LINAC2016 - List of Keywords (cavity)

Paper	Title	Other Keywords	Page
MO3A03	Spaceborne Electron Accelerators	linac, electron, gun, controls	32
	J.W. Lewellen, C.E. Buechler, G.E. Dale, N.A. Moody, D.C. Nguyen LANL, Los Alamos, New Mexico, USA
	High-power electron beam generators in space will enable the studies of solar and space physics, specifically the interrogation of magnetic connection between the magnetosphere and ionosphere. This study plans to map the magnetic connection between the magnetosphere and ionosphere, using a satellite equipped with an electron beam accelerator that can create a spot in the ionosphere, observable by optical and radar detectors on the ground. To date, a number of spacecraft carrying low-power, <50-keV DC electron beam sources have been launched to study the upper ionosphere. The overall instrument weight will likely be dominated by the weight of the energy storage, the RF power amplifiers and the accelerator structure. We present the notional concept of a quasi-CW, C-band electron accelerator with 1-MeV beam energy, 10-mA beam current, and requiring 40 kW of prime power during operation. Our novel accelerator concept includes the following features: individually powered cavities driven by 6-GHz high-electron mobility transistors (HEMT), passively cooled accelerator structures with heat pipe technology, and active frequency control for operating over a range of temperatures.
	Slides MO3A03 [3.191 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MO3A03
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MOOP02	Current Status of Superconducting Linac for the Rare Isotope Science Project	linac, cryomodule, ion, rfq	41
	H.J. Kim, I.S. Hong, H.C. Jung, W.K. Kim, Y.H. Kim, Y. Kim, B.-S. Park, I. Shin IBS, Daejeon, Republic of Korea
	The RISP (Rare Isotope Science Project) has been proposed as a multi-purpose accelerator facility for providing beams of exotic rare isotopes of various energies. It can deliver ions from proton to uranium. Proton and uranium ions are accelerated upto 600 MeV and 200 MeV/u respectively. The facility consists of three superconducting linacs of which superconducting cavities are independently phased. Requirement of the linac design is especially high for acceleration of multiple charge beams. We present the RISP linac design, the prototyping of superconducting cavity and cryomodule.
	Slides MOOP02 [5.566 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOOP02
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MOOP03	High Gradient Accelerating Structures for Carbon Therapy Linac	impedance, linac, ion, operation	44
	S.V. Kutsaev, R.B. Agustsson, L. Faillace, E.A. Savin RadiaBeam, Santa Monica, California, USA A. Goel, B. Mustapha, A. Nassiri, P.N. Ostroumov, A.S. Plastun ANL, Argonne, Illinois, USA E.A. Savin MEPhI, Moscow, Russia
	Funding: This work was supported by the U.S. Department of Energy, Office of High Energy Physics, under contract 0000219678 Carbon therapy is the most promising among techniques for cancer treatment, as it has demonstrated significant improvements in clinical efficiency and reduced toxicity profiles in multiple types of cancer through much better localization of dose to the tumor volume. RadiaBeam, in collaboration with Argonne National Laboratory, are developing an ultra-high gradient linear accelerator, Advanced Compact Carbon Ion Linac (ACCIL), for the delivery of ion-beams with end-energies up to 450 MeV/u for 12C⁶⁺ ions and 250 MeV for protons. In this paper, we present a thorough comparison of standing and travelling wave designs for high gradient S-Band accelerating structures operating with ions at varying velocities, relative to the speed of light, in the range 0.3-0.7. In this paper we will compare these types of accelerating structures in terms of RF, beam dynamics and thermo-mechanical performance.
	Slides MOOP03 [3.497 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOOP03
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MOOP04	Traveling Wave Linear Accelerator With RF Power Flow Outside of Accelerating Cavities	impedance, coupling, linac, electron	48
	V.A. Dolgashev SLAC, Menlo Park, California, USA
	Funding: Work supported by the U.S. DOE under Contract No. DE-AC02-76-SF00515. An accelerating structure is a critical component of particle accelerators for medical, security, industrial and scientific applications. Standing-wave side-coupled accelerating structures are used where available RF power is at a premium, while average current and average RF power lost in the structure are high. These structures are expensive to manufacture and typically require a circulator to divert structure-reflected power away from RF source, klystron or magnetron. In this report a traveling wave accelerating structure is presented which combines high shunt impedance of the side-coupled standing wave structure with such advantages as simpler tuning and manufacturing. In addition, the structure is matched to the RF source so no circulator is needed. This paper presents the motivation for this structure and shows a practical example.
	Slides MOOP04 [5.459 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOOP04
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MOOP05	Dry-Ice Cleaning of RF-Structures at DESY	gun, niobium, RF-structure, coupling	52
	A. Brinkmann, J. Ziegler DESY, Hamburg, Germany
	Dry-Ice cleaning is today a well established cleaning method in matters of reducing harmful dark current and field emission in copper RF-structures like RF-Guns such as for the European XFEL, FLASH and REGAE. This led to the idea to clean longer RF-structures, in particular 3GHz transverse deflecting structures for the European XFEL. We developed a cleaning device with the possibility to clean up to 2 m long structures in horizontal position with an inner diameter of not more than 40 mm. Furthermore this device also allows to clean 9-cell TESLA-type Nb-cavities as well. A report of the technical layout and results of RF-tests will be given.
	Slides MOOP05 [0.969 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOOP05
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MOOP07	Development of Ultracold Neutron Accelerator for Time Focusing of Pulsed Neutrons	neutron, focusing, controls, resonance	56
	S. Imajo Kyoto University, Kyoto, Japan T. Ino, K. Mishima KEK, Ibaraki, Japan Y. Iwashita Kyoto ICR, Uji, Kyoto, Japan M. Kitaguchi, H.M. Shimizu Nagoya University, Nagoya, Japan S. Yamashita ICEPP, Tokyo, Japan
	Low energy neutron accelerator can be realized by the combination of an adiabatic fast passage spin flipper and a gradient magnetic field. Neutrons have magnetic moments, so that the accumulated potential energies are not cancelled before and after passage of a magnetic field and their kinetic energies change in case their spins are flipped in the field. This accelerator handles lower kinetic energy neutrons than approximately 300 neV. Currently we have developed the advanced version which makes it possible to handle broader kinetic energy range. The design and measured characteristics are described.
	Slides MOOP07 [1.313 MB]
	Poster MOOP07 [1.389 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOOP07
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MOOP11	Operation of the CEBAF 100 MV Cryomodules	cryomodule, operation, electron, controls	65
	C. Hovater, T.L. Allison, R. Bachimanchi, G.H. Biallas, E. Daly, M.A. Drury, A. Freyberger, R.L. Geng, G.E. Lahti, R.A. Legg, C.I. Mounts, R.M. Nelson, T. E. Plawski, T. Powers JLab, Newport News, Virginia, USA
	Funding: Authored by JSA, LLC under U.S. DOE Contract DE-AC05- 06OR23177. The Continuous Electron Beam Accelerator Facility (CEBAF) 12 GeV upgrade reached its design energy in December of 2015. Since then CEBAF has been delivering 12 GeV beam to experimental Hall D and 11 GeV to experimental halls A and B in support of Nuclear physics. To meet this energy goal, ten new 100 MV cryomodules (80 cavities) and RF systems were installed in 2013. The superconducting RF cavities are designed to operate CW at a average accelerating gradient of 19.2 MV/m. To support the higher gradients and higher QL (3.2×107) operations, the RF system uses 13 kW klystrons and digital LLRF to power and control each cavity. This paper reports on the C100 operation and optimization improvements of the RF system and cryomodules.
	Slides MOOP11 [1.574 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOOP11
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MOOP12	Klynac Design Simulations and Experimental Setup	linac, electron, klystron, simulation	68
	K.E. Nichols, B.E. Carlsten, A. Malyzhenkov LANL, Los Alamos, New Mexico, USA
	Funding: The authors gratefully acknowledge the support of the US Department of Energy through the LANL/LDRD Program for this work. We present results of a proof-of-principle demonstration of the first ever klynac, a compact 1 MeV linear accelerator with integrated klystron source using one electron beam. This device is bi-resonant, utilizing one resonant circuit for the klystron input and gain cavities, and one for the klystron output and linac cavities. The purpose of a klynac-type device is to provide a compact and inexpensive alternative for a conventional 1 to 6 MeV accelerator. A conventional accelerator requires a separate RF source and linac and all the associated hardware needed for that architecture. The klynac configuration eliminates many of the components to reduce the weight of the entire system by 60%. We have built an 8-cavity, 2.84-GHz RF structure for a 1-MeV bi-resonant klynac. A 50-kV, 10-A electron gun provides the single beam needed. Numerical modeling was used to optimize the design. The separation between the klynac ouput cavity and the first accelerator cavity was adjusted to optimize the bunch capture and a pin-hole aperture between the two cavities reduces the beam current in the linac section to about 0.1 A. Standard high-shunt impedance linac cavities designs are used. We have fabricated the first test structure. The structure will be tested with beam in early Summer 2016. Results will be presented at LINAC 2016.
	Slides MOOP12 [1.136 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOOP12
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MOPRC006	Beam Tuning and Error Analysis of a Superconducting Linac	linac, simulation, quadrupole, lattice	77
	Y. Zhang FRIB, East Lansing, USA
	Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661 Beam tuning and error analysis of a superconducting linac for heavy ion beams are introduced in this paper. In simulation studies with accelerator codes, system errors to the beam tuning are analyzed numerically, which include random cavity and magnet errors and measurement errors of absolute beam phase, beam bunch length, and beam transverse profiles. Simple statistical equations are developed from the tedious and time-consuming numerical simulations, and they may provide advantage tools not only to analyze a linac beam tuning, such as phase and amplitude tuning of superconducting cavity, longitudinal and transverse beam matching, but also will be very helpful to linac design with practical beam diagnostics system and authentic accelerator lattice.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPRC006
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MOPRC015	Development Status of FRIB On-line Model Based Beam Commissioning Application	solenoid, lattice, linac, quadrupole	100
	Z.Q. He, M.A. Davidsaver, K. Fukushima, D.G. Maxwell, G. Shen, Y. Zhang, Q. Zhao FRIB, East Lansing, USA
	Funding: The work is supported by the U.S. National Science Foundation under Grant No. PHY-11-02511, and the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661. The new software FLAME has been developed to serve as physics model used for on-line beam commissioning applications. FLAME is specially designed to cover FRIB modeling challenges to balance between speed and precision. Several on-line beam commissioning applications have been prototyped based on FLAME and tested on the physics application prototyping environment. In this paper, components of the physics application prototyping environment are firstly described. Then, the design strategy and result of the four major applications: baseline generator, cavity tuning, orbit correction, transverse matching, are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPRC015
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MOPRC018	Improved Beam Dynamics and Cavity RF Design for the FAIR Proton Injector	linac, proton, DTL, quadrupole	111
	R. Tiede, A. Almomani, M. Busch, F.D. Dziuba, U. Ratzinger IAP, Frankfurt am Main, Germany
	The FAIR facility at GSI requires a dedicated 70 MeV, 70 mA proton injector for the research program with intense antiproton beams. The main accelerator part consists of six 'Crossbar H-type' (CH) cavities operated at 325 MHz. Based on a linac layout carefully developed over several years, recently the beam dynamics has been revised with the scope of finalising the design and thus being able to start the construction of the main linac components. As compared to previous designs the MEBT behind the RFQ was slightly extended, the gap numbers per CH cavity and the voltage distributions were optimised and the layout of the intermediate diagnostics section including a rebuncher cavity at 33 MeV was redesigned. Finally, detailed machine error studies were performed in order to check the error response of the new design and the steering concept in particular. In the consequence, the final parameters obtained from the beam dynamics update are used for finalizing the CH-DTL cavity design by CST-MWS calculations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPRC018
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MOPRC025	Final Design of the Fully Equipped HWR Cavities for SARAF	cryomodule, linac, multipactoring, simulation	123
	G. Ferrand CEA/DSM/IRFU, France L. Boudjaoui, P. Hardy, F. Leseigneur, C. Madec, N. Misiara, N. Pichoff CEA/IRFU, Gif-sur-Yvette, France
	SNRC and CEA collaborate to the upgrade of the SARAF accelerator to 5 mA CW 40 MeV deuteron and proton beams (Phase 2). CEA is in charge of the design, construction and commissioning of the superconducting linac (SARAF-LINAC Project). The SCL is made up of 4 cryomodules: the first two will host each 6 half-wave resonator (HWR) low beta cavities (β = 0.09) at 176 MHz; the last two will host each 7 HWR high-beta cavities (β = 0.18) at 176 MHz. The fully equipped cavity includes the niobium cavity with a helium tank, an input power couplers and a frequency tuning system. The final RF design of the low and high beta cavities will be presented in this poster, as well as the RF design of the couplers, the expected tuning range of the cavities and the multipactor analysis.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPRC025
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MOPRC026	Mechanical Design of the HWR Cavities for the SARAF SRF LINAC	linac, simulation, cryomodule, SRF	126
	N. Misiara, L. Boudjaoui, G. Ferrand, P. Hardy, F. Leseigneur, C. Madec, N. Pichoff CEA/IRFU, Gif-sur-Yvette, France
	SNRC and CEA collaborate to the upgrade of the SARAF accelerator to 5 mA CW 40 MeV deuteron and proton beams (Phase 2). CEA is in charge of the design, construction and commissioning of the superconducting linac (SARAF-LINAC Project). The SCL consists in 4 cryomodules. The first two identical cryomodules host 6 half-wave resonator (HWR) low beta cavities (β = 0.09) at 176 MHz. The last two identical cryomodules will host 7 HWR high-beta cavities (β = 0.18) at 176 MHz. The fully equipped cavity includes the niobium cavity with its helium tank, the couplers and the frequency tuning system. In this paper, the mechanical design and the foreseen qualification procedures for both cavities and tuning systems are presented with compliance, to the best extent, to the rules of Unfired Pressure Vessels NF-EN 13445 (1-5) standards.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPRC026
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MOPRC027	Surface Roughness Effect on the Performance of Nb3Sn Cavities	SRF, pulsed-power, niobium, klystron	129
	R.D. Porter, 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 award DE-SC0008431 Surface roughness of current Niobium-3 Tin (Nb3Sn) superconducting radio-frequency (SRF) accelerator cavities can cause enhancement of the surface magnetic field. This enhancement can push the surface magnetic field beyond the critical field, which, if it occurs over a large enough area, can cause the cavity to quench. This paper presents simulations of the surface magnetic field enhancements in SRF cavities caused by the surface roughness of current Cornell Nb3Sn cavities, which have achieved record efficiency. Simple, smooth cavity geometry is defined and surface magnetic fields calculated using SLANS2. The cavity geometry is modified with a small rough region for which the geometry is determined from AFM scans of a Nb3Sn coated sample and the surface fields are calculated again. The calculated surface fields of the smooth and rough cavities are compared to determine the extent of the field enhancement, the area over which the enhancement is significant, and which surface features cause large field enhancement. We find that 1% of the surface analyzed has fields enhance by more than 45%. On average the Q-factor is increased by (3.8 ± 1.0) \%.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPRC027
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MOPRC029	Experiment of Plasma Discharge on HWR Cavity for In-Situ Surface Cleaning Study	plasma, electron, experiment, operation	133
	A.D. Wu, Y. He, T.C. Jiang, C.L. Li, Y.M. Li, W.M. Yue, S.H. Zhang, H.W. Zhao IMP/CAS, Lanzhou, People's Republic of China L.M. Chen Institute of Physics, Chinese Academy of Sciences, Beijing, People's Republic of China L. Yang IHEP, Beijing, People's Republic of China
	Hydrocarbons, which migrate from the vacuum bumps system, will absorb on the cavity surface after periods of operation. The contaminants can reduce the surface electron work function to enhance the field emission effect and restrict the cavity accelerating gradient. The room temperature in-situ plasma surface processing to clean the hydrocarbon contaminants can act as a convenient and efficient technology for the accelerator on line performance recovery. For better control of the discharge inside the cavity, the experiment works on a single HWR cavity aims to research the ignition between the swarm parameters (gas flow, pressure, forward power).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPRC029
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MOPLR005	Design, Manufacturing and Installation of Two Dual-Feed Accelerating Structures for the FERMI Injector	linac, accelerating-gradient, FEL, emittance	139
	C. Serpico, A. Fabris, G. Penco, M. Svandrlik Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy B. Keune RI Research Instruments GmbH, Bergisch Gladbach, Germany
	FERMI is a seeded Free Electron Laser (FEL) driven by a warm S-band Linac. In the injector region, two 3- meter long Forward Traveling Wave (FTW) accelerating structures, coming from the old Elettra injector, were installed. In order to improve the e-beam quality at higher bunch charge, it was decided to replace the existing ones with two dual-feed accelerating structures. Those structures have been designed and manufactured by RI Research Instruments GmbH and delivered to Elettra in July 2015. The following paper will report about the RF design and the manufacturing of the new structures. Details about the RF conditioning and the installation will also be illustrated.
	Poster MOPLR005 [1.100 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR005
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MOPLR006	Monopole HOMs Dumping in the LCLS-II 1.3 GHz Structure	HOM, linac, coupling, damping	142
	A. Lunin, T.N. Khabiboulline, N. Solyak Fermilab, Batavia, Illinois, USA
	Funding: Operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the U.S. DOE Developing an upgrade of Linac Coherent Light Source (LCLS-II) is currently underway. The central part of LCLS-II is a continuous wave superconducting RF (CW SRF) electron linac. High order modes (HOMs) excited in SRF structures by passing beam may deteriorate beam quality and affect beam stability. In this paper we report the simulation results of monopole High Order Modes (HOM) spectrum in the 1.3 GHz accelerating structure. Optimum parameters of the HOM feedthrough are suggested for minimizing RF losses on the HOM antenna tip and for preserving an efficiency of monopole HOMs damping simultaneously.
	Poster MOPLR006 [0.647 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR006
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MOPLR007	Redesign of the End Group in the 3.9 GHz LCLS-II Cavity	HOM, dipole, linac, operation	145
	A. Lunin, I.V. Gonin, T.N. Khabiboulline, N. Solyak Fermilab, Batavia, Illinois, USA
	Funding: Operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the U.S. DOE Development and production of Linac Coherent Light Source II (LCLS-II) is underway. The central part of LCLS-II is a continuous wave superconducting RF (CW SCRF) electron linac. The 3.9 GHz third harmonic cavity similar to the XFEL design will be used in LCLS-II for linearizing the longitudinal beam profile. The initial design of the 3.9 GHz cavity developed for XFEL project has a large, 40 mm, beam pipe aperture for better higher-order mode (HOM) damping. It is resulted in dipole HOMs with frequencies nearby the operating mode, which causes difficulties with HOM coupler notch filter tuning. The CW linac operation requires an extra caution in the design of the HOM coupler in order to prevent its possible overheating. In this paper we present the modified 3.9 GHz cavity End Group for meeting the LCLS-II requirements LCLS-II 3.9 GHz Cryomodules, Physics Requirements Document, LCLSII-4.1-PR-0097-R1, SLAC, USA, 2015
	Poster MOPLR007 [1.590 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR007
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MOPLR009	X-Band Travelling Wave Accelerating Section R&D for HTF	electron, operation, coupling, vacuum	152
	K. Jin USTC/NSRL, Hefei, Anhui, People's Republic of China
	Hefei Light Source (HLS) was mainly composed of an 800 MeV electron storage ring and an 800MeV-1GeV constant-gradient accelerator in NSRL. The new Linac with Full Energy Injection and the Top-up Injection scheme has been developed successfully. And the other functioning as X Ray Free Electron Laser test facility has been considered. In the project, in order to compress the bunch length and to achieve the beam energy distribution linearization. A 15MeV, operation frequency 11.424GHz traveling wave accelerating section as harmonic compensation is being developed. In this paper, X Ray Free Electron Laser Hefei Test Facility (HTF) is introduce briefly. And the R&D of the x-band accelerating section with collinear load are presented in detail.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR009
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MOPLR010	4 K SRF Operation of the 10 MeV CEBAF Photo-Injector	cryomodule, operation, SRF, cryogenics	155
	G.V. Eremeev, M.A. Drury, J.M. Grames, R. Kazimi, M. Poelker, J.P. Preble, R. Suleiman, Y.W. Wang, M. Wright JLab, Newport News, Virginia, USA
	Funding: Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. SRF accelerating cavities are often operated in superfluid helium of temperature near 2 K to enhance the cavity quality factor Q0 and manage cryogenic heat loads, which are particularly important at large SRF accelerator facilities. This temperature paradigm, however, need not put SRF technology out of the reach of small institutions or even limit SRF operation at large facilities to provide 10-100 MeV beam energy. At the Jefferson Lab CEBAF accelerator there are regularly scheduled maintenance periods during which the liquid helium temperature is raised to 4 K, reducing cryogenic plant power consumption by ~50% and saving megawatts of electrical power. During such a recent period, we accelerated a continuous-wave electron beam at the CEBAF photo-injector to 6.3 MeV/c with current ~80μA using two niobium cavities at helium temperature of 4 K. This contribution describes the SRF and cryogenic performance and uses measured beam quality and energy stability as key metrics. These measurements indicate that 4 K operation of niobium SRF cavities in CEBAF and at small institutions may be a sensible and cost effective mode of operation, provided the cryogenic load associated with lower Q0 is manageable for the number of SRF cavities needed. For Jefferson Lab, this enhances our scientific reach allowing additional low-energy ~10 MeV experiments each year.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR010
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MOPLR015	Thermal-Mechanical Study of 3.9 GHz CW Coupler and Cavity for LCLS-II Project	simulation, resonance, cryomodule, linac	171
	I.V. Gonin, E.R. Harms, T.N. Khabiboulline, N. Solyak, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	Third harmonic system was originally developed by Fermilab for FLASH facility at DESY and then was adopted and modified by INFN for the XFEL project [1-3]. In contrast to XFEL project, all cryomodules in LCLS-II project will operate in CW regime with higher RF average power for 1.3 GHz and 3.9 GHz cavities and couplers. Design of the cavity and fundamental power coupler has been modified to satisfy LCLS-II requirements. In this paper we discuss the results of COMSOL thermal and mechanical analysis of the 3.9 GHz coupler and cavity to verify proposed modifica-tion of the design. For the dressed cavity we present simulations of Lorentz force detuning, helium pressure sensitivity df/dP and major mechanical resonances.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR015
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MOPLR016	Status of the Injection System of the CLARA FEL Test Facility	gun, FEL, solenoid, cathode	174
	B.L. Militsyn, D. Angal-Kalinin, R.K. Buckley, R.J. Cash, J.A. Clarke, L.S. Cowie, B.D. Fell, P. Goudket, T.J. Jones, K.B. Marinov, P.A. McIntosh, J.W. McKenzie, K.J. Middleman, T.C.Q. Noakes, B.J.A. Shepherd, R. Valizadeh, A.E. Wheelhouse STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom V.V. Paramonov RAS/INR, Moscow, Russia
	The 250 MeV CLARA FEL test facility is now under construction at Daresbury Laboratory. Electron beam for this facility is provided by two normal conducting S-band photocathode guns: a 10 Hz 2.5 cell gun earlier used as the injector for the VELA machine, and a 400 Hz 1.5 cell gun now under commissioning. At the initial stage of Phase I CLARA will operate with the 10 Hz gun and a 45 MeV 2 m long linac section working as a buncher and/or booster. The beam will be deflected into the existing VELA beamline with an S-bend and directed to the spectrometer line for analysing beam properties or into one of two VELA user areas. The 400 Hz gun will be installed in the VELA beamline for detailed high power RF and beam commissioning in the VELA beam diagnostics suite. As the 400 Hz gun is equipped with an interchangeable photocathode it is possible to investigate different metal photocathodes and select the one providing minimal beam emittance at highest quantum efficiency. A state of the art photocathode preparation system is under commissioning at Daresbury. After commissioning the 400 Hz gun will be installed to the CLARA beam line to deliver high energy, high repetition rate beams for the FEL facility, and the 10 Hz gun will be returned to the VELA beam line.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR016
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MOPLR020	Challenges in Realizing the LCLS-II Cryomodule Production	cryomodule, SRF, linac, superconducting-RF	181
	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-rays 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. One of the challenges of this project, and the topic of this paper, is coordinating the effort of three DOE labs in order to realize this machine in just a few years time. This coordination is necessary due to the fact that the cryomodules will be assembled at both Jefferson Lab and Fermi Lab, tested, and then shipped to SLAC for installation, commissioning and operation. This paper will report on our experiences to date, issues that have been identified and planned mitigation going forward.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR020
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MOPLR022	Commissioning and First Results from the Fermilab Cryomodule Test Stand	vacuum, cryomodule, controls, radiation	185
	E.R. Harms, M.H. Awida, C.M. Baffes, K. Carlson, S.K. Chandrasekaran, B.E. Chase, E. Cullerton, J.P. Edelen, J. Einstein, C.M. Ginsburg, A. Grassellino, B.J. Hansen, J.P. Holzbauer, S. Kazakov, T.N. Khabiboulline, M.J. Kucera, J.R. Leibfritz, A. Lunin, D. McDowell, M.W. McGee, D.J. Nicklaus, D.F. Orris, J.P. Ozelis, J.F. Patrick, T.B. Petersen, Y.M. Pischalnikov, P.S. Prieto, O.V. Prokofiev, J. Reid, W. Schappert, D.A. Sergatskov, N. Solyak, R.P. Stanek, D. Sun, M.J. White, C. Worel, G. Wu Fermilab, Batavia, Illinois, USA
	Funding: Operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the United States Department of Energy. A new test stand dedicated to SRF cryomodule testing, CMTS1, has been commissioned and is now in operation at Fermilab. The first device to be cooled down and powered in this facility is the prototype 1.3 GHz cryomodule assembled at Fermilab for LCLS-II. We describe the demonstrated capabilities of CMTS1, report on steps taken during commissioning, provide an overview of first test results, and survey future plans.
	Poster MOPLR022 [3.431 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR022
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MOPLR023	Examination of Cutouts Inner Surfaces from Nb3Sn Coated Cavity	niobium, SRF, ion, accelerating-gradient	189
	U. Pudasaini, M.J. Kelley The College of William and Mary, Williamsburg, Virginia, USA G.V. Eremeev, C.E. Reece JLab, Newport News, Virginia, USA 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 DE-AC05-06OR23177 and Office of High Energy Physics under grant SC00144475. The potential for higher operating temperature and higher gradient have motivated SRF cavity researchers to pursue Nb3Sn as an alternative to Nb for nearly fifty years. Far and away the most common embodiment has been a few micron-thick Nb3Sn layer on the cavity interior surface obtained by vapor diffusion coating, with one or another set of parameters. While many cavities have been made and RF tested, reports of dissecting a cavity in detail to examine the coating and relate it to RF measurements are rare. We coated a BCP-treated single cell cavity in a typical process of tin/tin chloride activation at 500 C followed by tin vapor deposition at 1200 C. After RF-testing, we cut and examined sections from several locations to learn composition, thickness topography of the interior surface. The effect of process variables, such as surface preparation, process temperature and duration, and vapor chemistry needs to be explored.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR023
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MOPLR024	Progress Towards Nb3Sn CEBAF Injector Cryomodule	cryomodule, niobium, operation, electron	193
	G.V. Eremeev, K. Macha, U. Pudasaini, C.E. Reece, A-M. Valente-Feliciano JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Operations at 4 K instead of 2 K have the potential to reduce the operational cost of an SRF linac by a factor of 3, if the cavity quality factor can be maintained. Cavities coated with Nb3Sn have been shown to achieve the accelerating gradients above 10 MV/m with a quality factor around 10¹⁰ at 4 K. Because such performance is already pertinent for CEBAF injector cryomodule, we are working to extend these results to CEBAF accelerator cavities envisioning coating of two CEBAF 5-cell cavities with Nb3Sn. They will be installed in an injector cryomodule and tested with beam. The progress on this path is reported in this contribution.
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MOPLR025	Investigation of Low-Level Nitrogen in Niobium by Secondary Ion Mass Spectrometry	ion, niobium, SRF, factory	196
	J. Tuggle Virginia Polytechnic Institute and State University, Blacksburg, USA M.J. Kelley The College of William and Mary, Williamsburg, Virginia, USA A.D. Palczewski, C.E. Reece JLab, Newport News, Virginia, USA F.A. Stevie NCSU AIF, Raleigh, North Carolina, USA
	Funding: Supported by the U.S. DOE Office of Science, ONP contract DE-AC05-06OR23177 and OHEP grant SC00144475. Tuggle is supported by Nanoscale Characterization and Fabrication Laboratory at Virginia Tech. Understanding the improvement of the SRF cavity quality factor by low-level nitrogen addition ("N-doping") is attracting much attention from researchers. Precise, repeatable measurement of the nitrogen profile in the parts-per-thousand to parts-per-million range is vital. Secondary Ion Mass Spectrometry (SIMS) is the approach of choice because of excellent sensitivity and depth resolution. Accurate quantitation must consider sample properties, such as surface topography and crystal structure, calibration of the instrument with reference materials, and data analysis. We report the results of a SIMS study in which polycrystal and single crystal coupons were N-doped, each accompanied by new SRF-grade niobium sheet equivalent to a single cell cavity.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR025
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MOPLR026	Material Qualification of LCLS-II Production Niobium Material Including RF and Flux Expulsion Measurements on Single Cell Cavities	niobium, cryomodule, SRF, controls	199
	A.D. Palczewski, F. Marhauser JLab, Newport News, Virginia, USA A. Grassellino, S. Posen Fermilab, Batavia, Illinois, USA
	Funding: Work at JLab is supported by the U.S. Department of Energy under contract DE-AC05-06OR23177 and Fermilab is operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359. It has been shown that cooldown details through transition temperature can significantly affect the amount of trapped magnetic flux in SRF cavities, which can lead to performance degradation proportional to the magnitude of the ambient magnetic field.[] It has also more recently been shown that depending on the exact material properties - even when the material used originated from the same batch from the same vendor - and subsequent heat treatment, the percent of flux trapped during a cool-down could vary widely for identical cool-down parameters.[] For LCLS-II, two material vendors have produced half of the niobium used for the cavity cells (Tokyo Denkai Co., Ltd. (TD) and Ningxia Orient Tantalum Industry Co., Ltd. (NX)). Both vendors delivered material well within specifications set out by the project (according to ASTM B 393-05), which allows yet some variation of material characteristics such as grain size and defect density. In this contribution, we present RF and magnetic flux expulsion measurements of four single cell cavities made out of two different niobium batches from each of the two LCLS-II material suppliers and draw conclusions on potential correlations of flux expulsion capability with material parameters. We present observations of limited flux expulsion in cavities made from the production material and treated with the baseline LCLS-II recipe. [] A. Romanenko et al J. Appl. Phys. 115, 184903 (2014) [**] S. Posenet et al., Journal of Applied Physics 119, 213903 (2016).
	Poster MOPLR026 [0.861 MB]
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MOPLR030	Electromagnetic Design of a Superconducting Twin Axis Cavity	HOM, coupling, linac, dipole	203
	S.U. De Silva, J.R. Delayen, H. Park ODU, Norfolk, Virginia, USA A. Hutton, F. Marhauser, H. Park JLab, Newport News, Virginia, USA
	The twin-axis cavity is a new kind of rf superconducting cavity that consists of two parallel beam pipes, which can accelerate or decelerate two spatially separated beams in the same cavity. This configuration is particularly effective for high-current beams with low-energy electrons that will be used for bunched beam cooling of high-energy protons or ions. The new cavity geometry was designed to create a uniform accelerating or decelerating fields for both beams by utilizing a TM110 dipole mode. This paper presents the design rf optimization of a 1497 MHz twin-axis single-cell cavity, which is currently under fabrication.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR030
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MOPLR031	Wakefield Analysis of Superconducting RF-Dipole Cavities	wakefield, impedance, HOM, dipole	206
	S.U. De Silva, J.R. Delayen ODU, Norfolk, Virginia, USA
	RF-dipole crabbing cavities are being considered for a variety of crabbing applications. Some of the applications are the crabbing cavity systems for LHC High Luminosity Upgrade and the proposed Electron-Ion Collider for Jefferson Lab. The design requirements in the current applications require the cavities to incorporate complex damping schemes to suppress the higher order modes that may be excited by the high intensity proton or electron beams traversing through the cavities. The number of cavities required to achieve the desired high transverse voltage, and the complexity in the cavity geometries also contributes to the wakefields generated by beams. This paper characterizes the wakefield analysis for single cell and multi-cell rf-dipole cavities.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR031
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MOPLR035	Fabrication of Superconducting Spoke Cavity for Compact Photon Source	laser, photon, linac, scattering	212
	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
	Funding: This study is supported by Photon and Quantum Basic Research Coordinated Development Program of MEXT, Japan. The spoke cavity is expected to have advantages for compact ERL accelerator for X-ray source based on laser Compton scattering. We have been developing the spoke cavity under a research program of MEXT, Japan to establish the fabrication process. Since our designed shape of the spoke is complicated due to increase the RF properties, one-step press forming with one set of molds will cause so large strain to break the sheet. We designed the mold components including the process of press work. The press forming tests of the spoke cavity have been done with the various materials of sheets to check molding performance. In this paper we present status of the spoke cavity fabrication.
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MOPLR037	Study of the Surface and Performance of Single-Cell Nb Cavities After Vertical EP Using Ninja Cathodes	cathode, experiment, polarization, niobium	217
	V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi MGH, Hyogo-ken, Japan P. Carbonnier, F. Éozénou, Y. Gasser, L. Maurice, C. Servouin CEA/DSM/IRFU, France F. Furuta, M. Ge, T. Gruber, J.J. Kaufman, J. Sears Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe KEK, Ibaraki, Japan K. Ishimi MGI, Chiba, Japan
	A 1.3 GHz single-cell niobium (Nb) coupon cavity was vertically electropolished (VEPed) with three different Ninja cathodes which were specially designed for VEP of 1.3 GHz superconducting RF elliptical (ILC/Tesla type) cavities. The cathodes were fabricated to have different surface areas and different distances between cathode surface and the equator. The Ninja cathode prepared with an enhanced cathode surface area was covered with a meshed shield to avoid bubble attack on the surface of the cavity cell. It has been turned out that the anode-cathode distance and the cathode area affect surface morphology of the equator. A smooth equator surface was obtained in the cases in which the cathode surface was geometrically close to the equator or instead the cathode surface area was sufficiently larger. Two 1.3 GHz ILC/Tesla type single-cell cavities VEPed with the Ninja cathodes and using optimized conditions showed good performance in vertical tests.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR037
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MOPLR038	Fabrication of 9 Cell Coupon Cavity for Vertical Electropolishing Test	SRF, cathode, polarization, controls	220
	S. Kato, H. Hayano, H. Inoue, H. Monjushiro, T. Saeki, M. Sawabe KEK, Ibaraki, Japan V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi MGH, Hyogo-ken, Japan
	We have been using single cell coupon cavities to establish vertical electropolishing (VEP) process for a couple of years. A series of in-situ measurements of an EP current at an individual coupon in a coupon cavity can help determination of appropriate EP conditions. VEPed coupons which are surface analysed with XPS, SEM and the other tools can also bring lot information and expertise to development of VEP cathode and optimization of VEP conditions. This time we fabricated the world first 9-cell coupon cavity where 3 sample coupons at the equators and 6 sample coupons at positions close to the irises can be installed. VEP of this coupon cavity with a newly developed Ninja cathode brought useful information for improvement of the VEP facility and optimization of the VEP conditions.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR038
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MOPLR039	Development of New Type "Ninja" Cathode for Nb 9-cell Cavity and Experiment of Vertical Electro-Polishing	cathode, experiment, target, collider	223
	K.N. Nii, V. Chouhan, Y.I. Ida, T.Y. Yamaguchi MGH, Hyogo-ken, Japan H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe KEK, Ibaraki, Japan K. Ishimi MGI, Chiba, Japan
	Marui Galvanizing Co. Ltd. has been improving Vertical Electro-Polishing (VEP) technologies and facilities for Nb 9-cell superconducting accelerator cavity for International Linear Collider (ILC) in collaboration with KEK. This time, we developed new type 'Ninja' cathode in order to improve VEP uniformity of Nb 9-cell cavity inner surface based on the results of 1-cell cavity VEP experiment. In this article, we will report construction of new type "Ninja" cathode for Nb 9-cell cavity and experiment of VEP using this.
	Poster MOPLR039 [0.610 MB]
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MOPLR041	Design and Fabrication of β=0.3 SSR1 for RISP	niobium, TRIUMF, cryogenics, linac	226
	Z.Y. Yao, R.E. Laxdal, B.S. Waraich, V. Zvyagintsev TRIUMF, Vancouver, Canada R. Edinger PAVAC, Richmond, B.C., Canada
	A 325MHz β=0.30 balloon variant of single spoke resonator, which was proposed to suppress multipacting around operational gradient, was chosen as the prototype cavity of SSR1 for Rare Isotope Science Project (RISP). It was also demonstrated to achieve good RF and mechanical properties by geometry optimization for both cavity and helium jacket. The details of RISP SSR1 design will be reported in this paper, accompanying with some particular considerations of fabrication for this new member to the spoke family.
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MOPLR043	Cavity Processing and Preparation of 650 MHz Elliptical Cell Cavities for PIP-II	SRF, vacuum, factory, cathode	229
	A.M. Rowe, S.K. Chandrasekaran, A. Grassellino, O.S. Melnychuk, M. Merio, D.A. Sergatskov Fermilab, Batavia, Illinois, USA T. Reid ANL, Argonne, Illinois, USA
	Funding: Operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the United States Department of Energy. The PIP-II project at Fermilab requires fifteen 650 MHz SRF cryomodules as part of the 800 MeV LINAC that will provide a high intensity proton beam to the Fermilab neutrino program. A total of fifty-seven high-performance SRF cavities will populate the cryomodules and will operate in both pulsed and continuous wave modes. These cavities will be processed and prepared for performance testing utilizing adapted cavity processing infrastructure already in place at Fermilab and Argonne. The processing recipes implemented for these structures will incorporate state-of-the art processing and cleaning techniques developed for 1.3 GHz SRF cavities for the ILC, XFEL, and LCLS-II projects. This paper describes the details of the processing recipes and associated chemistry, heat treatment, and cleanroom processes at the Fermilab and Argonne cavity processing facilities. This paper also presents single and multi-cell cavity test results with quality factors above 5·10¹⁰ and accelerating gradients above 30 MV/m.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR043
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MOPLR047	Advanced Vertical Electro-Polishing studies at Cornell with Faraday	SRF, niobium, status, target	233
	F. Furuta, M. Ge, T. Gruber, G.H. Hoffstaetter, J.J. Kaufman, M. Liepe, J. Sears Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA T.D. Hall, M.E. Inman, S.T. Snyder, E.J. Taylor Faraday Technology, Inc., Clayton, Ohio, USA
	Cornell's SRF group and Faraday Technology Inc. have started collaborations on two phase-II SBIR projects. Both projects are aiming for the development of advanced Vertical Electro-Polishing (VEP) for Nb SRF cavities, such as HF free or acid free VEP protocols. These could be eco-friendlier alternatives for the standard, HF-based EP electrolyte used, and could bring new breakthrough performance for Nb SRF cavities. Here we give a status update and report first results from these two projects.
	Poster MOPLR047 [2.852 MB]
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MOPLR050	Study and Development of CW Room Temperature Rebuncher for SARAF Accelerator	vacuum, linac, impedance, acceleration	244
	B. Kaizer, Z. Horvitz, A. Perry, J. Rodnizki Soreq NRC, Yavne, Israel M. Di Giacomo, J.F. Leyge, M. Michel, P. Toussaint GANIL, Caen, France A. Friedman Ariel University, Ariel, Israel
	The SARAF 176 MHz accelerator is designed to provide CW proton/deuteron beams up to 5 mA current and 40 MeV accelerated ion energy. Phase I of SARAF (up to 4-5 MeV) has been installed, commissioned, and is available for experimental work. Phase II of SARAF is currently in the planning stage and will contain larger MEBT with three rebunchers and four cryomodules, each consisting of SC HWRs and solenoids. Phase II MEBT line is designed to follow a 1.3 MeV/u RFQ, is 4.5 m long, and contains three 176 MHz rebunchers providing a field integral of 10⁵ kV. Different rebuncher configurations have been studied in order to minimize the RF losses and maximize the shunt impedance. Different apertures have also been tested with a required of 40 mm diameter by beam dynamics. The simulations were done using CST Microwave Studio. CEA leads the design for SARAF phase II linac including the MEBT rebunchers and has studied a mixed solid copper and Cu plated stainless steel, 3-gap cavity. SNRC is developing a 4-gap OFHC copper rebuncher as a risk reduction. Both designs are presented and discussed in the paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR050
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MOPLR053	Operating Status of Injector II RFQ for C-ADS Project	rfq, coupling, impedance, scattering	254
	L.P. Sun, Y. He, C.X. Li, L. Lu, A. Shi, L.B. Shi, W.B. Wang, X.B. Xu, Z.L. Zhang, H.W. Zhao IMP/CAS, Lanzhou, People's Republic of China
	The Radio Frequency Quadrupole system has been designed and constructed for C-ADS (Chinese Accelerator Driven System) Injector II in Institute of Modern Physics (IMP), Chinese Academy of Sciences, which has been running for more than one year until now. It is a quadrilateral four-vane resonator with two equal couplers operating in CW mode. In the paper, RF system upgrade will be presented in detail，especially the two-port configuration was introduced and the conditioning based on two new sets of solid-state amplifier instead of the original tetrodes power source due to system hardware upgrade are described in the paper. RFQ, solid-state amplifier, two-port configuration, coupler
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MOPLR062	European Spallation Source (ESS) Normal Conducting Front End Status Report	rfq, proton, plasma, status	274
	W. Wittmer, P.O. Gustavsson, F. Hellström, G. Hulla ESS, Lund, Sweden I. Bustinduy, P.J. González, G. Harper, S. Varnasseri, C. de la Cruz ESS Bilbao, Zamudio, Spain L. Celona, S. Gammino, L. Neri INFN/LNS, Catania, Italy A.C. Chauveau, D. Chirpaz-Cerbat CEA/IRFU, Gif-sur-Yvette, France F. Grespan, A. Pisent INFN/LNL, Legnaro (PD), Italy P. Mereu INFN-Torino, Torino, Italy O. Midttun University of Bergen, Bergen, Norway O. Piquet, B. Pottin CEA/DSM/IRFU, France
	The European Spallation Source (ESS) will deliver first protons on target by mid 2019. Civil construction of the accelerator tunnel has made good progress and will allow starting installation of the normal conducting frond end (NCFE) by end of 2017. To achieve these milestones the design of all major beam line components have been completed and the construction of the subsystems begun. We report on the advancement of the subsystems and the commissioning progress of the microwave discharge Proton Source (PS-ESS).
	Poster MOPLR062 [1.396 MB]
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MOPLR065	High-Gradient X-band Structures for Proton Energy Booster at LANSCE	linac, booster, proton, klystron	280
	S.S. Kurennoy, L. Rybarcyk LANL, Los Alamos, New Mexico, USA V.A. Dolgashev SLAC, Menlo Park, California, USA
	Increasing energy of proton beam at LANSCE from 800 MeV to 3 GeV improves radiography resolution ~10 times. Using superconducting RF cavities with gradients ~15 MV/m after the existing linac would result in a long and expensive booster. We propose accomplishing the same with a much shorter cost-effective booster based on normal conducting high-gradient (~100 MV/m) RF accelerating structures. Such X-band high-gradient structures have been developed for electron acceleration and operate with typical RF pulse lengths below 1 us. They have never been used for protons because typical wavelengths and apertures are smaller than the proton bunch sizes. However, these limitations do not restrict proton radiography (pRad) applications. A train of very short proton bunches with the same total length and charge as the original long proton bunch will create the same single radiography frame, plus pRad limits contiguous trains of beam micro-pulses to below 60 ns to prevent blur in images. For a compact pRad booster at LANSCE, we explore feasibility of two-stage design: a short S-band section to capture and compress the 800-MeV proton beam followed by the main high-gradient X-band linac.
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MOPLR066	ProBE: Proton Boosting Extension for Imaging and Therapy	proton, septum, linac, accelerating-gradient	283
	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 and IPS Proton beam therapy has been shown to be a promising alternative to traditional radiotherapy, especially for paedi- atric malignancies and radio-resistant tumours. Allowing a highly precise tumour irradiation, it is currently limited by range verification. Several imaging modalities can be utilised for treatment planning, but typically X-ray CT is used. CT scans require conversion from Hounsfield units to estimate the proton stopping power (PSP) of the tissue be- ing treated, and this produces inaccuracy. Proton CT (pCT) measures PSP and is thought to allow an improvement of the treatment accuracy. The Christie Hospital will use a 250 MeV cyclotron for proton therapy, in this paper a pulsed linac upgrade is proposed, to provide 350 MeV protons for pCT within the facility. Space contraints require a compact, high gradient (HG) solution that is reliable and affordable.
	Poster MOPLR066 [0.610 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR066
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MOPLR067	First High Power Tests at the 325 MHz RF Test Stand at GSI	linac, coupling, rfq, klystron	287
	G. Schreiber, E. Plechov, J. Salvatore, B. Schlitt, A. Schnase, M. Vossberg GSI, Darmstadt, Germany
	A dedicated RF test stand for testing RF components and accelerating structures at 325 MHz has been put into operation at GSI. It allows testing the klystrons and circulators as well as the RFQ and the CH-acceleration cavities for the planned FAIR proton linac (p-Linac) and further cavity projects. The system integration has been completed and first high power tests with the CH prototype cavity were successfully performed. The operation parameters are 2 Hz repetition rate and 200 microseconds pulse length. Investigations on the critical path from wave guide to coaxial high power cavity coupler have been made. Performance measurements of the klystron, circulator and directional couplers with up to 2.8 MW on dummy load and the following conditioning process of the CH-prototype cavity with its coupled RF structures will be presented. Additionally the results of the conditioning of a ladder RFQ prototype are shown.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR067
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MOPLR072	The Effect of DTL Cavity Field Errors on Beam Spill at LANSCE	DTL, linac, LLRF, target	301
	L. Rybarcyk, R.C. McCrady LANL, Los Alamos, New Mexico, USA
	The Los Alamos Neutron Science Center (LANSCE) accelerator comprises two (H⁺ and H⁻) 750-keV Cockcroft-Walton style injectors, a 201.25-MHz, 100-MeV drift-tube linac (DTL) and an 805-MHz, 800-MeV coupled-cavity linac (CCL). As part of the LANSCE Risk Mitigation project a new digital low-level radio frequency (LLRF) control system is being deployed across the linac, starting with the DTL. Related to this upgrade, a study was performed where specific cavity field errors were simultaneously introduced in all DTL tanks about the nominal stable, low-spill, production set points to mimic LLRF control errors. The impact of these errors on the resultant beam spill was quantified for the nominal 100 μA, 800-MeV Lujan beam. We present the details of the measurement approach and results that show a rapid increase in total linac beam spill as DTL cavity field phase and amplitude errors are increased.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR072
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MOP106001	Energy Stability of ERLs and Recirculating Linacs	linac, recirculation, operation, simulation	304
	R.G. Eichhorn, J. Hoke, Z. Mayle Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Energy recovery linacs can be seen as a hybrid between a linear and a circular accelerator. It has been shown in the past that an appropriate choice of the longitudinal working point can significantly improve the energy stability of a recirculating linac. In this contribution we will expand the concept of energy recovery linacs and investigate the energy spread of the beam as well as the recovery efficiency stability which can be a more demanding quantity in a high current ERL.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOP106001
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MOP106006	Electro-Mechanical Modeling of the LCLS-II Superconducting Cavities	simulation, damping, vacuum, linac	310
	O. Kononenko, C. Adolphsen, Z. Li, T.O. Raubenheimer, C.H. Rivetta SLAC, Menlo Park, California, USA
	Funding: Work supported by the Department of Energy, Office of Science, Office of Basic Energy Science, under Contract No. DEAC0276SF00515 The 4 GeV LCLS-II superconducting linac will contain 280, 1.3 GHz TESLA-style cavities operated CW at 16 MV/m. Because of the low beam current, the cavity bandwidth will be fairly small, about 32 Hz, which makes the field stability sensitive to detuning from external vibrations and He pressure fluctuations. Piezo-electric actuators will be used to compensate for the detuning, which historically has been difficult at frequencies above a few Hz due to excitation of cavity mechanical resonances. To understand this interaction better, we have been doing extensive modeling of the cavities including mapping out the mechanical modes and computing their coupling to pressure changes, Lorentz forces and piezo actuator motion. One goal is to reproduce the measured detuning response of the piezo actuators up to 1 kHz, which is sensitive to how the cavities are constrained within a cryomodule. In this paper, we summarize these results and their implications for suppressing higher frequency detuning.
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MOP106016	High Power RF Requirements for Driving Discontinuous Bunch Trains in the MaRIE Linac	linac, beam-loading, electron, booster	320
	J.T. Bradley III, D. Rees, A. Scheinker, R.L. Sheffield LANL, Los Alamos, New Mexico, USA
	Funding: Work supported by the US Department of Energy. The MaRIE project will use a superconducting linac to provide 12 GeV electron bunches to drive an X-ray FEL and to do electron radiography. Dynamic experiments planned for MaRIE require that the linac produce a series of micropulses that can be irregularly spaced within the macropulse, and these patterns can change from macropulse to macropulse. Irregular pulse structures create a challenge to optimizing the design of the RF and cryogenic systems. General formulas for cavities with beam loading can overestimate the power required for our irregular beam macropulse. The differing beam energy variations allowed for the XFEL and eRad micropulses produce cavity voltage control requirements that also vary within the macropulse. The RF pulse driving the cavities can be tailored to meet the needs of that particular beam macropulse because the macropulse structure is known before the pulse starts. We will derive a toolkit that can be used to determine the required RF power waveforms for arbitrary macropulse structures. We will also examine how the irregular RF power waveforms can impact RF and cryogenic system cost tradeoffs.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOP106016
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MOP106018	Measurement of the Transverse Beam Dynamics in a TESLA-type Superconducting Cavity	HOM, simulation, experiment, alignment	323
	A. Halavanau, P. Piot Northern Illinois University, DeKalb, Illinois, USA N. Eddy, D.R. Edstrom, A. Lunin, P. Piot, J. Ruan, N. Solyak Fermilab, Batavia, Illinois, USA
	Funding: US Department of Energy (DOE) under contract DE-SC0011831 with Northern Illinois University. Fermilab is operated by the Fermi Research Alliance LLC under US DOE contract DE-AC02-07CH11359. Superconducting linacs are capable of producing intense, ultra-stable, high-quality electron beams that have widespread applications in Science and Industry. Many project are based on the 1.3-GHz TESLA-type superconducting cavity. In this paper we provide an update on a recent experiment aimed at measuring the transfer matrix of a TESLA cavity at the Fermilab Accelerator Science and Technology (FAST) facility. The results are discussed and compared with analytical and numerical simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOP106018
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MOP106021	Superconducting Traveling Wave Cavity Tuning Studies	accelerating-gradient, feedback, SRF, acceleration	327
	R.A. Kostin LETI, Saint-Petersburg, Russia P.V. Avrakhov, A. Kanareykin Euclid TechLabs, LLC, Solon, Ohio, USA N. Solyak, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	Funding: Work supported by US DOE SBIR # DE-SC0006300 Superconducting traveling wave cavity (SCTW) can provide 1.2-1.4 times larger accelerating gradient than conventional standing wave SRF cavities [1]. Firstly, traveling wave opens the way to use other than Pi-mode phase advance per cell which increase transit time factor. Secondly, traveling wave is not so sensitive to cavity length as standing wave, which length is limited to 1 meter because of field flatness degradation. 3 cell SCTW cavity was proposed [2] and built for high gradient traveling wave demonstration and tuning studies. This paper describes analytical model that was used for cavity development. Tuning properties and requirements are also discussed. ' r.kostin@euclidtechlabs.com
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOP106021
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MOP106023	Intra Bunch Train Transverse Dynamics in the Superconducting Accelerators FLASH and European XFEL	beam-transport, HOM, transverse-dynamics, operation	333
	T. Hellert, W. Decking, M. Dohlus DESY, Hamburg, Germany
	At FLASH and the European XFEL accelerator superconducting 9-cell TESLA cavities accelerate long bunch trains at high gradients in pulsed operation. Several RF cavities with individual operating limits are supplied by one RF power source. Within the bunch train, the low-level-RF system is able to restrict the variation of the vector sum voltage and phase of one control line below 3·10^-4 and 0.06 degree, respectively. However, individual cavities may have a significant spread of amplitudes and phases. Misaligned cavities in combination with variable RF parameters will cause significant intra-pulse orbit distortions, leading to an increase of the multi-bunch emittance. An efficient model including coupler kicks was developed to describe the effect at low beam energies. Comparison with start-to-end tracking and experimental data will be shown.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOP106023
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TU1A03	Experience with the Construction and Commissioning of Linac4	linac, ion, emittance, DTL	342
	J.-B. Lallement CERN, Geneva, Switzerland
	In the framework of the LHC Injector Upgrade program, CERN is presently commissioning Linac4, a 160MeV H⁻ ion linac, which will replace the present 50 MeV proton linac (Linac2) as injector to the PS Booster during the next LHC long shut-down. The installation of the machine has proceeded in parallel with a staged beam commissioning at the energies of 3, 12, 50, 100 MeV and finally 160 MeV, foreseen for fall 2016. A seven month long reliability run will take place during 2017 to access potential weak points and find mitigations. The lessons learnt during its construction, the main outcomes of the beam commissioning and the remaining steps toward its connection to the PS Booster are presented in this paper.
	Slides TU1A03 [5.747 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TU1A03
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TU1A05	High Power Operation of SNS SC Linac	linac, ion, cryomodule, operation	348
	M.A. Plum ORNL, Oak Ridge, Tennessee, USA
	Funding: Work performed at (or work supported by) Oak Ridge National Laboratory, which is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. The SNS superconducting linac (SCL) provides 972 MeV, 1.5 MW H− beam for the storage ring and neutron spallation target. It has now been in operation for 11 years, and we have gained some experience in long-term operational issues. Three inter-related issues are gradient changes, errant beams, and trip rates. In this presentation we will provide an update on our progress to mitigate these issues, and also report on the overall status of the SCL.
	Slides TU1A05 [5.831 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TU1A05
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TU2A03	Resonance Control for Future Linear Accelerators	controls, resonance, SRF, electron	363
	W. Schappert Fermilab, Batavia, Illinois, USA
	Many of the next generation of particle accelerators (LCLS II, PIP II) are designed for relatively low beam loading. Low beam loading requirement means the cavities can operate with narrow bandwidths, minimizing capital and base operational costs of the RF power system. With such narrow bandwidths, however, cavity detuning from microphonics or dynamic Lorentz Force Detuning becomes a significant factor, and in some cases can significantly increase both the acquisition cost and the operational cost of the machine. In addition to the efforts to passive environmental detuning reduction (microphonics) active resonance control for the SRF cavities for next generation linear machine will be required. State of the art in the field of the SRF Cavity active resonance control and the results from the recent efforts at FNAL will be presented in this talk.
	Slides TU2A03 [0.897 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TU2A03
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TU3A01	Beam Commissioning Results From the R&D ERL at BNL	gun, cathode, SRF, laser	374
	D. Kayran, Z. Altinbas, D.R. Beavis, S.A. Belomestnykh, I. Ben-Zvi, D.M. Gassner, L.R. Hammons, J.P. Jamilkowski, P. K. Kankiya, R.F. Lambiase, V. Litvinenko, R.J. Michnoff, T.A. Miller, J. Morris, V. Ptitsyn, T. Seda, B. Sheehy, K.S. Smith, E. Wang, W. Xu BNL, Upton, Long Island, New York, USA S.A. Belomestnykh, I. Ben-Zvi, L.R. Hammons, V. Litvinenko, V. Ptitsyn 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 BNL R&D ERL beam commissioning started in June 2014 []. The key components of R&D ERL are the highly damped 5-cell 704 MHz superconducting RF cavity and the high-current superconducting RF gun. The gun is equipped with a multi-alkaline photocathode insertion system. The first photocurrent from ERL SRF gun has been observed in November 2014. In June 2015 a high charge 0.5nC and 20 uA average current were demonstrated. In July 2015 gun to dump beam test started. The beam was successfully transported from the SRF gun through the injection system, then through the linac to the beam dump. All ERL components have been installed. In October 2015, SRF gun cavity has been found contaminated during severe cathode stalk RF conditioning. This cavity has been sent for repair and modification for later use in low-energy RHIC electron cooler (LEReC)[]. LEReC scheduled to start commissioning in early of 2018. We present our results of BNL ERL beam commissioning, the measured beam properties, the operational status, and future prospects. ) D.Kayran et al., Status and commissioning results of the R&D ERL at BNL. Proc. ERL2015, p. 11-14 **)J. Kewisch et al., ERL for Low Energy Electron Cooling at RHIC (LEReC). Proc. ERL2015, p. 67-71
	Slides TU3A01 [12.502 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TU3A01
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TUOP07	High Performance Next-Generation Nb3Sn Cavities for Future High Efficiency SRF Linacs	niobium, SRF, accelerating-gradient, pulsed-power	398
	D.L. Hall, J.J. Kaufman, M. Liepe, J.T. Maniscalco, R.D. Porter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: DOE A 1.3 GHz ILC-shape single-cell Nb3Sn cavity fabricated at Cornell has shown record performance, exceeding the cryogenic efficiency of niobium cavities at the gradients and quality factors demanded by some contemporary accelerator designs. An optimisation of the coating process has resulted in more cavities of the same design that achieve similar performance, proving the reproducibility of the method. In this paper, we discuss the current limitations on the peak accelerating gradients achieved by these cavities. In particular, high-pulsed-power RF testing, and thermometry mapping of the cavity during CW operation, are used to draw conclusions regarding the nature of the quench limitation. In light of these promising results, the feasibility and utility of applying the current state of the technology to a real-life application is discussed.
	Slides TUOP07 [1.506 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUOP07
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TUOP08	On Magnetic Flux Trapping in Superconductors	solenoid, niobium, experiment, SRF	402
	R.G. Eichhorn, J. Hoke, Z. Mayle Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Magnetic flux trapped on the cool-down has become an important factor in the performance in superconducting cavities. We have conducted flux trapping experiments on samples that reveal a very interesting feature of the mechanism on flux trapping which might impact magnetic shielding concepts of future cryomodules.
	Slides TUOP08 [1.787 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUOP08
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TUOP09	State of the Art Advanced Magnetron for Accelerator RF Power Source	cathode, linac, radiation, electron	405
	H. Obata, K. Furumoto, H. Miyamoto New Japan Radio Co., Ltd., Fujimino Saitama, Japan
	X ray sources for linear accelerators continue to be a necessary requirement for industries such as medical, inspection, and nondestructive test equipment. Future requirements for such sources are; low cost, compact packaging and high performance of the RF source for electron acceleration. The magnetron has proven to be a perfect source over other RF sources for linear accelerator use. Because of its simple design, low cost per output, small size and proven performance it meets all required characteristics. New Japan Radio Co., Ltd. has improved and modified its linac magnetrons' performance and characteristics enabling easy matching to the linac modulator, long life and maximum output power. This paper will provide a detailed explanation on the improved magnetron design methodology and its effects on the performance of these magnetrons installed in linac systems. These technologies have been utilized successfully on a commercial level worldwide over the last few years. The technology has been deployed into linac systems operating in S and X band and soon C band, at various output power levels.
	Slides TUOP09 [1.127 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUOP09
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TUPRC007	An RFQ Based Neutron Source for BNCT	rfq, simulation, operation, neutron	427
	X.W. Zhu, Z.Y. Guo, Y.R. Lu, H. Wang, Z. Wang, K. Zhu, B.Y. Zou PKU, Beijing, People's Republic of China
	Boron Neutron Capture Therapy (BNCT), promises a bright prospect for future cancer treatment, in terms of effectiveness, safety and less expanse. The PKU RFQ group proposes an RFQ based neutron source for BNCT. A unique beam dynamics design of 162.5 MHz BNCT-RFQ, which accelerates 20 mA of H⁺ from 30 keV to 2.5 MeV in CW operation, has been performed in this study. The Proton current will be about 20 mA. The source will deliver a neutron yield of 1.76×10¹³ n/sec/cm² in the Li(p, n)Be reaction. Detailed 3D electromagnetic (EM) simulations of all components, including cross-section, tuners, pi-rods, and undercuts, of the resonant structure are performed. The design of a coaxial type coupler is developed. Two identical RF couplers will deliver approximately 153 kW CW RF power to the RFQ cavity. RF property optimizations of the RF structures are performed with the utilization of the CST MICROWAVE STUDIO.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC007
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TUPRC015	Final Acceptance Test of SRF Photo-Injector Cold String for the BERLinPro Energy Recovery Linac	cathode, SRF, gun, target	445
	A. Neumann, D. Böhlick, P. Echevarria, A. Frahm, F. Göbel, T. Kamps, J. Knobloch, O. Kugeler, M. Schuster, J. Ullrich, A. Ushakov HZB, Berlin, Germany A. Burrill SLAC, Menlo Park, California, USA G. Ciovati, P. Kneisel JLab, Newport News, Virginia, USA A. Matheisen, M. Schalwat, M. Schmökel DESY, Hamburg, Germany E.N. Zaplatin FZJ, Jülich, Germany
	Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin and grants of Helmholtz Association. Helmholtz-Zentrum Berlin (HZB) is currently designing and building an high average current all superconducting CW driven ERL as a prototype to demonstrate low normalized beam emittance of 1 mm·mrad at 100mA and short pulses of about 2 ps. In order to achieve these demanding goals HZB started a staged program for developing this class of required high current, high brightness SRF electron sources. In this contribution we will present the current status of the module assembly and testing of the prototype SRF photo-injector cavity cold string. The steps taken to install the cathode insert system with the cavity in the cleanroom and the following horizontal test of the cold string as final acceptance test prior installation into its cryostat are shown. First beam in a dedicated diagnostics teststand called Gunlab are planned for this winter.
	Poster TUPRC015 [2.077 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC015
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TUPRC017	Field Flatness and Frequency Tuning of the CLARA High Repetition Rate Photoinjector	cathode, coupling, FEL, gun	452
	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 B. Keune RI Research Instruments GmbH, Bergisch Gladbach, Germany
	The High Repetition Rate Photoinjector, designed for the CLARA FEL at Daresbury Laboratory, was tuned at the manufacturers for both field flatness and frequency. Due to the high average power in the cavity of 6.8 kW the cavity requires significant cooling, achieved by water channels in the cavity body. These channels prohibit the use of tuning studs to tune the cavity. The cavity was tuned by taking pre-braze clamped low power RF measurements and using the data to trim the cavity cells to the optimum length for both field flatness and frequency. The optimum field flatness is 100% and the design frequency is 2998.5 MHz. Both cells were trimmed in 3 stages, resulting in a post-braze frequency of 2998.51 MHz and field flatness of 98%.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC017
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TUPRC021	Low-Temperature Properties of 2.6-Cell Cryogenic C-Band RF-Gun Cold Model Cavity	gun, cryogenics, experiment, resonance	462
	T. Sakai, M. Inagaki, K. Nakao, K. Nogami, K. Takatsuka, T. Tanaka LEBRA, Funabashi, Japan M.K. Fukuda, D. Satoh, T. Takatomi, N. Terunuma, J. Urakawa, M. Yoshida KEK, Ibaraki, Japan
	Funding: Work supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT). Development of a cryogenic C-band photocathode RF gun cavity has been conducted at Nihon University in collaboration with KEK. Improved dimensions of the RF input coupler and the 2.6-cell accelerating structure from the first cold model were determined using the 3D simulation code CST Studio. The high-purity copper cavity was fabricated at KEK with ultraprecision machining and diffusion bonding technique. The low level RF properties of the cavity measured at room temperature have been in good agreement with the predictions based on the CST Studio calculation. Preparations for the 20-K cooling tests of the cavity are underway in KEK and Nihon University. The design of the improved cavity and the results of the cold test at low temperature will be discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC021
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TUPRC024	Design and Implementation of an Automated High-Pressure Water Rinse System for FRIB SRF Cavity Processing	SRF, alignment, operation, controls	468
	I.M. Malloch, E.S. Metzgar, L. Popielarski, S. Stanley FRIB, East Lansing, Michigan, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE SC0000661, the State of Michigan and Michigan State University. Traditionally, high-pressure water rinse (HPR) systems have consisted of relatively simple pump and rinse wand actuator systems intended to clean superconducting radio frequency (SRF) cavities during processing prior to test assembly. While these types of systems have proven effective at achieving satisfactory levels of cleanliness, large amounts of operator touch-labor are involved, especially in SRF cavities with complex geometries, where several fixture changes and cavity manipulations may be required. With this labor comes the risk of cavity damage or contamination, and the expense of the operator's time. To reduce this operator intervention and maximize cavity cleanliness and process throughput, a new, fully-automated, robotic HPR system has been commissioned in the Facility for Rare Isotope Beams (FRIB) cavity processing facility. This paper summarizes the design and commissioning process of the HPR system, and demonstrates improvements to the FRIB processing facility through the minimization of cavity contamination risk and reduction of technician labor through system automation. Comparative cavity RF test results are presented to further demonstrate system effectiveness.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC024
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TUPRC025	Low Temperature Nitrogen Baking of a Q0 SRF Cavities	niobium, SRF, radio-frequency, impedance	472
	P.N. Koufalis, F. Furuta, M. Ge, D. Gonnella, J.J. Kaufman, M. Liepe, J.T. Maniscalco, R.D. Porter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Nitrogen-doping has led to an unprecedented increase in the intrinsic quality factor of bulk-niobium superconducting RF cavities. So far, high temperature baking in a nitrogen atmosphere is used almost exclusively to dope cavities. Recently, we have set focus on low temperature baking to produce similar performance increases and we present those results here.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC025
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TUPLR007	LCLS-II Cryomodules Production at Fermilab	cryomodule, SRF, vacuum, alignment	481
	T.T. Arkan, C.J. Grimm, J.A. Kaluzny, Y.O. Orlov, T.J. Peterson, K. Premo Fermilab, Batavia, Illinois, USA
	Funding: US DOE LCLS-II is an upgrade project for the linear coherent light source (LCLS) at SLAC. The LCLS-II linac will consist of thirty-five 1.3 GHz and two 3.9 GHz superconducting RF continuous wave (CW) cryomodules that Fermilab and Jefferson Lab (JLab) will assemble in collaboration with SLAC. The LCLS-II 1.3 GHz cryomodule design is based on the European XFEL pulsed-mode cryomodule design with modifications needed for CW operation. Fermilab and JLab will each assemble and test a prototype 1.3 GHz cryomodule to assess the results of the CW modifications, in advance of 16 and 17 production 1.3 GHz cryomodules, respectively. Fermilab is solely responsible for the 3.9 GHz cryomodules. After the prototype cryomodule tests are complete and lessons learned incorporated, both laboratories will increase their cryomodule production rates to meet the challenging LCLS-II project requirement of approximately one cryomodule per month per laboratory. This paper presents the Fermilab Cryomodule Assembly Facility (CAF) infrastructure for LCLS-II cryomodule production, the Fermilab prototype 1.3 GHz CW cryomodule (pCM) assembly and readiness for production assembly.
	Poster TUPLR007 [2.474 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPLR007
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TUPLR009	An Iterative Learning Feedforward Controller for the TRIUMF e-linac	beam-loading, linac, TRIUMF, controls	485
	M.P. Laverty, K. Fong TRIUMF, Vancouver, Canada
	In the TRIUMF e-linac design, beam stability to within 0.1% within 10 μs in pulse mode is a design requirement. Traditional feedback control systems cannot respond within this time frame, so some form of feedforward control is needed. Even conventional feedforward may not be sufficient due to differences between the required feedforward signal and the actual beam-loading current. For this reason, an adaptive feedforward system using an iterative learning controller was developed for the e-linac LLRF. It can anticipate repetitive beam disturbance patterns by learning from previous iterations. The design and implementation of such a control algorithm is outlined, some simulation results are presented, and some preliminary test results with an actual cavity are illustrated.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPLR009
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TUPLR010	Measurements and Analysis of Cavity Microphonics and Frequency Control in the Cornell ERL Main Linac Prototype Cryomodule	linac, cryomodule, vacuum, LLRF	488
	M. Ge, N. Banerjee, J. Dobbins, R.G. Eichhorn, F. Furuta, G.H. Hoffstaetter, M. Liepe, P. Quigley, J. Sears, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	The Cornell Main Linac cryomodule (MLC) is a key component in the CBETA project. The SRF cavities with high loaded-Q in the MLC are very sensitive to microphonics from mechanical vibrations. Poor frequency stability of the cavities would dramatically increase the input RF power required to maintain stable accelerating fields in the SRF cavities. In this paper, we present detailed results from microphonics measurement for the cavities in the MLC, discuss dominant vibration sources, and show vibration damping results. The current microphonics level meets the CBETA requirement of a 36MeV energy gain without applying fast tuner compensation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPLR010
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TUPLR011	Performance of the Novel Cornell ERL Main Linac Prototype Cryomodule	linac, cryomodule, SRF, HOM	492
	F. Furuta, J. Dobbins, R.G. Eichhorn, M. Ge, D. Gonnella, G.H. Hoffstaetter, M. Liepe, T.I. O'Connell, 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) for the future energy-recovery linac (ERL) based X-ray light source at Cornell has been designed, fabricated, and tested. It houses six 7-cell SRF cavities with individual higher order-modes (HOMs) absorbers, cavity frequency tuners, and one magnet/BPM section. Cavities have achieved the specification values of 16.2MV/m with high-Q of 2.0·10¹⁰ in 1.8K in continuous wave (CW) mode. During initial MLC cavity testing, we encountered some field emission, reducing Q and lowering quench field. To overcome field emission and find optimal cool-down parameters, RF processing and thermal cycles with different cool-down conditions has been done. Here we report on these studies and present final results from the MLC cavity performance.
	Poster TUPLR011 [2.389 MB]
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TUPLR012	HOM Measurements for Cornell's ERL Main Linac Cryomodule	HOM, linac, cryomodule, simulation	496
	F. Furuta, R.G. Eichhorn, M. Ge, D. Gonnella, G.H. Hoffstaetter, M. Liepe, P. Quigley, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	The main linac cryomodule (MLC) for a future energy-recovery linac (ERL) based X-ray source at Cornell has been designed, fabricated, and tested. It houses six 7-cell SRF cavities with individual higher order-modes (HOMs) absorbers, cavity frequency tuners, and one magnet/BPM section. All HOMs in MLC have been scanned in 1.8K. The results show effective damping of HOMs, and also agree well with simulation results and the previous HOM scan results on one 7-cell cavity prototype test cryomodule. Here we present detailed results from these HOM studies.
	Poster TUPLR012 [2.773 MB]
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TUPLR015	Design of a Gamma-Ray Source Based on Inverse Compton Scattering at the Fast Superconducting Linac	laser, electron, photon, brightness	503
	D. Mihalcea Northern Illinois University, DeKalb, Illinois, USA B.T. Jacobson, A.Y. Murokh RadiaBeam, Santa Monica, California, USA P. Piot, J. Ruan Fermilab, Batavia, Illinois, USA
	Funding: This work is sponsored by the DNDO via contract with NIU. A Watt-level average-power gamma-ray source is currently under development at the FermiLab Accelerator Science & Technology (FAST) facility. The source is based on the inverse Compton scattering of a high-brightness 300-MeV beam against a high-power laser beam circulating in an optical cavity. The back scattered gamma rays are expected to have photon energies up to 1.5 MeV. This paper discusses the optimization of the source, its performance and the main challenges ahead.
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TUPLR022	Particulate Study on Materials for Cleanroom Assembly of SRF Cavities	niobium, SRF, operation, experiment	512
	L. Zhao, A.V. Reilly JLab, Newport News, Virginia, USA
	Reducing particulates is an important aspect for clean-room operation. Knowing that it is impossible to completely eliminate all particulates in a clean room, efforts have been made to prevent particulates from entering SRF cavities during high pressure rinsing (HPR) and assembly. At Jefferson Lab, one practice to achieve this goal has been clamping covers to cavity open flanges during assembly. Several cover materials that have been used are examined and alternative candidate materials are under development. Clamps as a known particulate generator are carefully examined and cleaning efficiency of different methods is studied. Cover tests were done on different cavity flanges, including an LCLS-II beam pipe flange, which helps the selection of cover materials for prototype and production of the project. Authored by Jefferson Science Associates, LLC under U.S. DOE Contracts DE-AC05-06OR23177 and DE-AC02-76SF00515 for the LCLS-II Project.
	Poster TUPLR022 [1.282 MB]
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TUPLR023	Impurity Content Optimization to Maximize Q-Factors of Superconducting Resonators	SRF, factory, niobium, superconductivity	515
	M. Martinello, M. Checchin, A. Grassellino, O.S. Melnychuk, S. Posen, A. Romanenko, D.A. Sergatskov Fermilab, Batavia, Illinois, USA M. Checchin Illinois Institute of Technology, Chicago, Illlinois, USA J. Zasadzinski IIT, Chicago, Illinois, USA
	Quality factor of superconducting radio-frequency (SRF) cavities is degraded whenever magnetic flux is trapped in the cavity walls during the cooldown. In this contribution we study how the trapped flux sensitivity, defined as the trapped flux surface resistance normalized for the amount of trapped flux, depends on the mean free path. A systematic study of a variety of 1.3 GHz cavities with different surface treatments (EP, 120 C bake and different N-doping) is carried out. A bell shaped trend appears for the range of mean free path studied. Over-doped cavities fall at the maximum of this curve defining the largest values of sensitivity. In addition, we have studied the trend of the BCS surface resistance contribution as a function of mean free path, showing that N-doped cavities follow close to the theoretical minimum. Adding these results together we show that the 2/6 N-doping treatment gives the highest Q-factor values at 2 K and 16 MV/m, as long as the magnetic field fully trapped during the cavity cooldown is lower than 10 mG.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPLR023
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TUPLR024	Enhancement of the Accelerating Gradient in Superconducting Microwave Resonators	induction, accelerating-gradient, factory, linac	519
	M. Checchin, A. Grassellino, M. Martinello, S. Posen, A. Romanenko Fermilab, Batavia, Illinois, USA M. Martinello Illinois Institute of Technology, Chicago, Illlinois, USA J. Zasadzinski IIT, Chicago, Illinois, USA
	Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DEAC02-07CH11359 with the United States Department of Energy. The accelerating gradient of superconducting resonators can be enhanced by engineering the thickness of a dirty layer grown at the cavity's rf surface. In this paper the description of the physics behind the accelerating gradient enhancement by meaning of the dirty layer is carried out by solving numerically the the Ginzburg-Landau (GL) equations for the layered system. The calculation shows that the presence of the dirty layer stabilizes the Meissner state up to the lower critical field of the bulk, increasing the maximum accelerating gradient.
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TUPLR025	Optimal Nitrogen Doping Level to Reach High Q0	cryomodule, SRF, niobium, electron	523
	D. Gonnella, T. Gruber, J.J. Kaufman, P.N. Koufalis, M. Liepe, J.T. Maniscalco Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: NSF and US DOE New continuous wave (CW) accelerators such as LCLS-II at SLAC require many SRF cavities operating in the medium field region at unprecedented high Q. In order to achieve this demanding goal, nitrogen-doping of the SRF cavities will be used. Nitrogen-doping has been shown to affect the BCS resistance both by a lowering of Rbcs at low fields and by the introduction of an anti-Q slope which enables the Q to continue increasing as the RF field is increased. The exact strength of this anti-Q slope is heavily dependent on the doping recipe and specifically the mean free path of the RF penetration layer of the doped cavities. In addition to its effect on Rbcs, the mean free path affects the amount of residual resistance obtained due to trapped magnetic flux. We have analyzed nine cavities prepared with different levels of nitrogen-doping to understand how BCS and residual resistance are affected by changes in the mean free path. Here we present a model based on these experimental results to predict the optimal doping level to reach the maximum Q at 16 MV/m based on the ambient magnetic field conditions. We find that if the cavities can be cooled with small amounts of trapped flux, moderate nitrogen-doping is better, while if they will have large amounts of trapped flux, lighter dopings should be used.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPLR025
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TUPLR027	Magnetic Field Management in LCLS-II 1.3 GHz Cryomodules	cryomodule, vacuum, controls, shielding	527
	S.K. Chandrasekaran, A. Grassellino, C.J. Grimm, G. Wu Fermilab, Batavia, Illinois, USA
	Funding: Operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the United States Department of Energy. The ambient magnetic field at the SRF cavity surface of the LCLS-II 1.3 GHz cryomodules is specified to be less than 0.5 μT (5 mG). Multiple methods were designed to lower the magnetic fields inside the prototype cryomodule. The resulting ambient magnetic field in this cryomodule just prior to its first cool down was <0.15 μT (1.5 mG), as measured using fluxgates inside and outside the cavity helium vessels.
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TUPLR028	Alternative Design for the RISP Pre-Stripper Linac	linac, cryomodule, simulation, solenoid	531
	B. Mustapha, Z.A. Conway, M.P. Kelly, P.N. Ostroumov, A.S. Plastun ANL, Argonne, USA J.-H. Jang, H. Jin, H.J. Kim, J.-W. Kim IBS, Daejeon, Republic of Korea
	Funding: This work was supported by the work-for-other grant WFO8550H titled "Pre-conceptual design, cost and schedule estimate of the 18.5 MeV/u Pre-stripper linac for the RISP/IBS" In a collaborative effort between Argonne's Linac Development Group and the RISP project team at the Korean Institute for Basic Science, we have developed an alternative design for the pre-stripper section of the RISP driver linac. The proposed linac design takes advantage of the recent accelerator developments at Argonne, namely the ATLAS upgrades and the Fermilab PIP-II HWR Cryomodule. In particular, the state-of-the-art performance of QWRs and HWRs, the integrated steering correctors and clean BPMs for a compact cryomodule design. To simplify the design and avoid frequency transitions, we used two types of QWRs at 81.25 MHz. The QWRs were optimized for β ~ 0.05 and ~ 0.11 respectively. Nine cryomodules are required to reach the stripping energy of 18.5 MeV/u. Following the lattice design optimization, end-to-end beam dynamics simulations including all sources of machine errors were performed. The results showed that the design is tolerant to errors with no beam losses observed for nominal errors. However, the robustness of the design could be further improved by a modified RFQ design, better optimized with the multi-harmonic buncher located upstream. This could lead to a significant reduction in the longitudinal beam emittance, offering much easier beam tuning and more tolerance to errors. The proposed design and the simulation results will be presented and discussed.
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TUPLR029	FRIB HWR Tuner Development	cryomodule, controls, alignment, cryogenics	535
	S. Stark, A. Facco, S.J. Miller, P.N. Ostroumov, J.T. Popielarski, K. Saito, B.P. Tousignant, T. Xu FRIB, East Lansing, USA A. Facco INFN/LNL, Legnaro (PD), Italy S.M. Gerbick, M.P. Kelly ANL, Argonne, USA
	Funding: * This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661, the State of Michigan and Michigan State University During the last two years the HWR pneumatic tuner development at FRIB evolved from the first prototypes to the final production design. A lot of warm testing and several cryogenic integrated tests with cavity were performed to optimize the tuner features. The main challenges included the bellow bushings binding and very tight space limitations for the assembly on the rail. The final design, based on the acquired experience, was prepared in collaboration with ANL and entered the preproduction phase.
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TUPLR030	First FRIB β=0.53 Prototype Coldmasss Build	cryomodule, vacuum, solenoid, SRF	538
	D.R. Victory, K. Elliott, B. Oja, J.T. Popielarski, M.S. Wilbur FRIB, East Lansing, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE SC0000661, the State of Michigan and Michigan State University. The β=0.53 coldmass consists of eight Superconducting Radio Frequency (SRF) β=0.53 cavities, eight Fundamental mode Power Couplers (FPC), and one 8 T solenoid. This is the first coldmass with this version of cavity and it has brought new challenges to overcome. The Facility for Rare Isotope Beams (FRIB) contains 18 cryomodules with β=0.53 cavity coldmasses, and this type of coldmass is the highest power and most produced ones in FRIB. During the final cleaning stage and the cavity assembly, particle detection equipment is used to verify the cavity cleanliness levels for cavity certification test and for coldmass assembly. This method allows for cleanliness detection of specific areas inside the cavity at any time a vacuum flange is off. The fixtures, techniques and procedures used to build the β=0.53 coldmasses will be presented.
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TUPLR033	First FRIB β=0.041 Production Coldmass Build	solenoid, SRF, alignment, cryomodule	541
	K. Elliott, S.J. Miller, B. Oja, J.T. Popielarski, L. Popielarski, D.R. Victory, M.S. Wilbur, T. Xu FRIB, East Lansing, USA M. Wiseman JLab, Newport News, Virginia, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE SC0000661, the State of Michigan and Michigan State University. Three β=0.041 cryomodules are required for the Facility for Rare Isotope Beams (FRIB) accelerator. Cleanroom assembly of all three coldmasses for these cryomodules has been completed. The cleanroom assembly includes; the superconducting radio frequency (SRF) cavities, the superconducting solenoids, fundamental power couplers (FPC), beam position monitors, alignment rail, and transport cart. This paper will provide an overview of the techniques and procedures used to assemble this cavity string such that it can be used in the FRIB accelerator.
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TUPLR035	RF Analysis of Electropolishing for EXFEL Cavities Production at Ettore Zanon Spa	shielding, cathode, SRF, superconductivity	544
	A.A. Sulimov DESY, Hamburg, Germany M. Giaretta, A. Gresele, A. Visentin Ettore Zanon S.p.A., Nuclear Division, Schio, Italy

Paper

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MO3A03

Spaceborne Electron Accelerators

linac, electron, gun, controls

32

J.W. Lewellen, C.E. Buechler, G.E. Dale, N.A. Moody, D.C. Nguyen
LANL, Los Alamos, New Mexico, USA

High-power electron beam generators in space will enable the studies of solar and space physics, specifically the interrogation of magnetic connection between the magnetosphere and ionosphere. This study plans to map the magnetic connection between the magnetosphere and ionosphere, using a satellite equipped with an electron beam accelerator that can create a spot in the ionosphere, observable by optical and radar detectors on the ground. To date, a number of spacecraft carrying low-power, <50-keV DC electron beam sources have been launched to study the upper ionosphere. The overall instrument weight will likely be dominated by the weight of the energy storage, the RF power amplifiers and the accelerator structure. We present the notional concept of a quasi-CW, C-band electron accelerator with 1-MeV beam energy, 10-mA beam current, and requiring 40 kW of prime power during operation. Our novel accelerator concept includes the following features: individually powered cavities driven by 6-GHz high-electron mobility transistors (HEMT), passively cooled accelerator structures with heat pipe technology, and active frequency control for operating over a range of temperatures.

Slides MO3A03 [3.191 MB]

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MOOP02

Current Status of Superconducting Linac for the Rare Isotope Science Project

linac, cryomodule, ion, rfq

41

H.J. Kim, I.S. Hong, H.C. Jung, W.K. Kim, Y.H. Kim, Y. Kim, B.-S. Park, I. Shin
IBS, Daejeon, Republic of Korea

The RISP (Rare Isotope Science Project) has been proposed as a multi-purpose accelerator facility for providing beams of exotic rare isotopes of various energies. It can deliver ions from proton to uranium. Proton and uranium ions are accelerated upto 600 MeV and 200 MeV/u respectively. The facility consists of three superconducting linacs of which superconducting cavities are independently phased. Requirement of the linac design is especially high for acceleration of multiple charge beams. We present the RISP linac design, the prototyping of superconducting cavity and cryomodule.

Slides MOOP02 [5.566 MB]

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MOOP03

High Gradient Accelerating Structures for Carbon Therapy Linac

impedance, linac, ion, operation

44

S.V. Kutsaev, R.B. Agustsson, L. Faillace, E.A. Savin
RadiaBeam, Santa Monica, California, USA
A. Goel, B. Mustapha, A. Nassiri, P.N. Ostroumov, A.S. Plastun
ANL, Argonne, Illinois, USA
E.A. Savin
MEPhI, Moscow, Russia

Funding: This work was supported by the U.S. Department of Energy, Office of High Energy Physics, under contract 0000219678
Carbon therapy is the most promising among techniques for cancer treatment, as it has demonstrated significant improvements in clinical efficiency and reduced toxicity profiles in multiple types of cancer through much better localization of dose to the tumor volume. RadiaBeam, in collaboration with Argonne National Laboratory, are developing an ultra-high gradient linear accelerator, Advanced Compact Carbon Ion Linac (ACCIL), for the delivery of ion-beams with end-energies up to 450 MeV/u for 12C⁶⁺ ions and 250 MeV for protons. In this paper, we present a thorough comparison of standing and travelling wave designs for high gradient S-Band accelerating structures operating with ions at varying velocities, relative to the speed of light, in the range 0.3-0.7. In this paper we will compare these types of accelerating structures in terms of RF, beam dynamics and thermo-mechanical performance.

Slides MOOP03 [3.497 MB]

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MOOP04

Traveling Wave Linear Accelerator With RF Power Flow Outside of Accelerating Cavities

impedance, coupling, linac, electron

48

V.A. Dolgashev
SLAC, Menlo Park, California, USA

Funding: Work supported by the U.S. DOE under Contract No. DE-AC02-76-SF00515.
An accelerating structure is a critical component of particle accelerators for medical, security, industrial and scientific applications. Standing-wave side-coupled accelerating structures are used where available RF power is at a premium, while average current and average RF power lost in the structure are high. These structures are expensive to manufacture and typically require a circulator to divert structure-reflected power away from RF source, klystron or magnetron. In this report a traveling wave accelerating structure is presented which combines high shunt impedance of the side-coupled standing wave structure with such advantages as simpler tuning and manufacturing. In addition, the structure is matched to the RF source so no circulator is needed. This paper presents the motivation for this structure and shows a practical example.

Slides MOOP04 [5.459 MB]

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MOOP05

Dry-Ice Cleaning of RF-Structures at DESY

gun, niobium, RF-structure, coupling

52

A. Brinkmann, J. Ziegler
DESY, Hamburg, Germany

Dry-Ice cleaning is today a well established cleaning method in matters of reducing harmful dark current and field emission in copper RF-structures like RF-Guns such as for the European XFEL, FLASH and REGAE. This led to the idea to clean longer RF-structures, in particular 3GHz transverse deflecting structures for the European XFEL. We developed a cleaning device with the possibility to clean up to 2 m long structures in horizontal position with an inner diameter of not more than 40 mm. Furthermore this device also allows to clean 9-cell TESLA-type Nb-cavities as well. A report of the technical layout and results of RF-tests will be given.

Slides MOOP05 [0.969 MB]

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MOOP07

Development of Ultracold Neutron Accelerator for Time Focusing of Pulsed Neutrons

neutron, focusing, controls, resonance

56

S. Imajo
Kyoto University, Kyoto, Japan
T. Ino, K. Mishima
KEK, Ibaraki, Japan
Y. Iwashita
Kyoto ICR, Uji, Kyoto, Japan
M. Kitaguchi, H.M. Shimizu
Nagoya University, Nagoya, Japan
S. Yamashita
ICEPP, Tokyo, Japan

Low energy neutron accelerator can be realized by the combination of an adiabatic fast passage spin flipper and a gradient magnetic field. Neutrons have magnetic moments, so that the accumulated potential energies are not cancelled before and after passage of a magnetic field and their kinetic energies change in case their spins are flipped in the field. This accelerator handles lower kinetic energy neutrons than approximately 300 neV. Currently we have developed the advanced version which makes it possible to handle broader kinetic energy range. The design and measured characteristics are described.

Slides MOOP07 [1.313 MB]

Poster MOOP07 [1.389 MB]

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MOOP11

Operation of the CEBAF 100 MV Cryomodules

cryomodule, operation, electron, controls

65

C. Hovater, T.L. Allison, R. Bachimanchi, G.H. Biallas, E. Daly, M.A. Drury, A. Freyberger, R.L. Geng, G.E. Lahti, R.A. Legg, C.I. Mounts, R.M. Nelson, T. E. Plawski, T. Powers
JLab, Newport News, Virginia, USA

Funding: Authored by JSA, LLC under U.S. DOE Contract DE-AC05- 06OR23177.
The Continuous Electron Beam Accelerator Facility (CEBAF) 12 GeV upgrade reached its design energy in December of 2015. Since then CEBAF has been delivering 12 GeV beam to experimental Hall D and 11 GeV to experimental halls A and B in support of Nuclear physics. To meet this energy goal, ten new 100 MV cryomodules (80 cavities) and RF systems were installed in 2013. The superconducting RF cavities are designed to operate CW at a average accelerating gradient of 19.2 MV/m. To support the higher gradients and higher QL (3.2×107) operations, the RF system uses 13 kW klystrons and digital LLRF to power and control each cavity. This paper reports on the C100 operation and optimization improvements of the RF system and cryomodules.

Slides MOOP11 [1.574 MB]

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MOOP12

Klynac Design Simulations and Experimental Setup

linac, electron, klystron, simulation

68

K.E. Nichols, B.E. Carlsten, A. Malyzhenkov
LANL, Los Alamos, New Mexico, USA

Funding: The authors gratefully acknowledge the support of the US Department of Energy through the LANL/LDRD Program for this work.
We present results of a proof-of-principle demonstration of the first ever klynac, a compact 1 MeV linear accelerator with integrated klystron source using one electron beam. This device is bi-resonant, utilizing one resonant circuit for the klystron input and gain cavities, and one for the klystron output and linac cavities. The purpose of a klynac-type device is to provide a compact and inexpensive alternative for a conventional 1 to 6 MeV accelerator. A conventional accelerator requires a separate RF source and linac and all the associated hardware needed for that architecture. The klynac configuration eliminates many of the components to reduce the weight of the entire system by 60%. We have built an 8-cavity, 2.84-GHz RF structure for a 1-MeV bi-resonant klynac. A 50-kV, 10-A electron gun provides the single beam needed. Numerical modeling was used to optimize the design. The separation between the klynac ouput cavity and the first accelerator cavity was adjusted to optimize the bunch capture and a pin-hole aperture between the two cavities reduces the beam current in the linac section to about 0.1 A. Standard high-shunt impedance linac cavities designs are used. We have fabricated the first test structure. The structure will be tested with beam in early Summer 2016. Results will be presented at LINAC 2016.

Slides MOOP12 [1.136 MB]

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MOPRC006

Beam Tuning and Error Analysis of a Superconducting Linac

linac, simulation, quadrupole, lattice

77

Y. Zhang
FRIB, East Lansing, USA

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
Beam tuning and error analysis of a superconducting linac for heavy ion beams are introduced in this paper. In simulation studies with accelerator codes, system errors to the beam tuning are analyzed numerically, which include random cavity and magnet errors and measurement errors of absolute beam phase, beam bunch length, and beam transverse profiles. Simple statistical equations are developed from the tedious and time-consuming numerical simulations, and they may provide advantage tools not only to analyze a linac beam tuning, such as phase and amplitude tuning of superconducting cavity, longitudinal and transverse beam matching, but also will be very helpful to linac design with practical beam diagnostics system and authentic accelerator lattice.

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MOPRC015

Development Status of FRIB On-line Model Based Beam Commissioning Application

solenoid, lattice, linac, quadrupole

100

Z.Q. He, M.A. Davidsaver, K. Fukushima, D.G. Maxwell, G. Shen, Y. Zhang, Q. Zhao
FRIB, East Lansing, USA

Funding: The work is supported by the U.S. National Science Foundation under Grant No. PHY-11-02511, and the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661.
The new software FLAME has been developed to serve as physics model used for on-line beam commissioning applications. FLAME is specially designed to cover FRIB modeling challenges to balance between speed and precision. Several on-line beam commissioning applications have been prototyped based on FLAME and tested on the physics application prototyping environment. In this paper, components of the physics application prototyping environment are firstly described. Then, the design strategy and result of the four major applications: baseline generator, cavity tuning, orbit correction, transverse matching, are discussed.

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MOPRC018

Improved Beam Dynamics and Cavity RF Design for the FAIR Proton Injector

linac, proton, DTL, quadrupole

111

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

The FAIR facility at GSI requires a dedicated 70 MeV, 70 mA proton injector for the research program with intense antiproton beams. The main accelerator part consists of six 'Crossbar H-type' (CH) cavities operated at 325 MHz. Based on a linac layout carefully developed over several years, recently the beam dynamics has been revised with the scope of finalising the design and thus being able to start the construction of the main linac components. As compared to previous designs the MEBT behind the RFQ was slightly extended, the gap numbers per CH cavity and the voltage distributions were optimised and the layout of the intermediate diagnostics section including a rebuncher cavity at 33 MeV was redesigned. Finally, detailed machine error studies were performed in order to check the error response of the new design and the steering concept in particular. In the consequence, the final parameters obtained from the beam dynamics update are used for finalizing the CH-DTL cavity design by CST-MWS calculations.

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MOPRC025

Final Design of the Fully Equipped HWR Cavities for SARAF

cryomodule, linac, multipactoring, simulation

123

G. Ferrand
CEA/DSM/IRFU, France
L. Boudjaoui, P. Hardy, F. Leseigneur, C. Madec, N. Misiara, N. Pichoff
CEA/IRFU, Gif-sur-Yvette, France

SNRC and CEA collaborate to the upgrade of the SARAF accelerator to 5 mA CW 40 MeV deuteron and proton beams (Phase 2). CEA is in charge of the design, construction and commissioning of the superconducting linac (SARAF-LINAC Project). The SCL is made up of 4 cryomodules: the first two will host each 6 half-wave resonator (HWR) low beta cavities (β = 0.09) at 176 MHz; the last two will host each 7 HWR high-beta cavities (β = 0.18) at 176 MHz. The fully equipped cavity includes the niobium cavity with a helium tank, an input power couplers and a frequency tuning system. The final RF design of the low and high beta cavities will be presented in this poster, as well as the RF design of the couplers, the expected tuning range of the cavities and the multipactor analysis.

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MOPRC026

Mechanical Design of the HWR Cavities for the SARAF SRF LINAC

linac, simulation, cryomodule, SRF

126

N. Misiara, L. Boudjaoui, G. Ferrand, P. Hardy, F. Leseigneur, C. Madec, N. Pichoff
CEA/IRFU, Gif-sur-Yvette, France

SNRC and CEA collaborate to the upgrade of the SARAF accelerator to 5 mA CW 40 MeV deuteron and proton beams (Phase 2). CEA is in charge of the design, construction and commissioning of the superconducting linac (SARAF-LINAC Project). The SCL consists in 4 cryomodules. The first two identical cryomodules host 6 half-wave resonator (HWR) low beta cavities (β = 0.09) at 176 MHz. The last two identical cryomodules will host 7 HWR high-beta cavities (β = 0.18) at 176 MHz. The fully equipped cavity includes the niobium cavity with its helium tank, the couplers and the frequency tuning system. In this paper, the mechanical design and the foreseen qualification procedures for both cavities and tuning systems are presented with compliance, to the best extent, to the rules of Unfired Pressure Vessels NF-EN 13445 (1-5) standards.

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MOPRC027

Surface Roughness Effect on the Performance of Nb3Sn Cavities

SRF, pulsed-power, niobium, klystron

129

R.D. Porter, 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 award DE-SC0008431
Surface roughness of current Niobium-3 Tin (Nb3Sn) superconducting radio-frequency (SRF) accelerator cavities can cause enhancement of the surface magnetic field. This enhancement can push the surface magnetic field beyond the critical field, which, if it occurs over a large enough area, can cause the cavity to quench. This paper presents simulations of the surface magnetic field enhancements in SRF cavities caused by the surface roughness of current Cornell Nb3Sn cavities, which have achieved record efficiency. Simple, smooth cavity geometry is defined and surface magnetic fields calculated using SLANS2. The cavity geometry is modified with a small rough region for which the geometry is determined from AFM scans of a Nb3Sn coated sample and the surface fields are calculated again. The calculated surface fields of the smooth and rough cavities are compared to determine the extent of the field enhancement, the area over which the enhancement is significant, and which surface features cause large field enhancement. We find that 1% of the surface analyzed has fields enhance by more than 45%. On average the Q-factor is increased by (3.8 ± 1.0) \%.

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MOPRC029

Experiment of Plasma Discharge on HWR Cavity for In-Situ Surface Cleaning Study

plasma, electron, experiment, operation

133

A.D. Wu, Y. He, T.C. Jiang, C.L. Li, Y.M. Li, W.M. Yue, S.H. Zhang, H.W. Zhao
IMP/CAS, Lanzhou, People's Republic of China
L.M. Chen
Institute of Physics, Chinese Academy of Sciences, Beijing, People's Republic of China
L. Yang
IHEP, Beijing, People's Republic of China

Hydrocarbons, which migrate from the vacuum bumps system, will absorb on the cavity surface after periods of operation. The contaminants can reduce the surface electron work function to enhance the field emission effect and restrict the cavity accelerating gradient. The room temperature in-situ plasma surface processing to clean the hydrocarbon contaminants can act as a convenient and efficient technology for the accelerator on line performance recovery. For better control of the discharge inside the cavity, the experiment works on a single HWR cavity aims to research the ignition between the swarm parameters (gas flow, pressure, forward power).

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MOPLR005

Design, Manufacturing and Installation of Two Dual-Feed Accelerating Structures for the FERMI Injector

linac, accelerating-gradient, FEL, emittance

139

C. Serpico, A. Fabris, G. Penco, M. Svandrlik
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
B. Keune
RI Research Instruments GmbH, Bergisch Gladbach, Germany

FERMI is a seeded Free Electron Laser (FEL) driven by a warm S-band Linac. In the injector region, two 3- meter long Forward Traveling Wave (FTW) accelerating structures, coming from the old Elettra injector, were installed. In order to improve the e-beam quality at higher bunch charge, it was decided to replace the existing ones with two dual-feed accelerating structures. Those structures have been designed and manufactured by RI Research Instruments GmbH and delivered to Elettra in July 2015. The following paper will report about the RF design and the manufacturing of the new structures. Details about the RF conditioning and the installation will also be illustrated.

Poster MOPLR005 [1.100 MB]

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MOPLR006

Monopole HOMs Dumping in the LCLS-II 1.3 GHz Structure

HOM, linac, coupling, damping

142

A. Lunin, T.N. Khabiboulline, N. Solyak
Fermilab, Batavia, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the U.S. DOE
Developing an upgrade of Linac Coherent Light Source (LCLS-II) is currently underway. The central part of LCLS-II is a continuous wave superconducting RF (CW SRF) electron linac. High order modes (HOMs) excited in SRF structures by passing beam may deteriorate beam quality and affect beam stability. In this paper we report the simulation results of monopole High Order Modes (HOM) spectrum in the 1.3 GHz accelerating structure. Optimum parameters of the HOM feedthrough are suggested for minimizing RF losses on the HOM antenna tip and for preserving an efficiency of monopole HOMs damping simultaneously.

Poster MOPLR006 [0.647 MB]

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MOPLR007

Redesign of the End Group in the 3.9 GHz LCLS-II Cavity

HOM, dipole, linac, operation

145

A. Lunin, I.V. Gonin, T.N. Khabiboulline, N. Solyak
Fermilab, Batavia, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the U.S. DOE
Development and production of Linac Coherent Light Source II (LCLS-II) is underway. The central part of LCLS-II is a continuous wave superconducting RF (CW SCRF) electron linac. The 3.9 GHz third harmonic cavity similar to the XFEL design will be used in LCLS-II for linearizing the longitudinal beam profile*. The initial design of the 3.9 GHz cavity developed for XFEL project has a large, 40 mm, beam pipe aperture for better higher-order mode (HOM) damping. It is resulted in dipole HOMs with frequencies nearby the operating mode, which causes difficulties with HOM coupler notch filter tuning. The CW linac operation requires an extra caution in the design of the HOM coupler in order to prevent its possible overheating. In this paper we present the modified 3.9 GHz cavity End Group for meeting the LCLS-II requirements
* LCLS-II 3.9 GHz Cryomodules, Physics Requirements Document, LCLSII-4.1-PR-0097-R1, SLAC, USA, 2015

Poster MOPLR007 [1.590 MB]

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MOPLR009

X-Band Travelling Wave Accelerating Section R&D for HTF

electron, operation, coupling, vacuum

152

K. Jin
USTC/NSRL, Hefei, Anhui, People's Republic of China

Hefei Light Source (HLS) was mainly composed of an 800 MeV electron storage ring and an 800MeV-1GeV constant-gradient accelerator in NSRL. The new Linac with Full Energy Injection and the Top-up Injection scheme has been developed successfully. And the other functioning as X Ray Free Electron Laser test facility has been considered. In the project, in order to compress the bunch length and to achieve the beam energy distribution linearization. A 15MeV, operation frequency 11.424GHz traveling wave accelerating section as harmonic compensation is being developed. In this paper, X Ray Free Electron Laser Hefei Test Facility (HTF) is introduce briefly. And the R&D of the x-band accelerating section with collinear load are presented in detail.

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MOPLR010

4 K SRF Operation of the 10 MeV CEBAF Photo-Injector

cryomodule, operation, SRF, cryogenics

155

G.V. Eremeev, M.A. Drury, J.M. Grames, R. Kazimi, M. Poelker, J.P. Preble, R. Suleiman, Y.W. Wang, M. Wright
JLab, Newport News, Virginia, USA

Funding: Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
SRF accelerating cavities are often operated in superfluid helium of temperature near 2 K to enhance the cavity quality factor Q0 and manage cryogenic heat loads, which are particularly important at large SRF accelerator facilities. This temperature paradigm, however, need not put SRF technology out of the reach of small institutions or even limit SRF operation at large facilities to provide 10-100 MeV beam energy. At the Jefferson Lab CEBAF accelerator there are regularly scheduled maintenance periods during which the liquid helium temperature is raised to 4 K, reducing cryogenic plant power consumption by ~50% and saving megawatts of electrical power. During such a recent period, we accelerated a continuous-wave electron beam at the CEBAF photo-injector to 6.3 MeV/c with current ~80μA using two niobium cavities at helium temperature of 4 K. This contribution describes the SRF and cryogenic performance and uses measured beam quality and energy stability as key metrics. These measurements indicate that 4 K operation of niobium SRF cavities in CEBAF and at small institutions may be a sensible and cost effective mode of operation, provided the cryogenic load associated with lower Q0 is manageable for the number of SRF cavities needed. For Jefferson Lab, this enhances our scientific reach allowing additional low-energy ~10 MeV experiments each year.

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MOPLR015

Thermal-Mechanical Study of 3.9 GHz CW Coupler and Cavity for LCLS-II Project

simulation, resonance, cryomodule, linac

171

I.V. Gonin, E.R. Harms, T.N. Khabiboulline, N. Solyak, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Third harmonic system was originally developed by Fermilab for FLASH facility at DESY and then was adopted and modified by INFN for the XFEL project [1-3]. In contrast to XFEL project, all cryomodules in LCLS-II project will operate in CW regime with higher RF average power for 1.3 GHz and 3.9 GHz cavities and couplers. Design of the cavity and fundamental power coupler has been modified to satisfy LCLS-II requirements. In this paper we discuss the results of COMSOL thermal and mechanical analysis of the 3.9 GHz coupler and cavity to verify proposed modifica-tion of the design. For the dressed cavity we present simulations of Lorentz force detuning, helium pressure sensitivity df/dP and major mechanical resonances.

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MOPLR016

Status of the Injection System of the CLARA FEL Test Facility

gun, FEL, solenoid, cathode

174

B.L. Militsyn, D. Angal-Kalinin, R.K. Buckley, R.J. Cash, J.A. Clarke, L.S. Cowie, B.D. Fell, P. Goudket, T.J. Jones, K.B. Marinov, P.A. McIntosh, J.W. McKenzie, K.J. Middleman, T.C.Q. Noakes, B.J.A. Shepherd, R. Valizadeh, A.E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
V.V. Paramonov
RAS/INR, Moscow, Russia

The 250 MeV CLARA FEL test facility is now under construction at Daresbury Laboratory. Electron beam for this facility is provided by two normal conducting S-band photocathode guns: a 10 Hz 2.5 cell gun earlier used as the injector for the VELA machine, and a 400 Hz 1.5 cell gun now under commissioning. At the initial stage of Phase I CLARA will operate with the 10 Hz gun and a 45 MeV 2 m long linac section working as a buncher and/or booster. The beam will be deflected into the existing VELA beamline with an S-bend and directed to the spectrometer line for analysing beam properties or into one of two VELA user areas. The 400 Hz gun will be installed in the VELA beamline for detailed high power RF and beam commissioning in the VELA beam diagnostics suite. As the 400 Hz gun is equipped with an interchangeable photocathode it is possible to investigate different metal photocathodes and select the one providing minimal beam emittance at highest quantum efficiency. A state of the art photocathode preparation system is under commissioning at Daresbury. After commissioning the 400 Hz gun will be installed to the CLARA beam line to deliver high energy, high repetition rate beams for the FEL facility, and the 10 Hz gun will be returned to the VELA beam line.

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MOPLR020

Challenges in Realizing the LCLS-II Cryomodule Production

cryomodule, SRF, linac, superconducting-RF

181

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-rays 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. One of the challenges of this project, and the topic of this paper, is coordinating the effort of three DOE labs in order to realize this machine in just a few years time. This coordination is necessary due to the fact that the cryomodules will be assembled at both Jefferson Lab and Fermi Lab, tested, and then shipped to SLAC for installation, commissioning and operation. This paper will report on our experiences to date, issues that have been identified and planned mitigation going forward.

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MOPLR022

Commissioning and First Results from the Fermilab Cryomodule Test Stand

vacuum, cryomodule, controls, radiation

185

E.R. Harms, M.H. Awida, C.M. Baffes, K. Carlson, S.K. Chandrasekaran, B.E. Chase, E. Cullerton, J.P. Edelen, J. Einstein, C.M. Ginsburg, A. Grassellino, B.J. Hansen, J.P. Holzbauer, S. Kazakov, T.N. Khabiboulline, M.J. Kucera, J.R. Leibfritz, A. Lunin, D. McDowell, M.W. McGee, D.J. Nicklaus, D.F. Orris, J.P. Ozelis, J.F. Patrick, T.B. Petersen, Y.M. Pischalnikov, P.S. Prieto, O.V. Prokofiev, J. Reid, W. Schappert, D.A. Sergatskov, N. Solyak, R.P. Stanek, D. Sun, M.J. White, C. Worel, G. Wu
Fermilab, Batavia, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the United States Department of Energy.
A new test stand dedicated to SRF cryomodule testing, CMTS1, has been commissioned and is now in operation at Fermilab. The first device to be cooled down and powered in this facility is the prototype 1.3 GHz cryomodule assembled at Fermilab for LCLS-II. We describe the demonstrated capabilities of CMTS1, report on steps taken during commissioning, provide an overview of first test results, and survey future plans.

Poster MOPLR022 [3.431 MB]

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MOPLR023

Examination of Cutouts Inner Surfaces from Nb3Sn Coated Cavity

niobium, SRF, ion, accelerating-gradient

189

U. Pudasaini, M.J. Kelley
The College of William and Mary, Williamsburg, Virginia, USA
G.V. Eremeev, C.E. Reece
JLab, Newport News, Virginia, USA
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 DE-AC05-06OR23177 and Office of High Energy Physics under grant SC00144475.
The potential for higher operating temperature and higher gradient have motivated SRF cavity researchers to pursue Nb3Sn as an alternative to Nb for nearly fifty years. Far and away the most common embodiment has been a few micron-thick Nb3Sn layer on the cavity interior surface obtained by vapor diffusion coating, with one or another set of parameters. While many cavities have been made and RF tested, reports of dissecting a cavity in detail to examine the coating and relate it to RF measurements are rare. We coated a BCP-treated single cell cavity in a typical process of tin/tin chloride activation at 500 C followed by tin vapor deposition at 1200 C. After RF-testing, we cut and examined sections from several locations to learn composition, thickness topography of the interior surface. The effect of process variables, such as surface preparation, process temperature and duration, and vapor chemistry needs to be explored.

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MOPLR024

Progress Towards Nb3Sn CEBAF Injector Cryomodule

cryomodule, niobium, operation, electron

193

G.V. Eremeev, K. Macha, U. Pudasaini, C.E. Reece, A-M. Valente-Feliciano
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Operations at 4 K instead of 2 K have the potential to reduce the operational cost of an SRF linac by a factor of 3, if the cavity quality factor can be maintained. Cavities coated with Nb3Sn have been shown to achieve the accelerating gradients above 10 MV/m with a quality factor around 10¹⁰ at 4 K. Because such performance is already pertinent for CEBAF injector cryomodule, we are working to extend these results to CEBAF accelerator cavities envisioning coating of two CEBAF 5-cell cavities with Nb3Sn. They will be installed in an injector cryomodule and tested with beam. The progress on this path is reported in this contribution.

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MOPLR025

Investigation of Low-Level Nitrogen in Niobium by Secondary Ion Mass Spectrometry

ion, niobium, SRF, factory

196

J. Tuggle
Virginia Polytechnic Institute and State University, Blacksburg, USA
M.J. Kelley
The College of William and Mary, Williamsburg, Virginia, USA
A.D. Palczewski, C.E. Reece
JLab, Newport News, Virginia, USA
F.A. Stevie
NCSU AIF, Raleigh, North Carolina, USA

Funding: Supported by the U.S. DOE Office of Science, ONP contract DE-AC05-06OR23177 and OHEP grant SC00144475. Tuggle is supported by Nanoscale Characterization and Fabrication Laboratory at Virginia Tech.
Understanding the improvement of the SRF cavity quality factor by low-level nitrogen addition ("N-doping") is attracting much attention from researchers. Precise, repeatable measurement of the nitrogen profile in the parts-per-thousand to parts-per-million range is vital. Secondary Ion Mass Spectrometry (SIMS) is the approach of choice because of excellent sensitivity and depth resolution. Accurate quantitation must consider sample properties, such as surface topography and crystal structure, calibration of the instrument with reference materials, and data analysis. We report the results of a SIMS study in which polycrystal and single crystal coupons were N-doped, each accompanied by new SRF-grade niobium sheet equivalent to a single cell cavity.

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MOPLR026

Material Qualification of LCLS-II Production Niobium Material Including RF and Flux Expulsion Measurements on Single Cell Cavities

niobium, cryomodule, SRF, controls

199

A.D. Palczewski, F. Marhauser
JLab, Newport News, Virginia, USA
A. Grassellino, S. Posen
Fermilab, Batavia, Illinois, USA

Funding: Work at JLab is supported by the U.S. Department of Energy under contract DE-AC05-06OR23177 and Fermilab is operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359.
It has been shown that cooldown details through transition temperature can significantly affect the amount of trapped magnetic flux in SRF cavities, which can lead to performance degradation proportional to the magnitude of the ambient magnetic field.[*] It has also more recently been shown that depending on the exact material properties - even when the material used originated from the same batch from the same vendor - and subsequent heat treatment, the percent of flux trapped during a cool-down could vary widely for identical cool-down parameters.[**] For LCLS-II, two material vendors have produced half of the niobium used for the cavity cells (Tokyo Denkai Co., Ltd. (TD) and Ningxia Orient Tantalum Industry Co., Ltd. (NX)). Both vendors delivered material well within specifications set out by the project (according to ASTM B 393-05), which allows yet some variation of material characteristics such as grain size and defect density. In this contribution, we present RF and magnetic flux expulsion measurements of four single cell cavities made out of two different niobium batches from each of the two LCLS-II material suppliers and draw conclusions on potential correlations of flux expulsion capability with material parameters. We present observations of limited flux expulsion in cavities made from the production material and treated with the baseline LCLS-II recipe.
[*] A. Romanenko et al J. Appl. Phys. 115, 184903 (2014)
[**] S. Posenet et al., Journal of Applied Physics 119, 213903 (2016).

Poster MOPLR026 [0.861 MB]

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MOPLR030

Electromagnetic Design of a Superconducting Twin Axis Cavity

HOM, coupling, linac, dipole

203

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

The twin-axis cavity is a new kind of rf superconducting cavity that consists of two parallel beam pipes, which can accelerate or decelerate two spatially separated beams in the same cavity. This configuration is particularly effective for high-current beams with low-energy electrons that will be used for bunched beam cooling of high-energy protons or ions. The new cavity geometry was designed to create a uniform accelerating or decelerating fields for both beams by utilizing a TM110 dipole mode. This paper presents the design rf optimization of a 1497 MHz twin-axis single-cell cavity, which is currently under fabrication.

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MOPLR031

Wakefield Analysis of Superconducting RF-Dipole Cavities

wakefield, impedance, HOM, dipole

206

S.U. De Silva, J.R. Delayen
ODU, Norfolk, Virginia, USA

RF-dipole crabbing cavities are being considered for a variety of crabbing applications. Some of the applications are the crabbing cavity systems for LHC High Luminosity Upgrade and the proposed Electron-Ion Collider for Jefferson Lab. The design requirements in the current applications require the cavities to incorporate complex damping schemes to suppress the higher order modes that may be excited by the high intensity proton or electron beams traversing through the cavities. The number of cavities required to achieve the desired high transverse voltage, and the complexity in the cavity geometries also contributes to the wakefields generated by beams. This paper characterizes the wakefield analysis for single cell and multi-cell rf-dipole cavities.

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MOPLR035

Fabrication of Superconducting Spoke Cavity for Compact Photon Source

laser, photon, linac, scattering

212

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

Funding: This study is supported by Photon and Quantum Basic Research Coordinated Development Program of MEXT, Japan.
The spoke cavity is expected to have advantages for compact ERL accelerator for X-ray source based on laser Compton scattering. We have been developing the spoke cavity under a research program of MEXT, Japan to establish the fabrication process. Since our designed shape of the spoke is complicated due to increase the RF properties, one-step press forming with one set of molds will cause so large strain to break the sheet. We designed the mold components including the process of press work. The press forming tests of the spoke cavity have been done with the various materials of sheets to check molding performance. In this paper we present status of the spoke cavity fabrication.

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MOPLR037

Study of the Surface and Performance of Single-Cell Nb Cavities After Vertical EP Using Ninja Cathodes

cathode, experiment, polarization, niobium

217

V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi
MGH, Hyogo-ken, Japan
P. Carbonnier, F. Éozénou, Y. Gasser, L. Maurice, C. Servouin
CEA/DSM/IRFU, France
F. Furuta, M. Ge, T. Gruber, J.J. Kaufman, J. Sears
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe
KEK, Ibaraki, Japan
K. Ishimi
MGI, Chiba, Japan

A 1.3 GHz single-cell niobium (Nb) coupon cavity was vertically electropolished (VEPed) with three different Ninja cathodes which were specially designed for VEP of 1.3 GHz superconducting RF elliptical (ILC/Tesla type) cavities. The cathodes were fabricated to have different surface areas and different distances between cathode surface and the equator. The Ninja cathode prepared with an enhanced cathode surface area was covered with a meshed shield to avoid bubble attack on the surface of the cavity cell. It has been turned out that the anode-cathode distance and the cathode area affect surface morphology of the equator. A smooth equator surface was obtained in the cases in which the cathode surface was geometrically close to the equator or instead the cathode surface area was sufficiently larger. Two 1.3 GHz ILC/Tesla type single-cell cavities VEPed with the Ninja cathodes and using optimized conditions showed good performance in vertical tests.

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MOPLR038

Fabrication of 9 Cell Coupon Cavity for Vertical Electropolishing Test

SRF, cathode, polarization, controls

220

S. Kato, H. Hayano, H. Inoue, H. Monjushiro, T. Saeki, M. Sawabe
KEK, Ibaraki, Japan
V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi
MGH, Hyogo-ken, Japan

We have been using single cell coupon cavities to establish vertical electropolishing (VEP) process for a couple of years. A series of in-situ measurements of an EP current at an individual coupon in a coupon cavity can help determination of appropriate EP conditions. VEPed coupons which are surface analysed with XPS, SEM and the other tools can also bring lot information and expertise to development of VEP cathode and optimization of VEP conditions. This time we fabricated the world first 9-cell coupon cavity where 3 sample coupons at the equators and 6 sample coupons at positions close to the irises can be installed. VEP of this coupon cavity with a newly developed Ninja cathode brought useful information for improvement of the VEP facility and optimization of the VEP conditions.

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MOPLR039

Development of New Type "Ninja" Cathode for Nb 9-cell Cavity and Experiment of Vertical Electro-Polishing

cathode, experiment, target, collider

223

K.N. Nii, V. Chouhan, Y.I. Ida, T.Y. Yamaguchi
MGH, Hyogo-ken, Japan
H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe
KEK, Ibaraki, Japan
K. Ishimi
MGI, Chiba, Japan

Marui Galvanizing Co. Ltd. has been improving Vertical Electro-Polishing (VEP) technologies and facilities for Nb 9-cell superconducting accelerator cavity for International Linear Collider (ILC) in collaboration with KEK. This time, we developed new type 'Ninja' cathode in order to improve VEP uniformity of Nb 9-cell cavity inner surface based on the results of 1-cell cavity VEP experiment. In this article, we will report construction of new type "Ninja" cathode for Nb 9-cell cavity and experiment of VEP using this.

Poster MOPLR039 [0.610 MB]

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MOPLR041

Design and Fabrication of β=0.3 SSR1 for RISP

niobium, TRIUMF, cryogenics, linac

226

Z.Y. Yao, R.E. Laxdal, B.S. Waraich, V. Zvyagintsev
TRIUMF, Vancouver, Canada
R. Edinger
PAVAC, Richmond, B.C., Canada

A 325MHz β=0.30 balloon variant of single spoke resonator, which was proposed to suppress multipacting around operational gradient, was chosen as the prototype cavity of SSR1 for Rare Isotope Science Project (RISP). It was also demonstrated to achieve good RF and mechanical properties by geometry optimization for both cavity and helium jacket. The details of RISP SSR1 design will be reported in this paper, accompanying with some particular considerations of fabrication for this new member to the spoke family.

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MOPLR043

Cavity Processing and Preparation of 650 MHz Elliptical Cell Cavities for PIP-II

SRF, vacuum, factory, cathode

229

A.M. Rowe, S.K. Chandrasekaran, A. Grassellino, O.S. Melnychuk, M. Merio, D.A. Sergatskov
Fermilab, Batavia, Illinois, USA
T. Reid
ANL, Argonne, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the United States Department of Energy.
The PIP-II project at Fermilab requires fifteen 650 MHz SRF cryomodules as part of the 800 MeV LINAC that will provide a high intensity proton beam to the Fermilab neutrino program. A total of fifty-seven high-performance SRF cavities will populate the cryomodules and will operate in both pulsed and continuous wave modes. These cavities will be processed and prepared for performance testing utilizing adapted cavity processing infrastructure already in place at Fermilab and Argonne. The processing recipes implemented for these structures will incorporate state-of-the art processing and cleaning techniques developed for 1.3 GHz SRF cavities for the ILC, XFEL, and LCLS-II projects. This paper describes the details of the processing recipes and associated chemistry, heat treatment, and cleanroom processes at the Fermilab and Argonne cavity processing facilities. This paper also presents single and multi-cell cavity test results with quality factors above 5·10¹⁰ and accelerating gradients above 30 MV/m.

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MOPLR047

Advanced Vertical Electro-Polishing studies at Cornell with Faraday

SRF, niobium, status, target

233

F. Furuta, M. Ge, T. Gruber, G.H. Hoffstaetter, J.J. Kaufman, M. Liepe, J. Sears
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
T.D. Hall, M.E. Inman, S.T. Snyder, E.J. Taylor
Faraday Technology, Inc., Clayton, Ohio, USA

Cornell's SRF group and Faraday Technology Inc. have started collaborations on two phase-II SBIR projects. Both projects are aiming for the development of advanced Vertical Electro-Polishing (VEP) for Nb SRF cavities, such as HF free or acid free VEP protocols. These could be eco-friendlier alternatives for the standard, HF-based EP electrolyte used, and could bring new breakthrough performance for Nb SRF cavities. Here we give a status update and report first results from these two projects.

Poster MOPLR047 [2.852 MB]

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MOPLR050

Study and Development of CW Room Temperature Rebuncher for SARAF Accelerator

vacuum, linac, impedance, acceleration

244

B. Kaizer, Z. Horvitz, A. Perry, J. Rodnizki
Soreq NRC, Yavne, Israel
M. Di Giacomo, J.F. Leyge, M. Michel, P. Toussaint
GANIL, Caen, France
A. Friedman
Ariel University, Ariel, Israel

The SARAF 176 MHz accelerator is designed to provide CW proton/deuteron beams up to 5 mA current and 40 MeV accelerated ion energy. Phase I of SARAF (up to 4-5 MeV) has been installed, commissioned, and is available for experimental work. Phase II of SARAF is currently in the planning stage and will contain larger MEBT with three rebunchers and four cryomodules, each consisting of SC HWRs and solenoids. Phase II MEBT line is designed to follow a 1.3 MeV/u RFQ, is 4.5 m long, and contains three 176 MHz rebunchers providing a field integral of 10⁵ kV. Different rebuncher configurations have been studied in order to minimize the RF losses and maximize the shunt impedance. Different apertures have also been tested with a required of 40 mm diameter by beam dynamics. The simulations were done using CST Microwave Studio. CEA leads the design for SARAF phase II linac including the MEBT rebunchers and has studied a mixed solid copper and Cu plated stainless steel, 3-gap cavity. SNRC is developing a 4-gap OFHC copper rebuncher as a risk reduction. Both designs are presented and discussed in the paper.

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MOPLR053

Operating Status of Injector II RFQ for C-ADS Project

rfq, coupling, impedance, scattering

254

L.P. Sun, Y. He, C.X. Li, L. Lu, A. Shi, L.B. Shi, W.B. Wang, X.B. Xu, Z.L. Zhang, H.W. Zhao
IMP/CAS, Lanzhou, People's Republic of China

The Radio Frequency Quadrupole system has been designed and constructed for C-ADS (Chinese Accelerator Driven System) Injector II in Institute of Modern Physics (IMP), Chinese Academy of Sciences, which has been running for more than one year until now. It is a quadrilateral four-vane resonator with two equal couplers operating in CW mode. In the paper, RF system upgrade will be presented in detail，especially the two-port configuration was introduced and the conditioning based on two new sets of solid-state amplifier instead of the original tetrodes power source due to system hardware upgrade are described in the paper.
RFQ, solid-state amplifier, two-port configuration, coupler

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MOPLR062

European Spallation Source (ESS) Normal Conducting Front End Status Report

rfq, proton, plasma, status

274

W. Wittmer, P.O. Gustavsson, F. Hellström, G. Hulla
ESS, Lund, Sweden
I. Bustinduy, P.J. González, G. Harper, S. Varnasseri, C. de la Cruz
ESS Bilbao, Zamudio, Spain
L. Celona, S. Gammino, L. Neri
INFN/LNS, Catania, Italy
A.C. Chauveau, D. Chirpaz-Cerbat
CEA/IRFU, Gif-sur-Yvette, France
F. Grespan, A. Pisent
INFN/LNL, Legnaro (PD), Italy
P. Mereu
INFN-Torino, Torino, Italy
O. Midttun
University of Bergen, Bergen, Norway
O. Piquet, B. Pottin
CEA/DSM/IRFU, France

The European Spallation Source (ESS) will deliver first protons on target by mid 2019. Civil construction of the accelerator tunnel has made good progress and will allow starting installation of the normal conducting frond end (NCFE) by end of 2017. To achieve these milestones the design of all major beam line components have been completed and the construction of the subsystems begun. We report on the advancement of the subsystems and the commissioning progress of the microwave discharge Proton Source (PS-ESS).

Poster MOPLR062 [1.396 MB]

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MOPLR065

High-Gradient X-band Structures for Proton Energy Booster at LANSCE

linac, booster, proton, klystron

280

S.S. Kurennoy, L. Rybarcyk
LANL, Los Alamos, New Mexico, USA
V.A. Dolgashev
SLAC, Menlo Park, California, USA

Increasing energy of proton beam at LANSCE from 800 MeV to 3 GeV improves radiography resolution ~10 times. Using superconducting RF cavities with gradients ~15 MV/m after the existing linac would result in a long and expensive booster. We propose accomplishing the same with a much shorter cost-effective booster based on normal conducting high-gradient (~100 MV/m) RF accelerating structures. Such X-band high-gradient structures have been developed for electron acceleration and operate with typical RF pulse lengths below 1 us. They have never been used for protons because typical wavelengths and apertures are smaller than the proton bunch sizes. However, these limitations do not restrict proton radiography (pRad) applications. A train of very short proton bunches with the same total length and charge as the original long proton bunch will create the same single radiography frame, plus pRad limits contiguous trains of beam micro-pulses to below 60 ns to prevent blur in images. For a compact pRad booster at LANSCE, we explore feasibility of two-stage design: a short S-band section to capture and compress the 800-MeV proton beam followed by the main high-gradient X-band linac.

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MOPLR066

ProBE: Proton Boosting Extension for Imaging and Therapy

proton, septum, linac, accelerating-gradient

283

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 and IPS
Proton beam therapy has been shown to be a promising alternative to traditional radiotherapy, especially for paedi- atric malignancies and radio-resistant tumours. Allowing a highly precise tumour irradiation, it is currently limited by range verification. Several imaging modalities can be utilised for treatment planning, but typically X-ray CT is used. CT scans require conversion from Hounsfield units to estimate the proton stopping power (PSP) of the tissue be- ing treated, and this produces inaccuracy. Proton CT (pCT) measures PSP and is thought to allow an improvement of the treatment accuracy. The Christie Hospital will use a 250 MeV cyclotron for proton therapy, in this paper a pulsed linac upgrade is proposed, to provide 350 MeV protons for pCT within the facility. Space contraints require a compact, high gradient (HG) solution that is reliable and affordable.

Poster MOPLR066 [0.610 MB]

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MOPLR067

First High Power Tests at the 325 MHz RF Test Stand at GSI

linac, coupling, rfq, klystron

287

G. Schreiber, E. Plechov, J. Salvatore, B. Schlitt, A. Schnase, M. Vossberg
GSI, Darmstadt, Germany

A dedicated RF test stand for testing RF components and accelerating structures at 325 MHz has been put into operation at GSI. It allows testing the klystrons and circulators as well as the RFQ and the CH-acceleration cavities for the planned FAIR proton linac (p-Linac) and further cavity projects. The system integration has been completed and first high power tests with the CH prototype cavity were successfully performed. The operation parameters are 2 Hz repetition rate and 200 microseconds pulse length. Investigations on the critical path from wave guide to coaxial high power cavity coupler have been made. Performance measurements of the klystron, circulator and directional couplers with up to 2.8 MW on dummy load and the following conditioning process of the CH-prototype cavity with its coupled RF structures will be presented. Additionally the results of the conditioning of a ladder RFQ prototype are shown.

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MOPLR072

The Effect of DTL Cavity Field Errors on Beam Spill at LANSCE

DTL, linac, LLRF, target

301

L. Rybarcyk, R.C. McCrady
LANL, Los Alamos, New Mexico, USA

The Los Alamos Neutron Science Center (LANSCE) accelerator comprises two (H⁺ and H⁻) 750-keV Cockcroft-Walton style injectors, a 201.25-MHz, 100-MeV drift-tube linac (DTL) and an 805-MHz, 800-MeV coupled-cavity linac (CCL). As part of the LANSCE Risk Mitigation project a new digital low-level radio frequency (LLRF) control system is being deployed across the linac, starting with the DTL. Related to this upgrade, a study was performed where specific cavity field errors were simultaneously introduced in all DTL tanks about the nominal stable, low-spill, production set points to mimic LLRF control errors. The impact of these errors on the resultant beam spill was quantified for the nominal 100 μA, 800-MeV Lujan beam. We present the details of the measurement approach and results that show a rapid increase in total linac beam spill as DTL cavity field phase and amplitude errors are increased.

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MOP106001

Energy Stability of ERLs and Recirculating Linacs

linac, recirculation, operation, simulation

304

R.G. Eichhorn, J. Hoke, Z. Mayle
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Energy recovery linacs can be seen as a hybrid between a linear and a circular accelerator. It has been shown in the past that an appropriate choice of the longitudinal working point can significantly improve the energy stability of a recirculating linac. In this contribution we will expand the concept of energy recovery linacs and investigate the energy spread of the beam as well as the recovery efficiency stability which can be a more demanding quantity in a high current ERL.

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MOP106006

Electro-Mechanical Modeling of the LCLS-II Superconducting Cavities

simulation, damping, vacuum, linac

310

O. Kononenko, C. Adolphsen, Z. Li, T.O. Raubenheimer, C.H. Rivetta
SLAC, Menlo Park, California, USA

Funding: Work supported by the Department of Energy, Office of Science, Office of Basic Energy Science, under Contract No. DEAC0276SF00515
The 4 GeV LCLS-II superconducting linac will contain 280, 1.3 GHz TESLA-style cavities operated CW at 16 MV/m. Because of the low beam current, the cavity bandwidth will be fairly small, about 32 Hz, which makes the field stability sensitive to detuning from external vibrations and He pressure fluctuations. Piezo-electric actuators will be used to compensate for the detuning, which historically has been difficult at frequencies above a few Hz due to excitation of cavity mechanical resonances. To understand this interaction better, we have been doing extensive modeling of the cavities including mapping out the mechanical modes and computing their coupling to pressure changes, Lorentz forces and piezo actuator motion. One goal is to reproduce the measured detuning response of the piezo actuators up to 1 kHz, which is sensitive to how the cavities are constrained within a cryomodule. In this paper, we summarize these results and their implications for suppressing higher frequency detuning.

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MOP106016

High Power RF Requirements for Driving Discontinuous Bunch Trains in the MaRIE Linac

linac, beam-loading, electron, booster

320

J.T. Bradley III, D. Rees, A. Scheinker, R.L. Sheffield
LANL, Los Alamos, New Mexico, USA

Funding: Work supported by the US Department of Energy.
The MaRIE project will use a superconducting linac to provide 12 GeV electron bunches to drive an X-ray FEL and to do electron radiography. Dynamic experiments planned for MaRIE require that the linac produce a series of micropulses that can be irregularly spaced within the macropulse, and these patterns can change from macropulse to macropulse. Irregular pulse structures create a challenge to optimizing the design of the RF and cryogenic systems. General formulas for cavities with beam loading can overestimate the power required for our irregular beam macropulse. The differing beam energy variations allowed for the XFEL and eRad micropulses produce cavity voltage control requirements that also vary within the macropulse. The RF pulse driving the cavities can be tailored to meet the needs of that particular beam macropulse because the macropulse structure is known before the pulse starts. We will derive a toolkit that can be used to determine the required RF power waveforms for arbitrary macropulse structures. We will also examine how the irregular RF power waveforms can impact RF and cryogenic system cost tradeoffs.

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MOP106018

Measurement of the Transverse Beam Dynamics in a TESLA-type Superconducting Cavity

HOM, simulation, experiment, alignment

323

A. Halavanau, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
N. Eddy, D.R. Edstrom, A. Lunin, P. Piot, J. Ruan, N. Solyak
Fermilab, Batavia, Illinois, USA

Funding: US Department of Energy (DOE) under contract DE-SC0011831 with Northern Illinois University. Fermilab is operated by the Fermi Research Alliance LLC under US DOE contract DE-AC02-07CH11359.
Superconducting linacs are capable of producing intense, ultra-stable, high-quality electron beams that have widespread applications in Science and Industry. Many project are based on the 1.3-GHz TESLA-type superconducting cavity. In this paper we provide an update on a recent experiment aimed at measuring the transfer matrix of a TESLA cavity at the Fermilab Accelerator Science and Technology (FAST) facility. The results are discussed and compared with analytical and numerical simulations.

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MOP106021

Superconducting Traveling Wave Cavity Tuning Studies

accelerating-gradient, feedback, SRF, acceleration

327

R.A. Kostin
LETI, Saint-Petersburg, Russia
P.V. Avrakhov, A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
N. Solyak, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Funding: Work supported by US DOE SBIR # DE-SC0006300
Superconducting traveling wave cavity (SCTW) can provide 1.2-1.4 times larger accelerating gradient than conventional standing wave SRF cavities [1]. Firstly, traveling wave opens the way to use other than Pi-mode phase advance per cell which increase transit time factor. Secondly, traveling wave is not so sensitive to cavity length as standing wave, which length is limited to 1 meter because of field flatness degradation. 3 cell SCTW cavity was proposed [2] and built for high gradient traveling wave demonstration and tuning studies. This paper describes analytical model that was used for cavity development. Tuning properties and requirements are also discussed.
' r.kostin@euclidtechlabs.com

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MOP106023

Intra Bunch Train Transverse Dynamics in the Superconducting Accelerators FLASH and European XFEL

beam-transport, HOM, transverse-dynamics, operation

333

T. Hellert, W. Decking, M. Dohlus
DESY, Hamburg, Germany

At FLASH and the European XFEL accelerator superconducting 9-cell TESLA cavities accelerate long bunch trains at high gradients in pulsed operation. Several RF cavities with individual operating limits are supplied by one RF power source. Within the bunch train, the low-level-RF system is able to restrict the variation of the vector sum voltage and phase of one control line below 3·10^-4 and 0.06 degree, respectively. However, individual cavities may have a significant spread of amplitudes and phases. Misaligned cavities in combination with variable RF parameters will cause significant intra-pulse orbit distortions, leading to an increase of the multi-bunch emittance. An efficient model including coupler kicks was developed to describe the effect at low beam energies. Comparison with start-to-end tracking and experimental data will be shown.

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TU1A03

Experience with the Construction and Commissioning of Linac4

linac, ion, emittance, DTL

342

J.-B. Lallement
CERN, Geneva, Switzerland

In the framework of the LHC Injector Upgrade program, CERN is presently commissioning Linac4, a 160MeV H⁻ ion linac, which will replace the present 50 MeV proton linac (Linac2) as injector to the PS Booster during the next LHC long shut-down. The installation of the machine has proceeded in parallel with a staged beam commissioning at the energies of 3, 12, 50, 100 MeV and finally 160 MeV, foreseen for fall 2016. A seven month long reliability run will take place during 2017 to access potential weak points and find mitigations. The lessons learnt during its construction, the main outcomes of the beam commissioning and the remaining steps toward its connection to the PS Booster are presented in this paper.

Slides TU1A03 [5.747 MB]

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TU1A05

High Power Operation of SNS SC Linac

linac, ion, cryomodule, operation

348

M.A. Plum
ORNL, Oak Ridge, Tennessee, USA

Funding: Work performed at (or work supported by) Oak Ridge National Laboratory, which is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.
The SNS superconducting linac (SCL) provides 972 MeV, 1.5 MW H− beam for the storage ring and neutron spallation target. It has now been in operation for 11 years, and we have gained some experience in long-term operational issues. Three inter-related issues are gradient changes, errant beams, and trip rates. In this presentation we will provide an update on our progress to mitigate these issues, and also report on the overall status of the SCL.

Slides TU1A05 [5.831 MB]

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TU2A03

Resonance Control for Future Linear Accelerators

controls, resonance, SRF, electron

363

W. Schappert
Fermilab, Batavia, Illinois, USA

Many of the next generation of particle accelerators (LCLS II, PIP II) are designed for relatively low beam loading. Low beam loading requirement means the cavities can operate with narrow bandwidths, minimizing capital and base operational costs of the RF power system. With such narrow bandwidths, however, cavity detuning from microphonics or dynamic Lorentz Force Detuning becomes a significant factor, and in some cases can significantly increase both the acquisition cost and the operational cost of the machine. In addition to the efforts to passive environmental detuning reduction (microphonics) active resonance control for the SRF cavities for next generation linear machine will be required. State of the art in the field of the SRF Cavity active resonance control and the results from the recent efforts at FNAL will be presented in this talk.

Slides TU2A03 [0.897 MB]

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TU3A01

Beam Commissioning Results From the R&D ERL at BNL

gun, cathode, SRF, laser

374

D. Kayran, Z. Altinbas, D.R. Beavis, S.A. Belomestnykh, I. Ben-Zvi, D.M. Gassner, L.R. Hammons, J.P. Jamilkowski, P. K. Kankiya, R.F. Lambiase, V. Litvinenko, R.J. Michnoff, T.A. Miller, J. Morris, V. Ptitsyn, T. Seda, B. Sheehy, K.S. Smith, E. Wang, W. Xu
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi, L.R. Hammons, V. Litvinenko, V. Ptitsyn
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
BNL R&D ERL beam commissioning started in June 2014 [*]. The key components of R&D ERL are the highly damped 5-cell 704 MHz superconducting RF cavity and the high-current superconducting RF gun. The gun is equipped with a multi-alkaline photocathode insertion system. The first photocurrent from ERL SRF gun has been observed in November 2014. In June 2015 a high charge 0.5nC and 20 uA average current were demonstrated. In July 2015 gun to dump beam test started. The beam was successfully transported from the SRF gun through the injection system, then through the linac to the beam dump. All ERL components have been installed. In October 2015, SRF gun cavity has been found contaminated during severe cathode stalk RF conditioning. This cavity has been sent for repair and modification for later use in low-energy RHIC electron cooler (LEReC)[**]. LEReC scheduled to start commissioning in early of 2018. We present our results of BNL ERL beam commissioning, the measured beam properties, the operational status, and future prospects.
*) D.Kayran et al., Status and commissioning results of the R&D ERL at BNL. Proc. ERL2015, p. 11-14
**)J. Kewisch et al., ERL for Low Energy Electron Cooling at RHIC (LEReC). Proc. ERL2015, p. 67-71

Slides TU3A01 [12.502 MB]

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TUOP07

High Performance Next-Generation Nb3Sn Cavities for Future High Efficiency SRF Linacs

niobium, SRF, accelerating-gradient, pulsed-power

398

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

Funding: DOE
A 1.3 GHz ILC-shape single-cell Nb3Sn cavity fabricated at Cornell has shown record performance, exceeding the cryogenic efficiency of niobium cavities at the gradients and quality factors demanded by some contemporary accelerator designs. An optimisation of the coating process has resulted in more cavities of the same design that achieve similar performance, proving the reproducibility of the method. In this paper, we discuss the current limitations on the peak accelerating gradients achieved by these cavities. In particular, high-pulsed-power RF testing, and thermometry mapping of the cavity during CW operation, are used to draw conclusions regarding the nature of the quench limitation. In light of these promising results, the feasibility and utility of applying the current state of the technology to a real-life application is discussed.

Slides TUOP07 [1.506 MB]

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TUOP08

On Magnetic Flux Trapping in Superconductors

solenoid, niobium, experiment, SRF

402

R.G. Eichhorn, J. Hoke, Z. Mayle
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Magnetic flux trapped on the cool-down has become an important factor in the performance in superconducting cavities. We have conducted flux trapping experiments on samples that reveal a very interesting feature of the mechanism on flux trapping which might impact magnetic shielding concepts of future cryomodules.

Slides TUOP08 [1.787 MB]

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TUOP09

State of the Art Advanced Magnetron for Accelerator RF Power Source

cathode, linac, radiation, electron

405

H. Obata, K. Furumoto, H. Miyamoto
New Japan Radio Co., Ltd., Fujimino Saitama, Japan

X ray sources for linear accelerators continue to be a necessary requirement for industries such as medical, inspection, and nondestructive test equipment. Future requirements for such sources are; low cost, compact packaging and high performance of the RF source for electron acceleration. The magnetron has proven to be a perfect source over other RF sources for linear accelerator use. Because of its simple design, low cost per output, small size and proven performance it meets all required characteristics. New Japan Radio Co., Ltd. has improved and modified its linac magnetrons' performance and characteristics enabling easy matching to the linac modulator, long life and maximum output power. This paper will provide a detailed explanation on the improved magnetron design methodology and its effects on the performance of these magnetrons installed in linac systems. These technologies have been utilized successfully on a commercial level worldwide over the last few years. The technology has been deployed into linac systems operating in S and X band and soon C band, at various output power levels.

Slides TUOP09 [1.127 MB]

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TUPRC007

An RFQ Based Neutron Source for BNCT

rfq, simulation, operation, neutron

427

X.W. Zhu, Z.Y. Guo, Y.R. Lu, H. Wang, Z. Wang, K. Zhu, B.Y. Zou
PKU, Beijing, People's Republic of China

Boron Neutron Capture Therapy (BNCT), promises a bright prospect for future cancer treatment, in terms of effectiveness, safety and less expanse. The PKU RFQ group proposes an RFQ based neutron source for BNCT. A unique beam dynamics design of 162.5 MHz BNCT-RFQ, which accelerates 20 mA of H⁺ from 30 keV to 2.5 MeV in CW operation, has been performed in this study. The Proton current will be about 20 mA. The source will deliver a neutron yield of 1.76×10¹³ n/sec/cm² in the Li(p, n)Be reaction. Detailed 3D electromagnetic (EM) simulations of all components, including cross-section, tuners, pi-rods, and undercuts, of the resonant structure are performed. The design of a coaxial type coupler is developed. Two identical RF couplers will deliver approximately 153 kW CW RF power to the RFQ cavity. RF property optimizations of the RF structures are performed with the utilization of the CST MICROWAVE STUDIO.

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TUPRC015

Final Acceptance Test of SRF Photo-Injector Cold String for the BERLinPro Energy Recovery Linac

cathode, SRF, gun, target

445

A. Neumann, D. Böhlick, P. Echevarria, A. Frahm, F. Göbel, T. Kamps, J. Knobloch, O. Kugeler, M. Schuster, J. Ullrich, A. Ushakov
HZB, Berlin, Germany
A. Burrill
SLAC, Menlo Park, California, USA
G. Ciovati, P. Kneisel
JLab, Newport News, Virginia, USA
A. Matheisen, M. Schalwat, M. Schmökel
DESY, Hamburg, Germany
E.N. Zaplatin
FZJ, Jülich, Germany

Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin and grants of Helmholtz Association.
Helmholtz-Zentrum Berlin (HZB) is currently designing and building an high average current all superconducting CW driven ERL as a prototype to demonstrate low normalized beam emittance of 1 mm·mrad at 100mA and short pulses of about 2 ps. In order to achieve these demanding goals HZB started a staged program for developing this class of required high current, high brightness SRF electron sources. In this contribution we will present the current status of the module assembly and testing of the prototype SRF photo-injector cavity cold string. The steps taken to install the cathode insert system with the cavity in the cleanroom and the following horizontal test of the cold string as final acceptance test prior installation into its cryostat are shown. First beam in a dedicated diagnostics teststand called Gunlab are planned for this winter.

Poster TUPRC015 [2.077 MB]

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TUPRC017

Field Flatness and Frequency Tuning of the CLARA High Repetition Rate Photoinjector

cathode, coupling, FEL, gun

452

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
B. Keune
RI Research Instruments GmbH, Bergisch Gladbach, Germany

The High Repetition Rate Photoinjector, designed for the CLARA FEL at Daresbury Laboratory, was tuned at the manufacturers for both field flatness and frequency. Due to the high average power in the cavity of 6.8 kW the cavity requires significant cooling, achieved by water channels in the cavity body. These channels prohibit the use of tuning studs to tune the cavity. The cavity was tuned by taking pre-braze clamped low power RF measurements and using the data to trim the cavity cells to the optimum length for both field flatness and frequency. The optimum field flatness is 100% and the design frequency is 2998.5 MHz. Both cells were trimmed in 3 stages, resulting in a post-braze frequency of 2998.51 MHz and field flatness of 98%.

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TUPRC021

Low-Temperature Properties of 2.6-Cell Cryogenic C-Band RF-Gun Cold Model Cavity

gun, cryogenics, experiment, resonance

462

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

Funding: Work supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT).
Development of a cryogenic C-band photocathode RF gun cavity has been conducted at Nihon University in collaboration with KEK. Improved dimensions of the RF input coupler and the 2.6-cell accelerating structure from the first cold model were determined using the 3D simulation code CST Studio. The high-purity copper cavity was fabricated at KEK with ultraprecision machining and diffusion bonding technique. The low level RF properties of the cavity measured at room temperature have been in good agreement with the predictions based on the CST Studio calculation. Preparations for the 20-K cooling tests of the cavity are underway in KEK and Nihon University. The design of the improved cavity and the results of the cold test at low temperature will be discussed.

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TUPRC024

Design and Implementation of an Automated High-Pressure Water Rinse System for FRIB SRF Cavity Processing

SRF, alignment, operation, controls

468

I.M. Malloch, E.S. Metzgar, L. Popielarski, S. Stanley
FRIB, East Lansing, Michigan, USA

Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE SC0000661, the State of Michigan and Michigan State University.
Traditionally, high-pressure water rinse (HPR) systems have consisted of relatively simple pump and rinse wand actuator systems intended to clean superconducting radio frequency (SRF) cavities during processing prior to test assembly. While these types of systems have proven effective at achieving satisfactory levels of cleanliness, large amounts of operator touch-labor are involved, especially in SRF cavities with complex geometries, where several fixture changes and cavity manipulations may be required. With this labor comes the risk of cavity damage or contamination, and the expense of the operator's time. To reduce this operator intervention and maximize cavity cleanliness and process throughput, a new, fully-automated, robotic HPR system has been commissioned in the Facility for Rare Isotope Beams (FRIB) cavity processing facility. This paper summarizes the design and commissioning process of the HPR system, and demonstrates improvements to the FRIB processing facility through the minimization of cavity contamination risk and reduction of technician labor through system automation. Comparative cavity RF test results are presented to further demonstrate system effectiveness.

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TUPRC025

Low Temperature Nitrogen Baking of a Q0 SRF Cavities

niobium, SRF, radio-frequency, impedance

472

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

Nitrogen-doping has led to an unprecedented increase in the intrinsic quality factor of bulk-niobium superconducting RF cavities. So far, high temperature baking in a nitrogen atmosphere is used almost exclusively to dope cavities. Recently, we have set focus on low temperature baking to produce similar performance increases and we present those results here.

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TUPLR007

LCLS-II Cryomodules Production at Fermilab

cryomodule, SRF, vacuum, alignment

481

T.T. Arkan, C.J. Grimm, J.A. Kaluzny, Y.O. Orlov, T.J. Peterson, K. Premo
Fermilab, Batavia, Illinois, USA

Funding: US DOE
LCLS-II is an upgrade project for the linear coherent light source (LCLS) at SLAC. The LCLS-II linac will consist of thirty-five 1.3 GHz and two 3.9 GHz superconducting RF continuous wave (CW) cryomodules that Fermilab and Jefferson Lab (JLab) will assemble in collaboration with SLAC. The LCLS-II 1.3 GHz cryomodule design is based on the European XFEL pulsed-mode cryomodule design with modifications needed for CW operation. Fermilab and JLab will each assemble and test a prototype 1.3 GHz cryomodule to assess the results of the CW modifications, in advance of 16 and 17 production 1.3 GHz cryomodules, respectively. Fermilab is solely responsible for the 3.9 GHz cryomodules. After the prototype cryomodule tests are complete and lessons learned incorporated, both laboratories will increase their cryomodule production rates to meet the challenging LCLS-II project requirement of approximately one cryomodule per month per laboratory. This paper presents the Fermilab Cryomodule Assembly Facility (CAF) infrastructure for LCLS-II cryomodule production, the Fermilab prototype 1.3 GHz CW cryomodule (pCM) assembly and readiness for production assembly.

Poster TUPLR007 [2.474 MB]

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TUPLR009

An Iterative Learning Feedforward Controller for the TRIUMF e-linac

beam-loading, linac, TRIUMF, controls

485

M.P. Laverty, K. Fong
TRIUMF, Vancouver, Canada

In the TRIUMF e-linac design, beam stability to within 0.1% within 10 μs in pulse mode is a design requirement. Traditional feedback control systems cannot respond within this time frame, so some form of feedforward control is needed. Even conventional feedforward may not be sufficient due to differences between the required feedforward signal and the actual beam-loading current. For this reason, an adaptive feedforward system using an iterative learning controller was developed for the e-linac LLRF. It can anticipate repetitive beam disturbance patterns by learning from previous iterations. The design and implementation of such a control algorithm is outlined, some simulation results are presented, and some preliminary test results with an actual cavity are illustrated.

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TUPLR010

Measurements and Analysis of Cavity Microphonics and Frequency Control in the Cornell ERL Main Linac Prototype Cryomodule

linac, cryomodule, vacuum, LLRF

488

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

The Cornell Main Linac cryomodule (MLC) is a key component in the CBETA project. The SRF cavities with high loaded-Q in the MLC are very sensitive to microphonics from mechanical vibrations. Poor frequency stability of the cavities would dramatically increase the input RF power required to maintain stable accelerating fields in the SRF cavities. In this paper, we present detailed results from microphonics measurement for the cavities in the MLC, discuss dominant vibration sources, and show vibration damping results. The current microphonics level meets the CBETA requirement of a 36MeV energy gain without applying fast tuner compensation.

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TUPLR011

Performance of the Novel Cornell ERL Main Linac Prototype Cryomodule

linac, cryomodule, SRF, HOM

492

F. Furuta, J. Dobbins, R.G. Eichhorn, M. Ge, D. Gonnella, G.H. Hoffstaetter, M. Liepe, T.I. O'Connell, 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) for the future energy-recovery linac (ERL) based X-ray light source at Cornell has been designed, fabricated, and tested. It houses six 7-cell SRF cavities with individual higher order-modes (HOMs) absorbers, cavity frequency tuners, and one magnet/BPM section. Cavities have achieved the specification values of 16.2MV/m with high-Q of 2.0·10¹⁰ in 1.8K in continuous wave (CW) mode. During initial MLC cavity testing, we encountered some field emission, reducing Q and lowering quench field. To overcome field emission and find optimal cool-down parameters, RF processing and thermal cycles with different cool-down conditions has been done. Here we report on these studies and present final results from the MLC cavity performance.

Poster TUPLR011 [2.389 MB]

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TUPLR012

HOM Measurements for Cornell's ERL Main Linac Cryomodule

HOM, linac, cryomodule, simulation

496

F. Furuta, R.G. Eichhorn, M. Ge, D. Gonnella, G.H. Hoffstaetter, M. Liepe, P. Quigley, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

The main linac cryomodule (MLC) for a future energy-recovery linac (ERL) based X-ray source at Cornell has been designed, fabricated, and tested. It houses six 7-cell SRF cavities with individual higher order-modes (HOMs) absorbers, cavity frequency tuners, and one magnet/BPM section. All HOMs in MLC have been scanned in 1.8K. The results show effective damping of HOMs, and also agree well with simulation results and the previous HOM scan results on one 7-cell cavity prototype test cryomodule. Here we present detailed results from these HOM studies.

Poster TUPLR012 [2.773 MB]

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TUPLR015

Design of a Gamma-Ray Source Based on Inverse Compton Scattering at the Fast Superconducting Linac

laser, electron, photon, brightness

503

D. Mihalcea
Northern Illinois University, DeKalb, Illinois, USA
B.T. Jacobson, A.Y. Murokh
RadiaBeam, Santa Monica, California, USA
P. Piot, J. Ruan
Fermilab, Batavia, Illinois, USA

Funding: This work is sponsored by the DNDO via contract with NIU.
A Watt-level average-power gamma-ray source is currently under development at the FermiLab Accelerator Science & Technology (FAST) facility. The source is based on the inverse Compton scattering of a high-brightness 300-MeV beam against a high-power laser beam circulating in an optical cavity. The back scattered gamma rays are expected to have photon energies up to 1.5 MeV. This paper discusses the optimization of the source, its performance and the main challenges ahead.

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TUPLR022

Particulate Study on Materials for Cleanroom Assembly of SRF Cavities

niobium, SRF, operation, experiment

512

L. Zhao, A.V. Reilly
JLab, Newport News, Virginia, USA

Reducing particulates is an important aspect for clean-room operation. Knowing that it is impossible to completely eliminate all particulates in a clean room, efforts have been made to prevent particulates from entering SRF cavities during high pressure rinsing (HPR) and assembly. At Jefferson Lab, one practice to achieve this goal has been clamping covers to cavity open flanges during assembly. Several cover materials that have been used are examined and alternative candidate materials are under development. Clamps as a known particulate generator are carefully examined and cleaning efficiency of different methods is studied. Cover tests were done on different cavity flanges, including an LCLS-II beam pipe flange, which helps the selection of cover materials for prototype and production of the project.
Authored by Jefferson Science Associates, LLC under U.S. DOE Contracts DE-AC05-06OR23177 and DE-AC02-76SF00515 for the LCLS-II Project.

Poster TUPLR022 [1.282 MB]

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TUPLR023

Impurity Content Optimization to Maximize Q-Factors of Superconducting Resonators

SRF, factory, niobium, superconductivity

515

M. Martinello, M. Checchin, A. Grassellino, O.S. Melnychuk, S. Posen, A. Romanenko, D.A. Sergatskov
Fermilab, Batavia, Illinois, USA
M. Checchin
Illinois Institute of Technology, Chicago, Illlinois, USA
J. Zasadzinski
IIT, Chicago, Illinois, USA

Quality factor of superconducting radio-frequency (SRF) cavities is degraded whenever magnetic flux is trapped in the cavity walls during the cooldown. In this contribution we study how the trapped flux sensitivity, defined as the trapped flux surface resistance normalized for the amount of trapped flux, depends on the mean free path. A systematic study of a variety of 1.3 GHz cavities with different surface treatments (EP, 120 C bake and different N-doping) is carried out. A bell shaped trend appears for the range of mean free path studied. Over-doped cavities fall at the maximum of this curve defining the largest values of sensitivity. In addition, we have studied the trend of the BCS surface resistance contribution as a function of mean free path, showing that N-doped cavities follow close to the theoretical minimum. Adding these results together we show that the 2/6 N-doping treatment gives the highest Q-factor values at 2 K and 16 MV/m, as long as the magnetic field fully trapped during the cavity cooldown is lower than 10 mG.

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TUPLR024

Enhancement of the Accelerating Gradient in Superconducting Microwave Resonators

induction, accelerating-gradient, factory, linac

519

M. Checchin, A. Grassellino, M. Martinello, S. Posen, A. Romanenko
Fermilab, Batavia, Illinois, USA
M. Martinello
Illinois Institute of Technology, Chicago, Illlinois, USA
J. Zasadzinski
IIT, Chicago, Illinois, USA

Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DEAC02-07CH11359 with the United States Department of Energy.
The accelerating gradient of superconducting resonators can be enhanced by engineering the thickness of a dirty layer grown at the cavity's rf surface. In this paper the description of the physics behind the accelerating gradient enhancement by meaning of the dirty layer is carried out by solving numerically the the Ginzburg-Landau (GL) equations for the layered system. The calculation shows that the presence of the dirty layer stabilizes the Meissner state up to the lower critical field of the bulk, increasing the maximum accelerating gradient.

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TUPLR025

Optimal Nitrogen Doping Level to Reach High Q0

cryomodule, SRF, niobium, electron

523

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

Funding: NSF and US DOE
New continuous wave (CW) accelerators such as LCLS-II at SLAC require many SRF cavities operating in the medium field region at unprecedented high Q. In order to achieve this demanding goal, nitrogen-doping of the SRF cavities will be used. Nitrogen-doping has been shown to affect the BCS resistance both by a lowering of Rbcs at low fields and by the introduction of an anti-Q slope which enables the Q to continue increasing as the RF field is increased. The exact strength of this anti-Q slope is heavily dependent on the doping recipe and specifically the mean free path of the RF penetration layer of the doped cavities. In addition to its effect on Rbcs, the mean free path affects the amount of residual resistance obtained due to trapped magnetic flux. We have analyzed nine cavities prepared with different levels of nitrogen-doping to understand how BCS and residual resistance are affected by changes in the mean free path. Here we present a model based on these experimental results to predict the optimal doping level to reach the maximum Q at 16 MV/m based on the ambient magnetic field conditions. We find that if the cavities can be cooled with small amounts of trapped flux, moderate nitrogen-doping is better, while if they will have large amounts of trapped flux, lighter dopings should be used.

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TUPLR027

Magnetic Field Management in LCLS-II 1.3 GHz Cryomodules

cryomodule, vacuum, controls, shielding

527

S.K. Chandrasekaran, A. Grassellino, C.J. Grimm, G. Wu
Fermilab, Batavia, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the United States Department of Energy.
The ambient magnetic field at the SRF cavity surface of the LCLS-II 1.3 GHz cryomodules is specified to be less than 0.5 μT (5 mG). Multiple methods were designed to lower the magnetic fields inside the prototype cryomodule. The resulting ambient magnetic field in this cryomodule just prior to its first cool down was <0.15 μT (1.5 mG), as measured using fluxgates inside and outside the cavity helium vessels.

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TUPLR028

Alternative Design for the RISP Pre-Stripper Linac

linac, cryomodule, simulation, solenoid

531

B. Mustapha, Z.A. Conway, M.P. Kelly, P.N. Ostroumov, A.S. Plastun
ANL, Argonne, USA
J.-H. Jang, H. Jin, H.J. Kim, J.-W. Kim
IBS, Daejeon, Republic of Korea

Funding: This work was supported by the work-for-other grant WFO8550H titled "Pre-conceptual design, cost and schedule estimate of the 18.5 MeV/u Pre-stripper linac for the RISP/IBS"
In a collaborative effort between Argonne's Linac Development Group and the RISP project team at the Korean Institute for Basic Science, we have developed an alternative design for the pre-stripper section of the RISP driver linac. The proposed linac design takes advantage of the recent accelerator developments at Argonne, namely the ATLAS upgrades and the Fermilab PIP-II HWR Cryomodule. In particular, the state-of-the-art performance of QWRs and HWRs, the integrated steering correctors and clean BPMs for a compact cryomodule design. To simplify the design and avoid frequency transitions, we used two types of QWRs at 81.25 MHz. The QWRs were optimized for β ~ 0.05 and ~ 0.11 respectively. Nine cryomodules are required to reach the stripping energy of 18.5 MeV/u. Following the lattice design optimization, end-to-end beam dynamics simulations including all sources of machine errors were performed. The results showed that the design is tolerant to errors with no beam losses observed for nominal errors. However, the robustness of the design could be further improved by a modified RFQ design, better optimized with the multi-harmonic buncher located upstream. This could lead to a significant reduction in the longitudinal beam emittance, offering much easier beam tuning and more tolerance to errors. The proposed design and the simulation results will be presented and discussed.

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TUPLR029

FRIB HWR Tuner Development

cryomodule, controls, alignment, cryogenics

535

S. Stark, A. Facco, S.J. Miller, P.N. Ostroumov, J.T. Popielarski, K. Saito, B.P. Tousignant, T. Xu
FRIB, East Lansing, USA
A. Facco
INFN/LNL, Legnaro (PD), Italy
S.M. Gerbick, M.P. Kelly
ANL, Argonne, USA

Funding: * This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661, the State of Michigan and Michigan State University
During the last two years the HWR pneumatic tuner development at FRIB evolved from the first prototypes to the final production design. A lot of warm testing and several cryogenic integrated tests with cavity were performed to optimize the tuner features. The main challenges included the bellow bushings binding and very tight space limitations for the assembly on the rail. The final design, based on the acquired experience, was prepared in collaboration with ANL and entered the preproduction phase.

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TUPLR030

First FRIB β=0.53 Prototype Coldmasss Build

cryomodule, vacuum, solenoid, SRF

538

D.R. Victory, K. Elliott, B. Oja, J.T. Popielarski, M.S. Wilbur
FRIB, East Lansing, USA

Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE SC0000661, the State of Michigan and Michigan State University.
The β=0.53 coldmass consists of eight Superconducting Radio Frequency (SRF) β=0.53 cavities, eight Fundamental mode Power Couplers (FPC), and one 8 T solenoid. This is the first coldmass with this version of cavity and it has brought new challenges to overcome. The Facility for Rare Isotope Beams (FRIB) contains 18 cryomodules with β=0.53 cavity coldmasses, and this type of coldmass is the highest power and most produced ones in FRIB. During the final cleaning stage and the cavity assembly, particle detection equipment is used to verify the cavity cleanliness levels for cavity certification test and for coldmass assembly. This method allows for cleanliness detection of specific areas inside the cavity at any time a vacuum flange is off. The fixtures, techniques and procedures used to build the β=0.53 coldmasses will be presented.

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TUPLR033

First FRIB β=0.041 Production Coldmass Build

solenoid, SRF, alignment, cryomodule

541

K. Elliott, S.J. Miller, B. Oja, J.T. Popielarski, L. Popielarski, D.R. Victory, M.S. Wilbur, T. Xu
FRIB, East Lansing, USA
M. Wiseman
JLab, Newport News, Virginia, USA

Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE SC0000661, the State of Michigan and Michigan State University.
Three β=0.041 cryomodules are required for the Facility for Rare Isotope Beams (FRIB) accelerator. Cleanroom assembly of all three coldmasses for these cryomodules has been completed. The cleanroom assembly includes; the superconducting radio frequency (SRF) cavities, the superconducting solenoids, fundamental power couplers (FPC), beam position monitors, alignment rail, and transport cart. This paper will provide an overview of the techniques and procedures used to assemble this cavity string such that it can be used in the FRIB accelerator.

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TUPLR035

RF Analysis of Electropolishing for EXFEL Cavities Production at Ettore Zanon Spa

shielding, cathode, SRF, superconductivity

544

A.A. Sulimov
DESY, Hamburg, Germany
M. Giaretta, A. Gresele, A. Visentin
Ettore Zanon S.p.A., Nuclear Division, Schio, Italy

After successful finishing of superconducting cavities mass production at Ettore Zanon S.p.A. (EZ) for the European XFEL (EXFEL), the authors had the possibility to provide a detailed analysis of the electropolishing (EP) process. The analysis of EP material removal is based on specified RF measurements and was used for the determination of both, the ratio between cavity's iris and equator and uniformity in different cells. A comparison of the RF measurements results with mechanical measurements is presented.

Poster TUPLR035 [0.195 MB]

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TUPLR038

The DTL Post Coupler - An Ingenious Invention Turns 50

DTL, linac, drift-tube-linac, proton

547

S. Ramberger
CERN, Geneva, Switzerland
M.R. Khalvati
IPM, Tehran, Iran

In September 1967, the patent for "A method and device for stabilization of the field distribution in drift tube linac" has been filed by Edward A. Knapp, Donald A. Swenson, and James M. Potter of Los Alamos National Laboratory. It is this invention which to a good part led to the success of highly efficient Alvarez drift tube linacs (DTLs) in that it considerably reduces field errors. The explanation for why the post coupler when tuned correctly has such a strong stabilizing effect has been given at the time in an accompanying paper by describing the modal confluence of the accelerating mode band with the post-coupler mode band, turning a comparatively sensitive 0-mode structure into a stable pi/2-mode like structure. As ingenious as the invention of the post-coupler appears, as poor has been the way of finding its optimum length by relying mainly on trial and error. With the design of the Linac4 DTL at CERN, a new technique has been derived by a DTL equivalent circuit model. Understanding stabilization on an almost cell by cell level provides a new way of optimizing post-couplers of an entire structure with few measurements and even without the extraction of the circuit model itself. Previous approaches to post-coupler stabilization are reviewed and the new, straightforward and accurate technique is described and demonstrated in the stabilization of the Linac4 DTL structures.

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TUPLR040

The RF System of Thomx

HOM, controls, feedback, storage-ring

551

M. El Khaldi, R. Marie, H. Monard, F. Wicek
LAL, Orsay, France
M. Diop, L.R. Lopes, A. Loulergue, M. Louvet, P. Marchand, F. Ribeiro, R. Sreedharan
SOLEIL, Gif-sur-Yvette, France

The RF system of the ThomX electron storage ring consists in a 500 MHz single cell copper cavity of the ELETTRA type, powered with a 50 kW CW solid state power amplifier (SSPA), and the associated Low Level RF feedback and control loops. The low operating energy of 50/70 MeV makes the impedances of the cavity higher order modes (HOMs) particularly critical for the beam stability. Their parasitic effects on the beam can be cured by HOM frequency shifting techniques, based on a fine temperature tuning and a dedicated plunger. A typical cavity temperature stability of ± 0.05°C within a range from 30 up to 70 °C can be achieved by a precise control of its water cooling temperature. On the other hand, the tuning of the cavity fundamental mode is achieved by changing its axial length by means of a motor-driven mechanism. A general description of the system and the state of its progress are reported together with some considerations of the effects of beam cavity interactions.

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TUPLR046

Design, Fabrication, Installation and Operation of New 201 MHz RF Systems at LANSCE

DTL, linac, controls, feedback

564

J.T.M. Lyles, W.C. Barkley, R.E. Bratton, M.S. Prokop, D. Rees
LANL, Los Alamos, New Mexico, USA

Funding: Work supported by the United States Department of Energy, National Nuclear Security Agency, under contract DE-AC52-06NA25396.
The LANSCE RM project has restored the proton linac to high power capability after the RF power tube manufacturer could no longer provide devices that consistently met the high average power requirement. Diacrodes® now supply RF power to three of the four DTL tanks. These tetrodes reuse the existing infrastructure including water-cooling systems, coaxial transmission lines, high voltage power supplies and capacitor banks. Each final power amplifier system uses a combined pair of LANL-designed cavity amplifiers using the TH628L Diacrode® to produce up to 3.5 MW peak and 420 kW of mean power. A new intermediate power amplifier was developed using a TH781 tetrode. These amplifiers are the first production of new high power 200 MHz RF sources at accelerators in three decades. Design and prototype testing of the high power stages was completed in 2012, with commercialization following in 2013. Each installation was accomplished during a 4 to 5 month beam outage each year staring in 2014. Simultaneously, a new digital low-level RF control system was designed and tested, and placed into operation this year, meeting the stringent field control requirements for the linac. The rapid-paced installation project changed over from old to new RF systems while minimizing beam downtime to the user facility schedule.

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TUPLR056

Results of Operation of 162.5 MHz RFQ Couplers

rfq, operation, vacuum, multipactoring

584

S. Kazakov, J.P. Edelen, T.N. Khabiboulline, O.V. Pronitchev, J. Steimel
Fermilab, Batavia, Illinois, USA

Two couplers for RFQ of PXEI facility were designed and manufactured. Each coupler designed to deliver 50 KW, CW to RFQ at 162.5 MHz. Results of couplers operation are reported.

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TUPLR058

Progress of a 162.5 MHz High-Current RFQ With Coupling Windows

rfq, Windows, coupling, simulation

589

Q. Fu, P.P. Gan, S.L. Gao, F.J. Jia, H.P. Li, Y.R. Lu, Z. Wang, K. Zhu
PKU, Beijing, People's Republic of China

Funding: Supported by National Basic Research Program of China(2014CB845503)
A 162.5 MHz, four-vane RFQ with magnetic coupling windows has been designed by the RFQ group of Peking University. Clear frequency separation of the resonant modes and smaller transverse dimension are the advantages of the window-type RFQ. The electromagnetic simulations have shown that the average power loss of this 1.809 m long RFQ is about 50 kW in continuous wave mode. Consequently, a water cooling system was designed via the multi-physics analysis. The mechanical design and assembling technology were also presented in this paper.

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TUPLR061

Cryomodule and Power Coupler for RIKEN Superconducting QWR

cryomodule, vacuum, linac, SRF

598

K. Ozeki, O. Kamigaito, H. Okuno, N. Sakamoto, K. Suda, Y. Watanabe, K. Yamada
RIKEN Nishina Center, Wako, Japan
E. Kako, H. Nakai, K. Umemori
KEK, Ibaraki, Japan
K. Okihira
MHI, Hiroshima, Japan
K. Sennyu, T. Yanagisawa
MHI-MS, Kobe, Japan

In RIKEN Nishina Center, we are constructing a prototype of low-beta superconducting QWR for ions. Presently, the designs of cryomodule, which contains two QWRs, and power coupler are being carried out. In this contribution, the progress situation for the construction of cryomodule and power coupler will be reported. This work was funded by ImPACT Program of Council for Science, Technology and innovation (Cabinet Office, Government of Japan).

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TUPLR063

IMPACT Model for ReA and its Benchmark with DYNAC

simulation, ion, rfq, lattice

601

T. Yoshimoto, M. Ikegami
FRIB, East Lansing, USA

Funding: * Work supported by the U.S. National Science Foundation under Grant No. PHY-11-02511 ** Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
Abstract New online model for ReAccelerator 3 (ReA3) has been developed for actual beam tunings using IMPACT, which is one of famous particle tracking codes in accelerator field. DYNAC model was used for ReA3 optics calculation. However it basically can calculate symmetric cavity, not axisymmetric ones such as super-conductive Quarter-Wave Resonators (QWRs), which are installed in ReA3. This means that it is difficult to effectively tune beams at present situation. In order to handle beams at ReA3, a new alternative and more precise model of IMPACT is under development, which would be acceptable to actual beam operation. This paper reports benchmarked results of IMPACT and DYNAC model for ReA3 acceleration line just after RFQ exit to a transport line with symmetric cavity as a first step before more precise simulation including non-axisymmetric cavity and RFQ calculation.

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TUPLR066

High Current Beam Injector for Cancer Therapy

ion, linac, injection, acceleration

604

L. Lu, Y. He, C.X. Li, W. Ma, L.B. Shi, L.P. Sun, X.B. Xu, L. Yang, H.W. Zhao
IMP/CAS, Lanzhou, People's Republic of China
T.L. He
USTC/NSRL, Hefei, Anhui, People's Republic of China

A hybrid single cavity (HSC) linac, which is formed by combining a radio frequency quadrupole (RFQ) and a drift tube (DT) structure into one interdigital-H (IH) cavity, is fabricated and assembled as a proof of principle injector for cancer therapy synchrotron, based on the culmination of several years of research. The HSC linac adopts a direct plasma injection scheme (DPIS), which can inject a high intensity heavy ion beam produced by a laser ion source (LIS). The input beam current of the HSC is designed to be 20 mA C⁶⁺ ions. According to numerical simulations, the HSC linac can accelerate a 6-mA C⁶⁺ beam, which meets the requirement of the needed particle number for cancer therapy (108~9 ions/pulse). The HSC injector with the DPIS method makes the existing multi-turn injection system and stripping system unnecessary, and can also bring down the size of the beam pipe in existing synchrotron magnets, which could reduce the whole cost of synchrotron. The radio frequency (RF) measurements show excellent RF properties for the resonator, with a measured Q equal to 91% of the simulated value. A C⁶⁺ ion beam extracted from the LIS was used for the HSC commissioning. In beam testing, we found the measured beam parameters agreed with simulations. More details of the measurements and the results of the high power test are reported in this paper.

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TUPLR067

Solenoid/Magnetic Shielding Test Results in FRIB-1&2 Cryomodules

solenoid, cryomodule, shielding, dipole

607

D. Luo, H. Ao, E.E. Burkhardt, J. Casteel, A. Ganshyn, W. Hartung, M.J. Holcomb, J.T. Popielarski, K. Saito, S. Shanab, E. Supangco, M. Thrush
FRIB, East Lansing, USA

Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661, the State of Michigan and Michigan State University.
Recently we did bunker tests for FRIB first cryomodule (CM-1) and second one (CM-2) which houses 0.085 QWRs and solenoid packages. Their performances were successfully validated in the full configuration. This paper reports the solenoid package tests results.

Poster TUPLR067 [4.899 MB]

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TUPLR070

Efficient Heavy Ion Acceleration with IH-Type Cavities for High Current Machines in the Energy Range up to 11.4 MeV/u

linac, emittance, DTL, simulation

616

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

Funding: BMBF 05P15RFRBA
We propose an efficient design for heavy ion acceleration from 1.4 to 11.4 MeV/u with a design current of 15 emA for a Uranium 28+ beam. The proposed linac is based on IH-DTL cavities and quadrupole triplet focusing. The KONUS beam dynamics concept is used to achieve high acceleration efficiency. By optimization of the transversal focusing scheme and the longitudinal bunch center motion, low emittance growth for the entire linac is achieved. Beam dynamics simulations were performed along with 3D rf-simulations of all cavities. The cavities are designed for 10⁸.408 MHz, reaching an effective shunt impedance of 100-200 MOhm/m. The overall length of the linac is below 25 m. A mechanical realization concept employing a modular tank design is presented. The proposed design is a viable option for the GSI UNILAC poststripper linac replacement, leaving free space in the UNILAC tunnel for future energy upgrades.

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TUPLR072

Fabrication and Low Temperature Test Plan for Rare Isotope Science Project

cryomodule, SRF, radiation, linac

619

W.K. Kim, M.J. Joung, Y. Jung, H. Kim, J.-W. Kim, Y. Kim, I. Shin
IBS, Daejeon, Republic of Korea

Quarter-wave resonator (QWR), half-wave resonator (HWR) and single-spoke resonator (SSR) cryomodules are used for RAON accelerator. The layout of RAON accelerator and three types of cryomodules such as QWR, HWR and SSR are shown in the linac. SRF test facility which consists of cryoplant, cleanroom, vertical test facility and horizontal test facility is constructed. Cleanroom has high pressure rinsing (HPR), ultrasonic cleaning (USC), buffered chemical polishing (BCP), high vacuum furnace and cavity assemble place. The test plan for cavity and cryomodules is presented.

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TUPLR073

Development of RAON QWR Cryomodule for Linac Demonstration

cryomodule, linac, PLC, controls

622

H. Kim, J.W. Choi, Y.W. Jo, Y. Jung, W.K. Kim, Y. Kim, M. Lee
IBS, Daejeon, Republic of Korea

Quarter-wave resonator (QWR) cryomodule is developed for linac demonstraction. The plan and layout of the linac demonstration are shown. 3D drawing and P&ID are shown for the quarter-wave resonator (QWR) cryomodule. The QWR cryomodule consists of cavity, coupler, tuner, liquid helium reservoir, thermal shield and magnetic shield. PLC rack is fabricated to control the QWR cryomodules. The PLC controls and monitors pumps, heaters, cryogenic valves, solenoid valves, gate valves and temperature sensors.

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TUP106001

Magnetic Field Measurements in a Cryomodule with Nearby Warm-Section Quadrupole Magnets of RAON Heavy Ion Accelerator

cryomodule, shielding, ion, heavy-ion

625

H.J. Cha, J.W. Choi, I. Chun, M. Lee
IBS, Daejeon, Republic of Korea

For the Korean heavy ion accelerator RAON, a normal-conducting quadrupole magnet doublet with an intermediate beam diagnostic devices between two cryomodules is served for collimating the heavy ion beam. Although the fringe field of a magnet at a superconducting cavity position is low enough, differently from a strong superconducting solenoid, it can degrade the acceleration performance in the case of quench of the cavity directly and/or indirectly by contaminating the cryomodule wall and magnetic shields. In this study, we analyze the magnetic measurement results in the cryomodule assembled with the magnet doublet compared to the calculated ones and discuss the future plan.

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TUP106004

Status of RRR Analysis for RAON Accelerator

niobium, vacuum, SRF, superconductivity

628

Y. Jung, H. Kim, W.K. Kim
IBS, Daejeon, Republic of Korea
J. Lee, J. Seo
Vitzrotech Co., Ltd., Ansan City, Kyunggi-Do, Republic of Korea

Residual resistance ratio (RRR) of 300-grade niobium has been analyzed to find optimal welding condition for a superconducting cavity. RRR values were not only measured along the welding directions, but also perpendicular to the welding lines. In this presentation, we will show the RRR analysis as a function of the distance, the welding speed, and the welding pressure.

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TUP106006

Vertical Test Results on ESS Medium Beta Elliptical Cavity Prototype

linac, cryomodule, SRF, status

631

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

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+ [1], 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 beta elliptical cavity prototypes. We describe the cavity preparation procedure from buffer chemical polishing to vertical test. Finally magnetic probes (Fluxgate) were installed on the cavity to determine magnetic field background during vertical test. The latest vertical test results showed that our cavity design performance are beyond requirements.

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TUP106024

Optimizing Cavity Choice for FRIB Energy Upgrade Plan

ion, linac, heavy-ion, cryomodule

637

S. Shanab, K. Saito, Y. Yamazaki
FRIB, East Lansing, USA

Isotope production yield rate is directly proportional to beam power, especially for heavy ions. Higher beam kinetic energy on target drives more isotope yield. FRIB has an energy upgrade plan up to ≥ 400 MeV/u for Uranium and already prepared a vacant space in the design stage and cryogenic capacity that accommodates for the energy upgrade plan[1]. This upgrade requires an optimized linac design and challenging technology for cavity performance improvement. In this paper, we will approach this issue concerning; maximizing final energy, optimum beta, cavity operating frequency, cryogenic power, fabrication and cost in order to develop a cavity that is suitable for the energy upgrade plan.

Poster TUP106024 [1.343 MB]

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WE1A02

Assembly of XFEL Cryomodules: Lessons and Results

cryomodule, vacuum, controls, HOM

646

S. Berry, O. Napoly
CEA/DSM/IRFU, France

The industrialized string and module assembly of 10³ European XFEL cryomodules has been performed at CEA-Saclay between September 2012 and the spring of 2016. The general features and achievements of this construction project will be reviewed, including lessons learned regarding organization, industrial transfer, quality control and assembly procedures. An overview of the cryomodule performance and RF test results will be presented.

Slides WE1A02 [7.300 MB]

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WE1A03

The Superconducting Radio-Frequency Linear Accelerator Components for the European Spallation Source: First Test Results

cryomodule, SRF, linac, proton

651

C. Darve, N. Elias, F. Schlander
ESS, Lund, Sweden
C. Arcambal, P. Bosland, E. Cenni, G. Devanz
CEA/IRFU, Gif-sur-Yvette, France
S. Bousson, P. Duthil, G. Olivier, G. Olry, D. Reynet
IPN, Orsay, France
G. Costanza
Lund University, Lund, Sweden
H. Li, R.J.M.Y. Ruber, R. Santiago Kern
Uppsala University, Uppsala, Sweden
F. Peauger
CEA/DSM/IRFU, France

The European Spallation Source requires a pulsed Linac with an average beam power on the target of 5MW which is about five times higher than the most powerful spallation source in operation today. Over 97% of the acceleration occurs in superconducting cavities. ESS will be the first accelerator to employ double spoke cavities to accelerate beam. Accelerating gradients of 9MV/meter is required in the spoke section. The spoke section will be followed by 36 elliptical 704 MHz cavities with a geometrical beta of 0.67 and elliptical 704 MHz cavities with a geometrical beta of 0.86. Accelerating gradients of 20MV/m is required in the elliptical section. Initial gradient test results will be presented in which results exceed expected requirements.

Slides WE1A03 [6.533 MB]

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WE1A04

Performance Analysis of the European XFEL SRF Cavities, From Vertical Test to Operation in Modules

cryomodule, linac, SRF, controls

657

N. Walker, D. Reschke, J. Schaffran, L. Steder, M. Wenskat
DESY, Hamburg, Germany
L. Monaco
INFN/LASA, Segrate (MI), Italy

More than 800 resonators have been fabricated, vertically qualified and operated in module tests before the accelerating module installation in the linac, which will be completed before the conference. An analysis of this experience, with correlation of the final cavity performances with production, preparation and assembly stages, is underway and at the time of the conference a summary of the activities will be available.

Slides WE1A04 [3.436 MB]

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WE1A05

HIE-ISOLDE SC Linac Progress and Commissioning in 2016

cryomodule, linac, coupling, cryogenics

663

W. Venturini Delsolaro, E. Bravin, N. Delruelle, M. Elias, E. Fadakis, J.A. Ferreira Somoza, F. Formenti, M.A. Fraser, J. Gayde, N. Guillotin, Y. Kadi, G. Kautzmann, T. Koettig, Y. Leclercq, M. Martino, M. Mician, A. Miyazaki, E. Montesinos, V. Parma, J.A. Rodriguez, S. Sadovich, E. Siesling, D. Smekens, M. Therasse, L. Valdarno, D. Valuch, G. Vandoni, U. Wagner, P. Zhang
CERN, Geneva, Switzerland

The HIE-ISOLDE project (High Intensity and Energy ISOLDE) reached an important milestone in October 2015 when the first physics run was carried out with radioactive Zn beams at 4 MV/m. This is a first stage in the upgrade of the REX post-accelerator, whereby the energy of the radioactive ion beams was increased from 3 to 4.3 MeV per nucleon. The facility will ultimately be equipped with four high-beta cryomodules that will accelerate the beams up to 10 MeV per nucleon for the heaviest isotopes available at ISOLDE. The first cryomodule of the new linac, hosting five superconducting cavities and one solenoid, was commissioned in summer 2015, while the second one was being assembled in clean room. The new high-energy beam transfer lines were installed and commissioned in the same lapse of time. Commissioning with two cryomodules is planned for Summer 2016 to prepare for a physics run at 5.5 MeV/u in the second half of the year. This contribution will focus on the results of the commissioning and operation of the SC linac in 2015. Plans for the second phase of the HIE-ISOLDE project will be highlighted.

Slides WE1A05 [4.194 MB]

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WE2A02

FRIB Cryomodule Design and Production

cryomodule, linac, SRF, alignment

673

T. Xu, H. Ao, B. Bird, N.K. Bultman, E.E. Burkhardt, F. Casagrande, C. Compton, J.L. Crisp, K.D. Davidson, K. Elliott, A. Facco, V. Ganni, A. Ganshyn, W. Hartung, M. Ikegami, P. Knudsen, S.M. Lidia, I.M. Malloch, S.J. Miller, D.G. Morris, P.N. Ostroumov, J.T. Popielarski, L. Popielarski, M.A. Reaume, K. Saito, S. Shanab, G. Shen, M. Shuptar, S. Stark, J. Wei, J.D. Wenstrom, M. Xu, Y. Xu, Y. Yamazaki, Z. Zheng
FRIB, East Lansing, Michigan, USA
A. Facco
INFN/LNL, Legnaro (PD), Italy
K. Hosoyama
KEK, Ibaraki, Japan
M.P. Kelly
ANL, Argonne, Illinois, USA
R.E. Laxdal
TRIUMF, Vancouver, Canada
M. Wiseman
JLab, Newport News, Virginia, USA

Funding: U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
The Facility for Rare Isotope Beams (FRIB), under con-struction at Michigan State University, will utilize a driver linac to accelerate stable ion beams from protons to ura-nium up to energies of >200 MeV per nucleon with a beam power of up to 400 kW. Superconducting technology is widely used in the FRIB project, including the ion sources, linac, and experiment facilities. The FRIB linac consists of 48 cryomodules containing a total of 332 superconducting radio-frequency (SRF) resonators and 69 superconducting solenoids. We report on the design and the construction of FRIB cryomodules.

Slides WE2A02 [3.823 MB]

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WE2A03

Plasma Processing to Improve the Performance of the SNS Superconducting Linac

plasma, cryomodule, linac, accelerating-gradient

679

M. Doleans, R. Afanador, J.A. Ball, D.L. Barnhart, W. Blokland, M.T. Crofford, B. DeGraff, S.W. Gold, B.S. Hannah, M.P. Howell, S.-H. Kim, S.W. Lee, J.D. Mammosser, C.J. McMahan, T.S. Neustadt, J. Saunders, S.E. Stewart, W.H. Strong, P.V. Tyagi, D.J. Vandygriff, D.M. Vandygriff
ORNL, Oak Ridge, Tennessee, USA

Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
An in-situ plasma processing technique has been developed at the Spallation Neutron Source (SNS) to improve the performance of the superconducting radio-frequency (SRF) cavities in operation. The technique uses a low-density reactive neon-oxygen plasma at room-temperature to improve the surface work function, to help removing adsorbed gases on the RF surface and to reduce its secondary emission yield. Recently, the plasma processing technique has been applied to one offline cryomodule and to two cryomodules in the linac tunnel. Improvement of the accelerating gradient has been observed in all three cryomodules.

Slides WE2A03 [4.433 MB]

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TH2A01

The Linac Laser Notcher for the Fermilab Booster

laser, linac, booster, injection

710

D.E. Johnson, K.L. Duel, M.H. Gardner, T.R. Johnson, D. Slimmer
Fermilab, Batavia, Illinois, USA
S. Patil
PriTel, Inc., Naperville, USA
J. Tafoya
Optical Engines, Inc., Colorado Springs, USA

In synchrotron machines, the beam extraction is accomplished by a combination of septa and kicker magnets which deflect the beam from an accelerator into another. Ideally the kicker field must rise/fall in between the beam bunches. However, in reality, an intentional beam-free time region (aka "notch") is created on the beam pulse to assure that the beam can be extracted with minimal losses. In the case of the Fermilab Booster, the notch is created in the ring near injection energy by the use of fast kickers which deposit the beam in a shielded collimation region within the accelerator tunnel. With increasing beam power it is desirable to create this notch at the lowest possible energy to minimize activation. The Fermilab Proton Improvement Plan (PIP) initiated an R&D project to build a laser system to create the notch within a linac beam pulse at 750 keV. This talk will describe the concept for the laser notcher and discuss our current status, commissioning results, and future plans.

Slides TH2A01 [15.170 MB]

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TH3A03

The VELA and CLARA Test Facilities at Daresbury Laboratory

FEL, electron, gun, laser

734

P.A. McIntosh, D. Angal-Kalinin, J.A. Clarke, L.S. Cowie, B.D. Fell, S.P. Jamison, B.L. Militsyn, Y.M. Saveliev, D.J. Scott, N. Thompson, P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
A. Gleeson, T.J. Jones
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

The Versatile Electron Linear Accelerator (VELA) provides enabling infrastructures targeted at the development and testing of novel and compact accelerator technologies, specifically through partnership with academia and industry, aimed at addressing applications in medicine, health, security, energy and industrial processing. The facility is now fully commissioned and is taking advantage of the variable electron beam parameters to demonstrate new techniques/processes or otherwise develop new technologies for future commercial realization. Examples of which include; electron diffraction and new cargo scanning processes. The Compact Linear Accelerator for Research and Applications (CLARA) will be a novel FEL test facility, focused on the generation of ultra-short photon pulses with extreme levels of stability and synchronization. The principal aim is to experimentally demonstrate that sub-cooperation length pulse generation with FELs is viable, and to compare the various schemes being championed. The results will translate directly to existing and future X-ray FELs, enabling attosecond pulse generation. Both the VELA and CLARA facilities are co-located at Daresbury Laboratory and provide the UK with a unique platform for scientific and commercial R&D using ultra-short pulse, high precision electron and photon beams.

Slides TH3A03 [11.795 MB]

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THOP02

Investigation of Nitrogen Absorption Rate and Nitride Growth on SRF Cavity Grade RRR Niobium as a Function of Furnace Temperature

niobium, SRF, ion, injection

744

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

Funding: Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The current state of the art processing of niobium superconducting radio frequency cavities with nitrogen diffusion is performed at 800C in a furnace with a partial pressure of approximately ~20 mtorr of nitrogen. Multiple studies have shown the bulk of the nitrogen absorbed by the niobium forms a thick (1-3 microns) non-superconducting nitride layer which must be removed to produce optimal RF results. The depth profiling of interstitial nitrogen and surface nitrides has already been probed using SIMS measurements. These measurements have also been modeled by extrapolating data from nitride growth studies performed at atmospheric pressure and temperatures above 1000 C (**). One open question is whether there is a diffusion zone at lower temperature in which the niobium will absorb nitrogen but not create a non-superconducting nitride layer; or is the absorption of nitrogen only possible by first forming a nitride buffer layer which then frees up nitrogen for absorption. A systematic study of absorption rate vs. temperature and correlated SIMS measurements needs to be performed to answer this question. We report on the absorption rate vs. temperature from 400 C to 900 C of cavity grade niobium with metallurgically flat witness samples. The witness samples surface depth profile of NbN via SIMS's will be presented and correlated to the absorption.**
* Gonnella et al., Proceedings of SRF2015 Pre-release MOPB042 (2015)
** Tuggle et al., Investigation of Low-Level Nitrogen in Niobium by Secondary Ion Mass Spectrometry, these proceedings (2016)

Poster THOP02 [2.235 MB]

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THOP03

Cold Bead-Pull Test Stand for SRF Cavities

HOM, niobium, SRF, simulation

748

A.V. Vélez, A. Frahm, J. Knobloch, A. Neumann
HZB, Berlin, Germany

Bead-pull measurements represent a final step in the fabrication process of an SRF cavity. These tests allow to characterize the flatness of the field profile in order to perform mechanical tuning if needed. These test has been always performed at room temperature, where material properties differ from the superconducting state properties. Still questions like mechanical deformation due to assymetrical thermal shrincage have not yet been answered experimentaly. In this paper, an upgrade of the former Cold-Bead pull system developed by HZB [1] is presented. This test stand is capable of holding a 9-cell Tesla cavity at LHe temperature providing a realistic insight to cavity parameters under realistic conditions. A copper test pill-box is placed in series with the multi-cell cavity in order to perform 1.8K calibration of the bead. Results will be presented on this paper and compared to electromagnetic simulations.

Slides THOP03 [2.731 MB]

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THOP06

Novel Scheme to Tune RF Cavities Using Reflected Power

controls, resonance, DTL, TRIUMF

757

R. Leewe, K. Fong, Z. Shahriari
TRIUMF, Vancouver, Canada
M. Moallem
SFU, Surrey, Canada

Tuning of the natural resonance frequency of an RF cavity is essential for accelerator structures to achieve efficient beam acceleration and to reduce power requirements. Typically operational cavities are tuned using phase comparison techniques. The phase measurement is subject to temperature drifts and renders this technique labor and time intensive. To eliminate the phase measurement, reduce human oversight and speed up the start-up time for each cavity, this paper presents a control scheme that relies solely on the reflected power measurements. A sliding mode extremum seeking algorithm is used to minimize the reflected power. To avoid tuning motor abrasion, a variable gain minimizes motor movement around the optimum operating point. The system has been tested and is fully commissioned on two drift tube linear accelerator tanks in TRIUMF's ISAC I linear accelerator. Experimental results show that the resonance frequency can be tuned to its optimum operating point while the start-up time of a single cavity and the accompanied human oversight are significantly decreased.

Poster THOP06 [0.244 MB]

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THOP10

Design and Commissioning of FRIB Multipacting-Free Fundamental Power Coupler

electron, cryomodule, controls, impedance

767

Z. Zheng, J.T. Popielarski, K. Saito, S. Stark, T. Xu, Y. Yamazaki
FRIB, East Lansing, USA

Funding: *Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
The original Fundamental Power Coupler (FPC) of Half-Wave Resonator (HWR) for the Facility of Rare Isotope Beams (FRIB) requires multipacting conditioning at operating RF power which is up to 5 kW Continue Wave (CW). Conditioning takes a lot of time and RF power, and its elimination is highly desirable. To significantly shorten the RF conditioning, we developed a multipacting-free coupler design. This paper reports the latest progress in the optimization and prototype tests of multipacting-free coupler. The choke structure is removed and coupler geometry is further modified to protect the coupler RF window from the electron bombardment. The comparison result of multipacting-free coupler with original coupler was performed on automatic conditioning system, which showed significantly time reducing for RF conditioning.

Slides THOP10 [2.442 MB]

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THPRC006

Development of 704.4 MHz Power Coupler Window for Myrrha Project

simulation, linac, Windows, electron

776

F. Geslin, P. Blache, M. Chabot, J. Lesrel
IPN, Orsay, France
Ch.L. Lievin, S. Sierra
TED, Velizy, France

Myrrha is an accelerator driven system (ADS) hybrid research reactor designed for spent nuclear fuel burning. The linac controlling the reactor has to be highly reliable (low failure rate). In order to fulfill requirements of ADS projects like Myrrha, IPNO and Thales are involved in a power couplers research and development program. We develop a power coupler window, with MAX RF design, for 80 kW CW input power. During the study, we take account of fabrication and cost issues. We present in this paper the result of simulations needed to design this coupler window. The electromagnetic, thermal and thermo-mechanical simulations were performed with Ansys. The multipacting simulations were performed with Musicc3D, software developed by IPNO. The conditioning and test bench is also described as two prototypes have to be tested this autumn.

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THPRC007

Development of 352.2 Mhz Power Coupler Window for R&D Purposes

klystron, simulation, electron, vacuum

779

F. Geslin, M. Chabot, J. Lesrel, D. Reynet
IPN, Orsay, France
Ch.L. Lievin, S. Sierra
TED, Velizy, France

IPNO and Thales are conducting power couplers research and development. This paper present a new window design that fulfills European Spallation Source (ESS) requirements (400 kW RF peak power). The results of electromagnetic, thermal, thermo-mechanical, multipacting simulations and the consequences of the new ceramic window of power coupler will be reported. The multipacting simulations were performed with Musicc3D, software developed by IPNO. The new design overcome ceramic's weakness in tension and allows stronger constraints in the power coupler window.

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THPRC009

IF-Mixture Performance During Cavity Conditioning at STF-KEK

controls, LLRF, feedback, flattop

785

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

The Superconducting rf Test Facility (STF) at High Energy Accelerator Research Organization (KEK) was built for research and development of the International Linear Collider (ILC). In order to satisfy the stability requirement of the accelerating field, a digital low-level RF (LLRF) control system is employed. In this control system, signal from a cavity is down-converted into intermediate frequency (IF) signal before being digitized by analog-to-digital converter (ADC). In order to reduce the required number of ADCs, we proposed a technique that combines several IFs and to be read by a single ADC. Signal reconstruction of each IF is performed by digital signal processing. The performance of this technique, which is named IF-mixture, is reported in this paper.

Poster THPRC009 [0.992 MB]

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THPRC012

Resonance Control System for the CEBAF Separator Upgrade

controls, resonance, LLRF, extraction

792

T. E. Plawski, R. Bachimanchi, B. Bevins, L. Farrish, C. Hovater, G.E. Lahti, M.J. Wissmann
JLab, Newport News, Virgina, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The Continuous Electron Beam Accelerator Facility (CEBAF) energy upgrade from 6 GeV to 12 GeV includes the installation of four new 748.5 MHz normal conducting deflecting cavities in the 5th pass extraction region. The RF system employs two digital LLRF systems controlling four normal conducting cavities in a vector sum setting. Cavity tune information of the individual cavities is obtained using a multiplexing scheme of the forward and reflected RF signals. Water skids equipped with heaters and valves are used to control resonance. A new FPGA-based hardware and EPICS-based predictive control algorithm has been developed to support reliable operation of the beam extraction process. This paper presents the architecture design of the existing hardware and software as well as a plan to develop a model predictive control system.

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THPRC014

RF Losses in 1.3 GHz Cryomodule of The LCLS-II Superconducting CW Linac

cryomodule, HOM, linac, cryogenics

798

A. Saini, A. Lunin, N. Solyak, A.I. Sukhanov, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

The Linac Coherent Light Source (LCLS) is an x-ray free electron laser facility. The proposed upgrade of the LCLS facility is based on construction of a new 4 GeV superconducting (SC) linac that will operate in continuous wave (CW) mode. The major infrastructure investments and the operating cost of a SC CW linac are outlined by its cryogenic requirements. Thus, a detail understanding of RF losses in the cryogenic environment is critical for the entire project. In this paper we review RF losses in a 1.3 GHz accelerating cryomodule of the LCLS-II linac. RF losses due to various sources such untrapped higher order modes (HOMs), resonant losses etc. are addressed and presented here.

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THPRC015

Cool-Down Performance of the Cornell ERL Cryomodules

cryomodule, linac, operation, cryogenics

802

R.G. Eichhorn, F. Furuta, M. Ge, G.H. Hoffstaetter, M. Liepe, S.R. Markham, T.I. O'Connell, P. Quigley, D.M. Sabol, J. Sears, E.N. Smith, V. Veshcherevich, D. Widger
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

In the framework of the ERL prototyping, Cornell University has built two cryomodules, one injector module and one prototype Main Linac Cryomodule (MLC). In 2015, the MLC was successfully cooled down for the first time. We will report details on the cool-down as well as cycle tests we did in order to achieve slow and fast cool-down of the cavities. We will also report on the improvement we made on the injector cryomodule which also included a modification of the heat exchanger can that allows now a more controlled cool-down, too.

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THPRC016

Assembling Experience of the First Two HIE-ISOLDE Cryomodules

vacuum, linac, ion, status

805

M. Therasse, G. Barlow, S. Bizzaglia, O. Capatina, A. Chrul, P. Demarest, J-B. Deschamps, J. Gayde, M. Gourragne, A. Harrison, G. Kautzmann, Y. Leclercq, D. Mergelkuhl, T. Mikkola, A. Miyazaki, V. Parma, J.A.F. Somoza, M. Struik, S. Teixeira L'pez, W. Venturini Delsolaro, L.R. Williams, P. Zhang
CERN, Geneva, Switzerland
J. Dequaire
Intitek, Lyon, France

The assembly of the first two cryomodules (CM1 and CM2) of the new superconducting linear accelerator HIE-ISOLDE (High Intensity and Energy ISOLDE), located downstream of the REX-ISOLDE normal conducting accelerator, started one year and half ago. After a delicate assembly phase in the cleanroom which lasted nine months, the first cryomodule was transported to the ISOLDE hall on 2 May 2015 and coupled to the existing REX-ISOLDE accelerator, increasing the energy of the radioactive ion beams from 2.8 to 4.3 MeV per nucleon. The superconducting linac supplied the CERN-ISOLDE Facility, with radioactive zinc ions until the end of the proton run in November 2015. At the beginning of 2016, the second cryomodule was installed in the machine, increasing the energy to 5.5 MeV per nucleon. During commissioning of the first cryomodule in summer 2015, it was found that the performance of the RF superconductive cavities was limited by the over-heating of their RF couplers. The decision was taken to refurbish CM1 and reinstall it at the end of April. In this paper, we present the challenges faced and the experience gained with the cleanroom assembly of the first two cryomodules, especially the construction of the SC RF cavities and their RF ancillaries.

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THPRC017

Performance of SRF Cavity Tuners at LCLS II Prototype Cryomodule at FNAL

cryomodule, SRF, operation

808

J.P. Holzbauer, Y.M. Pischalnikov, W. Schappert, J.C. Yun
Fermilab, Batavia, Illinois, USA

Performances of the fast/slow tuners mounted on the 8 SRF cavities of first LCLS-II prototype cryomodule assembled at FNAL will be presented.

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THPRC021

Status of β=0.53 Pre-Production Cryomodule

linac, SRF, cryomodule, alignment

811

H. Ao, B. Bird, G.D. Bryant, B. Bullock, N.K. Bultman, C. Compton, A. Facco, J.D. Hulbert, S.J. Miller, J.T. Popielarski, L. Popielarski, M.A. Reaume, K. Saito, M. Shuptar, J. Simon, S. Stark, B.P. Tousignant, J.D. Wenstrom, K. Witgen, T. Xu, Z. Zheng
FRIB, East Lansing, USA

Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE SC0000661.
The driver linac for the Facility for Rare Isotope Beams (FRIB) comprises four kinds of cavities (=0.041, 0.085, 0.29, and 0.53) and six types of cryomodules including matching modules. FRIB has started the fabrication of a β=0.53 preproduction cryomodule, which is the first prototype for a half-wave (=0.29 and 0.53) cavity. This paper describes the fabrication progress and the lessons learned from the β=0.53 preproduction cryomodule.

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THPRC022

The Cryogenic Performance of the ARIEL E-Linac Cryomodules

cryomodule, linac, TRIUMF, cryogenics

815

Y. Ma, K. Fong, P.R. Harmer, T. Junginger, D. Kishi, A.N. Koveshnikov, R.E. Laxdal, N. Muller, Z.Y. Yao, V. Zvyagintsev
TRIUMF, Vancouver, Canada
E. Thoeng
UBC & TRIUMF, Vancouver, British Columbia, Canada

The Advanced Rare Isotope Laboratory (ARIEL) project at TRIUMF requires a 50 MeV superconducting electron Linac consisting of five nine cell 1.3 GHz cavities divided into three cryomodules with one, two and two cavities in each module respectively. The cryomodule design utilizes a unique box cryomodule with a top-loading cold mass. LHe is distributed in parallel to each cryomodule at 4 K and at ~1.2 bar. Each cryomodule has a cryogenic insert on board that receives the 4 K liquid and produces 2 K liquid into a cavity phase separator. In the cryomodules the natural two-phase convection loops, i.e. siphon loop, are installed which supply 4 K liquid to thermal intercepts and return the vaporized liquid to the 4 K reservoir as a refrigerator load. The design of the cryomodule, the simulation results with Ansys Fluent and the results of the cold tests will be presented.
mayanyun@triumf.ca

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THPRC023

Cost Reduction for FRIB Magnetic Shielding

shielding, cryomodule, cryogenics, simulation

818

Z. Zheng, J.T. Popielarski, K. Saito, T. Xu
FRIB, East Lansing, USA

Funding: *Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
Cryogenic magnetic shielding (A4K) is generally used in SRF cryomodules which is much more expensive than mu-metal used in room temperature. In order to reduce the cost, FRIB QWR and HWR magnetic shieldings were redesign to improve the shielding performance so that mu-metal can be implemented as an alternative shielding material. The magnetic shielding of first FRIB β=0.085 cryomodule was made up of 50% by A4K and 50% by mu-metal. Cavities were tested in 4K and 2K, the results showed that the Q0 of cavities were similar for both shielding materials, which is a success as a validation test for mu-metal magnetic shielding.

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THPLR004

Development of 1.3 Ghz Single-Cell Superconducting Cavities With Nb Material Developed by Ulba Metallurgical Plant

accelerating-gradient, niobium, vacuum, radiation

849

T. Ota, N. Kuroiwa, S. Nomura, Y. Otani, M. Takasaki, M. Yamada
Toshiba, Yokohama, Japan
H. Hayano, T. Saeki
KEK, Ibaraki, Japan
Y.V. Krygin, V. Kuznetsov, A.A. Tsorayev
Ulba Metallurgical Plant, Ust-Kamenogorak, Kazakhstan
Y. Shirota
BE International Corporation, Tokyo, Japan
T. Tosaka
Toshiba Corporation, Power And Industrial Systems Research and Development Center, Yokohama, Japan

TOSHIBA has been developing high purity niobium (Nb) material for superconducting cavities with ULBA Metallurgical Plant (UMP) since 2008. Recently, we have produced the high purity Nb plates. Two 1.3 GHz single-cell superconducting cavities using UMP's Nb plates have been fabricated by TOSHIBA and RF tested at High Energy Accelerator Research Organization (KEK). One of the cavities has achieved the accelerating gradient of Eacc=31.8 MV/m. The development of high purity Nb plates, details of the fabrication of the cavities and the RF test results are presented in this article.

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THPLR006

Design Study of a Test Cavity for Evaluating RF Critical Magnetic Field of Thin-Film Superconductor

target, electromagnetic-fields, cryogenics, resonance

852

H. Oikawa
Utsunomiya University, Utsunomiya, Japan
H. Hayano, S. Kato, T. Kubo, T. Saeki
KEK, Ibaraki, Japan
T. Higashiguchi
Center for Optical Research and Education, Utsunomiya University, Utsunomiya, Japan
M. Hino
Kyoto University, Research Reactor Institute, Osaka, Japan
Y. Iwashita
Kyoto ICR, Uji, Kyoto, Japan

Superconducting cavities of higher gradient has been demanded in various fields of the accelerator science. Also, according to the Technical Design Report (TDR) of International Linear Collider (ILC), the higher gradient of 45 MV/m is required in the second stage of ILC. To realize such higher gradient, several methods are proposed. One of such methods is to coat multi-layer thin-film superconductor on the inner surface of RF cavity where the thin film increases the RF critical field on the inner surface of the cavity. To demonstrate the RF performance of thin-film structure on a small coupon sample, we designed the RF mushroom-shaped cavity with which the RF critical magnetic field is measured on a thin-film coupon sample set on the inner surface of the cavity. If the RF cavity is cooled down below the critical temperature of thin-film superconductor with supplying RF power, the heat dissipation might be measured on the coupon sample in the cavity. We designed the shape of the cavity so as to produce a strong RF magnetic field parallel to the sample surface efficiently. We report the design, manufacturing and RF property measurements of the cavity in this presentation.

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THPLR008

3-Cell Superconducting Traveling Wave Cavity Tuning at Room Temperature

accelerating-gradient, SRF, feedback, factory

858

R.A. Kostin
LETI, Saint-Petersburg, Russia
P.V. Avrakhov, A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
T.N. Khabiboulline, A.M. Rowe, N. Solyak, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Funding: Work supported by US DOE SBIR # DE-SC0006300
A superconducting traveling wave (SCTW) cavity with a feedback waveguide will support a higher average acceleration gradient compared to conventional SRF standing wave cavities [1]. Euclid Techlabs, in collaboration with Fermilab, previously demonstrated a high accelerating gradient in a single cell cavity with a feedback waveguide [2], and the new waveguide design did not limit the cavity performance. The next step is high gradient traveling wave SRF cavity test. A 3-Cell SCTW cavity was designed and developed [3] to demonstrate the SRF traveling wave regime. Two Nb SCTW cavities were built, characterized and cold tested in 2016. This paper presents the results of cavity inspection, field flatness analysis, along with a discussion of the tuning procedure.

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THPLR009

A Compact Muon Accelerator for Tomography and Active Interrogation

linac, electron, target, simulation

861

R.W. Garnett, S.S. Kurennoy, L. Rybarcyk
LANL, Los Alamos, New Mexico, USA
K. Hasegawa
JAEA, Ibaraki-ken, Japan
S. Portillo, E. Schamiloglu
University of New Mexico, Albuquerque, USA
N. Saito
J-PARC, KEK & JAEA, Ibaraki-ken, Japan

Funding: This work is supported by the United States Department of Energy, National Nuclear Security Agency, under contract DE-AC52-06NA25396.
Muons have been demonstrated to be great probes for imaging large and dense objects due to their excellent penetrating ability. At present there are no muon accelerators. Development of a compact system that can produce an intense beam of accelerated muons would provide unique imaging options for stockpile stewardship while delivering minimal radiation dose, as well as various homeland-security and industrial applications. Our novel compact accelerator approach allows a single linac to be used to first accelerate an electron beam to 800 MeV to generate muons by interacting with a production target in a high-field solenoid magnet and then to collect and accelerate these low-energy muons to 1 GeV to be used for imaging or active interrogation. The key enabling technology is a high-gradient accelerator with large energy and angular acceptances. Our proposed solution for efficient acceleration of low-energy muons is a 0-mode linac coupled with conventional electron RF accelerating structures to provide a compact system that could deliver a controllable high-flux beam of muons with well-defined energy to allow precise radiographic inspections of complicated objects. The details of the conceptual design will be discussed.

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THPLR012

Beam-Loading Compensation of a Multi-Bunch Electron Beam by Using RF Amplitude Modulation in Laser Undulator Compact X-Ray Source (LUCX)

gun, laser, electron, beam-loading

867

M.K. Fukuda, S. Araki, Y. Honda, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan
K. Sakaue
Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan
M. Washio
Waseda University, Tokyo, Japan

Funding: This work was supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
We have been developing a compact X-ray source via laser Compton scattering(LCS) at Laser Undulator Compact X-ray source(LUCX) accelerator in KEK. In here, a multi-bunch electron beam is generated by a 3.6cell photo-cathode RF-gun and accelerated to 18-24MeV by a 12cell booster. And then 6-10 keV X-rays are generated by LCS between the beam and a laser pulse stored in a 4-mirror planar optical cavity. Our aim is to take a phase contrast image with Talbot interferometer within a few minutes at present. The target flux of X-ray is 1.7x10⁷ photons/pulse with 10% bandwidth. For an electron beam, the target of the intensity is 500nC/pulse with 1000 bunches at 30 MeV. Presently, we have achieved the generation of 24MeV beam with total charge of 600nC in 1000bunches. The energy difference is within 1.3% peak to peak. The beam-loading is compensated by delta T method and amplitude modulation(AM) of the RF pulse*. However there is the energy difference at the RF-gun. It is assumed that this causes the reduction of the X-ray flux due to change of the focused beam size. To reduce the energy difference, AM is also applied to the RF pulse for the gun. We will show the results of the beam-loading compensation and the generation of X-rays.
* Y. Yokoyama et al. , Proceedings IPAC2011, TUPC059 (2011).

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THPLR018

HOM Suppression Improvement for Mass Production of EXFEL Cavities at RI

HOM, damping, linac, coupling

879

A.A. Sulimov, J.H. Thie
DESY, Hamburg, Germany
M. Pekeler, D. Trompetter
RI Research Instruments GmbH, Bergisch Gladbach, Germany

During cold RF tests of the European XFEL (EXFEL) cavities at DESY it was observed that the damping of the second monopole mode (TM011) showed the largest variation, which was sometimes up to 2-3 times lower than the originally allowed limit. It was concluded that this TM011-damping degradation was caused by cavity geometry deviation within the specified mechanical tolerances. The particular influence of different mechanical parameters was analyzed and additional RF measurements were carried out to find the most critical geometry parameters. Stability of the equator welding and regularity of chemical treatment were investigated for different cavity cells. In spite of the high fabrication rate during EXFEL cavity mass production the TM011 suppression was improved to an acceptable level.

Poster THPLR018 [0.378 MB]

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THPLR025

Modernisation of the 10⁸ MHz RF Systems at the GSI UNILAC

controls, operation, PLC, LLRF

898

B. Schlitt, G. Eichler, S. Hermann, M. Hoerr, M. Mueh, S. Petit, A. Schnase, G. Schreiber, W. Vinzenz, J. Zappai
GSI, Darmstadt, Germany

A substantial modernisation of the RF systems at the 10⁸ MHz Alvarez type post-stripper section of the GSI heavy ion linac UNILAC was launched in 2014 to prepare the existing facility for the future FAIR operation. A new 1.8 MW RF cavity amplifier prototype for low duty-cycle operation (2 ms pulse length at 10 Hz repetition rate) based on the widely-used tetrode TH558SC was designed and built by THALES and is under commissioning. A call for tenders was started for a 150 kW solid state driver amplifier. An RF test bench for the amplifier prototypes is in preparation at GSI including new control racks, commercial grid power supplies, and a modern PLC system for amplifier control. The existing powerful 1 MVA anode power supplies will be reused and are also being equipped with new PLC systems. The development of a digital low-level RF system based on the MTCA.4 standard and commercial vector modulator and FPGA boards was started. Status and details of the modernisation as well as first commissioning results of the new high power amplifier prototype will be reported.

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THPLR027

Progress Towards a 2.0 K Half-Wave Resonator Cryomodule for Fermilab's PIP-II Project

cryomodule, vacuum, linac, SRF

906

Z.A. Conway, A. Barcikowski, G.L. Cherry, R.L. Fischer, B.M. Guilfoyle, C.S. Hopper, M. Kedzie, M.P. Kelly, S.H. Kim, S.W.T. MacDonald, P.N. Ostroumov, T. Reid
ANL, Argonne, Illinois, USA
V.A. Lebedev, A. Lunin
Fermilab, Batavia, Illinois, USA

Funding: This material is supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics and Office of High-Energy Physics, Contracts No. DE-AC02-76-CH03000 and DE-AC02-06CH11357.
In support of Fermilab's Proton Improvement Plan-II project Argonne National Laboratory is constructing a superconducting half-wave resonator cryomodule. This cryomodule is designed to operate at 2.0 K, a first for low-velocity ion accelerators, and will accelerate ≥1 mA proton/H⁻ beams from 2.1 to 10.3 MeV. Since 2014 the construction of 9 162.5 MHz b = 0.112 superconducting half-wave resonators, the vacuum vessel and the majority of the cryomodule subsystems have been finished. Here we will update on the status of this work and report on preliminary cavity test results. This will include cavity performance measurements where we found residual resistances of < 3 nanoOhms at low fields and peak voltage gains of 5.9 MV, which corresponds to peak surface fields of 134 MV/m and 144 mT electric and magnetic respectively.

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THPLR028

Simulation of Mechanical Oscillations in PIP-II Cryomodule Using ACE3P

simulation, SRF, linac, proton

910

L. Xiao, O. Kononenko, C.-K. Ng
SLAC, Menlo Park, California, USA

Funding: Work supported by the US DOE under contract DE-AC02-76SF00515.
The linac in the PIP-II project at Fermilab consists of different sections of superconducting rf (SRF) cavities that can accelerate the proton beams to 800 MeV. At the end of the linac is a section containing a number of HB (β = 0.92) cryomodules operating at 650 MHz, with each cryomodule consisting of six SRF cavities. Previous calculations have been carried out to determine the mechanical modes of a single cavity in the 650 MHz cryomodule. In this paper, the parallel code suite ACE3P is used to evaluate the mechanical modes for a string of SRF cavities in the 650 MHz cryomodule. The effects of multi cavities on the mechanical mode frequencies and any possible coupling between cavities will be investigated.

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THPLR029

Update on the SC 325 MHz CH-Cavity and Power Coupler Processing

linac, ion, SRF, heavy-ion

913

M. Busch, M. Amberg, M. Basten, F.D. Dziuba, P.A. Mundine, H. Podlech, U. Ratzinger
IAP, Frankfurt am Main, Germany

Funding: Work supported by GSI, BMBF Contr. No. 05P15RFRBA
The 325 MHz CH-Cavity which has been developed and successfully vertically tested at the Institute for Applied Physics, Frankfurt, has reached the final production stage. The helium vessel has been welded to the frontal joints of the cavity and further tests in a horizontal environment are in preparation. Furthermore the corresponding power couplers have been conditioned and tested at a dedicated test stand up to the power level of 40 kW (pulsed) for the targeted beam operation. The final step of the whole prototype development is a beam test with a 11.4 AMeV, 10 mA ion beam at GSI, Darmstadt.

Poster THPLR029 [1.858 MB]

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THPLR030

Performances of the Two First Single Spoke Prototypes for the MYRRHA Project

cryomodule, simulation, superconductivity, linac

916

D. Longuevergne, J.-L. Biarrotte, S. Blivet, P. Duchesne, G. Olry, H. Saugnac
IPN, Orsay, France
Y. Gómez Martínez
LPSC, Grenoble Cedex, France

Funding: This work is being supported by the Euratom research and training program 2014-2018 under grant agreement N°662186 (MYRTE project)
The MYRRHA project aims at the construction of an accelerator driven system (ADS) at MOL (Belgium) for irradiation and transmutation experiment purposes. The facility will feature a superconducting LINAC able to produce a proton flux of 2.4 MW (600 MeV - 4 mA). The first section of the superconducting LINAC will be composed of 352 MHz (β = 0.37) Single Spoke Resonators (SSR) housed in short cryomodules operating at 2K. After a brief presentation of the cryomodule design, this paper will aim at presenting the RF performances of the SSR tested in vertical cryostat in the framework of European MYRTE project (MYRRHA Research and Transmutation Endeavour) and at comparing experimental results (Lorentz forces, pressure sensitivity, multipacting barriers…) to simulated values.

Poster THPLR030 [1.610 MB]

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THPLR032

Update on SSR2 Cavity EM Design for PIP-II

linac, simulation, quadrupole, acceleration

920

P. Berrutti, T.N. Khabiboulline, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Proton Improvement Plan II (PIP-II) is the future plan for upgrading the Fermilab proton accelerator complex to a beam power capability of at least 1 MW delivered to the neutrino production target. A room temperature section accelerates H⁻ ions to 2.1 MeV and creates the desired bunch structure for injection into the superconducting (SC) linac. SC linac using five cavity types. One 162.5 MHz half wave resonator, two 325 MHz spoke resonators and two 650 MHz elliptical 5-cell cavities, provide acceleration to 800 MeV. The EM design of the second family of spoke resonator is presented in this paper. The work reported is a thorough electromagnetic study including: the RF parameters, multipacting mitigation and transverse field asymmetry. The cavity is now ready for structural design analysis.

Poster THPLR032 [1.947 MB]

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THPLR033

R&D Status of the New Superconducting CW Heavy Ion LINAC@GSI

linac, ion, pick-up, heavy-ion

923

M. Basten, M. Amberg, M. Busch, F.D. Dziuba, H. Podlech, M. Schwarz
IAP, Frankfurt am Main, Germany
W.A. Barth, V. Gettmann, S. Mickat, M. Miski-Oglu
HIM, Mainz, Germany
M. Heilmann, S. Mickat, S. Yaramyshev
GSI, Darmstadt, Germany

For future research in the field of Super Heavy Elements (SHE) a superconducting (sc) continuous wave (cw) ion LINAC with high intensity is highly desirable. Presently a multi-stage R&D program conducted by GSI, HIM and IAP[*] is in progress. The fundamental linac design composes a high performance ion source, a new low energy beam transport line, the High Charge State Injector (HLI) upgraded for cw, and a matching line (1.4 MeV/u) followed by the new sc-DTL LINAC for acceleration up to 7.3 MeV/u. The successful commissioning of the first Crossbar-H-mode (CH) cavity (Demonstrator), in a vertical cryo module, was a major milestone in 2015[**]. The next stage of the new sc cw heavy ion LINAC is the advanced demonstrator comprising a string of cavities and focusing elements build from several short constant-beta sc CH-cavities operated at 217MHz. Currently the first two sc 8 gap CH-cavities are under construction at Research Instruments (RI), Bergisch Gladbach, Germany. The new design without girders and with stiffening brackets at the front and end cap potentially reduces the overall technical risks during the construction phase and the pressure sensitivity of the cavity. The recent status of the construction phase as well as an outlook for further cavity development of the new cw heavy ion LINAC will be presented.
*W.Barth et al.,Further R&D for a new Superconducting cw Heavy Ion LINAC@GSI, IPAC14, THPME004
**F.Dziuba et al.,First Performance Test on the Superconducting 217 MHz CH Cavity at 4K,LINAC16, THPLR033

Poster THPLR033 [2.502 MB]

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THPLR035

FZJ SRF TSR with Integrated LHe Vessel

simulation, SRF, operation, electromagnetic-fields

926

E.N. Zaplatin
FZJ, Jülich, Germany

Single- or Multi-Spoke SRF cavities are one of the basic accelerating structures for the low and intermediate energy part of many accelerators. Different types of external loads on the resonator walls predetermine the main working conditions of the SC cavities. The most important of them are very high electromagnetic fields that result in strong Lorentz forces acting on cavity walls and the pressure on cavity walls from the helium tank that also deforms the cavity shape. For the accelerators operating in pulsed regime the Lorentz forces are the dominant factor. The liquid helium vessel pressure instability even for 2K operations is the source of large microphonics and dominates for cw operation. Here we propose an innovative integrated helium vessel-cavity and stiffener design that will provide an effective passive damping minimizing df/dp ratio. Minimizing df/dp may be accomplished without an enhancement of the structure rigidity, which in turn minimizes the load on the cavity tuner. A separate stiffening scheme reducing Lorentz force cavity detuning to be added without violation of df/dp optimization. The developed at the Research Center in Jülich, Germany (FZJ) the 352 MHz, β=v/c=0.48 Triple-Spoke Resonator was used as an example to demonstrate the proposed conceptual integrated helium vessel-cavity design.

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THPLR036

SRF Low-Beta Elliptical Resonator Two-Ring Stiffening

simulation, SRF, resonance, vacuum

929

E.N. Zaplatin
FZJ, Jülich, Germany
I.V. Gonin, T.N. Khabiboulline, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Elliptical SRF cavities are the basic accelerating structures for the high energy part of many accelerators. Since a series of external loads on the resonator walls predetermine the main working conditions of the SC cavities the detailed investigation of their mechanical properties should be conducted in parallel with the main RF design. The effects of very high electromagnetic fields that result in strong Lorentz forces and the pressure on cavity walls from the helium tank that also deforms the cavity shape, the tuning scheme resulting in the change of accelerating field profile and mechanical eigen resonances of cavities which are the main source of the microphonics must be taken into account during integrated design of the resonator and its liquid helium vessel. SRF elliptical cavities for the medium energies (β=v/c is around 0.6) inherently have more flexible shape and their ultimate stiffening with a "standard" stiffening rings installed between resonator cells becomes problematic. The second row of the rings should enhance the overall cavity rigidity. In the paper we report the basic investigations of the cavity two-row ring stiffening using FNAL 650 MHz β=0.61 as an example. The single-cell investigation results were used as the reference to develop the ultimate scheme of the helium vessel structure to ensure the best resonator stability.

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THPLR037

Development of a Superconducting Twin Axis Cavity

HOM, niobium, linac, SRF

932

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

Superconducting cavities with two separate accelerating axes have been proposed in the past for energy recovery linac applications. While the study showed the advantages of such cavity, the designs present serious fabrication challenges. Hence the proposed cavities have never been built. The new design, elliptical twin cavity, proposed by Jefferson Lab and optimized by Center for Accelerator Science at Old Dominion University, allows similar level of engineering and fabrication techniques of a typical elliptical cavity. This paper describes preliminary LOM and HOM spectrum, engineering and fabrication processes of the twin axis cavity.

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THPLR038

Resonance Control for Narrow Bandwidth PIP-II Cavities

resonance, flattop, SRF, FPGA

936

W. Schappert, J.P. Holzbauer, Y.M. Pischalnikov
Fermilab, Batavia, Illinois, USA

The PIP-II project at FNAL calls for a SRF pulsed proton driver linac to support the expanding neutrino physics program including DUNE/LBNF. The relatively low beam current and high quality factors called for in the design means that these cavities will be operated with small RF bandwidths, meaning that they will be sensitive to microphonics. Combined with a 20 Hz pulsed operational structure and the use of four different, complex cavity geometries means that resonance control will be extremely challenging. Work is ongoing at FNAL to develop active resonance stabilization techniques using fast piezoelectric tuners in support of PIP-II. These techniques as well as testing and development results using a prototype, dressed low-beta single-spoke cavity will be presented along with an outlook for future efforts.

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THPLR041

650 MHz Elliptical Superconducting RF Cavities for PIP-II Project

linac, cryomodule, controls, beam-transport

943

I.V. Gonin, E. Borissov, A. Grassellino, C.J. Grimm, V. Jain, S. Kazakov, V.A. Lebedev, A. Lunin, C.S. Mishra, D.V. Mitchell, T.H. Nicol, Y.M. Pischalnikov, G.V. Romanov, A.M. Rowe, N.K. Sharma, N. Solyak, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

The PIP-II 800 MeV linac employs 650 MHz elliptical 5-cell CW-capable cavities to accelerate up to 2 mA peak beam current of H⁻ in the energy range 185 - 800 MeV. The low beta (LB) βG = 0.61 portion should accelerate from 185 MeV-500 MeV using 33 LB dressed cavities in 11 cryomodules. The high beta (HB) βG = 0.92 portion of the linac should accelerate from 500 to 800 MeV using 24 HB dressed cavities in 4 cryomodules. The development of both LB and HB cavities is going on under IIFC collaboration. The development of LB cavity initiated at VECC Kolkatta and HB cavity is going at RRCAT, Indore. This paper present design methodology adopted starting from RF design to get mechanical dimensions of the RF cells and then explains dressing of the cavity for both low beta and high beta cavities. Further the tuner design and its integration to the dressed cavity is discussed. Paper also explains the salient design features of these dressed cavities.

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THPLR044

First Performance Test on the Superconducting 217 MHz CH Cavity at 4.2 K

linac, controls, operation, low-level-rf

953

F.D. Dziuba, M. Amberg, M. Basten, M. Busch, H. Podlech
IAP, Frankfurt am Main, Germany
W.A. Barth, M. Miski-Oglu
GSI, Darmstadt, Germany
W.A. Barth, M. Miski-Oglu
HIM, Mainz, Germany

Funding: HIM, GSI, BMBF Contr. No. 05P15RFRBA, EU Project MYRTE
At the Institute for Applied Physics (IAP) of Frankfurt University a superconducting (sc) 217 MHz Crossbar-H-mode (CH) cavity with 15 accelerating cells and a gradient of 5.5 MV/m has been designed. The cavity is the key component of the demonstrator project at GSI which is the first stage to a new sc continuous wave (cw) linac for the production of Super Heavy Element (SHE) in the future. A successful and reliable beam operation of this first prototype will be a milestone on the way to the proposed linac. After fabrication at Research Instruments (RI) GmbH, Germany, the cavity without helium vessel has been commissioned at the new cryogenic test facility of the IAP with low level rf power at 4 K. The results of this first cold test will be presented in this contribution.

Poster THPLR044 [4.540 MB]

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THPLR048

Development of a Digital LLRF Control System at LNL

FPGA, controls, LLRF, radio-frequency

966

S. Pavinato, M. Betti, D. Bortolato, F. Gelain, D. Marcato, D. Pedretti
INFN/LNL, Legnaro (PD), Italy
M.A. Bellato, R. Isocrate
INFN- Sez. di Padova, Padova, Italy
M. Bertocco
UNIPD, Padova (PD), Italy

The new Low-Level Radio Frequency (LLRF) control system for linear accelerator at Legnaro National Laboratories (LNL) of INFN is presently being commissioned. A digital Radio Frequency (RF) controller was implemented. Its goal is to stabilize the amplitude, the phase and the frequency of the superconducting cavities of the Linac. The resonance frequency of the low beta cavities is 80 MHz, while medium and high beta cavities resonate at 160 MHz. Each RF controller controls at the same time eight different cavities. The hardware complexity of the RF controller (RF IOC) is reduced by adopting direct RF sampling and the RF to baseband conversion method. The main hardware components are RF ADCs for the direct undersampling of the signals picked up from cavities, a Xilinx Kintek 7 FPGA for the signal processing and DACs for driving the power amplifiers and hence the cavities. In the RF IOC the serial communication between FPGA and ADCs and between FPGA and DACs is based on JESD204b standard. An RF front-end board (RFFE) is placed between cavities and the RF IOC. This is used to adapt the power level of the RF signal from the cavities to the ADCs and from the DACs to the power amplifiers. This paper addresses the LLRF control system focusing on the hardware design of the RF IOC and RFFE boards and on the first test results carried out with the new controller.

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THPLR050

IFMIF RFQ Module Characterization via Mechanical and RF Measurements

rfq, controls, alignment, linac

972

L. Ferrari, A. Palmieri, A. Pisent
INFN/LNL, Legnaro (PD), Italy
R. Dima, A. Pepato, A. Prevedello, E. Udup
INFN- Sez. di Padova, Padova, Italy

The RFQ of the IFMIF/EVEDA project is a 9.9 m long cavity able to accelerate a 130 mA deuteron beam from the input energy of 100 keV to the output energy of 5 MeV. Such RFQ operates at the frequency of 175 MHz and is composed of 18 mechanical modules approximately 0.55 m long each. The RFQ realization involves the I.N.F.N. Sections of Padova, Torino and Bologna, as well as the Legnaro National Laboratories (L.N.L.). The metrological measurements via CMM (Coordinate Measuring Machine) provided to be a very effective tool both for quality controls along the RFQ production phases and in the reconstruction of the cavity geometric profile for each RFQ module. The scans in the most sensitive regions with respect to RF frequency, such as modulation, tips, base-vane width and vessel height provided the values of the cavity deviations from nominal geometry to be compared with design physic-driven tolerances and with RF measurements. Moreover, the comparison between mechanical and RF measurements suggests a methodology for the geometric reconstruction of the cavity axis and determines the final machining of the end surfaces of each module in view of the coupling with the adjacent ones. In this paper a description of the meteorological procedures and tests and of the RFQ along its production and assembly phases will be described.

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THPLR051

High-Power RF Test of IFMIF-EVEDA RFQ at INFN-LNL

rfq, controls, operation, vacuum

975

E. Fagotti, L. Antoniazzi, M.G. Giacchini, F. Grespan, M. Montis, A. Palmieri
INFN/LNL, Legnaro (PD), Italy

A partial test at full power and CW duty cycle will be performed at INFN-LNL on the last elements of the IFMIF RFQ, approximately two meters of structure, using a specific electromagnetic boundary element on the low energy end. The aim is to reach, in the RFQ coupled with its power coupler system, after an adequate period of conditioning, cw operation at nominal field level (132 kV between electrodes) for at least two hours without breakdown. The description of the experimental setup and procedure, as well as the main results of the conditioning procedure will be reported in this paper.

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THPLR054

Recent RF and Mechanical Developments for the ESS RFQ

rfq, operation, vacuum, simulation

978

N. Misiara, A. Albéri, G. Bourdelle, A.C. Chauveau, D. Chirpaz-Cerbat, M. Desmons, A.C. France, M. Lacroix, P.-A. Leroy, J. Neyret, G. Perreu, O. Piquet, B. Pottin, H. Przybilski, N. Sellami
CEA/IRFU, Gif-sur-Yvette, France

The ESS Radio-Frequency Quadrupole (RFQ) is a 4-vane resonant cavity designed at the frequency of 352.21 MHz frequency. It must accelerate and bunch a 70 mA proton beams from 75 keV to 3.62 Mev of energy with a 4% duty cycle. The current 3D design evolved and is currently divided in 5 segments for a total length of 4.54 m. This paper presents a complete radiofrequency (RF) analysis using the ANSYS Multiphysics 3D RF simulating code HFSS and a RFQ 4-wire transmission line model (TLM). It describes the integrated cooling strategy based on a coupling between the RF power losses and the thermo-mechanical physics in order to allow a proper RFQ tuning once under operation.

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THPLR059

Status of a 325 MHz High Gradient CH - Cavity

linac, ion, operation, resonance

982

A. Almomani, U. Ratzinger
IAP, Frankfurt am Main, Germany

Funding: BMBF with contract number 05P12RFRB9
The reported linac developments aim on compact ion accelerators and on an increase of the effective accelerat-ing field (voltage gain per meter). Within a funded pro-ject, a high gradient Crossbar H-type CH-cavity operat-ed at 325 MHz was developed and successfully built at IAP-Frankfurt. The effective accelerating field for this cavity is expected to reach about 13.3 MV/m at a beam energy of 12.5 AMeV, corresponding to β=0.164. The results from this cavity might influence the later energy upgrade of the Unilac at GSI Darmstadt. The aim is a compact pulsed high current ion accelerator for significantly higher energies up to 200 AMeV. Detailed investigations for two different types of copper plating (high lustre and lustre less) with respect to the high spark limit will be performed on this cavity. The 325 MHz GSI 3 MW klystron test stand is best suited for these investigations. Additionally, operating of normal conducting cavities for the case of very short RF pulses will be discussed at cryogenic temperature.

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THPLR060

Experience with the Conditioning of Linac4 RF Cavities

vacuum, linac, DTL, coupling

985

S. Papadopoulos, F. Gerigk, J.-M. Giguet, J. Hansen, J. Marques Balula, A.I. Michet, S. Ramberger, N. Thaus, R. Wegner
CERN, Geneva, Switzerland

Linac4, the future H⁻ injector of the PS complex at CERN has reached the hardware and beam commissioning phase. This paper summarizes the experience gained in RF conditioning of the DTL, CCDTL and PIMS cavities. The behaviour in conditioning of these cavities strongly depends on the cavity type and assembly conditions. Examples of conditioning history and vacuum measurements before, during and after conditioning are discussed.

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THPLR061

Research on a Two-beam Type Drift Tube Linac

ion, DTL, heavy-ion, acceleration

989

L. Lu, C.X. Li, W. Ma, L.B. Shi, L.P. Sun, X.B. Xu, H.W. Zhao
IMP/CAS, Lanzhou, People's Republic of China
T.L. He
USTC/NSRL, Hefei, Anhui, People's Republic of China
L. Yang
USTC, Hefei, Anhui, People's Republic of China

The very high intense heavy-ion beam is a high attraction for heavy ion researches and heavy-ion applications, but it is limited by heavy-ion production of ion source and space-charge-effect in acceleration. There is one way, accelerating several heavy-ion beams in one cavity at same time and funneling them, which could achieve the acceleration of very high intense heavy-ion beam with existing ion source and accelerating technology. In this paper, we will introduce our designs, calculations and simulations of a 2-beam type drift tube linac.

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THPLR063

RF Design of a Deuteron Beam RFQ

rfq, dipole, simulation, operation

996

C.X. Li, W.P. Dou, Y. He, F.F. Wang, Z.J. Wang, X.B. Xu, Z.L. Zhang
IMP/CAS, Lanzhou, People's Republic of China

In a material irradiation facility in IMP, a RFQ is required for accelerating deuteron beam from 20 keV/u to 1.52 MeV/u. The structure design of the RFQ is drawing on the experience of the RFQ of Injector II of China ADS LINAC. Four-vane structure is adopted and the operation frequency is 162.5 MHz. Inter vane voltage is 65 kV and the Kilpatrick factor is 1.4. Π-mode stabilizing loops are used to move the dipole modes away from the working mode. Slug tuners are used to compensate for capacitance errors induced by machining. Cutbacks and end plate are modified to reach a reasonable field flatness. After the structure design and optimization, the simulation results of the cavity frequency is 162.459 MHz, the power loss is 10⁹ kW. The multiphysics simulations are also performed to determine the frequency shift caused by the shift of the cooling water temperature.

Poster THPLR063 [0.971 MB]

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THPLR066

Preparation and Installation of IFMIF-EVEDA RFQ at Rokkasho Site

rfq, alignment, coupling, vacuum

1005

E. Fagotti, L. Antoniazzi, A. Baldo, A. Battistello, P. Bottin, L. Ferrari, M.G. Giacchini, F. Grespan, M. Montis, A. Pisent, D. Scarpa
INFN/LNL, Legnaro (PD), Italy
D. Agguiaro, A.G. Colombo, A. Pepato, L. Ramina
INFN- Sez. di Padova, Padova, Italy
F. Borotto Dalla Vecchia, G. Dughera, G. Giraudo, E.A. Macri, P. Mereu, R. Panero
INFN-Torino, Torino, Italy

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 pre-assembled, aligned and vacuum tested at INFN-LNL and then shipped to Rokkasho (Japan). At Rokkasho site a series of test were performed in order to verify the effect of the shipment on the cavity. The assembly debug, shipment equipment and the sequence of operations are described in this paper.

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THPLR067

Series Production of the RF Power Distribution for the European XFEL

klystron, coupling, cryogenics, status

1008

S. Choroba, V.V. Katalev
DESY, Hamburg, Germany
E.M. Apostolov
Technical University of Sofia, Sofia, Bulgaria

The RF power distribution for the European XFEL allows for individual RF power for the 808 superconducting cavities of the European XFEL. It consists of a number of elements, not only waveguide components, but also girders, cables or cooling systems. The production of the RF distribution consists of several tasks. In order to deal with the schedule of the entire project a detailed planning, organization and monitoring of the series production of the RF power distribution was required. This paper describes the RF power distribution layout and the series production process.

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THPLR069

Quality Factor Measurement Method Using Multi Decay Time Constants on Cavity

pick-up, superconducting-cavity, coupling, cryomodule

1011

J.W. Kim, H. Kim
IBS, Daejeon, Republic of Korea

Quality factor measurement method using multi decay time constants on superconducting cavity is suggested. In most cases of vertical test, one decay time constant is measured around critical coupling and coupling constants are measured using forward and reflected rf power to get intrinsic quality factor. We use multi decay time constants method to measure the quality factor, which uses three decay time constants. Two more switches before and after the cavity are added to the measurement system. Decay time constants are measured by switching off the rf power switch in front of rf source, the forward power switch in front of input power coupler, and then the pickup power switch behind the pickup coupler, respectively, at the same power of steady state.

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THPLR074

N-Doped Niobium Accelerating Cavities: Analyzing Model Applicability

niobium, electron, vacuum, embedded

1014

R.G. Eichhorn, N.A. Stilin
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
W. Weingarten
CERN, Geneva, Switzerland

So-called Nitrogen-doped cavities show a rather strange field dependent behavior of the surface resistance. We had come up with a rather straightforward two fluid model description of the Q-slope in the low and high field domains in an earlier publication based on one dataset of a cavity. In this contribution we report on successfully applying this model to other cavity performance data as well as cases were the model fails.

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FR1A05

Development of a Muon Linac for the G-2/EDM Experiment at J-PARC

rfq, acceleration, linac, emittance

1037

M. Otani, N. Kawamura, T. Mibe, F. Naito, M. Yoshida
KEK, Tsukuba, Japan
K. Hasegawa, Y. Kondo
JAEA, Ibaraki-ken, Japan
N. Hayashizaki
RLNR, Tokyo, Japan
T. Ito
JAEA/J-PARC, Tokai-mura, Japan
Y. Iwashita
Kyoto ICR, Uji, Kyoto, Japan
Y. Iwata
NIRS, Chiba-shi, Japan
R. Kitamura
University of Tokyo, Tokyo, Japan
N. Saito
J-PARC, KEK & JAEA, Ibaraki-ken, Japan

Precision measurements of the muon's anomalous magnetic moment (g-2) and electric dipole moment (EDM) are one of the effective ways to test the standard model. An ultra-cold muon beam is generated from a surface muon beam by a thermal muonium production and accelerated to 300 MeV/c by a linac. The muon linac consists of an RFQ, an inter-digital IH, a Disk And Washer structure, and a disk loaded structure. The ultra-cold muons will have an extremely small momentum spread of 0.3 % with a normalized transverse emittance of around 1.5 pi mm-mrad. The design and status of the muon linac at J-PARC will be presented.

Slides FR1A05 [13.154 MB]

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FR2A01

Status of the PAL-XFEL

undulator, FEL, linac, gun

1042

H.-S. Kang, D.E. Kim, K.W. Kim, I.S. Ko, T.-Y. Koo, H.-S. Lee, K.-H. Park
PAL, Pohang, Kyungbuk, Republic of Korea

The construction of the PAL-XFEL was completed at the end of 2015 and the FEL commissioning started from the beginning of 2016. The commissioning aims for the lasing of 0.5 nm FEL in the first campaign by July 2016, and for the lasing of 0.1 nm hard X-ray FEL in the second campaign by December 2016. The commissioning results of the 0.5 nm FEL lasing will be presented.

Slides FR2A01 [92.474 MB]

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