3 [15.800 MB]

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THOBB3

ESS SRF Linear Accelerator Components Preliminary Results and Integration

SRF, cryomodule, linac, accelerating-gradient

3666

C. Darve, N. Elias, C.G. Maiano, F. Schlander
ESS, Lund, Sweden
C. Arcambal, G. Devanz, F. Peauger
CEA/DRF/IRFU, Gif-sur-Yvette, France
E. Cenni
CEA/IRFU, Gif-sur-Yvette, France
G. Costanza
Lund University, Lund, Sweden
P. Duthil, G. Olry, D. Reynet
IPN, Orsay, France
L. Hermansson
Uppsala University, Uppsala, Sweden
P. Michelato, D. Sertore
INFN/LASA, Segrate (MI), Italy

The European Spallation Source (ESS) is a pan-European project and one of world's largest research infrastructures based on neutron sources. This collaborative project is funded by a collaboration of 17 European countries and is under construction in Lund, Sweden. The 5 MW, 2.86 ms long pulse proton accelerator has a repetition frequency of 14 Hz (4 % duty cycle), and a beam current of 62.5 mA. The Superconducting Radio-Frequency (SRF) linac is composed of three families of Superconducting Radio-Frequency (SRF) cavities, which are being prototyped, counting the spoke resonators with a geometric beta of 0.5, medium-beta elliptical cavities (beta_g=0.67) and high-beta elliptical cavities (beta_g=0.86). After a description of the ESS linear accelerator layout, this article will focus on the recent progress towards integration of the first test results of the main critical components to be assembled in cryomodules, then in the ESS tunnel.

Slides THOBB3 [25.611 MB]

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THPAB003

Harmonic RF System for the ESRF EBS

impedance, simulation, beam-loading, synchrotron

3684

N. Carmignani, J. Jacob, B. Nash, S.M. White
ESRF, Grenoble, France

A harmonic RF system for bunch lengthening to increase the Touschek lifetime of the ESRF Extemely Brilliant Source (EBS) is under study. Multiparticle simulations have been performed to study the bunch lengthening and the bunch shape with impedance effect and with third or fourth harmonic cavities. The effect of a harmonic RF system on the microwave instability is studied, finding an increase in the threshold. The AC Robinson instability threshold with a superconducting harmonic cavity has been studied with multiparticle simulations.

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THPAB011

Optimization of Multicell Microwave Cavities Using YACS

controls, dipole, multipole, software

3708

B.D. Isbarn, B. Riemann, M. Sommer, T. Weis
DELTA, Dortmund, Germany

Funding: Work supported by the BMBF under contract no. 05K13PEB.
YACS is a 2.5D finite element method solver capable of solving for the full 3D eigenfrequency spectra of resonant axisymmetric structures while reducing the computational problem to a 2D rotation plane. The most recent revision of the code introduced arbitrary order basis functions and curved meshes, for both triangular and quadrilateral unstructured meshes. This led to significant increases in convergence rates. However, due to the utilization of curved meshes and the complex coordinate transformations that are involved, spurious modes were introduced when solving the axisymmetric problem. Although workarounds do exist that circumvent these issues by lowering the likelihood and frequency of spurious modes, linear triangular meshes with higher order basis functions were chosen due to their simplicity and spurious free solutions. In order to support the usage of spline cavities as an alternative parameterization to the well known elliptical cavities, parameter space scans were carried out for non-reentrant spline cavities. In addition a new optimization strategy is presented that exploits the arbitrary polynomial order of Bézier curves by utilizing the degree elevation technique.

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THPAB034

Generation of Short Intense Heavy-Ion Pulses in HIAF

acceleration, ion, injection, heavy-ion

3774

D.Y. Yin, H. Du, L.J. Mao, G.D. Shen, J.W. Xia, J.C. Yang
IMP/CAS, Lanzhou, People's Republic of China

The HIAF is a new accelerator complex under design at IMP to provide intense primary and radioactive ion beams for nuclear physics, atomic physics, high energy density physics and other applications. As a key part of HIAF, the Booster Ring (BRing) is designed to accumulate and accelerate heavy ion beams provided by iLinac up to high intensity and energy. The high quality, well focused, strongly bunched intense Uranium beam (U³⁴⁺) with high energy and high intensity of 10¹¹ will open a new area for the HED physics research in laboratory. Based on the beam parameters of 238U³⁴⁺ proposed by the BRing, the two critical issues of producing short bunch with high beam intensity are studied. One is efficiency of adiabatic capture which can be a necessary prerequisite to ensure the beam intensity, and the other one is bunch compression in longitudinal which is an effective way of producing short pulse duration bunch. In this article, the analytical calculations and tracking simulations are described, the capture efficiency and possible bunch length under the action of planning RF system are presented

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THPAB051

A GPU Variant of Mbtrack and Its Application in SLS-2

simulation, GPU, storage-ring, synchrotron

3827

U. Locans, A. Adelmann, L. Stingelin, H.S. Xu
PSI, Villigen PSI, Switzerland
U. Locans
University of Latvia, Riga, Latvia

Mbtrack is a widely used multi-bunch tracking code, developed at SOLEIL, for modeling the collective instabilities in electron storage rings. It has been applied to the Swiss Light Source upgrade proposal (SLS-2) for the study of single bunch instabilities. However, an n-bunch simulation using mbtrack requires to run n+1 MPI processes. Therefore, a large scale computing cluster may be necessary to perform the simulation. In order to reduce the demands of computing resources for multi-bunch simulations, a CUDA version of mbtrack has been developed, in which the computations of mbtrack are offloaded to a graphics processing unit (GPU). With the mbtrack-cuda variant, multi-bunch simulations can now run in a standalone workstation equipped with an Nvidia graphics card for scientific computing. The implementation and benchmark of the mbtrack-cuda code together with the applications in the study of longitudinal instabilities for SLS-2 will be presented.

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THPAB057

Method to Calculate the Longitudinal Impedance From a Partial Wakefield Simulation

impedance, wakefield, simulation, factory

3844

N.C. Shipman
UMAN, Manchester, United Kingdom
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
R. Calaga
CERN, Geneva, Switzerland
J.A. Mitchell
Lancaster University, Lancaster, United Kingdom

When simulating modes with high Q-factors, the wakefield length necessary to calculate the impedance spectrum can often mean a computation time of several weeks or more. A method has been developed which enables the longitudinal impedance and Q-factors of multiple modes to be calculated from a partially decayed wakefield simulation. This paper presents an overview of the method along with preliminary, proof of principle, results showing that considerable simulation time can be saved whilst maintaining a good degree of accuracy.

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THPAB077

Opal Simulations of the PSI Ring Cyclotron and a Design for a Higher Order Mode Flat Top Cavity

cyclotron, simulation, flattop, injection

3891

N. Pogue
LLNL, Livermore, California, USA
A. Adelmann, L. Stingelin
PSI, Villigen PSI, Switzerland

Funding: The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/ 2007-2013) under grant agreement n.°290605 (PSI-FELLOW/COFUND).
The PSI cyclotron has been producing high power proton beam for 41 years. Over its lifetime it has been upgraded from producing 100 μA to 2.2 mA at 590 MeV. As the power reaches higher levels, it become more important to understand how the machine's beam dynamics will reach to new features of devices introduced. We present an OPAL (Object Oriented Parallel Accelerator Library) model of the cyclotron and compared it to the probe measurements from the machine. This model has good agreement with the measurements over the ~180 revolutions in the machine. Using this same model, a higher order mode flat top cavity was inserted into the machine to illustrate that its design and field structure allowed beam to be extracted. The HOM cavity design will also be presented. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

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THPAB095

Detuning Compensation in SC Cavities Using Kalman Filters

controls, FPGA, operation, coupling

3938

A. Ushakov, P. Echevarria, A. Neumann
HZB, Berlin, Germany

For CW driven superconducting cavities operating at small bandwidth, like in ERL or FEL light sources, it is mandatory to precisely control any source of detuning. Therefore, a Kalman [1] filter based approach was developed and implemented as FPGA firmware to act as the core part of a detuning compensation algorithm. It relies on a fit by a second order model to a measured transfer function of cavity's forced oscillations with damping, caused by piezo drives and data about observed current phase with some adjustable confidence rate. The initial data for this core is taken from field detection firmware on mTCA.4's SIS8300-L2 digitizer, transferred by low latency links to a carrier board equipped by piezo drive controller where the DSP processing by the Kalman algorithm performed. The processing is characterized by a 550 kHz rate in pipeline mode and occupies almost all DSP resources of the Spartan 6 FPGA chip. The experimental results of detuning compensating technique applied to a SC photoinjector cavity are presented in this contribution.
Kalman, R. E. (1960): A New Approach to Linear Filtering and Prediction Problems, Transaction of the ASME, Journal of Basic Engineering, Pages 35-45.

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THPAB097

Phase Calibration of Synchrotron RF Signals

operation, synchrotron, LLRF, timing

3945

A. Andreev, H. Klingbeil
TEMF, TU Darmstadt, Darmstadt, Germany
H. Klingbeil, D.E.M. Lens
GSI, Darmstadt, Germany

In the scope of FAIR's scientific program higher beam intensities will be achieved and several new synchrotrons (including storage rings) are being built. The low-level RF (LLRF) systems of FAIR have to support multi-harmonic operations, barrier bucket generation and bunch compression in order to meet the desired beam quality requirements. All this imposes several requirements on the LLRF systems. For example the phase error of the gap voltage of a specific RF cavity must be less than 3 degrees. Thus, each individual component must have a better accuracy. The RF reference signals for the FAIR synchrotron RF cavity systems are generated by direct digital synthesis (DDS). Four so-called Group DDS modules are mounted in one crate. In the supply rooms, the reference signals of such a crate are then distributed to local cavity LLRF systems. Therefore, the precise phase calibration of Group DDS modules is of importance. A phase calibration method with respect to the absolute phases of DDS modules defined by means of the FAIR Bunch Phase Timing System (BuTiS) is developed, and its precision is under evaluation.

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THPAB098

Test Setup for Automated Barrier Bucket Signal Generation

operation, controls, synchrotron, antiproton

3948

K. Groß, D. Domont-Yankulova, J. Harzheim, H. Klingbeil
TEMF, TU Darmstadt, Darmstadt, Germany
M. Frey, H. Klingbeil
GSI, Darmstadt, Germany

Funding: Work supported by the German Federal Ministry of Education and Research (BMBF) under the project 05P15RDRBA.
For sophisticated beam manipulation several ring accelerators at FAIR and GSI like the main synchrotron SIS100 and the ESR will be equipped with barrier bucket systems. Hence, the associated LLRF has to be applicable to different RF systems, with respect to the cavity layout and the power amplifier used, as well as to variable repetition rates and amplitudes. Since already the first barrier bucket pulse of a long sequence has to meet certain minimum demands, an open-loop control on the basis of calibration data is foreseen. Closed-loop control is required to improve the signal quality during a sequence of pulses and to adapt to changing conditions like temperature drifts. A test setup was realized that allows controlling the signal generator, reading out the oscilloscope as well as processing the collected data. Frequency and time domain methods can be implemented to approach the dynamics of the RF system successively and under operating conditions, i.e. generating single sine pulses. The setup and first results from measurements are presented as a step towards automated acquisition of calibration data and iterative improvement of the same.

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THPAB100

On the Impact of Empty Buckets on the Ferrite Cavity Control Loop Dynamics in High Intensity Hadron Synchrotrons

controls, resonance, beam-loading, simulation

3954

D. Mihailescu Stoica, D. Domont-Yankulova
Technische Universität Darmstadt (TU Darmstadt, RMR), Darmstadt, Germany
D. Domont-Yankulova, H. Klingbeil
TEMF, TU Darmstadt, Darmstadt, Germany
H. Klingbeil, D.E.M. Lens
GSI, Darmstadt, Germany

Funding: Supported by the Helmholtz Graduate School for Hadron and Ion Research
Due to technical reasons two of ten buckets have to stay empty in the planned SIS100 synchrotron at the GSI Helmholtzzentrum für Schwerionenforschung. The planned low level RF control systems consist of linear P and PI type controllers. These are responsible to maintain a desired phase and amplitude of the gap voltage. In addition the cavity is controlled to follow a prescribed resonance frequency ramp. In SIS100 the acceleration will be performed by ferrite cavities with comparatively small quality factors. Therefore, effects resulting from transient beam loading have to be expected. Influences due to empty buckets are analysed in the frequency domain and particle tracking simulations are carried out to estimate the effect on the overall system with particular consideration of emittance growth and particle loss.

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THPAB103

On-Line RF Amplitude and Phase Calibration

controls, operation, LLRF, beam-loading

3957

M.K. Grecki, V. Ayvazyan, J. Branlard, M. Hoffmann, M. Omet, H. Schlarb, Ch. Schmidt
DESY, Hamburg, Germany

The accelerating RF field has crucial importance on the beam properties. It is not only used just to accelerate particles but also to shape the bunches at bunch compressors. It is really important to control and measure the field as seen by the beam while usually only indirect (not using the beam) field measurements are available*. Since they are affected by many contributions the measurements must be always calibrated to the beam. Usually this calibration is performed at special operating conditions that prevents normal operation of the accelerator. During normal operation the calibrations is assumed to not drift which is certainly not perfectly true and introduce some control errors. The paper shows how to extract the RF-beam calibration from RF signals during normal operating condition (when RF feed-back, beam loading compensation, learning feed-forward etc. are active). All the algorithms and computations were performed on signals recorded at FLASH accelerator but the main idea is general and can be used at other locations as well.

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THPAB106

Experience with Single Cavity and Piezo Controls for Short, Long Pulse and CW Operation

feedback, operation, controls, experiment

3966

K.P. Przygoda, V. Ayvazyan, R. Rybaniec, H. Schlarb, Ch. Schmidt, J.K. Sekutowicz
DESY, Hamburg, Germany
P. Echevarria
HZB, Berlin, Germany

We present a compact RF control system for SCRF single cavities based on MicroTCA.4 equipped with specialized advanced mezzanine cards (AMCs) and rear transition modules (RTMs). To sense the RF signals from the cavity and to drive the high power source, a DRTM-DWC8VM1 module is used equipped with 8 analog field detectors and one RF vector modulator. Fast cavity frequency tuning is achieved by piezo-actuators attached to the cavity and a RTM piezo-driver module (DRTM-PZT4). Data processing of the RF signals and the real-time control algorithms are implemented on a Virtex-6 FPGA and a Spartan FPGAs within two AMCs (SIS8300-L2V2 and DAMC-FMC20). The compact single cavity control system was tested at Cryo Module Test Bench (CMTB) at DESY. Software and firmware were developed to support all possible modes, the short pulse (SP), the long pulse (LP) and CW operation mode with duty cycles ranging from 1 % to 100%. The SP mode used a high power multi-beam klystron at low QL ~3·10⁶. For the LP mode (up to 50% duty cycle) and the CW mode a 120 kW IOT tube was used at QL up to 1.5·10⁷. Within this paper we present the achieved performance and report on the operation experience on such system.

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THPAB111

Sub-Femtosecond Jitter Ultra High Performance Oscillators for Accelerator Timing

controls, coupling, electron, impedance

3979

A. Gronefeld
Ingenieurbüro Gronefeld, Herten, Germany

Extremely stable RF-Sources are at the heart of Electron Beam Accelerators and impact beam quality and beam energy. Jitter requirements on those sources are very tight and linked to the quest of ever decreasing (XFEL) laser pulse length, currently in the tens of femtoseconds. For the Pohang Accelerator Laboratory in Pohang/Korea, a 2.856GHz phase-lockable oscillator with a jitter performance of 0.8fS (10kHz..10MHz) was developed and deployed, together with a master oscillator that supplies rubidium-stabilized 476MHz for synchronization. In terms of phase noise, these 2.856GHz oscillators exhibit -125dBc/Hz@1kHz, -145dBc/Hz@10kHz and -165dBc/Hz@100kHz offset, while reaching a noise floor of -180dBc/Hz. Using the same technology of a dielectric resonator oscillator, a 3.9GHz source was developed for the European XFEL at DESY/Hamburg, achieving 0.3fS (10kHz/10MHz). Phase noise is down to -125dBc/Hz@1kHz, -155dBc/Hz@10kHz and -175dBc/Hz@100kHz offset, with a noise floor of -180dBc/Hz. The strategy of designing ultra low phase-noise sources with dielectric resonators is outlined, and challenges and limitations within the oscillator design, but also measurement technology are presented.

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THPAB114

Operation of LLRF Control Systems in SuperKEKB Phase-1 Commissioning

controls, LLRF, simulation, operation

3986

T. Kobayashi, K. Akai, K. Ebihara, A. Kabe, K. Nakanishi, M. Nishiwaki, J.-I. Odagiri, S.I. Yoshimoto
KEK, Ibaraki, Japan
K. Hirosawa
Sokendai, Ibaraki, Japan

First beam commissioning of SuperKEKB (Phase-1), which had started in February 2016 and continued until the end of June, has been successfully accomplished. Target beam current for Phase-1 needed for sufficient vacuum scrubbing was achieved in both 7-GeV electron and 4-GeV positron rings. This presentation summarize the operation results related to low level RF (LLRF) control issues during the Phase-1 commissioning, including the system tuning, the coupled bunch instability and the bunch gap transient effect. RF system of SuperKEKB consists of about thirty klystron stations in both rings. Newly developed LLRF control system, which is composed of recent digital technique, is applied to the nine stations among the thirty for Phase-1. The RF reference signal distribution system has been also upgraded for SuperKEKB. These new systems worked well without serious problem and they contributed to smooth progress of the commissioning. The old existing systems, which had been used in the KEKB operation, were still reused for the most stations, and they also worked as soundly as performed in the KEKB operation.

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THPAB115

Development of a Longitudinal Feedback System for Coupled Bunch Instabilities Caused by the Accelerating Mode at Superkekb

impedance, operation, damping, target

3989

K. Hirosawa, K. Akai, E. Ezura, T. Kobayashi, K. Nakanishi, M. Nishiwaki, S.I. Yoshimoto
KEK, Ibaraki, Japan

SuperKEKB is an asymmetric energy electron-positron circular collider. Phase-I commissioning was operated from February to June in 2016. The purpose of this accelerator is to aim at the higher luminosity than KEKB, so a larger beam current is made for it. In the future plan, beam currents in the electron and positron rings will be increased to 2.6A and 3.6A, respectively. As we consider beam dynamics in the storage ring, higher mode instability associated with the accelerating mode will be caused by a large beam current. Especially the target instability of this study is called μ=-2 mode Coupled Bunch Instability. To suppress it, we developed new feedback components for longitudinal coupled bunch instability. We have same mechanism feedback components for KEKB, but it supports only μ=-1 mode instability. Since a large current makes μ=-1 mode instability big, there is a possibility that suppression is difficult only by using KEKB components. In order to deal with this problem, new components we developed support μ=-1, -2, and -3 mode instabilities, and we improved the performance and usability as compared to existing components. We schedule studies using a beam at Phase-II.

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THPAB116

Evaluation of Digital LLRF Control System Performance at STF in KEK

LLRF, controls, klystron, cryomodule

3992

S.B. Wibowo, N. Liu
Sokendai, Ibaraki, Japan
T. Matsumoto, S. Michizono, T. Miura, F. Qiu
KEK, Ibaraki, Japan

The Superconducting RF Test Facility (STF) at the High Energy Accelerator Research Organization (KEK) was built for research and development of the International Linear Collider (ILC). Several digital low-level radio frequency (LLRF) control systems were developed at the STF. The purposes of these developments are to construct a minimal configuration of the ILC LLRF system and achieve the amplitude and phase stability of the accelerating field in the superconducting accelerator. Evaluations of digital LLRF control systems were conducted during the conditioning of eight superconducting cavities performed between October and November 2016. The digital LLRF control system configured for ILC was demonstrated and the performance fulfilled the required stability criteria of the accelerating field in the ILC. These evaluations are reported in this paper.

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THPAB117

Development of a New LLRF System Based on MicroTCA.4 for the SPring-8 Storage Ring

klystron, controls, LLRF, storage-ring

3996

T. Ohshima, H. Ego, N. Hosoda, H. Maesaka
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
T. Fukui
RIKEN SPring-8 Center, Innovative Light Sources Division, Hyogo, Japan
M. Ishii
JASRI/SPring-8, Hyogo-ken, Japan

SPring-8 is a 3rd generation synchrotron radiation facility, which has been operated since 1997. The analog-circuit-based rf modules now in use at the storage ring are obsolete and hard to be maintained. The renewal of them with modern digital ones is underway and the developed LLRF system will be used for the operation of SPring-8-II. We built an amplitude and phase stabilizing system with commercial MicroTCA.4 modules. A motor driver controlled through EtherCAT was newly adapted to the cavity tuner. The system was implemented to the high power rf test stand which consists of a 1 MW klystron, a circulator, and a 508.58 MHz cavity. The rf power was successfully regulated to keep the cavity voltage with an amplitude deviation of less than 0.1% and a phase stability of less than 0.1 degree in rms. We are also developing new MTCA.4 modules: a digitizer AMC having sampling rate of 370 MHz and 16bit resolution, and a signal conditioning RTM. These modules are used for under-sampling rf detection achieving simple composition and more robustness to the ambient parameter changes. We will start installation of the digital system to one of four rf stations in the storage ring in summer 2017.

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THPAB127

Development of 1.3 GHz Cavity Combiner for 24 kW CW SSA

coupling, simulation, linac, electromagnetic-fields

4020

W. Liu, B. Du, G. Huang, L. Lin, L. Shang, W.B. Song
USTC/NSRL, Hefei, Anhui, People's Republic of China

The 24KW CW SSA (Solid-State Amplifier) is being developed to drive the 1.3GHz SC Linac used in a THz light source. The SSA adopts the compact all-in-one combining method ' cavity combiner, which is proposed and developed in recent years. This paper reports the R&D of the cavity combiner. The cavity combiner resonates in TM010 mode, coupling with 24 coaxial-connected 1kW amplifier modules. The cavity's electromagnetic characteristic is calculated by CST, and the mechanical structure including the input and output coupler has been designed.

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THPAB128

Beam Arrival Time Analisis Based on CBPM at DCLS

simulation, experiment, FEL, undulator

4023

S.S. Cao, J. Chen, L.W. Lai, Y.B. Leng
SINAP, Shanghai, People's Republic of China
N. Zhang
SSRF, Shanghai, People's Republic of China

Dalian Coherent Light Source is the first high gain free electron lasers (FEL) user facility in China, which is dedicated at extreme ultraviolet (EUV) spectral regime of 150-50nm for various scientific fields. In its undulator section, the beam-line was equipped with ten pair of high-precision cavity beam position monitor (CBPM), which can be used for beam position and beam arrival time (BAT) measurement. Based on this, we have done some preliminary research about the beam fight time with the reference cavities of CBPMs for the future research on BAT. In this paper, we presented the scheme of the beam fight time (BFT) research, analyzed the results, and evaluated the consistency and stability of BFT.

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THPAB129

Contribution to the ESS LLRF System by Polish Electronic Group

LLRF, controls, resonance, FPGA

4026

J. Szewiński, M. Gosk, Z. Gołębiewski, P. Krawczyk, I.M. Kudla
NCBJ, Świerk/Otwock, Poland
A. Abramowicz, K. Czuba, M.G. Grzegrzolka, I. Rutkowski
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
W. Cichalewski, D.R. Makowski, A. Napieralski
TUL-DMCS, Łódź, Poland

Funding: Described work will be done as a part of polish in-kind contribution, granted by the Polish Ministry of Science and Higher Education in the decision number DIR/WK/2016/03.
Development of the LLRF system at ESS is coordinated by the Lund University, but part of it, LLRF systems for M-Beta and H-Beta sections, will be delivered within in-kind contribution from Poland. This document will describe the scope of work, work plan, and technical details of the selected components of the M-Beta and H-Beta LLRF systems sections. Described contribution will be made by the Polish Electronic Group (PEG), a consortium of three scientific units. LLRF system for ESS will be made of both, commercially available components and components designed specially for this project, and those last ones will be presented and described here. Except the technical details, the organizational aspects, such as schedule, project management or quality control, will be presented as well.

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THPAB134

Latest Development of the ALBA DLLRF

LLRF, beam-loading, interlocks, rf-amplifier

4034

A. Salom, B. Bravo, M. Broseta, E. Morales, J.R. Ocampo, F. Pérez, P. Solans
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

The Digital LLRF of ALBA has been implemented using commercial cPCI boards with Virtex-4 FPGA, fast ADCs and fast DACs. The firmware of the FPGA is based on IQ demodulation technique and the main feed-back loops adjust the phase and amplitude of the cavity voltage and also the resonance frequency of the cavity. This paper summarizes the latest LLRF developments done to improve performance of the RF systems and beam stability, including feed-forward loops based on phase modulation to compensate disturbances due to RF trip, beam loading compensation and Power Unbalance Compensation Loop for RF amplifiers Combination.

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THPAB135

Digital LLRF for MAX IV

LLRF, FPGA, vacuum, interlocks

4037

A. Salom, F. Pérez
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
Å. Andersson, R. Lindvall, L. Malmgren, A.M. Milan, A.M. Mitrovic
MAX IV Laboratory, Lund University, Lund, Sweden

The MAX IV facility consists of a 3 GeV Storage Ring(SR), a 1.5 GeV SR, and a linear accelerator (fed by two guns) that serves as a full-energy injector to the rings, but also as a driver for the Short Pulse Facility. The RF systems of the two SRs work at 100MHz. There are 6 normal conducting capacity loaded accelerating cavities and three Landau passive cavities in the 3GeV SR. In the 1.5GeV SR there are two accelerating cavities and two Landau cavities with the same characteristics. Each of these cavities is fed by a modular 60kW SSA. In the 3 GeV SR the power will be doubled by adding a second SSA when required. A digital Low Level RF system has been developed using commercial uTCA boards, with a Virtex-6 FPGA mother board (Perseus 601X) and two double stack FMC boards with fast ADCs and DACs. The large capabilities of state-of-the-art FPGAs allowed including the control of two normal conducing cavities and two landau cavities in one single LLRF system, reducing the development costs. Other utilities like the handling of fast interlocks and post-mortem analysis were also added to this system. This paper summarizes the main capabilities and performance of this DLLRF.

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THPAB148

DIGITAL LOW LEVEL RF CONTROL SYSTEM FOR THE TAIWAN PHOTON SOURCE

controls, FPGA, feedback, booster

4077

F.Y. Chang, L.-H. Chang, M.H. Chang, L.J. Chen, F.-T. Chung, M.-C. Lin, Z.K. Liu, C.H. Lo, C.L. Tsai, Ch. Wang, M.-S. Yeh, T.-C. Yu
NSRRC, Hsinchu, Taiwan

The Taiwan Photon Source (TPS) is a 3 GeV, 500 mA, 499.65 MHz, 3rd generation synchrotron light source at NSRRC. To achieve the requirements of system flexibil-ity, fault diagnosis, precise control and high noise reduc-tion, a digital low level RF (DLLRF) control system based on Field Programmable Gate Array (FPGA) was developed. The communication interface is based on Raspberry Pi. The feedback loop performance of the control system was tested on the booster of the Taiwan Photon Source (TPS) with 950 kV gap voltage.

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THPAB152

Digital Low Level RF Systems for Diamond Light Source

booster, storage-ring, LLRF, hardware

4089

P. Gu, C. Christou, P. Hamadyk, D. Spink, I.S. Uzun
DLS, Oxfordshire, United Kingdom
E. Morales, F. Pérez, A. Salom
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

Analogue low level RF (LLRF) systems have been used to date for both Diamond storage ring and booster RF cavities. They have been in operation for nearly ten years without a major problem. However, digital LLRF can offer new desirable functionalities such as fast data logging, 'probe blip' blockage and automation of routine tasks. Better performance is also envisaged with up to date hardware. A digital LLRF system has been developed with Alba Synchrotron as a common platform for the storage ring and booster, including superconducting and normal conducting RF cavities. The new digital LLRF is based on Virtex6 FPGA and fast ADCs and DACs. One system has been built and verified in the Diamond booster with beam. The design will be implemented for all other Diamond RF cavities.

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THPIK002

Development of a Range of High Peak Power Solid-State Amplifiers for Use in the Heavy Ion Linac at JINR, Dubna

ion, linac, heavy-ion, impedance

4108

S.C. Dillon, J.L. Reid
Tomco Technologies, Stepney, South Australia, Australia
A.V. Butenko
JINR, Dubna, Moscow Region, Russia
H. Höltermann, H. Podlech, U. Ratzinger
BEVATECH, Frankfurt, Germany

A range of LDMOS based amplifiers rated for up to 340kW peak power and operating at 100.625MHz were developed for use as RF sources for driving cavities in the heavy ion LINAC (HILac) at JINR, Dubna. The final solution had to be compact and competitive while addressing technical challenges such as phase and amplitude stability, long term reliability, reflected power handling and serviceability. Design considerations and performance results are presented.

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THPIK003

Novel RF Structure for Energy Matching into an RFQ

rfq, ion, booster, ISAC

4111

V. Zvyagintsev, Z.T. Ang, T. Au, N.V. Avreline, J.J. Keir, R.E. Laxdal, M. Marchetto, B.S. Waraich
TRIUMF, Vancouver, Canada
A. Cote
UBC, Vancouver, Canada

Funding: National Research Council of Canada
The ISAC RFQ at TRIUMF is designed to accelerate ions with A/q<=30 and requires an ion injection energy of 2.04 keV/u (β=0.002) for successful matching. This means that the ions (typically radioactive ions produced via the ISOL method) have to be extracted from a source at a terminal voltage in excess of 60 kV. Presently the ISAC target modules cannot hold more than 54 kV (and some lower than this) so that some of the higher masses cannot be successfully accelerated. A small 3-gap RF structure at 11.8 MHz has been designed to provide an energy matching to the RFQ. The structure operates in pi-mode and provides a maximum effective accelerating voltage of 16 kV to the low energy ions. Beam dynamics considerations, RF and mechanical design will be described. First results of RF tests of the structure will be given.

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THPIK005

RF Conditionning of the Spiral 2 CW RFQ

rfq, controls, LLRF, pick-up

4114

O. Piquet, Y. Lussignol
CEA/DSM/IRFU, France
M. Desmons, A.C. France, P. Galdemard
CEA/IRFU, Gif-sur-Yvette, France
M. Di Giacomo, R. Ferdinand, J.-M. Lagniel
GANIL, Caen, France

The SPIRAL2 RFQ is designed to accelerate light and heavy ions with A/Q from 1 to 3 at 0.73 MeV/A. The nominal beam intensities are up to 5 mA CW for both proton and deuteron beams and up to 1 mA CW for heavier ions. The four-vane cavity is made with 5 1-meter long sections mechanically assembled, it works at 88 MHz and is powered up to 180 kW CW to achieve the nominal vane voltage of 113.7 kV for A/Q = 3 ions. This paper describes the RF conditioning of the RFQ at GANIL with the setting of its RF systems and cooling system used to tune the cavity resonance frequency.

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THPIK013

Renewal of Bessy Ii Rf System - Solid State Amplifiers and Hom Damped Cavities

klystron, HOM, storage-ring, synchrotron

4127

W. Anders, P. Goslawski, A. Heugel, H.-G. Hoberg, H. Hoffmann, A. Jankowiak, J. Knobloch, G. Mielczarek, M. Ries, M. Ruprecht, A. Schälicke, B. Schriefer, H. Stein
HZB, Berlin, Germany
M. Haucke
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany
K. Ludwig
BESSY GmbH, Berlin, Germany

Due to the fact that the klystrons run out of production and due to the aging of the old cavities, a renewal of the RF system was necessary. Solid state based transmitters and HOM damped nc single cell cavities have been installed at the BESSY II storage ring. The parameters of the components, the installation phase and the results to the beam will be presented.

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THPIK014

Travelling Wave Accelerating Structure for Areal 50 MeV Energy Upgrade

impedance, simulation, electron, gun

4130

A. Vardanyan, V. Danielyan, S.G. Dekhtiarov, B. Grigoryan, L. Hakobyan, T. Markosyan, A.S. Simonyan
CANDLE SRI, Yerevan, Armenia
W. Ackermann
TEMF, TU Darmstadt, Darmstadt, Germany
A.V. Tsakanian
HZB, Berlin, Germany

AREAL facility development implies energy upgrade to 50 MeV in order to drive a THz free electron laser. To reach this goal, the installation of two 1.6 m long S-Band travelling wave accelerating sections, with nominal accel-erating gradient of 15 MV/m, are foreseen. In this paper the design study of accelerating sections along with the matching performance of RF couplers are presented. The simulations are performed using the CST Microwave Studio. The first results of the accelerating structure proto-type fabrication are discussed.

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THPIK015

Prototype Results of the ESR Barrier-Bucket System

impedance, accumulation, coupling, injection

4133

M. Frey, P. Hülsmann, H. Klingbeil
GSI, Darmstadt, Germany
D. Domont-Yankulova, K. Groß, J. Harzheim, H. Klingbeil
TEMF, TU Darmstadt, Darmstadt, Germany

The experimental storage ring (ESR), operated at the GSI facility in Darmstadt, Germany, allows experiments with a variety of ion species. In combination with the existing electron cooler, its RF cavities have been used to demonstrate longitudinal beam accumulation in order to increase the beam intensity. Limitations of the existing narrow-band cavities led to the development of a magnetic alloy (MA) based broad-band cavity for the generation of Barrier-Bucket signals. The application of a pre-distortion method demands high linearity of the driver amplifier and highlights the importance of its selection process. In this contribution, the cavity and amplifier system design is described and data measured at a prototype system are presented.

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THPIK016

Status of the SIS100 RF Systems

feedback, status, synchrotron, power-supply

4136

H. Klingbeil, R. Balß, M. Frey, P. Hülsmann, A. Klaus, H.G. König, U. Laier, D.E.M. Lens, K.-P. Ningel
GSI, Darmstadt, Germany

Four different types of RF cavities are realized for the heavy-ion synchrotron SIS100 which is built in the scope of the FAIR (Facility for Antiproton and Ion Research) project. The standard acceleration is performed by ferrite cavities. Barrier bucket cavities will allow a pre-compression of the beam by means of moving barriers. Bunch compressor cavities are used to realize a rotation in longitudinal phase space by 90 degrees, thereby reducing the bunch length. Finally, a longitudinal feedback system reduces undesired beam oscillations. In contrast to the ferrite-loaded accelerating cavities, the last-mentioned three cavity types are based on magnetic alloy (MA) material. Depending on the type of the cavity system, the realization is done by - or in close collaboration with - different industrial companies and institutions. In this contribution, the realization status of all these synchrotron RF systems is summarized.

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THPIK023

Concept of the High Power RF Systems for MESA

linac, experiment, SRF, LLRF

4147

R.G. Heine, F. Fichtner
IKP, Mainz, Germany

Funding: work supported by DFG under the cluster od Excellence PRISMA, EXC 1098/2014
The Mainz Energy-recovering Superconducting Accelerator (MESA) is currently designed and built at the Institut für Kernphysik (KPH) at Johannes Gutenberg-Universität Mainz. The main accelerator incorporates four superconducting cavities of the TESLA type, while the preaccelerator MAMBO (Milliampere Booster) is a room temperature linac. The MESA high power RF-systems have to cover a vast power range starting at some 10kW per cavity for the main linac modules and more 50kW per cavity for MAMBO. In this paper we will present the concept of a unified high power RF system for both main accelerator and preaccelertor, based on solid state technology.

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THPIK029

THE RF CAVITY FOR THE INDUS-2 STORAGE RING

HOM, vacuum, dipole, operation

4154

C. P. Pasotti, M. Bocciai, P. Pittana, M. Rinaldi
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

A new Elettra-type cavity has been delivered to the Raja Ramanna Centre for Advanced Technology (RRCAT) Indus-2 facility. This cavity is the very same of those already installed several years ago with some optimization of the cooling channels. It is the Elettra-type cavity, normal conducting copper single cell but resonating at 505.8 MHz. The cavity description, the full characterization of the accelerating mode (L0) and high order modes (HOM) and the acceptance tests are presented in this paper.

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THPIK030

THE RF CAVITY FOR THE SESAME FACILITY

storage-ring, vacuum, controls, pick-up

4158

C. P. Pasotti, M. Bocciai, M. Rinaldi
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
D.S. Foudeh, E. Huttel
SESAME, Allan, Jordan

SESAME is a 2.5 GeV Synchrotron Light Source under commissioning in Allan (Jordan). It will be the first inter-national research centre in the Middle East [1]. It is a cooperative venture with support provided by several international organizations and scientific laboratories. Elettra-Sincrotrone Trieste (Italy) is among them. In the framework of the collaboration agreement among SESAME (Jordan), INFN (Italy) and Elettra-Sincrotrone Trieste, four 500 MHz normal conducting (NC) copper cavities have been built and commissioned at Elettra and then successfully installed in the SESAME storage ring. The cavities properties, their fabrication process, their characterization at low and high RF power is presented here.

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THPIK032

Installation and Low Power Test of IFMIF-EVEDA RFQ at Rokkasho Site

rfq, linac, vacuum, dipole

4162

E. Fagotti, L. Antoniazzi, A. Baldo, A. Battistello, L. Bellan, P. Bottin, M. Comunian, A. Conte, L. Ferrari, M.G. Giacchini, F. Grespan, M. Montis, A. Palmieri, A. Pisent, D. Scarpa
INFN/LNL, Legnaro (PD), Italy
D. Agguiaro, A.G. Colombo
INFN- Sez. di Padova, Padova, Italy
F. Borotto Dalla Vecchia, G. Dughera, G. Giraudo, P. Mereu, R. Panero
INFN-Torino, Torino, Italy
P. Cara, R. Heidinger
Fusion for Energy, Garching, Germany
M. Furini, C. Gessi
INFN-Bologna, Bologna, Italy
D. Gex
F4E, Germany
R. Ichimiya, Y. Ikeda, A. Kasugai, K. Kondo, S. O'hira, K. Sakamoto, T. Shinya, M. Sugimoto
QST, Aomori, Japan
J. Knaster, A. Marqueta, G. Pruneri, F. Scantamburlo
IFMIF/EVEDA, Rokkasho, Japan

The IFMIF-EVEDA RFQ is composed of 18 modules for a total length of 9.8 m and is designed to accelerate the 125 mA D⁺ beam up to 5 MeV at the frequency of 175 MHz. The RFQ is subdivided into three Super-Modules of six modules each. The Super-Modules were shipped to Rokkasho (Japan) at the beginning of 2016, pre-assembled 3 m far from the final location and tuned to reach target field flatness requirements. Just after conclusion of injector commissioning, the tuned RFQ was disassembled, moved and reassembled in the final location. After confirmation that field flatness was not affected by this movement, high power couplers were installed and tuned and all the structure was baked. Assembling, tuning and coupling results will be presented.

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THPIK036

Design Study of Damped Accelerating Cavity Based on the TM020-Mode and HOM Couplers for the KEK Light Source Project

HOM, damping, target, simulation

4172

T. Takahashi, S. Sakanaka, N. Yamamoto
KEK, Ibaraki, Japan

A novel damped-cavity scheme was recently proposed by Ego et al.*. In this design, TM020 resonant mode is used for beam acceleration. Power of higher-order (or lower-order) modes are extracted through cylindrical slots which are placed at the position where the magnetic fields of HOMs are strong while that of TM020 mode is zero. Extracted powers are absorbed by lossy ferrites. In this scheme, excellent HOM damping is possible while occupying less space of the straight section in storage rings. We propose in this paper an alternative design which is based on the same TM020 mode but with rod-type HOM couplers. The rod-type HOM couplers are placed where the electric fields of HOMs are strong while that of TM020 mode is zero. In this scheme, openings needed for HOM extraction can be made smaller, which is desirable for stiffening the mechanical structure of the cavity. Potential use of lossy dielectric materials is another merit. We present external Q-values of HOMs that can be achieved in this scheme, as well as an effect of HOM couplers on the TM020 mode. Our current study is directed to a 1.5 GHz higher-harmonic cavity for the proposed KEK Light Source project**.
* H. Ego et al., in Proceedings of the 11-th Annual Meeting of Particle Accelerator Society of Japan, Aug. 9-11, 2014, MOOL14 [in Japanese].
** K. Harada et al., IPAC2016, THPMB012.

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THPIK037

Simulation Study of Normal-Conducting Double RF System for the 3-GeV KEK Light Source Project

beam-loading, storage-ring, emittance, simulation

4176

N. Yamamoto, S. Sakanaka, T. Takahashi
KEK, Ibaraki, Japan

For the proposed 3-GeV KEK Light Source (KEK-LS) project*, a double RF system using 500-MHz accelerating and 1.5-GHz third-harmonic cavities is under consideration. To mitigate intrabeam scattering due to ultra-low emittance, the bunch length will be elongated using the harmonic cavities which is based on the TM020 resonant mode. An accelerating cavity based on this mode was first proposed by Ego et al.**, and we found it very suitable for the harmonic cavities due to the following reasons: 1) it has high unloaded-Q and high stored electromagnetic energy which result in the reduction of transient beam-loading effect due to bunch gaps, and 2) efficient damping of higher (or lower) order modes is possible. Our investigations based on numerical simulations predicted the bunch elongation by a factor of 3.1 when realistic bunch-gaps were assumed. To improve the bunch elongation further, we also proposed to compensate the transient beam loading with two realistic measures: 1) compensation of rf voltages due to feedforward technique, and 2) compensation using a separate rf cavity. We will present our study on the double rf system based on numerical simulations.
* K. Harada et al., IPAC2016, THPMB012.
** H. Ego et al., Proceedings of the 11-th Annual Meeting of Particle Accelerator Society of Japan, Aug. 9-11, 2014, MOOL14 [in Japanese].

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THPIK038

Design of a 100 kW Solid-State RF Pulse Amplifier with a TE011 Mode RF Combiner at 476 MHz

electron, FEL, klystron, laser

4180

Y. Otake, T. Asaka, T. Inagaki
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan

Solid-state RF amplifiers, which have long lifetimes and small failures, are the recent current of high-power RF sources for particle accelerators. Hence, we designed a 100 kW solid-state amplifier with a TE011 mode cavity (Q0=100, 000) power combiner with extreme low-loss operated at 476 MHz and a 6 us pulse width. Developing this amplifier is for replacement of a high-power amplifier using an induction output tube, IOT, in the X-ray free-electron laser, SACLA. In SACLA, highly RF phase and amplitude stabilities of less than 0.01 deg. and 10^-4 in rms are necessary to stable lasing within a 10 % intensity fluctuation. The amplifier comprises a drive amplifier, a reentrant cavity RF power divider, 100 final amplifier modules with a 1 kW output each and a TE011 mode cavity combiner. Water-cooling within 10 mK and a DC power supply with a noise of less than -100 dBV at 10 Hz for the amplifier is necessary to realize the previously mentioned stabilities. Based on the experimental results of a test amplifier module and test combiner cavities, possibility to realize the above-mentioned specifications is large. We report the detail and a part of the performance of the 100 kW amplifier.

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THPIK039

Multipactor Problem of J-PARC SDTL

multipactoring, simulation, linac, operation

4184

T. Ito, T. Morishita, J. Tamura
JAEA/J-PARC, Tokai-mura, Japan
K. Nanmo, T. Sugimura
KEK, Ibaraki, Japan

We have suffered from multipactor problem of some SDTL after the Great East Japan Earthquake. As a designed operating rf power of the SDTL is in the multipactor region, we had to operate at higher power of the designed one. From the result of the simulation and the observation of the SDTL cavity, it became clear that the multipactor occurred on the inner surface of the cavity. We think that one of the cause of the maultipactor is the contamination on the inner surface of the cavity, we performed the cleaning of the inner surface of the cavity by using acetone. The cleaning was very effective and the multipactor region was reduced dramatically or disappeared. The multipactor problem has not occurred since then.

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THPIK041

The RF System of the SESAME Storage Ring

storage-ring, controls, LLRF, operation

4187

D.S. Foudeh, E. Huttel, N.Kh. Sawai
SESAME, Allan, Jordan

SESAME the Synchrotron Radiation Light Source in Allan (Jordan) consists of a 22 MeV Microtron, an 800 MeV Booster Synchrotron (originally from BESSY I, Berlin, Germany) and a 2.5 GeV Storage Ring (new de-sign). The RF system consists of four 500 MHz ELET-TRA cavities powered by four 80 kW Solid State Ampli-fiers whereas the first amplifier is produced by SOLEIL and the other three are produced by SIGMA-PHI. The RF plant is controlled by the digital Low Level Electronics from DIMTEL. The system has been installed end of 2016. This report describes the setup of the facility and the results of the commissioning.

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THPIK045

Design of a C-band Travelling-wave Accelerating Structure at IHEP

impedance, linac, simulation, wakefield

4196

J.R. Zhang, Y.L. Chi, J. Lei, H. Wang, X. Wang
IHEP, Beijing, People's Republic of China
S. Shu
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China

A C-band travelling wave accelerating structure has been developed at IHEP. The structure is a constant gra-dient type and operating with a 3'/4 mode. The total length of the structure is 1.8-meters long with 85 regular cells and two coupler cells. 2D program Superfish is used to optimize the cavity shape and the iris size. The wall cells are rounded for it can improved the Q value for about 10%. The cell irises have an elliptical profile to minimize the peak surface electric fields. In order to compatible with the compact of the short-range wake field on the beam dynamics, the average iris radius is 7.15 mm. The group velocity of the designed structure is from 2.8% to 1.4%. Between the rectangular waveguide and the accelerating structure, magnetic coupling is adopted. The coupled cavity is racetrack type in order to minimize the asymmetry in the coupler. Kyhl's method is used to match the input and output coupler.

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THPIK046

Design, Fabrication and Cold Test of a C-Band Barrel Open Cavity Pulse Compressor

coupling, klystron, simulation, vacuum

4200

S. Shu
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
M. Hou, S. Pei, N.B. Song, J.R. Zhang, F. Zhao
IHEP, Beijing, People's Republic of China

The first prototype of the C band barrel open cavity (BOC) pulse compressor has been manufactured by the Institute of High Energy Physics (IHEP), Beijing, which is used to test the brazing process and the RF properties of the structure at low power. The whispering gallery mode TM6, 1,1 with an unload Q of 100, 000 was adopt to oscillate in the cavity, and the coupling factor was optimized to achieve the highest power gain. This paper mainly deals with the RF design, mechanical design and cold test of the C band BOC pulse compressor.

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THPIK048

Design of Rapid Tuning System for a Ferrite-Loaded Cavity with Heavy Beam Loading

controls, beam-loading, feedback, LLRF

4203

X. Li, H. Sun, F.C. Zhao, J.Y. Zhu
IHEP, Beijing, People's Republic of China

A high power, broadband and rapid frequency sweeping RF system was developed to satisfy the demand of China Spallation Neutron source (CSNS)/ Rapid Cycling Synchrotron (RCS). The cavity tuning is the key issue which has great impact on the performance of the whole RF system. In order to satisfy the requirement of cavity dynamic tuning caused by the nonlinear characteristics of the ferrite material, some new technologies were developed and applied. In this paper, the overall design of the tuning system will be introduced. The ensuing discussion will be focused on the choice of different types bias current supplies, the control algorithm of LLRF system and the beam loading compensation issues.

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THPIK049

High Power Conditioning of the DTL-1 for CSNS

DTL, vacuum, linac, ion

4207

H.C. Liu, Q. Chen, K.Y. Gong
IHEP, Beijing, People's Republic of China
M.X. Fan, A.H. Li, B. Li, J. Peng, P.H. Qu, Y. Wang, X.L. Wu
CSNS, Guangdong Province, People's Republic of China

The RF tuning of the first DTL tank for the China spalla-tion neutron source was finished leading to a stabilized-uniform accelerating field. After the installation of the DTL-1 in the linac tunnel, the high power conditioning was carried out deliberately. Consequently a peak RF power of 1.6MW with 25Hz repetition rate and 650'sec pulse width was put into the tank stably. A 3MeV H⁻ ion was injected into the DTL-1 and was successfully accel-erated to 21.6MeV with almost 100% transmission. Dur-ing the operation, The DTL-1 tank worked stable in the design power level. The conditioning details will be pre-sented in this paper.

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THPIK050

Measurement and Tuning of the RF Field for the CSNS DTL

DTL, operation, coupling, experiment

4210

A.H. Li, M.X. Fan, B. Li, J. Peng, P.H. Qu, Y. Wang, X.L. Wu
CSNS, Guangdong Province, People's Republic of China
Q. Chen, S. Fu, K.Y. Gong, H.C. Liu
IHEP, Beijing, People's Republic of China

The CSNS DTL accelerates negative hydrogen ions from 3MeV to 80MeV with resonant frequency of 324MHz and peak current of 15mA. The CSNS includes four DTL cavities with diameter of 56.6cm and each length of 9 meters. RF properties research and measurement have been done to make sure the design and manufacture validate for beam operation. A new automatic system has been developed for measuring field distribution. The secondary derivation method is used to calculate the amount of the tuners to tune axial field flatness. The tilt of TS curve is used to judge the gap between the post couplers and drift tubes to achieve stability. At last the tanks have good flatness and strong stabilization, the field deviation is 2% with the standard deviation of 0.96%, and the maximum TS parameter is 65%/MHz. After the low power RF tuning experiment, the four tans have been installed in the tunnel, and have gotten good results of high power test and beam acceleration experiment.

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THPIK054

The X-Band Pulse Compressor for Tsinghua Thomson Scattering X-Ray Source

coupling, simulation, klystron, scattering

4214

Y.L. Jiang, H.B. Chen, C. Cheng, W. Gai, J. Shi, P. Wang, X.W. Wu, H. Zha
TUB, Beijing, People's Republic of China

An X-band (11.424 GHz) high-power RF station is being built for Tsinghua Thomson scattering X-ray Source (TTX). The station aims to feed several X-band accelerating structures working at a high gradient of 80 MV/m. An X-band pulse compressor is designed to compress the RF pulse from 1.5 us to 100 ns and to generate more than 250 MW peak power from a 50MW klystron. This pulse compressor implements a resonate cavity housing the HE11-mode as the energy storage cavity, with a high quality factor Q of more than 10⁵. The detailed design of the high-Q cavity as well as the dedicate couplers of this pulse compressor are present in this work.

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THPIK055

Power-Conditioning Cavity Design and Measurement of the Coaxial Coupler for the Injector of XiPAF Project

rfq, coupling, vacuum, DTL

4218

Y. Lei, X. Guan, W. Wang, X.W. Wang, Q.Z. Xing, H.Y. Zhang, S.X. Zheng
TUB, Beijing, People's Republic of China

For the RF high power conditioning on coaxial power couplers of the XiPAF (Xi'an Proton Application Facility), the RF high power-conditioning cavity was designed and manufactured. The cavity consists of a rectangular reso-nant cavity with two ports, which one is connected with input coupler from RF power source and the other one is connected with output coupler, and a tuner. The tuning frequency range could cover 325 (+0.5, -9.5) MHz. The measured Q factors are matched with the design results generally. But the S-parameter is not ideal compared to the simulation. This paper will present the design and low power measurement results of the cavity

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THPIK056

Design of a C-Band High-Efficiency Multi-Beam Klystron

klystron, electron, bunching, simulation

4221

Z.N. Liu, H.B. Chen, M.M. Peng, J. Shi
TUB, Beijing, People's Republic of China

A multi-beam klystron at 5.712GHz has been designed with efficiency of more than 80%. It can generate a pulse with output power of about 3MW and a pulse length of 5 us. Space charge effect and large signal theory, which both increase the accuracy theoretically, are considered in the simulation. A series of parameters of cavities are given after optimizing, including the frequency, R/Q, Q0 and Qe. This paper describes the beam dynamics design of the klystron as well as a preliminary machenical design.

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THPIK058

Development of a S-Band Pulse Compressor

klystron, coupling, linac, laser

4227

P. Wang, H.B. Chen, C. Cheng, J. Shi, X.W. Wu, H. Zha
TUB, Beijing, People's Republic of China

We designed and fabricated a pulse compressor for S-band high power test stand at Tsinghua University. This pulse compressor is made up of a sphere resonant cavity with quality factor of 100000 and a rf polarizer. It has the ability of compressing a pulse from 3.6 us to 300 ns with the power gain of 7. A short description of the pulse compressor is presented, together with the RF design and low level RF measurement.

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THPIK059

Experimental Study on PM-AM Method in Pulse Compression System

LLRF, klystron, experiment, acceleration

4230

P. Wang, H.B. Chen, C. Cheng, M.M. Peng, J. Shi, X.W. Wu, J. Yang, H. Zha
TUB, Beijing, People's Republic of China

We experimentally demonstrate the PM-AM method (Phase Modulation to Amplitude Modulation) at the S-band high power test stand, which consists of two S-band klystrons, a SLED type pulse compressor and two high power stainless steel RF loads, in Tsinghua University. A LLRF (low level RF) system has been developed to modulate the phases of the two klystrons in real time such that pulse compressor could generate a flat output pulse. Experimental results presents that the efficiency of the pulse compression system is 45% and the power gain is 2.9.

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THPIK060

Tuning of an S-Band 10 MeV Traveling-Wave Accelerating Structure with a Non-uniform Section

impedance, network, electron, collider

4233

J.H. Shao, H.B. Chen, C. Gong, J. Shi, X.W. Wu, S.X. Zheng
TUB, Beijing, People's Republic of China

A tuning method of nonuniform travelling wave structures has been developed based on non-resonant perturbation measurement at Tsinghua University. The filed distribution is normalized with the shunt impedance and attenuation of each cell. Then their internal reflection can be deduced and corrected by cavity deforming. This method has been applied to an S-band 10 MeV travelling wave structure successfully. In this paper, the detailed tuning method and cold test results will be presented.

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THPIK061

3D Model Analysis of Cavity for CSNS DTL

DTL, simulation, insertion, neutron

4236

P.H. Qu, M.X. Fan, B. Li, Y. Wang
CSNS, Guangdong Province, People's Republic of China
Q. Chen, K.Y. Gong, A.H. Li, H.C. Liu, F.X. Zhao
IHEP, Beijing, People's Republic of China

An Alvarez-type Drift tube linac (DTL) was utilized to accelerate an H⁻ ion beam from 3 MeV to 80 MeV of China Spallation neutron source (CSNS). RF field profile is always deviate from the design curve due to errors in fabrication and assembly of the structure cells, thus RF tuning of DTL is necessary. CSNS DTL operates in zero mode and has long tank, so accelerating field of which is unstable, this problem was solved through adding post couplers at the both side of cavity wall. In order to speed up the schedule of DTL low power RF tuning, we analyzed the operating mode, field flatness with slug tuners, field stabilization with post couplers by CST Micro wave studio (MWS) mainly with eigenmode solver in advance. Considering saving the computer memory and increasing the calculation speed, we divided each tank model into three short units. Slug tuner depth and PC-DT gap of DTL-1 and DTL-3 by simulation were shown which improved the efficiency of CSNS DTL RF tuning.

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THPIK063

The RF System of Infrared Free Electron Laser Facility at NSRL

electron, simulation, LLRF, laser

4239

L. Lin, B. Du, G. Huang, K. Jin, F.F. Wu
USTC/NSRL, Hefei, Anhui, People's Republic of China

Funding: The Natural Science Foundation of China
An infrared free electron laser light source (IRFEL) is being constructed at National Synchrotron Radiation Laboratory, which could be used in the study of far infrared detection, light dissociation and light excitation. The accelerator of IRFEL deliver a average current 300 A electron beam at 15~60 MeV, the energy spread is less than 240 keV, and the emittance is less than 30 mm*mrad. IRFEL is consisted of two optical resonator system, which could create 2.5~50 um, 40~200um infrared laser respectively. The design of IRFEL RF system is introduced, the recent progress of prebuncher, buncher, frequency distribution, accelerator and DLLRF system are also present in this paper.

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THPIK067

A C-Band Compact Spherical RF Pulse Compressor for the SXFEL Linac Energy Upgrade

coupling, electron, simulation, linac

4248

Z.B. Li, W. Fang, Q. Gu, Z.T. Zhao
SINAP, Shanghai, People's Republic of China

A new compact C-band (5712 MHz) spherical RF pulse compressor has been designed for Shanghai Soft X-ray Free Electron Laser (SXFEL) facility energy upgrading at Shanghai Institute of Applied Physics (SINAP), Chinese Academy of Sciences (CAS). This pulse compressor contains one high Q0 spherical RF resonant cavity which works on two TE113 modes and a novel coupler. As there is only one storage cavity, this pulse compressor can be much smaller than the traditional SLED. With the coupling coefficient 4.9, the average power gain can be as high as 3.8. In this paper, the scheme of the C-band spherical pulse compressor and RF design are presented.

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THPIK068

High Power Test of SINAP X-Band Deflector at KEK

electron, impedance, operation, laser

4251

J.H. Tan, W. Fang, Q. Gu, X.X. Huang, Z.B. Li, Z.T. Zhao
SINAP, Shanghai, People's Republic of China
T. Higo
KEK, Ibaraki, Japan
D.C. Tong
TUB, Beijing, People's Republic of China

A crucial RF structure used for bunch length measurement for Shanghai X-ray Free Electron Lasers (SXFEL) at the Shanghai Institute of Applied Physics (SINAP), Chinese Academy of Science [1]. The design, fabrication, measurement and tuning have been completed at SINAP [2], and the high power test was carried out at Nextef of KEK with international collaboration. This paper presents the RF conditioning process and test results.

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THPIK070

Localization of RF Breakdown Point in a Coaxially Loaded LINAC Cavity

linac, electron, operation, accelerating-gradient

4254

Q.S. Chen, T. Hu, B. Qin
HUST, Wuhan, People's Republic of China
Y.J. Pei
USTC/NSRL, Hefei, Anhui, People's Republic of China

Here we report how the RF breakdown point (RFBP) can be localized in a coaxially loaded linac cavity with just the forward and the reflected power signal. The cavity uses 4 load cells instead of output coupler to absorb remanent power, so no transmitted power signal could be recorded. We propose two methods to analyze the measured signals and localize the RFBP. One method focuses on the time delay of the two signals while the other one focuses on the amplitude. Quantitative analysis showed the two methods were well consistent with each other and indicated the RFBP located at the end of the linac cavity.

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THPIK072

Development of High Power RF Amplifier System for the KBSI RFQ

rfq, LLRF, operation, rf-amplifier

4257

J. Bahng
Kyungpook National University, Daegu, Republic of Korea
M.-H. Chun
PAL, Pohang, Kyungbuk, Republic of Korea
J.G. Hong, B.S. Lee, J.W. Ok
Korea Basic Science Institute, Busan, Republic of Korea
D.S. Kim
DAWONSYS, Ansan-si, Republic of Korea
E.-S. Kim
Korea University Sejong Campus, Sejong, Republic of Korea

KBSI (Korean Basic Science Institute) has been developed a compact accelerator system for generation of fast neutron by 2.7 MeV/u of lithium beam. The facility consists of 28 GHz SC-ECR ion source, LEBT, RFQ and DTL. The developed RFQ accelerator provides lithium ion beam from 12 keV/u to 500 keV/u with 98.88 % of high transmission rate at 165 MHz of operation frequency. RF power system for RFQ accelerator has been developed to provide sufficient RF power into RFQ cavity. which consists of LLRF system for control, 5 KW of SSPA as IPA, tetrode tube amplifier as FPA, coaxial transmission line and circulator for protection from reflection power provides 100 kW at operation frequency with CW mode, In this paper, we discuss about development of RF system and performance test in detail.

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THPIK073

Development of RFQ for BNCT Accelerator

rfq, operation, proton, emittance

4260

J. Bahng
Kyungpook National University, Daegu, Republic of Korea
B.H. Choi
IBS, Daejeon, Republic of Korea
B.H. Choi, D.S. Kim
DAWONSYS, Ansan-si, Republic of Korea
E.-S. Kim
Korea University Sejong Campus, Sejong, Republic of Korea

A accelerator for Boron Neutron Capture Therapy (BNCT) based on proton linac has been developed as a domestic project. The accelerator system consists of duo plasmatron as an ion source, low energy beam transport (LEBT), radio frequency quarupole (RFQ) accelerator, drift tube linac (DTL). In order to achieve beam power of 50 kW, the required beam intensity and energy are 50 mA and 10 MeV, respectively. Since high duty rate provides high efficient medical treatment, the design of the cw RFQ has been investigated to accelerate proton beam from 50 keV to 3 MeV with beam intensity of 60 mA. In this paper, beam dynamics and design of the RFQ are presented in detail.

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THPIK078

1.5 GHz Cavity Design for the CLIC Damping Ring and as Active Third Harmonic Cavity for ALBA

HOM, damping, impedance, simulation

4263

B. Bravo, J.M. Alvarez, F. Pérez, A. Salom
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

In a collaboration framework between CERN and ALBA, we are designing a normal conducting active 1.5 GHz cavity which could serve as main RF system for the Damping Ring of CLIC and as an active third harmonic cavity for the ALBA Storage Ring. The third harmonic cavity at ALBA will be used to increase the bunch length in order to improve the beam lifetime and increase the beam stability thresholds. The main advantage of an active third harmonic cavity is that optimum conditions can be reached for any beam current. This paper presents the preliminary design of this cavity: an active, normal conducting cavity tuned at 1.5 GHz based on the 500 MHz European Higher Order Mode (HOM) damped normal conducting with nose cones using ridged circular waveguides for HOM damping. Electromagnetic simulations, mechanical and thermal stress analysis will be presented together with the calculations on beam stability improvement due to the third harmonic system.

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THPIK083

Mechanical Fabrication of ESS-Bilbao RFQ

rfq, vacuum, linac, software

4279

J.L. Muñoz, I. Bustinduy, J. Martin, A. Ortega, I. Rueda, A. Zugazaga
ESS Bilbao, Zamudio, Spain
M.A. Carrera, A. Garbayo
AVS, Elgoibar, Spain

The fabrication of the first segment of ESS-Bilbao's RFQ has started in 2016. The segment, of about 800 mm in length, is an assembly of 4 elements: two major vanes and two minor ones. The assembly will be done by making use of carefully-designed vacuum polymeric gaskets instead of brazing. Electron beam welding has been used during fabrication of the vanes. Apart from conventional CAD systems, a home-made tool for vane modulation solid generation has been successfully used. Machining process from copper blocks to final elements is described in detail. Also, the software tools created to assess the quality of the vanes by analyzing the metrology measurements, particularly of the modulation, are described in the paper. In order to test and validate the chosen vacuum strategy, an aluminum model using the same gaskets as the final model was built and tested. Results will also be presented. The fabrication of the first segment is expected to end up in early 2017, so assembly, segment alignment and vacuum tests with the real device will also be included in the paper.

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THPIK086

Design and Implementation of Stripline Feedback Kickers in the MAX IV 3 GeV Ring

feedback, kicker, impedance, storage-ring

4285

D. Olsson, L. Malmgren, K. Åhnberg
MAX IV Laboratory, Lund University, Lund, Sweden

The commissioning of a bunch-by-bunch feedback system for the MAX IV 3 GeV storage ring was started in early 2016. At date, the actuators are two stripline kickers oriented in the horizontal and in the vertical plane, respectively. Apart from providing feedback in the transverse plane, the horizontal stripline is simultaneously operating as a longitudinal kicker. This is done by upconverting the longitudinal 0 - 50 MHz baseband signal to the 150 MHz - 250 MHz range where the longitudinal shunt impedance of the stripline is higher. This signal is then fed to the stripline electrodes in common-mode. The design of the stripline kickers and the layout of the bunch-by bunch feedback system in the 3 GeV ring are presented in this report. Results from instability studies in this ring are also discussed.

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THPIK087

A Waveguide Overloaded Cavity Kicker for the MAX IV Bunch-by-Bunch Feedback System

feedback, kicker, impedance, storage-ring

4289

D. Olsson, L. Malmgren, K. Åhnberg
MAX IV Laboratory, Lund University, Lund, Sweden

The higher-order modes (HOMs) in the main and the 3:rd harmonic cavities are driving longitudinal coupled-bunch mode instabilities (CBMIs) in the MAX IV 3 GeV storage ring. This far, negative feedback has been applied in the longitudinal plane by a stripline kicker at lower ring currents. However, the maximum longitudinal feedback voltage provided by the stripline is rather weak, and a waveguide overload cavity was therefore designed in order to suppress CBMIs at higher ring currents as well. Due to the long bunch length in the MAX IV storage rings, a relatively low center frequency of 625 MHz is selected. The new cavity kicker has been manufactured, and will be installed in the 3 GeV ring during the summer shut-down of 2017. In this paper, the RF and mechanical design of the cavity is presented. Simulation results are also compared with measurements of the manufactured cavity.

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THPIK094

Linac4 PIMS Construction and First Operation

linac, vacuum, alignment, operation

4307

R. Wegner, G. Favre, P. Françon, J.-M. Geisser, F. Gerigk, J.-M. Giguet, J. Hansen, J.-B. Lallement, A.M. Lombardi, S. Papadopoulos, M. Polini, M. Redondas Monteserin, T. Tardy, N. Thaus, M. Vretenar
CERN, Geneva, Switzerland
W. Behr, M. Pap
Forschungszentrum Jülich GmbH, Central Institute of Engineering, Electronics and Analytics, Jülich, Germany
G. Brzezinski, P. Krawczyk, L. Kujawinski, M. Marczenko
NCBJ, Świerk/Otwock, Poland

Linac4, CERN's new H⁻ injector Linac uses PI-Mode Structures (PIMS) for the energy range between 10³ and 160 MeV. 180 copper elements for 12 PIMS cavities have been fabricated in a collaboration between CERN, NCBJ and FZJ from 2011 to 2016. The cavities have been assembled, RF tuned and validated at CERN. This paper reports on the results as well as the experience with construction, installation, RF conditioning and first operation with beam.

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THPIK102

Commissioning of the SLRI Storage Ring Second RF System

electron, LLRF, storage-ring, rf-amplifier

4328

N. Juntong, S. Boonsuya, S. Cheedket, Ch. Dhammatong, S. Krainara, W. Phacheerak, R.R. Rujanakraikarn, N. Suradet
SLRI, Nakhon Ratchasima, Thailand

The old RF cavity in the storage ring of SIAM Photon Source (SPS), the 1.2 GeV second generation synchrotron light source in Thailand, has been pushed to its maximum capability to compensate electron energy lost in the storage ring. This energy lost is the effect from two additional insertion devices, which have been installed in SPS storage ring during June to August 2013. The new RF system has been planned since 2012, but with some technical and procurement difficulty the new system was successfully commissioning and running in August 2016. The installation, acceptance testing, conditioning and commissioning results of the new RF cavity, RF high power transmitter, and the low level RF system will be presented

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THPIK103

Six Months of Operation of the New RF Cavity System of SLRI

operation, storage-ring, radiation, status

4331

N. Juntong, Ch. Dhammatong, P. Sudmuang, N. Suradet
SLRI, Nakhon Ratchasima, Thailand

The new RF cavity system has been installed in the storage ring of SIAM Photon Source (SPS) since August 2016. The RF cavity was designed base on the MAX-IV laboratory capacitive loaded type cavity. The solid-state technology was implemented in the RF high power transmitter. The low-level RF system utilized the digital technology. The system has been successfully commissioned and run with a capability to compensate an energy lost from a full capacity run of insertion devices since August 2016. This paper summarizes the problems and actions of the new RF system and presents an overview of six months of operation of the new RF system in the storage ring of SPS.

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THPIK106

Low Power RF Characterisation of the 400 Hz Photoinjector for CLARA

cathode, simulation, linac, vacuum

4342

L.S. Cowie, P. Goudket, B.L. Militsyn
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
T.J. Jones
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

The CLARA High Repetition Rate Photoinjector comprises an S-band dual feed cavity and will operate at a repetition rate of up to 400 Hz and is capable of reaching an electric field strength on the cathode of 120 MV/m. The cavity was brazed after tuning and arrived at Daresbury Laboratory in February 2016. Extensive low power RF testing has been performed including measurements of the quality factors and coupling, pass-band mode frequencies, on axis field and RF repeatability of replacement of cathode plug. The dual feed coupler has been tuned and a Magic Tee type splitter installed. The photoinjector is now installed on the VELA beam line for commissioning and characterisation.

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THPIK108

Bead Pull Measurements of the FETS RFQ at RAL

rfq, quadrupole, site, radio-frequency

4349

W. Promdee, T.R. Edgecock
IIAA, Huddersfield, United Kingdom
G.E. Boorman
Royal Holloway, University of London, Surrey, United Kingdom
G.E. Boorman
JAI, Egham, Surrey, United Kingdom
T.R. Edgecock, J.K. Pozimski
STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
A.P. Letchford
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
J.K. Pozimski
Imperial College of Science and Technology, Department of Physics, London, United Kingdom

A Radio Frequency Quadrupole (RFQ) is a part of the Front End Test Stand (FETS) at the Rutherford Appleton Laboratory (RAL), Didcot, UK. The aim of the FETS project is to produce a 60 mA H⁻ beam at 3 MeV. The RFQ is a four-vane type with 4 modules, each of 1 m length, and is designed to accelerate the beam from 65 keV to 3 MeV at 324 MHz. A bead pull system has been designed to measure the field along the RFQ. This will be used in conjunction with 64 tuners to produce a uniform field. In order to optimise the tuning procedure, a model of the RFQ has been creat-ed in COMSOL Multiphysics. This study shows the results from the bead pull measurements and the tuning studies.

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THPIK109

The RF Distribution System for the ESS

detector, linac, neutron, insertion

4352

T.R. Edgecock, N. Turner
University of Huddersfield, Huddersfield, United Kingdom
P. Aden, D. Naeem, R. Smith
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
A. Sunesson, R.A. Yogi
ESS, Lund, Sweden

The RF distribution system for the European Spallation Source will be one of the largest systems ever built. It will distribute the power from 146 power sources to the two types of ESS cavity at two different frequencies and will use one line per cavity for resilience. It will consist of a total of around 3.5 km of waveguide and coaxial line and over 1500 hundred bends. It is designed to transport this RF power over a distance of up to 40m per line, while minimising losses, avoiding reflections and allowing the monitoring of performance. This contribution will give an overview of the design of the system and its status. Installation is due to start in September 2017.

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THPIK110

RF Cavity Design for a Low Cost 1 MeV Proton Source

proton, simulation, acceleration, impedance

4355

D. Soriano Guillén, R. Seviour
University of Huddersfield, Huddersfield, United Kingdom
S. Hunt
Alceli Accelerator Technology Ltd., Huddersfield, United Kingdom

In this paper we present the design for a low-cost RF cavity capable of accelerating protons from 100 keV to 1 MeV. The system is designed to meet the specifications from the proposed Alceli LTD medical proton therapy linac, to deliver a 1 nA proton beam current with a 1 kHz repetition rate. We present a design of an RF normal conducting (NC) re-entrant Cu cavity operating at 40 MHz consisting of a coupled two cavity system, both driven by a single Marx generator. The choice of such a low operating frequency for the cavity system enables us to use a relatively low-cost cost Marx Generator as the RF source. Marx generators work in a similar fashion to a Cockcroft-Walton accelerator (without the expensive components), creating a high-voltage pulse by charging a number of capacitors relatively slowly in parallel, then rapidly discharging in series, via spark gaps. Marx generators can deliver 2.5 GW, 1 ns pulses, with rise times of 200 ps, and (relatively) low jitter.

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THPIK112

Progress With the Diamond Light Source RF Upgrade

operation, storage-ring, superconducting-cavity, HOM

4358

C. Christou, A.G. Day, M.J. Duignan, P. Gu, N.P. Hammond, P.J. Marten, S.A. Pande, D. Spink
DLS, Oxfordshire, United Kingdom

Failure of a superconducting cavity in the Diamond storage ring can lead to extended down-time because of the time required to remove the module from the ring, the inability to access the cavity without removal from the cryostat and the long time to repair of the module. To reduce the risk to storage ring operation, normal conducting cavities are being installed to support operation of the superconducting cavities. Two cavities will be introduced in 2017 and work is progressing with RF amplifiers, transmission lines and low-level RF as well as storage ring engineering and controls. A summary of progress so far is presented and the plan for installation and further RF upgrades is outlined.

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THPIK113

Tuner of a Second Harmonic Cavity of the Fermilab Booster

injection, booster, resonance, extraction

4362

I. Terechkine, K.L. Duel, R.L. Madrak, A.V. Makarov, G.V. Romanov, D. Sun, C.-Y. Tan
Fermilab, Batavia, Illinois, USA

Introducing a second harmonic cavity in the accelerating system of the Fermilab Booster promises significant reduction of the particle beam loss during the injection, transition, and extraction stages. To follow the changing energy of the beam during acceleration cycles, the cavity is equipped with a tuner that employs perpendicularly biased AL800 garnet material as the frequency tuning media. The required tuning range of the cavity is from 75.73 MHz at injection to 10⁵.64 MHz at extraction. This large range necessitates the use of a relatively low bias magnetic field at injection, which could lead to high RF loss power density in the garnet, or a strong bias magnetic field at extraction, which could result in high power consumption in the tuner's bias magnet. The required 15 Hz repetition rate of the device and high sensitivity of the local RF power loss to the level of the magnetic field added to the challenges of the bias system design. In this report, the main features of a proposed prototype of the second harmonic cavity tuner are presented.

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THPIK115

Status of the Perpendicular Biased 2nd Harmonic Cavity for the Fermilab Booster

Windows, booster, simulation, solenoid

4366

C.-Y. Tan, J.E. Dey, K.L. Duel, J. Kuharik, R.L. Madrak, A.V. Makarov, W. Pellico, J. Reid, G.V. Romanov, M. Slabaugh, D. Sun, I. Terechkine
Fermilab, Batavia, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
This is a status report on the 2nd harmonic cavity for the Fermilab Booster as part of the Proton Improvement Plan (PIP) for increasing beam transmission efficiency, and thus reducing losses. A set of tuner rings has been procured and is undergoing quality control tests. The Y567 tube for driving the cavity has been successfully tested at both injection and extraction frequencies. A cooling scheme for the tuner and cavity has been developed after a thorough thermal analysis of the system. RF windows have been procured and substantial progress has been made on the mechanical designs of the cavity and the bias solenoid. The goal is to have a prototype cavity ready for testing by the end of 2017.

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THPIK116

Static Magnetization Properties of AL800 Garnet Material

booster, injection, extraction, power-supply

4370

J. Kuharik, R.L. Madrak, A.V. Makarov, W. Pellico, D. Sun, C.-Y. Tan, I. Terechkine
Fermilab, Batavia, Illinois, USA

A second harmonic tunable RF cavity is being developed for the Fermilab Booster. This device, which promises reduction of the particle beam loss at the injection, transition, and extraction stages, employs perpendicularly biased garnet material for the frequency tuning. The required range of the tuning is significantly wider than in previously built and tested tunable RF devices. As a result, the magnetic field in the garnet becomes fairly close to the gyromagnetic resonance line at the lower end of the frequency range. The chosen design concept of a tuner for the cavity cannot ensure uniform magnetic field in the garnet material; thus it is important to know the static magnetic properties of the material to avoid significant increase in the local RF loss power density. This report summarizes studies performed at Fermilab to understand variations in the magnetic properties of the AL-800 garnet material used to build the tuner of the cavity.

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THPIK117

High Efficiency High Power Resonant Cavity Amplifier for Accelerator Applications

operation, coupling, impedance, network

4374

M.P.J. Gaudreau, D.B. Cope, E.G. Johnson, M.K. Kempkes, J. Kinross-Wright, R.E. Simpson
Diversified Technologies, Inc., Bedford, Massachusetts, USA

Funding: Work supported by US Department of Energy under contract DE-SC0015780
Diversified Technologies, Inc. (DTI) has designed and built a unique integrated resonant-cavity combined solid-state amplifier. The design radically simplifies solid-state transmitters to create favorable and straightforward scaling to high power levels. A crucial innovation is demonstration of an inherently reliable soft-failure mode of operation; a failure in one or several of these myriad combined transistors has negligible performance impact. In addition, this design couples the transistor drains directly to the cavity without first transforming to 50 Ohms, avoiding the otherwise-necessary multitude of circulators, cables, and connectors. A conventional amplifier has a complete set of electrical and cooling connections for every stage, resulting in many hundreds of connections for a high power transmitter'in some DTI designs, there are as few as four. This construction both reduces the cost and increases the power level at which it is cost-effective to employ a solid-state transmitter. The prototype has demonstrated multiple-transistor combining from 300 MHz to 1300 MHz, at powers up to 5 kW. This prototype is scalable to several hundred kW at these frequencies.

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THPIK118

Final Assembly and Testing of MICE RF Modules at LBNL

vacuum, coupling, low-level-rf, HOM

4377

T.H. Luo, A.R. Lambert, D. Li, S.P. Virostek, J.G. Wallig
LBNL, Berkeley, California, USA
T.G. Anderson, A.D. Bross, D.W. Peterson
Fermilab, Batavia, Illinois, USA
M.A. Palmer
BNL, Upton, Long Island, New York, USA
Y. Torun
Illinois Institute of Technology, Chicago, Illlinois, USA

Funding: Work supported by the Office of Science, U.S. Department of Energy under DOE contract number DE-AC02-05CH11231
The international Muon Ionization Cooling Experiment aims to demonstrate the transverse cooling of a muon beam by ionization interaction with absorbers and re-acceleration in RF cavities. The final MICE cooling channel configuration has two RF modules, each housing a 201 MHz RF cavity to compensate the longitudinal energy loss in the absorbers. Two RF modules have been assembled and tested at LBNL. This paper reports the final assembly work, as well as the vacuum test and low level RF measurements.

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THPIK120

The RF and Mechanical Design of a Compact, 2.5 kW, 1.3 GHz Resonant Loop Coupler for the APEX Buncher Cavity

vacuum, electron, operation, resonance

4380

S.P. Virostek, F. Sannibale, J.W. Staples
LBNL, Berkeley, California, USA
H.J. Qian
DESY Zeuthen, Zeuthen, Germany

Funding: This work is supported by the Office of Science, United States Department of Energy under DOE contract DE-AC02-05CH11231.
The Advanced Photo-injector Experiment (APEX) at the Lawrence Berkeley National Laboratory (LBNL) is an injector system designed to demonstrate the capability of a normal conducting 186 MHz RF gun operating in CW mode to deliver the brightness required by X-ray FEL applications operating at MHz repetition rate, such as LCLS-II. A 240 kV, 1.3 GHz CW buncher cavity design was developed as part of the APEX experiment. The two-cell cavity profile has been optimized to minimize the RF power requirements and to remove multipacting resonances over the full range of operation. In order to excite the cavity stably at pi-mode and remove the dipole-like coupler kick, the two cells are to be independently driven by four, 2.5 kW, coaxial resonant loop couplers with integrated ceramic windows and a matching section in the body of the coupler. The coupler's inner conductor has a single diameter change at a specified distance from the ceramic insulator in order to cancel the wave reflected from the ceramic window, thus comprising the matching section. The details of the RF analysis, mechanical design, fabrication and testing of the coupler are presented here.

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THPIK121

Eddy Current Analysis for a 1.495 GHz Injection-Locked Magnetron

interaction-region, injection, klystron, SRF

4383

S.A. Kahn, A. Dudas, R.P. Johnson, M.L. Neubauer
Muons, Inc, Illinois, USA
R.A. Rimmer, H. Wang
JLab, Newport News, Virginia, USA

Funding: U.S. DOE SBIR/STTR grant DE-SC0013203
An injection-locked amplitude modulated magnetron is being developed as a reliable, efficient RF source that could replace klystrons used in particle accelerators. A trim magnetic coil is used to alter the magnetic field in conjunction with the anode voltage to maintain an SRF cavity voltage while the cavity is experiencing microphonics and changing beam loading. The microphonic noise modes have frequencies in the range 10-100 Hz. The changing magnetic field will induce transient eddy currents in the copper anode of the magnetron which will buck the field in the interaction region. This paper will describe the calculation and handling of the eddy currents in the magnetron.

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THPIK123

Magnetron Design for Amplitude Modulation

injection, cryomodule, radiation, vacuum

4389

M.L. Neubauer, A. Dudas, S.A. Kahn
Muons, Inc, Illinois, USA
R.A. Rimmer, H. Wang
JLab, Newport News, Virginia, USA

The amplitude modulation (AM) of a magnetron is accomplished by varying the magnetic field which changes the current to the anode and the output power of the injection locked magnetron. The purpose of the AM is to compensate for microphonics in super conducting cavities by maintaining a constant gradient. The frequency range for the microphones is below 200 Hz. At these frequencies, eddy currents are encountered in the magnetron anode that reduce the effectiveness of the varying magnetic field on the magnetron current. A novel anode design is described which minimizes eddy currents and a method for manufacturing this novel magnetron anode is presented

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THPIK124

Using Conductive Nanoparticles to Reduce the Surface Charging of Ceramics

cryogenics, electron, experiment, vacuum

4392

M.L. Neubauer, A. Dudas
Muons, Inc, Illinois, USA
F. Marhauser
JLab, Newport News, Virginia, USA

Beam pipe ceramics used for various purposes suffer from the problem of surface charging in the presence of an electron beam. A novel technique has been proposed for a method for reducing the charging effects by filling nano sized pores in the ceramic with a conductive medium. Pores in ceramics can be formed in a chain with varying depths depending on sintering temperatures and methods for creating the pores. In the pre-formed condition of these novel ceramics, a nanoparticle slurry is infused by capillary action into the ceramic and fired at temperatures and atmospheres to stabilize the conductive medium inside the ceramic. The microwave characteristics of these ceramics will be investigated in a Phase I program with the design of a complete beam pipe lossy ceramic in a Phase II.

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THPIK125

Ultra High Gradient Breakdown Rates in X-Band Cryogenic Normal Conducting Rf Accelerating Cavities

accelerating-gradient, cryogenics, experiment, electron

4395

A.D. Cahill, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
V.A. Dolgashev, S.G. Tantawi, S.P. Weathersby
SLAC, Menlo Park, California, USA

Funding: Work Supported by DOE/SU Contract DE-AC02-76-SF00515, US NSF Award PHY-1549132, the Center for Bright Beams, and DOE SCGSR Fellowship.
RF breakdown is one of the major factors limiting the operating accelerating gradient in rf particle accelerators. We conjecture that the breakdown rate is linked to the movements of crystal defects induced by periodic mechanical stress. Pulsed surface heating possibly creates a major part of this stress. By decreasing crystal mobility and increasing yield strength we hope to reduce the breakdown rate for the same accelerating gradient. We can achieve these properties by cooling a copper accelerating cavity to cryogenic temperatures. We tested an 11.4 GHz cryogenic copper accelerating cavity at high power and observed that the rf and dark current signals are consistent with Q₀ changing during rf pulses. To take this change in Q₀ into account, we created a non-linear circuit model in which the Q₀ is allowed to vary inside the pulse. We used this model to process the data obtained from the high power test of the cryogenic accelerating structure. We present the results of measurements with low rf breakdown rates for surface electric fields near 500 MV/m for a shaped rf pulse with 150 ns of flat gradient.

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THPIK126

Design of a Field-Emission X-Band Gun Driven by Solid-State RF Source

electron, gun, experiment, linac

4399

E.A. Nanni, V.A. Dolgashev, J. Neilson, S.G. Tantawi
SLAC, Menlo Park, California, USA
B.E. Carlsten, J.W. Lewellen, D.C. Nguyen
LANL, Los Alamos, New Mexico, USA
M. Othman
UCI, Irvine, California, USA

We present the design of a field-emission X-band gun designed to be powered using a solid-state RF source. The source of the electron beam is a field emission nano-tip array. The RF gun is intended to be a beam source for 1 MeV solid-state driven linac for deployment on a satellite to map magnetic fields in the magnetosphere. The gun has to satisfy strict requirements on both average and peak power consumption, as well as rapid turn on time. In order to achieve low power consumption, the RF gun operates at relatively low accelerating gradient of 2 MeV/m. The beam exit energy is ~20 keV for an RF power 1.5 kW. Each cell of the RF gun is separately powered by commercially available, GaN high electron mobility transistors. In proof of principle experiments we successfully powered a 9.3 GHz accelerating cavity with a 100 W transistor and a 1% duty cycle.

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THPVA044

Detector Structure Development Using Active And Passive Thermography

detector, target, laser, experiment

4531

E. Rosenthal, D. Grunwald, G. Natour
Forschungszentrum Jülich GmbH, Central Institute of Engineering, Electronics and Analytics, Jülich, Germany

During the development and production of the mechanical support structures of the PANDA-Micro-Vertex-Detector(MVD)* experiments of passive and active thermography were applied and shown. The combination of mostly carbon-based materials enables the development of lightweight structures, which satisfy the mechanical stability and thermal requirements. The carrier structure of the MVD stripe detector is mainly composed of carbon foams, high fiber content CFC materials and PMI-based foams. This enables to selectively cool areas where heat is generated and to decouple them from the temperature-sensitive areas of the sensor system. Passive thermography is used during our development work mainly to validate the results of thermal simulations, for design optimization and for the functional control of the carrier structure. Additionally active thermography allows us to identify anomalies and thermal disturbances, which remain unnoticed in static processes. Also the investigation and characterization of adhesive layers are possible. For this purpose we developed special software algorithms which are sensitive to small-scale differences in temperature conductivity.
* PANDA Collaboration: W. Erni et al., arXiv: 1207.6581

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THPVA047

Developing an Yb/Nd Doped Hybrid Solid Laser of RF Gun for SuperKEKB Phase II Commissioning

laser, gun, electron, emittance

4540

X. Zhou, T. Natsui, Y. Ogawa, M. Yoshida, R. Zhang
KEK, Ibaraki, Japan

The electron beams with a charge of several nC and a normalized emittance of less than 10 'm are expected to be generated in the photocathode RF gun for injector linac of SuperKEKB accelerator project. By development of the Yb-doped laser system, more than 1.0 nC electron has been obtained in 25 Hz. The laser system is already for commissioning phase I. But, the 30 ps pulse width stretch limit the pulse energy of the amplifier laser system. As well-established laser material, Nd:YAG rods with high optical homogeneity and high damage threshold, simplify the design of high-pulse-energy amplifier. Therefore, a new Nd/Yb hybrid laser system is development to increase the pulse energy of the laser source. For phase II commissioning, more than 3 nC electron beam is expected. Also, a chirped pulse amplification (CPA) laser system is prepared for the phase III commissioning, both pulse energy and pulse shaping controller are expected.

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THPVA059

Development of a New High Power RF Window for S-band Linac

klystron, linac, vacuum, high-voltage

4576

W.H. Hwang, J.Y. Choi, Y.D. Joo, S.H. Kim, B.-J. Lee
PAL, Pohang, Kyungbuk, Republic of Korea
S.J. Roh
Vitzrotech Co., Ltd., Ansan City, Kyunggi-Do, Republic of Korea

A prototype rf window was developed in collaboration with Pohang Accelerator Laboratory (PAL) and domestic companies. The PAL designed the S-band TE012 rf window and conducted the high power performance tests of single rf window to verify the operation characteristics for the application to the PLSII Linac. The test was performed in the in-situ facility consisting of a modulator, klystron, waveguide network, vacuum system, cooling system, and rf analyzing equipment. As the test results with SLED, no breakdown appeared up to 75 MW peak power with 4.5 micro-seconds rf pulse width at a repetition rate of 10 Hz. The test results with the current operation level of PLSII Linac confirms that the rf window well satisfies the criteria of PLS Linac operation.

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THPVA060

Technical Overview of Inter-Undulator Support System for PAL XFEL

undulator, quadrupole, controls, feedback

4579

H.-G. Lee, S.-H. Jeong, Y.G. Jung, H.-S. Kang, D.E. Kim, S.B. Lee, B.G. Oh, K.-H. Park, H.S. Suh
PAL, Pohang, Kyungbuk, Republic of Korea

Pohang Accelerator Laboratory (PAL) has been developing a SASE X-ray Free Electron Laser based on 10 GeV linear accelerator. The inter-Undulator (IU) support system was developed to be used in the intersections of the Undulator Systems. The IU supports consist of phase shifter, quadrupole magnet with mover, beam loss monitor, cavity BPM with mover, two corrector magnets and vacuum components. The adjusting mechanism of IU Support has manual alignment system to be easily adjusting the component. The mover of quadruple magnet and cavity BPM with submicron repeatability has auto-adjusting systems with stepping motor. The mover main specifications include compact dimensions and a ±1.5 mm stroke in the vertical and horizontal direction. Linear motion guide based on 5-phase stepping motors have been chosen. This paper describes the design of the stages used for precise movement and results of mechanical measurements including reproducibility will be reported.

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THPVA062

Fabrication and Tests of a RF Cavity for a Novel Compact Superconducting Cyclotron for Radioisotope Production

cyclotron, vacuum, simulation, pick-up

4585

D. Gavela, J. Calero, L. García-Tabarés, P. Gómez, D. López, D. Obradors-Campos, C. Oliver, J.M. Pérez Morales, I. Podadera, F. Toral
CIEMAT, Madrid, Spain
B. Bravo, R. Fos, J.R. Ocampo, F. Pérez, A. Salom, P. Solans
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

Funding: Work partially funded by CDTI and supported by the Spanish Ministry of Economy and Competitiveness, under project AMIT, within the subprogram CEN-20101014
The AMIT cyclotron will be a 8.5 MeV, 10 microAmp, CW, H⁻ accelerator for radioisotope production, including a superconducting, weak focusing, 4 T magnet, allowing for a low extraction radius and a compact design. The cavity is a 60 MHz, quarter wave resonator powered by a modular 8 kW solid state amplifier. The design of the cavity dealed with challenging requirements: high electric fields required by a high voltage (60 kV) on a small gap, a small aperture of the magnet leading to high capacitances and thermal losses and a requirement for a low overall size of the cavity. The fabrication process included high precision machining, soft soldering, laser welding and careful metrologies, which are described together with other technical and practical aspects. The low power tests showed a good agreement with the simulations. The conditioning of the cavity was performed with a 1.1 T magnetic field applied on the central region. It was successfully finished regarding to maximum voltage reached, power losses and temperatures. The cavity was also tested at high power with a constant hydrogen flow injected in the central region (as expected in the cyclotron) with success.

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THPVA071

A Method to Design Multi-Cell Accelerator Cavities

DTL, linac, drift-tube-linac, focusing

4610

S.S. Kurennoy
LANL, Los Alamos, New Mexico, USA

An efficient method for designing multi-cell accelerator cavities has been developed. It is similar to the approach used by Superfish codes for drift-tube linacs (DTL), where a few single cells at representative beam velocities are tuned in 2D and their geometrical parameters are interpolated to cover the required beam-velocity range. The method is implemented using 3D electromagnetic (EM) modeling with CST MicroWave Studio, which allows its application for various types of resonators, e.g., for H-mode cavities. Interpolating results of 3D EM design of tuned representative single-cell cavities leads to a 3D multi-cell cavity model that can be finalized with just a few small adjustments. As a challenging application example, we design multi-cell resonators of three types - cross-bar (CH) and inter-digital (IH) H-mode, as well as DTL - for accelerating muons in the velocity range of v/c = 0.08-0.3, and compare their performance.

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THPVA085

Design and Construction of 126 MHz Capacity Loaded Aluminium Cavity Prototype

simulation, higher-order-mode, impedance, pick-up

4653

S. Ahmadiannamin, J. Rahighi, Kh.S. Sarhadi
ILSF, Tehran, Iran
F. Abbasi
Shahid Beheshti University, Tehran, Iran
M. Lamehi Rashti
IPM, Tehran, Iran

Iranian light source Facility (ILSF)isa 3 GeV Ultra low emittance synchrotron with 528 meter circumference that will be constructed in the city of Qazvin, located 150km west of Tehran. Motivated by the development of HOM damped cavity with simpler structure at 100 MHz at MAX Lab and also lower costs, 100 MHz RF system is envisaged for ILSF booster and storage ring. An RF cavity prototype was fabricated for better understandingof characteristics of capacity loaded RF cavities by practical investigation. In this paper, design and development of this prototype is presentedwith the simulation and measurement results.

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THPVA087

Thermal and Mechanical Analysis of 3 GHz Side Coupled RF Cavity for Medical Linacs

simulation, electron, linac, operation

4660

M. Mohseni Kejani, F. Abbasi
Shahid Beheshti University, Tehran, Iran
S. Ahmadiannamin
ILSF, Tehran, Iran
F. Ghasemi
NSTRI, Tehran, Iran
S. Zarei
Nuclear Science and Technology Research, InstituteRadiation Application School, Tehran, Iran

Medical linear accelerators have wide applications for cancer treatment in the world. Side coupled RF cavities was used in this accelerators for production of X-ray in range of energies between 4 to 25 MeV. Usually, the RF source is magnetron with lower cost in comparison to klystron in this type of applications. Side coupled cavity is a biperiodic structure with sensitive performance to operational thermal and mechanical conditions. In this paper, thermal and mechanical simulations for a period of the structure are presented.

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THPVA088

DESIGN AND CONSTRUCTION OF BRAZED SIDE COUPLED CAVITY OF MEDICAL ACCELERATOR

coupling, simulation, vacuum, electron

4664

S. Ahmadiannamin, Kh.S. Sarhadi
ILSF, Tehran, Iran
F. Abbasi, M. Mohseni Kejani
Shahid Beheshti University, Tehran, Iran
M. Bahrami, M. Lamehi
IPM, Tehran, Iran
F. Ghasemi
NSTRI, Tehran, Iran
S. Zarei
Nuclear Science and Technology Research, InstituteRadiation Application School, Tehran, Iran

Two types of standing wave RF cavities are used routinely in construction of medical linear accelerators. These two types are Side coupled and on-axis coupled standing wave cavities. This selection is based on higher shunt impedance and compactness in comparison to travelling wave RF cavities. In this paper, we present the simulation, construction and measurement results of brazed section of 3 GHz side coupled RF cavity. It is the first successful experience of its kind in Iran. The obtained experiences can be used effectively for construction of side coupled thermionic RF guns and RF cavities of medical or industrial linacs.

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THPVA105

A Novel Side Coupling Standing-Wave Accelerating Structure for a Medical Linac

coupling, electron, impedance, linac

4710

Zh. X. Tang, Z.H. Bai, Y.J. Pei
USTC/NSRL, Hefei, Anhui, People's Republic of China

A novel side coupling standing-wave (SW) accelerat-ing tube for low energy medical linac has been designed that operating frequency is 2998 MHz, operating mode is ', final energy is 6 MeV and beam current is 130 mA. A novel bridge hole between an accelerating cavity and coupling cavity has been utilized to reduce the mutual effect between two cavities and improve the anti-jamming capability and the long term stability. The inner end plate of the inlet of the first accelerating cavity in-cludes the nose cone to realize self-focusing in transverse to improve the beam quality. The simulation of the elec-tromagnetic field of structure and beam dynamic has been carried out with the SUPERFISH, CST Microwave studio and Parmela, respectively.

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THPVA114

Status of High-Efficiency Klystron Development for the PLS-II and PAL-XFEL

klystron, electron, gun, cathode

4726

S.J. Park, H.S. Han, W.H. Hwang, S.D. Jang, Y.D. Joo, K.R. Kim, C.D. Park, Y.J. Park
PAL, Pohang, Kyungbuk, Republic of Korea
J.H. Hwang, S.S. Jang
POSTECH, Pohang, Kyungbuk, Republic of Korea
S.Y. Hyun, H.S. Seo, D.H. Yu
Vitzrotech Co., Ltd., Ansan City, Kyunggi-Do, Republic of Korea

Funding: This work was supported by the National R&D program (grant number: 2016R1A6B2A01016828) through the National Research Foundation of Korea (NRF).
We are developing a high-efficiency klystron for use in the PLS-II(Pohang Light Source II) and the PAL-XFEL in the Pohang Accelerator Laboratory. Since the PLS-II and the PAL-XFEL are already running with ~70 klystron modulator systems, newly developed klystrons should be designed to fit into existing installation spaces and power supplies, and their overall lengths(< 2 m) and beam perveances(2 upervs) should not be changed. In order to achieve the high efficiency with aforementioned boundary conditions, we are going to adopt a multi-cell output cavity in which, unlike those of the the SLAC X-band and KEK C-band klystrons, the cell frequencies are independently tuned to provide maximum beam-to-rf power conversion. In this article we report on our physics and engineering design efforts to achieve the high efficiency with minimum instabilities.

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THPVA120

Present Status of the SC202 Superconducting Cyclotron Project

cyclotron, simulation, extraction, proton

4730

G.A. Karamysheva, S. Gurskiy, O. Karamyshev, G. Kazakova, N.A. Morozov, D.V. Popov, E.V. Samsonov, G. Shirkov, S.G. Shirkov, G.V. Trubnikov
JINR, Dubna, Moscow Region, Russia
Y.F. Bi, G. Chen, Y. Chen, K.Z. Ding, H. Feng, J. Li, Y. Song, Y.H. Xie, Q. Yang, J. Zheng
ASIPP, Hefei, People's Republic of China
V. Malinin
JINR/DLNP, Dubna, Moscow region, Russia

In 2015 the joint project with ASIPP (Hefei, China) on design and construction of superconducting proton cyclotron SC202 was started. Two copies of SC202 shall be produced, according to the Collaboration Agreement between JINR and ASIPP. One will be used for proton therapy in Hefei and the second one will be used to replace the Phasotron in the research and treatment program on proton therapy at JINR. Recent status of the SC202 superconducting cyclotron for hadron therapy design and manufacture is presented.

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THPVA134

Coupled Longitudinal and Transverse Beam Dynamics Studies for Hadron Therapy Linacs

simulation, proton, cyclotron, linac

4772

R. Apsimon, G. Burt, S. Pitman
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
A.F. Green, H.L. Owen
UMAN, Manchester, United Kingdom

Precise proton therapy planning can be assisted by augmenting conventional medical imaging techniques with proton computed tomography (pCT). For adults this requires an incident proton energy up to at least 330 MeV, an energy not readily accessible using cyclotrons. We are presently constructing a prototype of the ProBE 54 MV/m 3GHz post-cyclotron booster linac as a compact method to achieve 330 MeV in the context of the Christie Hospital proton therapy centre, to be tested in the research room there. In this paper, we present beam dynamics studies and tracking simulations of proton beams through the booster region. The longitudinal and transverse particle transmission is calculated from tracking simulations and compared to theoretical models to help understand how best to optimise the optics design through the ProBE region.

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THPVA135

ProBE: Proton Boosting Extension for Imaging and Therapy

proton, cyclotron, booster, linac

4776

S. Pitman, R. Apsimon, G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
A.F. Green, H.L. Owen
UMAN, Manchester, United Kingdom
A. Grudiev, A. Solodko, W. Wuensch
CERN, Geneva, Switzerland

Funding: This work was funded by STFC
The ProBE linac aims at accelerating protons from a particle therapy cyclotron to the c.330 MeV required for proton tomography. To obtain the c. 55 MV/m gradients required to achieve 100 MeV gain in a suitably short distance, we propose the use of a high-gradient S-band side-coupled standing-wave structure. In this paper we discuss the progress toward the testing of the prototype at the S-box facility at CERN.

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THPVA143

Beam-Breakup Studies for the 4-Pass Cornell-Brookhaven Energy Recovery LINAC Test Accelerator

HOM, simulation, lattice, dipole

4801

W. Lou, J.A. Crittenden, G.H. Hoffstaetter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Cornell University and Brookhaven National Laboratory are currently designing the Cornell-BNL ERL Test Accelerator (CBETA). To be built at Cornell's Wilson Lab, CBETA utilizes the existing ERL injector and main linac cryomodule (MLC). As the electron bunches pass through the MLC cavities, higher order modes (HOMs) are excited. The recirculating bunches interact with the HOMs, which can give rise to beam-breakup instability (BBU). Here we present simulation results on how BBU limits the maximum achievable current, and potential ways to improve the threshold current.

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THPVA147

KlyLac Conceptual Design for Borehole Logging

linac, klystron, electron, vacuum

4808

A.V. Smirnov, S. Boucher, M.A. Harrison, A.Y. Murokh
RadiaBeam Systems, Santa Monica, California, USA
R.B. Agustsson, D. Chao, J.J. Hartzell, K.J. Hoyt, A.Yu. Smirnov
RadiaBeam, Santa Monica, California, USA
E.A. Savin
MEPhI, Moscow, Russia

Funding: This work was supported by the U.S. Department of Energy (award No. DE-SC0015721).
Linac-based system for borehole logging exploits KlyLac approach combing klystron and linac sharing the same electron beam, vacuum volume, and RF net-work. The conceptual design tailors delivering 3.5-4 MeV electrons within 3.5 inch borehole at ambient temperatures 150 degrees C to replace 137Cs, >1 Ci source used in borehole logging. The linac part is based on a very robust, high group velocity, cm-wave, standing wave accelerating structure. The design concept features i) self-oscillation analog feedback that automatically provides modal stability; ii) ferrite-free isolation of the klystron; and iii) long accelerating section with large (0.3%) frequency separation between adjacent modes; and iv) low-voltage klystron.

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THPVA154

LLRF Hardware Testbench

LLRF, hardware, controls, cryomodule

4821

J.A. Diaz Cruz, S. Biedron, S.V. Milton
CSU, Fort Collins, Colorado, USA
A.L. Benwell, A. Ratti
SLAC, Menlo Park, California, USA

With continual advances and the development of new technologies, such as superconducting cavities, particle accelerators have become more complex. New accelerator designs have more demanding stability requirements for the cavity RF fields, up to 0.01% in amplitude and 0.01' in phase for hundreds of cavities in Continuous Wave (CW) operation. Compensating for disturbances from mechanical resonances, microphonics, natural couplings and unwanted channel crosstalk is a challenge for the Low Level Radio Frequency (LLRF) control systems. For the upgrade to the Linac Coherent Light Source (LCLS-II) at SLAC, a high performance LLRF control system is being designed and developed to drive the Solid State Amplifiers (SSA) and control the cavity fields within specifications. The different components of the LLRF hardware have been designed, constructed and tested separately. Here, we describe a test environment, still under development, for integration, characterization and qualification of the LLRF system with all the LLRF hardware integrated in a single prototype rack.

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FRXCB1

The Energy Efficiency of High Intensity Proton Driver Concepts

proton, linac, cyclotron, SRF

4842

V.P. Yakovlev
Fermilab, Batavia, Illinois, USA
J. Grillenberger, M. Seidel
PSI, Villigen PSI, Switzerland
S.-H. Kim
ORNL, Oak Ridge, Tennessee, USA
M. Yoshii
KEK, Tokai, Ibaraki, Japan

For MW class proton driver accelerators the energy efficiency is an important aspect; the talk reviews the efficiency of different accelerator concepts including s.c./n.c. linac, rapid cycling synchrotron, cyclotron; the potential of these concepts for very high beam power is discussed.

Slides FRXCB1 [2.964 MB]

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