IPAC2017 - List of Keywords (SRF)

Paper	Title	Other Keywords	Page
MOYBA1	The Future of Superconducting Technology for Accelerators	collider, cavity, superconducting-magnet, linear-collider	19
	A. Yamamoto KEK, Ibaraki, Japan
	Superconducting magnets and RF cavities are widely used in accelerators, and future accelerator projects heavily rely on this technology. There may be several questions on the future of the SC technology, concerning the feasibility of very high field dipoles (~15 T or more), possible technology evolution(s) with new materials, operation at higher temperature, and final sustainability of the technology in terms of helium procurement. The talk will cover a brief history/achievements and some interesting (future) developments, partly or fully answering these question.
	Slides MOYBA1 [25.792 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOYBA1
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MOOCA2	First Results From New Single-Cell Nb3Sn Cavities Coated at Cornell University	cavity, niobium, factory, radio-frequency	40
	D.L. Hall, J.J. Kaufman, M. Liepe, R.D. Porter, J. Sears Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Cavities coated with Nb3Sn at Cornell University demonstrate quality factors of >10¹⁰ at 4.2 K, outperforming equivalent niobium cavities by a factor of >30 at these bath temperatures. These quality factors have been maintained up to fields of 17-18 MV/m without significant Q-slope. Recently, new single-cell cavities have been added to the Cornell Nb3Sn programme in an effort to improve statistics and allow further exploration of the available parameter space. In this paper we report on the first results of these new cavities, as well as the latest performance from other cavities already in use on the programme. Furthermore, continuing work to optimise the coating procedure is reported on, and the latest understanding of the ideal coating profile is discussed.
	Slides MOOCA2 [10.366 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOOCA2
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MOPAB033	Optics Development and Trajectory Tuning of BERLinPro at Low Energies	linac, gun, booster, diagnostics	153
	B.C. Kuske, M. Abo-Bakr HZB, Berlin, Germany
	Funding: Work supported by the German Bundesministerium fr Bildung und Forschung, Land Berlin and grants of the Helmholtz Association The Berlin Energy Recovery Linac project has taken shape during the past year. The magnets have been set up in the newly constructed subterraneous hall; first electrons are expected in the SRF-gun test laboratory in June 2017. Starting in February 2018 the complete gun module will be transferred to the accelerator hall for the commissioning of BERLinPro. For the first months, operation is planned without further accelerating structures (booster and linac), due to delays in their fabrication. Several modes of operation are applicable at this early stage [1]. The available hardware is displayed and the adapted optics at 2.7 MeV and at 6.5 MeV (including the booster) are presented. The trajectory distortions under the influence of the earth magnetic field are studied. The concept for trajectory correction is outlined.
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MOPIK003	Improvement of the Photoemission Efficiency of Magnesium Photocathodes	cathode, gun, laser, cavity	500
	R. Xiang, A. Arnold, P.N. Lu, P. Michel, P. Murcek, J. Teichert, H. Vennekate HZDR, Dresden, Germany P. Patra IUAC, New Delhi, India
	Funding: The work is supported by the European Community under the FP7 programme (EuCARD-2) and by the German Federal Ministry of Education and Research (BMBF) grant 05K12CR1. To improve the quality of photocathodes is one of the critical issues in enhancing the stability and reliability of photo-injector systems. Presently the primary choice is to use metallic photocathodes for the ELBE SRF Gun-II to reduce the risk of contamination of the superconducting cavity. Magnesium has a low work function (3.6 eV) and shows high quantum efficiency (QE) up to 0.3 % after laser cleaning. The SRF Gun II with an Mg photocathode has successfully provided electron beam for ELBE users. However, the present cleaning process with a high intensi-ty laser (activation) is time consuming and generates unwanted surface roughness. This paper presents the investigation of alternative surface cleaning procedures, such as thermal treatment. The QE and topography of Mg samples after treatment are reported.
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MOPIK008	Numerical Studies on a Modified Cathode Tip for the ELBE Superconducting RF Gun	electron, cathode, gun, simulation	515
	E.T. Tulu, U. van Rienen Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany A. Arnold HZDR, Dresden, Germany
	Future light sources such as synchrotron radiation sources driven by an Energy Recovery Linac (ERL), Free Electron Laser (FEL) or THz radiation sources have in common that they require injectors, which provide high-brilliance, high-current electron beams in almost continuous operation. Thus, the development of appropriate highly brilliant electron sources is a central factor. A promising approach for this key component is provided by superconducting radiofrequency photoinjectors (SRF guns) []. Since 2007, the free-electron laser FELBE at HZDR successfully operates such a SRF gun under real conditions and equipped with all components []. Nevertheless, there are limitations caused by multipacting which should be overcome in order to further improve the gun []. One aspect in order to reach this aim lies in studying various modifications of the cathode tip [*]. This contribution will present the effectiveness of isosceles triangular grooves with respect to MP. Arnold, et al., NIM A, 593, 57, (2008). J. Teichert, et al., 2008 NSS/MIC, Dresden, Germany. * J. Teichert, et al., J. Phys.: Conf. Ser. 298(2011), 012008. **** E. T. Tulu, et al., IPAC2014, p652, Dresden, Germany.
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MOPVA005	Status of the Berlin Energy Recovery Linac Project BERLinPro	gun, linac, booster, cavity	855
	M. Abo-Bakr, W. Anders, K.B. Bürkmann-Gehrlein, A.B. Büchel, P. Echevarria, A. Frahm, H.-W. Glock, F. Glöckner, F. Göbel, B.D.S. Hall, S. Heling, H.-G. Hoberg, A. Jankowiak, C. Kalus, T. Kamps, G. Klemz, J. Knedel, J. Knobloch, J. Kolbe, G. Kourkafas, J. Kühn, B.C. Kuske, J. Kuszynski, D. Malyutin, A.N. Matveenko, M. McAteer, A. Meseck, C.J. Metzger-Kraus, R. Müller, A. Neumann, N. Ohm, K. Ott, E. Panofski, F. Pflocksch, J. Rahn, M. Schmeißer, O. Schüler, M. Schuster, J. Ullrich, A. Ushakov, J. Völker HZB, Berlin, Germany
	Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association. The Helmholtz-Zentrum Berlin is constructing the Energy Recovery Linac Prototype BERLinPro, a demonstration facility for the science and technology of ERLs for future light source applications. BERLinPro is designed to accelerate a high current (100 mA, 50 MeV), high brilliance (norm. emittance below 1 mm mrad) cw electron beam. We report on the project status. This includes the completion of the building and the installation of the first accelerator components as well as the assembly of the SRF gun and GunLab beam diagnostics, which are now ready for commissioning.
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MOPVA010	Setup and Status of an SRF Photoinjector for Energy-Recovery Linac Applications	gun, laser, cathode, emittance	865
	T. Kamps, D. Böhlick, A.B. Büchel, M. Bürger, P. Echevarria, A. Frahm, F. Göbel, S. Heling, A. Jankowiak, S. Keckert, H. Kirschner, G. Klemz, J. Knobloch, G. Kourkafas, J. Kühn, O. Kugeler, A.N. Matveenko, A. Neumann, N. Ohm-Krafft, E. Panofski, F. Pfloksch, S. Rotterdam, M.A.H. Schmeißer, M. Schuster, H. Stein, J. Ullrich, A. Ushakov, J. Völker HZB, Berlin, Germany I. Will MBI, Berlin, Germany
	Funding: The work is funded by the Helmholtz-Association, BMBF, the state of Berlin and HZB. The Superconducting RF (SRF) photoinjector programme for the energy-recovery linac (ERL) test facility BERLinPro sets out to push the brightness and average current limits for ERL electron sources by tackling the main challenges related to beam dynamics of SRF photoinjectors, the incorporation of high quantum efficiency (QE) photocathodes, and suppression of unwanted beam generation. The paper details the experimental layout of the SRF photoinjector and the gun test facility GunLab at Helmholtz-Zentrum Berlin.
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MOPVA036	High Average Brilliance Compact Inverse Compton Light Source	electron, gun, brilliance, laser	932
	K.E. Deitrick, J.R. Delayen, G.A. Krafft ODU, Norfolk, Virginia, USA J.R. Delayen, G.A. Krafft JLab, Newport News, Virginia, USA
	Funding: Partially authored by Jefferson Science Associates, LLC under U.S. DOE contract NO. DE-AC05-6OR23177. There exists an increasing demand for compact Inverse Compton Light Sources (ICLS) capable of producing substantial fluxes of narrow-band X-rays. While multiple design proposals have been made, compared to typical bremsstrahlung sources, most of these have comparable fluxes and improve on the brilliance within a 0.1% bandwidth by only a few orders of magnitude. By applying cw superconducting rf beam acceleration and rf focusing to produce a beam of small emittance and magnetic focusing to produce a small spot size on the order of a few microns at collision, the source presented here provides a 12 keV X-ray beam which outperforms other compact designs and bremsstrahlung sources. Compared to a bremsstrahlung source, the flux is improved by at least an order of magnitude and the average brilliance by six orders of magnitude. Surpassing other compact ICLS designs, the source presented here is attractive to a wide variety of potential users.
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MOPVA038	Manufacturing Status of the IFMIF LIPAc SRF Linac	cryomodule, vacuum, cavity, linac	939
	N. Bazin, P. Carbonnier, P. Contrepois, J. Plouin, B. Renard CEA/DSM/IRFU, France C. Boulch, A. Bruniquel, J.K. Chambrillon, G. Devanz, P. Hardy, H. Jenhani, N. N'Doye, O. Piquet, A. Riquelme, D. Roudier CEA/DRF/IRFU, Gif-sur-Yvette, France P. Charon, S. Chel, G. Disset, J. Relland CEA/IRFU, Gif-sur-Yvette, France D. Regidor, F. Toral CIEMAT, Madrid, Spain
	This paper gives the fabrication status of the IFMIF cryomodule. This cryomodule will be part of the Linear IFMIF Prototype Accelerator (LIPAc) whose construction is ongoing at Rokkasho, Japan. It is a full scale of one of the IFMIF accelerator, from the injector to the first cryomodule. The cryomodule contains all the necessary equipment to transport and accelerate a 125 mA deuteron beam from an input energy of 5 MeV up to the output energy of 9 MeV. It consists of a horizontal vacuum tank of around 6 m long, 3 m high and 2.0 m wide, which includes 8 superconducting HWRs for beam acceleration, working at 175 MHz and at 4.45 K, 8 Power Couplers to provide RF power to cavities up to 70 kW CW in LIPAc case and 200 kW CW in IFMIF case, and 8 Solenoid Packages as focusing elements.
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MOPVA039	Manufacturing and Validation Tests of IFMIF Low-Beta HWRs	cavity, cryomodule, operation, simulation	942
	G. Devanz, F. Éozénou, L. Maurice, P. Sahuquet, C. Servouin CEA/DSM/IRFU, France N. Bazin, P. Carbonnier, P. Charon, G. Disset, P. Hardy, E. Jacques, O. Piquet, D. Roudier CEA/IRFU, Gif-sur-Yvette, France J.K. Chambrillon, T. Percerou CEA/DRF/IRFU, Gif-sur-Yvette, France
	The IFMIF accelerator aims to provide an accelerator-based D-Li neutron source to produce high intensity high energy neutron flux to test samples as possible candidate materials to a full lifetime of fusion energy reactors. A prototype of the low energy part of the accelerator is under construction at Rokkasho in Japan. It includes one cryomodule containing 8 half-wave resonators (HWR) operating at 175 MHz .The first manufactured HWR has passed low power tests at 4.2K in vertical cryostat succesfully and exceeds the specifications. It has also been tested in the dedicated horizontal Sathori cryostat equiped with its cold tuning system. The serial production and qualification tests of the 8 cavities which will eventually equip the cryomodule are carried out in parallel. In this paper, we focus on the HWR preparation and test results and give a status of the manufacturing activities.
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MOPVA040	Status of the ESS Elliptical Cryomodules at CEA Saclay	cryomodule, cavity, cryogenics, vacuum	945
	P. Bosland, C. Arcambal, F. Ardellier, S. Berry, A. Bouygues, A. Bruniquel, E. Cenni, J.-P. Charrier, C. Cloué, G. Devanz, F. Éozénou, T. Hamelin, X. Hanus, P. Hardy, C. Marchand, O. Piquet, J. Plouin, J.P. Poupeau, T. Trublet CEA/DRF/IRFU, Gif-sur-Yvette, France G. Costanza Lund University, Lund, Sweden C. Darve ESS, Lund, Sweden P. Michelato INFN/LASA, Segrate (MI), Italy G. Olivier IPN, Orsay, France F. Peauger CEA/DSM/IRFU, France
	The first ESS prototype cryomodule with medium beta cavities named M-ECCTD is being assembled at CEA Saclay. The Q curves of the 4 cavities mounted inside the cryomodule are presented, and the four power couplers have been conditioned at high power before their assembly onto the cavity string. Completion of the M-ECCTD assembly outside clean room is in progress as well as the finalization of the RF power test stand preparation. RF power tests of the M-ECCTD will be performed during summer 2017. CEA is preparing the production of the ESS medium and high beta cryomodules of the series before the test of the M-ECCTD and the contracts for the procurement of the most critical components have already been signed
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MOPVA043	Assembly Preparation of the IFMIF SRF Cryomodule	cavity, solenoid, cryomodule, vacuum	954
	J.K. Chambrillon, N. N'Doye CEA/DRF/IRFU, Gif-sur-Yvette, France N. Bazin, P. Charon, G. Devanz, P. Hardy, O. Piquet, J. Plouin CEA/IRFU, Gif-sur-Yvette, France P. Contrepois, C. Servouin CEA/DSM/IRFU, France
	This article presents the preparation work performed by CEA for the assembly of the IFMIF Cryomodule. Before the shipping of the components to Japan many tests and trial assemblies has been realized on the CEA site of Saclay, France. The cryomodule, which is part of the Linear IFMIF Prototype Accelerator (LIPAc) under construction at Rokkasho in Japan, will be assembled there under the responsibility of F4E (Fusion for Energy) with CEA assistance. To fulfill the assembly of the cavity string, a cleanroom will be built at Rokkasho under the responsibility of QST.
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MOPVA046	120kW RF Power Input Couplers for BERLinPro	booster, cavity, coupling, linac	960
	B.D.S. Hall, V. Dürr, F. Göbel, J. Knobloch, A. Neumann HZB, Berlin, Germany
	The 50-MeV, 100-mA energy-recovery-linac (ERL) demonstration facility BERLinPro is currently undergoing construction at HZB. The high power injection system, that will deliver a beam at 6.5MeV, is split into a 1.4 cell SRF Photo injector and three Cornell-style 2-cell boosters. The injector and two of the booster cavities will provide about 2MeV each and must handle up to 220 kW of beam loading. New, cERL-based 115-kW high power couplers needed for the cavities' twin coupler system have begun manufacture. The design, optimization and manufacturing considerations of these couplers are presented.
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MOPVA048	Simulation of the Thermoelectrically Generated Magnetic Field in a SC Nine-Cell Cavity	cavity, simulation, operation, superconducting-RF	968
	J.M. Köszegi, J. Knobloch, O. Kugeler HZB, Berlin, Germany
	Several studies showed that thermocurrents generate a magnetic field in a horizontal cavity test assembly or cryomodul, which may get trapped during the supercon-ducting phase transition. The trapped flux causes additional dissipation in the order of 1 to 10 n' during operation and can therefore significantly degrade the quality factor in a TESLA cavity. We simulated the distribution of the generated magnetic field over the whole cavity-tank system for an asymmetric temperature distribution. The asymmetry allows the field to penetrate the RF surface which would be field free in the symmetric case. The calculated results complemented a direct measurement of trapped magnetic flux inside the cavity with a small number of field probes. Finally, the obtained data was combined with RF measurements in three passband modes to determine the overall distribution of trapped magnetic flux due to thermocurrents.
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MOPVA049	First Commissioning of an SRF Photo-Injector Module for BERLinPro	cavity, cathode, solenoid, linac	971
	A. Neumann, A. Burrill, D. Böhlick, A.B. Büchel, M. Bürger, P. Echevarria, A. Frahm, H.-W. Glock, F. Göbel, S. Heling, K. Janke, T. Kamps, S. Keckert, S. Klauke, G. Klemz, J. Knobloch, G. Kourkafas, J. Kühn, O. Kugeler, N. Ohm, E. Panofski, H. Plötz, S. Rotterdam, M. Schenk, M.A.H. Schmeißer, M. Schuster, H. Stein, Y. Tamashevich, J. Ullrich, A. Ushakov, J. Völker HZB, Berlin, Germany A. Matheisen, M. Schmökel DESY, Hamburg, Germany
	Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association. Helmholtz-Zentrum Berlin (HZB) is currently building an high average current superconducting ERL to demonstrate ERL operation with low normalized beam emittance of 1 mm·mrad at 100mA and short pulses of about 2 ps. For the injector section a series of SRF photoinjector cavities is being developed. The medium power prototype presented here features a 1.4 x λ/2 cell SRF cavity with a normal-conducting, high quantum efficiency CsK2Sb cathode, implementing a modified HZDR-style cathode insert. This injector potentially allows for 6 mA beam current at up to 3.5 MeV kinetic energy. In this contribution, the first RF commissioning results of the photo-injector module will be presented and compared to the level of performance during the cavity production and string assembly process.
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MOPVA050	Setup of a Spatially Resolving Vector Magnetometry System for the Investigation of Flux Trapping in Superconducting Cavities	cavity, niobium, experiment, radio-frequency	975
	B. Schmitz, K.Alomari. Alomari, J. Knobloch, O. Kugeler, J.M. Köszegi, Y. Tamashevich HZB, Berlin, Germany
	Flux trapping is the major contribution to the residual resistance of superconducting cavities. In order to gain a better understanding of the mechanisms involved and aiming at an eventual minimization of trapped flux, a measurement setup based on AMR sensors was devised that allows for monitoring the magnetic field vector at various positions near the cavity surface. First results of the efforts are presented.
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MOPVA052	Study on HOM Power Levels in the BESSY VSR Module	HOM, cavity, operation, resonance	982
	A.V. Tsakanian, H.-W. Glock, J. Knobloch, A.V. Vélez HZB, Berlin, Germany
	The BESSY VSR upgrade of the BESSY II light source represents a novel approach to simultaneously store of long (ca. 15ps) and short (ca. 1.5ps) bunches in the storage ring with the 'standard' user optics. This challenging goal requires installation of four new SRF cavities (2x1.5GHz and 2x1.75GHz) in a single module to minimize space requirements. These cavities are equipped with strong waveguide and beam tube HOM dampers necessary for stable operation. The expected HOM power and spectrum has been analyzed for the complete module. This study is performed for various BESSY VSR bunch filling patterns with 300 mA beam current. In the module different cavity arrangements are analyzed to reach the optimal operation conditions with equally distributed power portions in warm HOM loads and tolerable beam coupling impedance.
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MOPVA053	The SRF Module Developments for BESSY VSR	HOM, cavity, synchrotron, damping	986
	A.V. Vélez, H.-W. Glock, F. Glöckner, B.D.S. Hall, J. Knobloch, A. Neumann, P. Schnizer, E. Sharples, A.V. Tsakanian HZB, Berlin, Germany
	Helmholtz-Zentrum Berlin is developing BESSY VSR, a novel upgrade of the BESSY II facility to provide highly flexible pulse lengths while maintaining the flux and brilliance. The project goal is to simultaneously circulate both standard (some 10 ps long) and short (ps and sub-ps long) pulses offering the BESSY user community picosecond dynamics and high-resolution experiments. The concept relies on the installation of high-voltage SRF cavities operating at the 3rd and 3.5th harmonic whereby the beating of the two frequencies provides RF buckets for long and short bunches. Since these cavities will operate in CW and with high beam current (Ib=300 mA), the cavity design represents a challenging goal. In addition the need to avoid coupled bunch instabilities (CBI's), the installation of the VSR Cryomodule must fit in one of the available 4-m long low beta straights. To address the technological and engineering challenges techniques such as waveguide-damped cavities have been developed. First prototypes have been produced. In this paper, the present SRF developments are presented, including the cavities, high power couplers, higher-order mode absorbers and the cryomodule design.
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MOPVA055	Upgrade of the Capture Section of the S-DALINAC Injector	cavity, electron, operation, accelerating-gradient	993
	D.B. Bazyl, H. De Gersem, W.F.O. Müller TEMF, TU Darmstadt, Darmstadt, Germany
	Funding: This work is supported by the DFG through GRK 2128. In order to reduce the energy spread of the recirculated beam, the injector of the S-DALINAC needs to be optimized, because the non-isochronous recirculation cannot correct for errors originating from the injector linac. For the S-DALINAC, spatial restrictions suggest the use of SRF technology for the capture section. In this work, we consider various SRF cavities with an operating frequency of 3 GHz for a possible upgrade of the capture section of the S-DALINAC. The first results of the RF and beam dynamics simulations for the proposed options are presented in this paper.
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MOPVA057	Structural Investigations of Nitrogen-Doped Niobium for Superconducting RF Cavities	niobium, vacuum, radio-frequency, cavity	996
	M. Major, L. Alff, M. Arnold, J. Conrad, S. Flege, R. Grewe, N. Pietralla TU Darmstadt, Darmstadt, Germany F. Hug IKP, Mainz, Germany
	Funding: Work supported by BMBF through 05H15RDRBA. Niobium is the standard material for superconducting RF (SRF) cavities. Superconducting materials with higher critical temperature or higher critical magnetic field allow cavities to work at higher operating temperatures or higher accelerating fields, respectively. Enhancing the surface properties of the superconducting material in the range of the penetration depth is also beneficial. One direction of search for new materials with better properties is the modification of bulk niobium by nitrogen doping. In the Nb-N phase diagram the cubic delta-phase of NbN has the highest critical temperature (16 K). Already slight nitrogen doping of the alpha-Nb phase results in higher quality factors.* Nb samples will be N-doped at the refurbished UHV furnace at IKP Darmstadt. The first results on the structural investigations of the processed Nb samples at the Materials Research Department of TU Darmstadt are presented. * Grassellino et al., Proc. SRF2015, MOBA06, 48.
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MOPVA062	Test, Diagnostics and Computed Tomographic Inspection of a Large Grain 3.9 GHz Prototype Cavity	cavity, niobium, diagnostics, radio-frequency	1011
	M. Bertucci, A. Bignami, A. Bosotti, J.F. Chen, C.G. Maiano, P. Michelato, L. Monaco, R. Paparella, P. Pierini, D. Sertore INFN/LASA, Segrate (MI), Italy G. Ciovati, G.R. Myneni JLab, Newport News, Virginia, USA C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy
	A large grain 3.9 GHz prototype cavity made of RRR = 10⁵ ±10 has been tested at LASA. The cavity suffered of quench at moderate levels of accelerating field, for all nine fundamental pass-band modes. Several diagnostic techniques have been employed to determine the quench positions, which occur close to significant grain-boundary steps, visible from the external cavity surface. The cavity has been scanned with a high resolution X-ray tomographic machine, confirming the existence of remarkable topographic features on the inner RF surface at the suspected quench positions. A strategy for a future surface treatment for recover the cavity performances is here presented.
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MOPVA064	Multipacting Study in INFN-LASA ESS Medium-Beta Cavity	cavity, simulation, site, electron	1019
	J.F. Chen, M. Bertucci, A. Bosotti, P. Michelato, L. Monaco, C. Pagani, R. Paparella, D. Sertore INFN/LASA, Segrate (MI), Italy S. Pirani ESS, Lund, Sweden
	We present Multipacting studies in ESS Medium-Beta cavities of INFN-LASA design with both simulation and experimental results. The simulation on the ideal cavity shape with both FishPact and MultiPac2.1 codes shows that multipacting appears in a very small region near equator where the weld seam exists. A simulation with more realistic cavity shape considering the weld seam at cell equators has also been done out showing similar results for end cell but a remarkable mitigation for inner cell. During the vertical tests at LASA, Multipacting is frequently observed but with no limitation to the cavity performance, which well confirms the MP predicted by the simulations.
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MOPVA074	Fabrication of Superconducting QWR at MHI-MS	cavity, linac, superconducting-RF, niobium	1037
	N. Shigeoka, H. Hara, A. Miyamoto, K. Sennyu, T. Yanagisawa MHI-MS, Kobe, Japan O. Kamigaito, K. Ozeki, N. Sakamoto, K. Suda, Y. Watanabe, K. Yamada RIKEN Nishina Center, Wako, Japan
	Mitsubishi Heavy Industries Mechatronics Systems, Ltd. (MHI-MS), a subsidiary campany of MHI, took over MHI's accelerator business on October 1, 2015, and has been developing the business. MHI-MS is manufacturing the prototype Superconducting QWR for RIKEN Superconducting linac project. MHI-MS has dedicated surface treatment facilities for superconducting cavities, the QWR will be treated using this facilities. In this presentation, recent progress will be reported.
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MOPVA079	A 166.6 MHz Superconducting RF System for the HEPS Storage Ring	cavity, HOM, LLRF, injection	1049
	P. Zhang, H.X. Hao, T.M. Huang, Z.Q. Li, H.Y. Lin, F. Meng, Z.H. Mi, Y. Sun, G.W. Wang, Q.Y. Wang, X.Y. Zhang IHEP, Beijing, People's Republic of China
	Funding: This work has been supported by HEPS-TF project and partly by Pioneer 'Hundred Talents Program' of Chinese Academy of Science. A superconducting 166.6 MHz quarter-wave β=1 cavity was recently proposed for the High Energy Photon Source (HEPS), a 6 GeV kilometer-scale light source. Four 166.6 MHz cavities will be used for main acceleration in the newly planned on-axis beam injection scheme realized by a double-frequency RF system. The fundamental frequency, 166.6 MHz, was dictated by the fast injection kicker technology and the preference of using 499.8 MHz SC RF cavity as the third harmonic. Each 166.6 MHz cavity will be operated at 4.2 K providing 1.2 MV accelerating voltage and 150 kW of power to the electron beam. The input coupler will use single-window coaxial type graded up to 200 kW CW power. Each cavity will be equipped with a 200 kW solid-state amplifier and digital low-level RF system. This paper will describe the 166.6 MHz RF system with a focus on the design and optimization of the RF cavity and its ancillaries, the LLRF system and the status of the solid-state amplifiers.
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MOPVA082	PLASMA PROCESSING R&D OF THE 1.3 GHZ SINGLE-CELL SRF CAVITY AT IMP	plasma, cavity, accelerating-gradient, electromagnetic-fields	1055
	L. Yang, L. Chen, Y. He, S.C. Huang, C.X. Li, C.L. Li, Y.M. Li, L. Lu, A. Shi, L.P. Sun, A.D. Wu, S.H. Zhang IMP/CAS, Lanzhou, People's Republic of China
	The China-Accelerator Driven Sub-critical System (C-ADS) injector II has already commissioned with a CW 1 mA and a pulsed 10 mA proton beam. The beam energy achieved 10 MeV. The superconducting linac (SCL) is routinely operating at 4.7 MV/m average accelerating gradient in the low-beta cryomodules. Field emission and surface contaminants of the SCL limit the gradient in-crease in the beam commissioning. Hence, in order to increase the SCL accelerating gradient, reduce field emis-sion and remove surface pollutants, in-situ plasma pro-cessing R&D in a 1.3 GHz single-cell SRF cavity has being studied. In this paper, the current effort of plasma processing R&D in a 1.3 GHz single-cell SRF cavity will be presented in details and the future plan will be also reported.
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MOPVA090	ESS Superconducting RF Collaboration	cryomodule, cavity, linac, proton	1068
	C. Darve, H. Danared, N. Elias, N.F. Hakansson, M. Lindroos, C.G. Maiano, F. Schlander ESS, Lund, Sweden F. Ardellier, P. Bosland CEA/DRF/IRFU, Gif-sur-Yvette, France S. Bousson, G. Olry IPN, Orsay, France M. Ellis, A.E. Wheelhouse STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom L. Hermansson, R.J.M.Y. Ruber Uppsala University, Uppsala, Sweden P. Michelato, D. Sertore INFN/LASA, Segrate (MI), Italy
	The European Spallation Source (ESS) project is a neutron-scattering facility, currently under construction by a partnership of at least 17 European countries, with Sweden and Denmark as host nations. The ESS was designated a European Research Infrastructure Consortium, or ERIC, by the European Commission in October of 2015. Scientists and engineers from 50 different countries are members of the workforce in Lund who participate in the design and construction of the European Spallation Source. In complement to the local workforce, the superconducting RF linear accelerator is being prototyped and will be constructed based on a collaboration with European institutions: CEA-Saclay, CNRS-IPN Orsay, INFN-LASA, STFC-Daresbury, Uppsala and Lund Universities. After a description of the ESS collaborative project and its in-kind model for the SRF linac, this article will introduce the linac component first results.
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MOPVA095	First RF Performance Results for the DQW Crab Cavities to be Tested in the CERN SPS	cavity, monitoring, operation, cryomodule	1077
	A. Castilla, R. Calaga, O. Capatina, K.M. Dr. Schirm, K.G. Hernández-Chahín, A. Macpherson, N.C. Shipman, K. Turaj CERN, Geneva, Switzerland I. Ben-Zvi BNL, Upton, Long Island, New York, USA G. Burt, J.A. Mitchell Lancaster University, Lancaster, United Kingdom K.G. Hernández-Chahín DCI-UG, León, Mexico N.C. Shipman Cockcroft Institute, Lancaster University, Lancaster, United Kingdom N.C. Shipman UMAN, Manchester, United Kingdom
	As part of the High Luminosity LHC (HL-LHC) project strategy, crab cavity correctors shall be installed around CMS and ATLAS experiments of the LHC. To accommodate the different crossing angle planes, two distinct cavity designs have been selected: the RF Dipole (RFD) and the Double Quarter Wave resonator (DQW). CERN has fabricated two double quarter wave resonators (DQW_SPS), for validation with a proton beam at the CERN SPS accelerator. Standard superconducting rf surface preparation protocols have been applied to the two bulk niobium cavities, followed by cryogenic testing in a vertical cryostat at CERN's SM18 facility. The performance results obtained after the first bare cavity tests for cavities DQW_SPS₀01 and DQW_SPS₀02 are shown in this paper, and include Q0 vs Vt curves, Lorentz Force Detuning (LFD) analyses and pressure sensitivity of a higher order mode.
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MOPVA097	Finite Element Analysis on Helium Discharge from Superconducting RF in the Storage Ring Tunnel	simulation, cryogenics, cavity, distributed	1085
	J.-C. Chang, F. Z. Hsiao, J.C. Huang, S.P. Kao, H.C. Li, W.R. Liao, C.Y. Liu, H.H. Tsai, Z.-D. Tsai NSRRC, Hsinchu, Taiwan
	Liquid helium for transferring cooling power from the cryogenic plant to the magnets and SRF cavities had been widely applied on the advanced large superconducting particle accelerators. For requirements of high stable and reliable operation, many efforts have been put into the improvement and modification of the cryogenic system. However, personnel safety is another critical issue of the cryogenic system. Once large liquid helium was released on the atmospheric tunnel, the volume of helium will expand several hundred times and cause oxygen deficiency in short time due to sudden change of helium density. In this study, we applied numerical simulation to analyze helium discharge through a SRF cavity in the TPS tunnel.
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MOPVA098	Strategy Towards Non-Interrupted Operation of Superconducting Radio Frequency Modules at NSRRC	operation, vacuum, cryogenics, cavity	1088
	Ch. Wang, F.Y. Chang, L.-H. Chang, M.H. Chang, J. Chen, L.J. Chen, F.-T. Chung, M.-C. Lin, Z.K. Liu, C.H. Lo, C.L. Tsai, M.-S. Yeh, T.-C. Yu NSRRC, Hsinchu, Taiwan
	Two modern 3rd generation light sources, the well-developed 1.5-GeV Taiwan Light Source (TLS) and the new constructed 3-GeV Taiwan Photon Source (TPS), are now in routine operation. Both storage rings are powered by the superconducting RF (cavity) modules, one CESR-type SRF module for the TLS since 2005 and two KEKB-type SRF modules for the TPS since 2014. Thanks to continuous efforts, the operational reliability of SRF modules at NSRRC is now compatible or better in comparison with the best operation record of room temperature cavities ever achieved at TLS (1992-2004). How to improve the long term availability but hold the achieved reliability of SRF modules such as to maximize the available annual user beam time, especially, under requirements on high RF power operation, become a new operational challenge, especially for the SRF modules at TPS which is now routinely operated with a forward RF power around 150-kW individually and expected to push to 300-kW in the coming future. Here we report our strategy and achievement to minimize long term interrupt of SRF operation owing to regular full-thermal cycling and annual maintenance of cryogenic plant.
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MOPVA099	The Study of Electromagnet Compensated High Power Ferrite Circulator Operation With Superconducting RF Cavity	cavity, klystron, operation, vacuum	1091
	T.-C. Yu, F.Y. Chang, L.-H. Chang, M.H. Chang, L.J. Chen, F.-T. Chung, M.-C. Lin, Z.K. Liu, C.H. Lo, C.L. Tsai, M.H. Tsai, Ch. Wang, M.-S. Yeh NSRRC, Hsinchu, Taiwan
	In a high power RF system for accelerator application, the circulator is very important for protecting klystron or IOT from damage due to high reflection power from the cavity. When there is no beam current passing through the superconducting RF cavity of the accelerator, almost 100% RF power will be reflected from the cavity even the cavity is on resonance. The circulator shall be able to forward the reflected power to the load and remain good matching and isolation condition between ports at klystron and the cavity. However, for a ferrite material based circulator, the magnetic field within circulator would be temperature dependent which would cause the variation of input return loss and isolation between ports. Additional DC current driving electromagnet field is thus re-quired for compensating the temperature variation. Even with the compensating DC current, the circulator is still not ideal for practical operation especially when the performance of the circulator is strongly phase dependent. The phenomenon observed in actual operation with one set of SRF systems in NSRRC is thus reported in this article.
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MOPVA102	Modeling the Low Level RF Response on the Beam during Crab Cavity Quench	cavity, simulation, luminosity, klystron	1098
	R. Apsimon, G. Burt, A.C. Dexter Cockcroft Institute, Lancaster University, Lancaster, United Kingdom R.B. Appleby UMAN, Manchester, United Kingdom P. Baudrenghien, K.N. Sjobak CERN, Geneva, Switzerland
	The High Luminosity Upgrade for the LHC (HL-LHC) relies on crab cavities to compensate for the luminosity reduction due to the crossing angle of the colliding bunches at the interaction points. In this paper we present the simulation studies of cavity quenches and the impact on the beam. The cavity voltage and phase during the quench is determined from a simulation in Matlab and used to determine the impact on the beam from tracking simulations in SixTrack. The results of this study are important for determining the required machine protection and interlock systems for HL-LHC.
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MOPVA104	Physical Vapour Deposition of NbTiN Thin Films for Superconducting RF Cavities	cathode, power-supply, target, superconductivity	1102
	S. Wilde, B. Chesca Loughborough University, Loughborough, Leicestershire, United Kingdom E. Alves AssociaÃ§Ã£o EURATOM/IST, Instituto de Plasmas e FusÃ£o Nuclear, Lisboa, Portugal N.P. Barradas Universidade de Lisboa, Instituto Superior Técnico, Bobadela, Portugal A.N. Hannah, O.B. Malyshev, N. Pattalwar, S.M. Pattalwar, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom G.B.G. Stenning STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	The production of superconducting coatings for radio frequency cavities is a rapidly developing field that should ultimately lead to acceleration gradients greater than those obtained by bulk Nb RF cavities. The use of thin films made from superconductors with thermodynamic critical field, H_C>H_C^Nb, allows the possibility of multilayer superconductor ' insulator ' superconductor (SIS) films and accelerators that could operate at temperatures above the 2 K typically used. SIS films theoretically allow increased acceleration gradient due to magnetic shielding of underlying superconducting layers [1] and higher operating temperature can reduce cost [2]. High impulse magnetron sputtering (HiPIMS) and pulsed DC magnetron sputtering processes were used to deposit NbTiN thin films onto Si(100) substrate. The films were characterised using scanning electron microscopy (SEM), x-ray diffraction (XRD), Rutherford back-scattering spectroscopy (RBS) and a four-point probe.
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MOPVA114	Materials Characterization for SRF Cavities: Gaining Insight Into Nb3Sn	ion, interface, cavity, electron	1111
	J. Tuggle Virginia Polytechnic Institute and State University, Blacksburg, USA G.V. Eremeev, A.D. Palczewski, C.E. Reece JLab, Newport News, Virginia, USA M.J. Kelley, U. Pudasaini The College of William and Mary, Williamsburg, Virginia, USA
	Funding: JLab work supported by U.S. DOE Contract No. DE-AC05-06OR23177. Work at William & Mary and Virginia Tech supported by the Office of High Energy Physics, U.S. Department of Energy grant DE-SC-0014475 Although SRF accelerators are an invaluable research tool they can be painfully expensive to construct and operate at the current level of SRF technology. This cost is significantly due to the necessity to operate at a temperature of only 2K. Considerable research is currently underway into next generation SRF cavity technologies such as Ndoping and Nb3Sn coating. Both of these technologies will lower the cryogenic load of accelerators, correspondingly lowering both construction and operating costs. However, current understanding of either technology is incomplete and in order to elucidate the underlying mechanisms there is a need to push current characterization methods forward. In this work, ion beam techniques (e.g. focused ion beam (FIB)), and electron backscatter diffraction (EBSD) were applied to help understand Nb3Sn coating mechanisms. This presentation will focus on characterization, providing examples of EBSD work, along with discussion of some of the issues encountered while trying to produce high quality EBSD data.
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MOPVA115	Status and Challenges of Vertical Electro-Polishing R&D at Cornell	cathode, cavity, niobium, linac	1115
	F. Furuta, M. Ge, T. Gruber, D.L. Hall, J.J. Kaufman, M. Liepe, R.D. Porter, J. Sears Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi MGH, Hyogo-ken, Japan T.D. Hall, M.E. Inman, R. Radhakrishnan, S.T. Snyder, E.J. Taylor Faraday Technology, Inc., Clayton, Ohio, USA H. Hayano, S. Kato, T. Saeki KEK, Ibaraki, Japan
	Advanced Vertical Electro-Polishing (VEP) R&D for SRF Niobium cavities continues at Cornell's SRF group. One focus of this work is new EP cathode development in collaboration with KEK and Marui Galvanizing Co. Ltd (Marui) in Japan, and another focus is on HF free or acid free VEP protocols in collaboration with Faraday Technology Inc. The outcomes of these activities could be a significant cost reduction and an environmentally-friendlier VEP, which would be a breakthrough for future large scale EP applications on SRF cavities. Here we give a status update and report latest results from these R&D activities.
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MOPVA117	Performance of a SRF Half-Wave-Resonator Tested at Cornell for the RAON Project	cavity, radiation, simulation, pick-up	1123
	M. Ge, F. Furuta, T. Gruber, D.L. Hall, S.W. Hartman, C. Henderson, M. Liepe, S. Lok, T.I. O'Connell, P.J. Pamel, J. Sears, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA B.H. Choi, J. Joo, J.W. Kim, W.K. Kim, J. Lee, I. Shin IBS, Daejeon, Republic of Korea
	A prototype half-wave-resonator (HWR) with frequency 162.5MHz and geometrical \beta=0.12 for the RAON project is currently undergoing testing at Cornell University. Detailed vertical performance testing includes (1) test of the bare cavity without the helium tank; (2) test of the dressed cavity with helium tank. In this paper, we report on the development of the test infrastructure, test results, and performance data analysis.
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MOPVA119	Surface Analysis of Features Seen on Nb3Sn Sample Coupons Grown by Vapour Diffusion	niobium, simulation, cavity, site	1130
	D.L. Hall, M. Liepe, J.T. Maniscalco, R.D. Porter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA T. Arias, P. Cueva, D.A. Muller, N. Sitaraman Cornell University, Ithaca, New York, USA
	As a high-kappa superconductor with a coherence length of 7 nm, the superconductor Nb3Sn is highly susceptible to material features at the sub-micron scale. For niobium surfaces coated with a thin layer of Nb3Sn using the vapour diffusion method, the polycrystalline nature of the film grown lends to the possibility that performance-degrading non-uniformities may develop. In particular, regions of insufficiently thick coating and tin-depletion have been seen to occur in sample coupons. In the interests of understanding how to control the presence and nature of such features, it is necessary to know how they form. In this paper we stop the coating at defined instances to gain a stop-motion image of the growth of the layer, and use SEM and TEM techniques to image the development of the features seen in previously coated samples. We demonstrate that surface pre-anodisation can suppress the formation of thin film regions, and apply this technique to a single-cell cavity. Contemporarily, we use TEM with EDS mapping to monitor grain boundaries and tin-depleted regions within the layer.
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MOPVA122	Microphonics Studies of the CBETA Linac Cryomodules	cavity, cryomodule, operation, linac	1138
	N. Banerjee, J. Dobbins, F. Furuta, D.L. Hall, G.H. Hoffstaetter, M. Liepe, P. Quigley, E.N. Smith, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: This work was performed through the support of NYSERDA (New York State Energy Research and Development Agency). The Cornell BNL ERL Test Accelerator (CBETA) incorporates two SRF linacs; one for its injector and another for the energy recovery loop. Microphonics in both the cryomodules play a crucial role in determining the energy stability of the electron beam in high current operation. We have measured vibrations and frequency detuning of the SRF cavities and determined that the cryogenic system is the major source of microphonics in both cryomodules. In this paper we discuss these measurements and demonstrate an Active Microphonics Compensation system implemented using fast piezo-electric tuners which we incorporated in our Low Level RF control system to be used in routine operation.
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MOPVA123	Cornell Sample Host Cavity: Recent Results	cavity, niobium, electron, operation	1142
	J.T. Maniscalco, D.L. Hall, M. Liepe, R.D. Porter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA V.M. Arrieta, S.R. McNeal, W.E. Williams Ultramet, Pacoima, California, USA
	Funding: NSF-PHY 1416318 NSF-PHY 1549132 The Cornell sample host cavity is a 3.9~GHz testing system for RF analysis of novel superconducting surfaces. The cavity applies fields up to 100~mT on a removable and replaceable 5-inch sample plate in order to measure the surface resistance of the material under investigation. The cavity also includes a temperature-mapping system for localization of quench events and surface defects. In this paper, we present recent experimental results from the host cavity of niobium deposited onto molybdenum and copper substrates using chemical vapor deposition, in collaboration with industry partner Ultramet. The results indicate low BCS resistance and good adhesion but also areas of high residual resistance due to chemical and morphological defects.
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MOPVA124	Effectiveness of Chemical Treatments for Reducing the Surface Roughness of Nb3Sn	niobium, linac, klystron, cavity	1145
	R.D. Porter, F. Furuta, D.L. Hall, M. Liepe, J.T. Maniscalco Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: DOE DE-SC008431, NSF-PHY 1549132, NSF DMR-1120296 Current Niobium-3 Tin (Nb3Sn) superconducting radio-frequency (SRF) accelerator cavities have rougher surfaces than conventional electropolished Niobium accelerator cavities. The surface roughness can cause enhancement of the surface magnetic field, pushing it beyond the critical field. If this occurs over a large enough area it can cause the cavity to quench. The surface roughness may cause other effects that negatively impact cavity quality factor (Q) performance. Reducing surface roughness of Nb3Sn cavities may be necessary to achieve higher gradient with high Q. Current chemical treatments for reducing the surface roughness of Niobium are challenging for Nb3Sn: the Nb3Sn layer is only ~2 um thick while it is difficult to remove less than 1 mu uniformly with most chemical treatments. This paper presents measurements of the surface roughness before and after Buffered Chemical Polish, Electropolishing and oxipolishing.
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MOPVA126	Sample Host Cavity Design for Measuring Flux Entry and Quench	cavity, niobium, dipole, klystron	1149
	R.D. Porter, M. Liepe, J.T. Maniscalco, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: NSF-PHY 1549132 Current state-of-the-art Niobium superconducting radio-frequency (SRF) accelerator cavities have reached surface magnetic field close to the theoretical maximum set by the superheating field. Further increasing accelerating gradients will require new superconducting materials for accelerator cavities that can support higher surface magnetic fields. This necessitates measuring the quench fields of new materials in high power RF fields. In this paper, we present designs and simulations of a sample host cavity. The cavity design is optimized to maximize the surface magnetic field achieved on the sample.
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MOPVA127	Vertical Test Results for the LCLS-II 1.3 GHz First Article Cavities	cavity, cryomodule, linac, FEL	1152
	A. Burrill, D. Gonnella, M.C. Ross SLAC, Menlo Park, California, USA G.K. Davis, A.D. Palczewski, L. Zhao JLab, Newport News, Virginia, USA A. Grassellino, O.S. Melnychuk Fermilab, Batavia, Illinois, USA
	The LCLS-II project requires 35 1.3 GHz cryomodules to be installed in the accelerator in order to deliver a 4 GeV electron beam to the undulators hall. These 35 cryomodules will consist of 8 1.3 GHz TESLA style SRF cavities, a design most recently used for the XFEL project in Hamburg, Germany. The cavity design has remained largely unchanged, but the cavity treatment has been modified to utilize the nitrogen doping process to allow for Quality factors in excess of 3x10¹⁰ at 16 MV/m, the designed operating gradient of the cavities in the CM. Two industrialized vendors are producing most of the SRF cavities for these cryomodules; and the performance of the first article cavities, 16 from each vendor, will be reported on in this paper.
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MOPVA128	RF Performance of Nitrogen-Doped Production SRF Cavities for LCLS-II	cavity, niobium, operation, accelerating-gradient	1156
	D. Gonnella, A. Burrill, M.C. Ross SLAC, Menlo Park, California, USA S. Aderhold, A. Grassellino, C.J. Grimm, T.N. Khabiboulline, O.S. Melnychuk, S. Posen, D.A. Sergatskov Fermilab, Batavia, Illinois, USA E. Daly, G.K. Davis, F. Marhauser, K.M. Wilson JLab, Newport News, Virginia, USA
	Funding: DOE and the LCLS-II Project The Linac Coherent Light Source II (LCLS-II) requires 280 9-cell superconducting RF cavities for operation in continuous wave mode. Two vendors have previously been selected to produce the cavities, Research Instruments GmbH and Ettore Zanon S.p.a. Here we present results from manufacturing and cavity preparation for the cavities constructed at these two vendors for LCLS-II. We show how the cavity preparation method has been changed mid-production in order to improve flux expulsion in the cavities and maintain high performance in realistic magnetic field environments (~5 mG). Additionally, we show that the nitrogen-doping process has been carried out successfully and repeatedly on over 70 cavities.
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MOPVA130	Development of Waveguide HOM Loads for BERLinPro and BESSY-VSR SRF Cavities	HOM, cavity, simulation, network	1160
	J. Guo, F. Fors, J. Henry, R.A. Rimmer, H. Wang JLab, Newport News, Virginia, USA H.-W. Glock, A. Neumann, A.V. Tsakanian, A.V. Vélez HZB, Berlin, Germany
	Two ongoing accelerator projects at Helmholtz-Zentrum Berlin (HZB), BERLinPro and BESSY-VSR, need to design three different SRF cavities, a 1.3GHz cavity in BERLinPro and 1.5GHz/1.75GHz cavities in BESSY-VSR. These cavities have adopted waveguide HOM dampers in their design, with a few tens of watts HOM power in each load for BERLinPro and a few hundred watts for BESSY-VSR. JLab is collaborating with HZB prototyping these HOM loads. In this paper, we will report on the integrated RF-thermal-mechanical design of the loads, as well as the fabrication and testing results.
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MOPVA133	Optimization of the RF Cavity Heat Load and Trip Rates for CEBAF at 12 GeV	linac, cavity, operation, electron	1170
	H. Zhang, A. Freyberger, G.A. Krafft, Y. Roblin JLab, Newport News, Virginia, USA B. Terzić ODU, Norfolk, Virginia, USA
	Funding: Work supported by the Department of Energy under Contract No. DE-AC05-06OR23177 The Continuous Electron Beam Accelerator Facility at JLab has 200 RF cavities in the north linac and the south linac respectively after the 12 GeV upgrade. The purpose of this work is to simultaneously optimize the heat load and the trip rate for the cavities and to reconstruct the pareto-optimal front in a timely manner when some of the cavities are turned down. By choosing an efficient optimizer and strategically creating the initial gradients, the pareto-optimal front for no more than 15 cavities down can be re-established within 20 seconds.
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MOPVA140	Multipacting Behavior Study for the 112 MHz Superconducting Photo-Electron Gun	cavity, gun, electron, cathode	1180
	I. Petrushina SUNY SB, Stony Brook, New York, USA V. Litvinenko, G. Narayan, I. Pinayev, F. Severino, K.S. Smith BNL, Upton, Long Island, New York, USA V. Litvinenko Stony Brook University, Stony Brook, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Superconducting 1.2 MV 112 MHz quarter-wave photo-electron gun (SRF gun) is used as a source of electron beam for the Coherent electron Cooling experiment (CeC) at BNL. During the CeC commissioning we encountered a number of multipacting zones in the gun. It was also observed that introduction of CsK2Sb photocathode creates additional multipacting zone. This paper presents numerical and experimental study of the multipactor discharge in the SRF gun. We also discuss ways of crossing the multipacting levels to the operational voltage. Finally, we compare the results of our numerical simulations of the multipactor discharge using ACE3P with experimental data.
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MOPVA144	Post-Processing of Nb3Sn Coated Nb	niobium, superconductivity, cavity, experiment	1190
	U. Pudasaini, M.J. Kelley The College of William and Mary, Williamsburg, Virginia, USA G.V. Eremeev, M.J. Kelley, C.E. Reece JLab, Newport News, Virginia, USA M.J. Kelley, J. Tuggle Virginia Polytechnic Institute and State University, Blacksburg, USA
	Funding: Supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DEÂAC05Â06OR23177 and Office of High Energy Physics under grant SC00144475. Practical SRF cavities may be subjected to one or more processes after nominally complete preparation. Successful implementation of such processes in Nb3Sn coated cavities requires the understanding of material's response to these treatments. SRF-grade Nb samples, coated with Nb3Sn by the widely used tin vapor diffusion process were subjected to one or more of the following: hydrofluoric acid (HF) rinsing, oxypolishing, buffered chemical polishing (BCP) or electrochemical treatment. They were examined by materials characterization tech-niques including scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), and X-ray photoelectron spec-troscopy (XPS). The effects compared to niobium are different enough in most cases that further development is desirable to routinely obtain a favorable result.
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TUPAB027	Production, Tuning and Processing Challenges of the BERLinPro Gun1.1 Cavity	cavity, gun, cathode, niobium	1375
	H.-W. Glock, A. Frahm, J. Knobloch, A. Neumann HZB, Berlin, Germany B. Rosin, D. Trompetter RI Research Instruments GmbH, Bergisch Gladbach, Germany
	Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of the Helmholtz Association For the BERLinPro energy recovery LINAC, HZB is developing a superconducting 1.4-cell electron gun, which, in its final version, is planned to be capable of CW 1.3 GHz operation with 77 pC/bunch. For this purpose a series of three superconducting cavities, denoted as Gun 1.0, Gun 1.1 (both designed for 6 mA) and Gun 2.0 (100 mA) are foreseen. Gun 1.0 now reached operational status and the Gun 1.1 cavity is completely manufactured. In the paper the chronology of manufacturing, tuning and processing of the Gun 1.1-cavity is described, also giving details about combined mechanical/electrodynamic simulations, which were performed in order to gain deeper understanding of the cavity's unexpected tuning behavior.
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TUPAB028	Measuring the Spectral Response of Cs-K-Sb Photocathodes for BERLinPro	cathode, electron, linac, emittance	1378
	H. Kirschner, A. Jankowiak, T. Kamps, J. Kühn, M.A.H. Schmeißer HZB, Berlin, Germany
	A spectral response setup was commissioned at the Cs-K-Sb photocathode preparation and analysis system developed for the BERLinPro project. The setup is designed to measure the spectral quantum efficiency from 370 to 700 nm and to monitor the photocurrent during the photocathode growth process and the photocathode lifetime at 515 nm.
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TUPAB029	UHV Photocathode Plug Transfer Chain for the BERLinPro SRF-Photoinjector	vacuum, cathode, cavity, laser	1381
	J. Kühn, J. Borninkhof, M. Bürger, A. Frahm, A. Jankowiak, T. Kamps, M.A.H. Schmeißer, M. Schuster HZB, Berlin, Germany P. Murcek, J. Teichert, R. Xiang HZDR, Dresden, Germany
	A dedicated particle free UHV photocathode plug transfer chain from the preparation system to the SRF-Photoinjector was set up and commissioned at HZB for the BERLinPro project. The plug handling system was designed in collaboration with the ELBE team at HZDR, where the same transfer chain is in commissioning phase. In the future the exchange of photocathodes between the laboratories offers the possibility to test different types of photocathodes in different SRF-photoinjectors.
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TUPAB107	Study of 60 Hz Beam Orbit Fluctuations in the Taiwan Photon Source	vacuum, shielding, photon, insertion-device	1566
	C.H. Huang, Y.-S. Cheng, P.C. Chiu, K.T. Hsu, K.H. Hu, C.Y. Liao, C.Y. Wu NSRRC, Hsinchu, Taiwan
	The Taiwan Photon Source is a 3 GeV synchrotron light source at NSRRC. To achieve high quality experimental results, it is important to minimize beam motion. During the installation of insertion devices and front-ends, the beam motion around 60 Hz became significant. The response matrix together with singular value decomposition was used to identify the transmitter of the superconducting radio frequency system as the source for the 60 Hz perturbations. This was subsequently corrected by rerouting the grounding of the mains in the transmitters. Yet, the 60Hz orbit fluctuation became even more serious after the next shutdown. A serious of experiments are performed to dig out that the beam was disturbed by the magnetic field from newly installed fan motors. Shielding the fans with mu-metal and increasing the distance between fan and beam pipe drastically reduced the leakage field and greatly increased beam stability. These errors could be prevented at the design stage in the ideal case. However, these errors happened finally and need to be dug out and eliminated. The method and experiences are summarized in this report. These will benefit others who facing the similar problems.
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TUPIK042	Solenoid Alignment for the SRF Photoinjector of BERLinPro at HZB	solenoid, alignment, software, electron	1778
	G. Kourkafas, A. Jankowiak, T. Kamps, J. Li, J. Völker HZB, Berlin, Germany M. Schebek Humboldt University Berlin, Berlin, Germany
	The Berlin Energy Recovery Linac Prototype (BERLinPro) at Helmholtz Zentrum Berlin (HZB) aims to deliver a continuous-wave (cw) electron beam of high average current (100 mA) and brilliance (normalized emittance below 1 mm mrad). The achievement of these demanding goals depends significantly on the performance of the electron source, a superconducting RF (SRF) photoinjector. A critical component for the quality of the generated beam is the superconducting solenoid magnet. In order to optimize its operation and minimize parasitic contributions, special attention has been given to the precise alignment of this element using a hexapod mover. Due to the strict limitations inside a cryostat, a complex coupling between the solenoid in vacuum and the hexapod in air has been realized, requiring sophisticated software and hardware mechanisms to prevent collisions. Along with this setup, the developed beam-based alignment procedure and its performance are demonstrated in this article.
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TUPIK107	Upgrade of the Existing PID Controller and Oxygen Detection Alarm System for SRF Modules Operating in the Taiwan Light Source	controls, electronics, status, operation	1968
	F.-T. Chung, F.Y. Chang, L.-H. Chang, M.H. Chang, L.J. Chen, M.-C. Lin, Z.K. Liu, C.H. Lo, C.L. Tsai, Ch. Wang, M.-S. Yeh, T.-C. Yu NSRRC, Hsinchu, Taiwan
	A Cornell-type superconducting RF cavity module was installed in the Taiwan Light Source (TLS) in 2004. New control electronics for the existing SRF modules have been designed, based on the original designs. In addition to the functions for operation, this SRF electronics system in the TLS also provides protection for the SRF modules and cryogenic system. This paper presents the SRF electronics modifications, which will enhance machine protection and make it easy to adjust and optimize operational parameters.
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WEPIK036	ERL Cryomodule Testing and Beam Capabilities	cavity, linac, cryomodule, operation	3010
	F. Furuta, N. Banerjee, J. Dobbins, R.G. Eichhorn, M. Ge, D.L. Hall, G.H. Hoffstaetter, M. Liepe, R.D. Porter, P. Quigley, D.M. Sabol, J. Sears, E.N. Smith, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	The main linac cryomodule (MLC) prototype is a key component for the Cornell-BNL ERL Test Accelerator (CBETA) project, which is a 4-turn FFAG ERL under construction at Cornell University. This novel cryomodule is the first SRF module ever to be fully optimized simul-taneously for high efficient SRF cavity operation and for supporting very high CW beam currents. Initial MLC testing has demonstrated that cavity performance and HOMs damping meet specification values. Recent, addi-tional tests have focused on RF field stability, and cavity microphonics. In this paper, we summarize the perfor-mance of this novel ERL cryomodule and evaluate its beam capabilities based on the measured performance.
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WEPVA048	Particle Generation of CapaciTorr Pumps	vacuum, operation, detector, synchrotron	3363
	S. Lederer, L. Lilje DESY, Hamburg, Germany E. Maccallini, P. Manini, F. Siviero SAES Getters S.p.A., Lainate, Italy
	Non Evaporable Getter pumps have been used since four decades in various scientific and industrial Ultra High and Extremely Ultra High Vacuum applications. For the majority of applications properties like high pumping speed vs. small size, powerless operation and hydrocarbon cleanliness are main aspects for the usage. In addition to this a growing number of applications nowadays also require particle free systems. In this paper we report on investigations on in-vacuum particle creation during the conditioning and activation process of CapaciTorr pumps.
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WEPVA145	Analysis of Mean Free Path and Field Dependent Surface Resistance	cavity, niobium, electron, radio-frequency	3609
	J.T. Maniscalco, F. Furuta, D.L. Hall, P.N. Koufalis, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: NSF-PHY 1416318 Work from Cornell in 2016 built on recent theoretical research in the field of SRF to link the electron mean free path to the field-dependent BCS surface resistance. This research relates the magnitude of the ‘‘anti-Q-slope'', the puzzling reduction of surface resistance with increasing RF field intensity observed in certain cavities, to the doping level of nitrogen-doped niobium, quantified by the mean free path: shorter mean free paths correspond directly with stronger anti-Q-slopes. The theoretical connection comes through the overheating of the quasiparticles, which more effectively transfer their energy to the lattice at short mean free paths. In this report, we present an update of this analysis, investigating recent test results of low-temperature-doped single-cell and nine-cell cavities. We also study the theoretical implications for cavities at frequencies higher and lower than the often-studied 1.3~GHz.
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THOBB3	ESS SRF Linear Accelerator Components Preliminary Results and Integration	cavity, cryomodule, linac, accelerating-gradient	3666
	C. Darve, N. Elias, C.G. Maiano, F. Schlander ESS, Lund, Sweden C. Arcambal, G. Devanz, F. Peauger CEA/DRF/IRFU, Gif-sur-Yvette, France E. Cenni CEA/IRFU, Gif-sur-Yvette, France G. Costanza Lund University, Lund, Sweden P. Duthil, G. Olry, D. Reynet IPN, Orsay, France L. Hermansson Uppsala University, Uppsala, Sweden P. Michelato, D. Sertore INFN/LASA, Segrate (MI), Italy
	The European Spallation Source (ESS) is a pan-European project and one of world's largest research infrastructures based on neutron sources. This collaborative project is funded by a collaboration of 17 European countries and is under construction in Lund, Sweden. The 5 MW, 2.86 ms long pulse proton accelerator has a repetition frequency of 14 Hz (4 % duty cycle), and a beam current of 62.5 mA. The Superconducting Radio-Frequency (SRF) linac is composed of three families of Superconducting Radio-Frequency (SRF) cavities, which are being prototyped, counting the spoke resonators with a geometric beta of 0.5, medium-beta elliptical cavities (beta_g=0.67) and high-beta elliptical cavities (beta_g=0.86). After a description of the ESS linear accelerator layout, this article will focus on the recent progress towards integration of the first test results of the main critical components to be assembled in cryomodules, then in the ESS tunnel.
	Slides THOBB3 [25.611 MB]
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THPAB009	Multi-Objective Optimization of an SRF Photoinjector for ERL and UED Applications	gun, laser, electron, emittance	3704
	E. Panofski, A. Jankowiak, T. Kamps, G. Kourkafas HZB, Berlin, Germany S. Eisebitt MBI, Berlin, Germany
	Superconducting RF photoinjectors, running in continuous-wave (cw) mode, are able to generate electron beams of high average brightness and ultra-short bunches. Therefore, they satisfy the requirements of future accelerator facilities, such as energy recovery linacs (ERL). Further, SRF guns are able to provide relativistic probe beams for ultrafast electron diffraction (UED). Choosing suitable values for the drive laser, cavity and solenoid settings poses a great challenge for the injector commissioning and operation. Using multi-objective optimization based on an evolutionary algorithm, optimum gun parameter settings are extracted from Pareto-optimum solutions. The development of a universal multi-objective optimization algorithm for SRF photoinjectors as well as first Pareto optimum results for an ERL and UED application of GunLab, the compact SRF gun test facility at Helmholtz-Zentrum Berlin, will be presented.
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THPAB012	Beam Transport Optimization for Applying an SRF Gun at the ELBE Center	electron, gun, linac, radiation	3712
	P.N. Lu, A. Arnold, P. Murcek, J. Teichert, H. Vennekate, R. Xiang HZDR, Dresden, Germany
	An SRF gun at the ELBE center has been operated with a magnesium cathode. Electron beams were produced with a maximum bunch charge of 200 pC and an emit-tance of 7.7 μm. Simulations have been conducted with ASTRA and Elegant for applying the SRF gun to ELBE user experiments, including neutron beam generation, positron beam generation, THz radiation and Compton backscattering experiment. Beam transport has been optimized to solve the best beam performance for these user stations at the bunch charge of 200 pC. Simulation results indicate that the SRF gun is potential to benefit the high bunch charge applications at ELBE.
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THPAB087	Emittance Measurements and Simulations in 112 MHz Super-Conducting RF Electron Gun With CsK2Sb Photo-Cathode	emittance, gun, solenoid, electron	3921
	K. Mihara Stony Brook University, Stony Brook, USA D. Kayran, V. Litvinenko, T.A. Miller, I. Pinayev BNL, Upton, Long Island, New York, USA
	The commissioning of the coherent electron cooling (CeC) proof of principle experiment is under way at Relativistic Heavy Ion Collider (RHIC).. A 112 MHz superconducting radio frequency photo-emission gun is used to generate the electron beam for this experiment. In this paper we report selected results of experimental emittance measurements and compare them with our simulations.
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THPAB104	Engineering Documentation and Asset Management for the European XFEL Accelerator	operation, database, interface, status	3960
	L. Hagge, J.A. Dammann, T.T. Hongisto, J. Kreutzkamp, D. Käfer, B. List, S. Rohwedder, S. Sühl, N. Welle DESY, Hamburg, Germany A. Frank European XFEL, Schenefeld, Germany
	At the European XFEL, extensive technical documentation has been created during design and construction of the accelerator. It is based on a configuration database (the DESY EDMS), which provides an inventory of major accelerator systems. The configuration database registers components and their used materials, tracks component design and fabrication history, and contains engineering documents and drawings, and work and inspection records. Technical documentation can be accessed through intuitive reports and navigational tree structures, representing specific beamline sections or areas of the facility. Access on mobile devices in the accelerator tunnel is supported by component tags with QR codes. A dedicated front-end has been developed for automatically uploading and cross-linking documents to the configuration database, reducing documentation efforts in the project teams. The configuration database now serves as a foundation for upcoming technical operation and maintenance activities. The paper provides an overview of the available engineering documentation and its access methods, and discusses its expected role and benefits in future maintenance processes.
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THPIK023	Concept of the High Power RF Systems for MESA	cavity, linac, experiment, LLRF	4147
	R.G. Heine, F. Fichtner IKP, Mainz, Germany
	Funding: work supported by DFG under the cluster od Excellence PRISMA, EXC 1098/2014 The Mainz Energy-recovering Superconducting Accelerator (MESA) is currently designed and built at the Institut für Kernphysik (KPH) at Johannes Gutenberg-Universität Mainz. The main accelerator incorporates four superconducting cavities of the TESLA type, while the preaccelerator MAMBO (Milliampere Booster) is a room temperature linac. The MESA high power RF-systems have to cover a vast power range starting at some 10kW per cavity for the main linac modules and more 50kW per cavity for MAMBO. In this paper we will present the concept of a unified high power RF system for both main accelerator and preaccelertor, based on solid state technology.
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THPIK121	Eddy Current Analysis for a 1.495 GHz Injection-Locked Magnetron	interaction-region, cavity, injection, klystron	4383
	S.A. Kahn, A. Dudas, R.P. Johnson, M.L. Neubauer Muons, Inc, Illinois, USA R.A. Rimmer, H. Wang JLab, Newport News, Virginia, USA
	Funding: U.S. DOE SBIR/STTR grant DE-SC0013203 An injection-locked amplitude modulated magnetron is being developed as a reliable, efficient RF source that could replace klystrons used in particle accelerators. A trim magnetic coil is used to alter the magnetic field in conjunction with the anode voltage to maintain an SRF cavity voltage while the cavity is experiencing microphonics and changing beam loading. The microphonic noise modes have frequencies in the range 10-100 Hz. The changing magnetic field will induce transient eddy currents in the copper anode of the magnetron which will buck the field in the interaction region. This paper will describe the calculation and handling of the eddy currents in the magnetron.
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THPIK122	Methods of Phase and Power Control in Magnetron Transmitters for Superconducting Accelerators	controls, injection, power-supply, operation	4386
	G.M. Kazakevich, R.P. Johnson, M.L. Neubauer Muons, Inc, Illinois, USA V.A. Lebedev, W. Schappert, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	Various methods of phase and power control in magnetron RF sources of superconducting accelerators intended for ADS-class projects were recently developed and studied with conventional 2.45 GHz, 1 kW, CW magnetrons operating in pulsed and CW regimes. Magnetron trans-mitters excited by a resonant (injection-locking) phase-modulated signal can provide phase and power control with the rates required for precise stabilization of phase and amplitude of the accelerating field in Superconducting RF (SRF) cavities of the intensity-frontier accelerators. An innovative technique that can significantly increase the magnetron transmitter efficiency at the wide-range power control required for superconducting accelerators was developed and verified with the 2.45 GHz magnetrons operating in CW and pulsed regimes. High efficiency magnetron transmitters of this type can significantly reduce the capital and operation costs of the ADS-class accelerator projects.
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THPVA078	The Beam Quality Assurance of the MedAustron Particle Therapy Accelerator	framework, synchrotron, hardware, software	4634
	L.C. Penescu Abstract Landscapes, Montpellier, France A. De Franco, F. Farinon, M. Kronberger, C. Kurfürst, S. Myalski, S. Nowak, F. Osmić, M.T.F. Pivi, C. Schmitzer, P. Urschütz, A. Wastl EBG MedAustron, Wr. Neustadt, Austria T.K.D. Kulenkampff CERN, Geneva, Switzerland
	The delivery of clinical beams for patient treatment at the MedAustron Ion Therapy Center requires extensive accelerator performance verifications, which are performed in several steps. In first instance, the key parameters of the beam delivered to the irradiation rooms (beam position, spot size, energy and intensity) are verified via measurements performed with beam diagnostic devices distributed along the accelerator. The second verification step consists in testing the full functionality of the therapy accelerator, including the medical frontend: scanning magnets performance, intensity monitoring and safety features. The final verification step is the quality assurance (QA) done by the medical department. An extended set of reference measurements assures the fast identification of the faulty components in case of a performance deviation, and the totality of the accumulated data allows in-depth analysis of the accelerator performance. We present here the trends and correlations observed during the first verification step for the most important parameters, as well as the lessons learned through all the implementation stages of the beam quality assurance.
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FRXCB1	The Energy Efficiency of High Intensity Proton Driver Concepts	proton, linac, cavity, cyclotron	4842
	V.P. Yakovlev Fermilab, Batavia, Illinois, USA J. Grillenberger, M. Seidel PSI, Villigen PSI, Switzerland S.-H. Kim ORNL, Oak Ridge, Tennessee, USA M. Yoshii KEK, Tokai, Ibaraki, Japan
	For MW class proton driver accelerators the energy efficiency is an important aspect; the talk reviews the efficiency of different accelerator concepts including s.c./n.c. linac, rapid cycling synchrotron, cyclotron; the potential of these concepts for very high beam power is discussed.
	Slides FRXCB1 [2.964 MB]
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Paper

Title

Other Keywords

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MOYBA1

The Future of Superconducting Technology for Accelerators

collider, cavity, superconducting-magnet, linear-collider

19

A. Yamamoto
KEK, Ibaraki, Japan

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

Slides MOYBA1 [25.792 MB]

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MOOCA2

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

cavity, niobium, factory, radio-frequency

40

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

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

Slides MOOCA2 [10.366 MB]

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MOPAB033

Optics Development and Trajectory Tuning of BERLinPro at Low Energies

linac, gun, booster, diagnostics

153

B.C. Kuske, M. Abo-Bakr
HZB, Berlin, Germany

Funding: Work supported by the German Bundesministerium fr Bildung und Forschung, Land Berlin and grants of the Helmholtz Association
The Berlin Energy Recovery Linac project has taken shape during the past year. The magnets have been set up in the newly constructed subterraneous hall; first electrons are expected in the SRF-gun test laboratory in June 2017. Starting in February 2018 the complete gun module will be transferred to the accelerator hall for the commissioning of BERLinPro. For the first months, operation is planned without further accelerating structures (booster and linac), due to delays in their fabrication. Several modes of operation are applicable at this early stage [1]. The available hardware is displayed and the adapted optics at 2.7 MeV and at 6.5 MeV (including the booster) are presented. The trajectory distortions under the influence of the earth magnetic field are studied. The concept for trajectory correction is outlined.

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MOPIK003

Improvement of the Photoemission Efficiency of Magnesium Photocathodes

cathode, gun, laser, cavity

500

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

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

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MOPIK008

Numerical Studies on a Modified Cathode Tip for the ELBE Superconducting RF Gun

electron, cathode, gun, simulation

515

E.T. Tulu, U. van Rienen
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
A. Arnold
HZDR, Dresden, Germany

Future light sources such as synchrotron radiation sources driven by an Energy Recovery Linac (ERL), Free Electron Laser (FEL) or THz radiation sources have in common that they require injectors, which provide high-brilliance, high-current electron beams in almost continuous operation. Thus, the development of appropriate highly brilliant electron sources is a central factor. A promising approach for this key component is provided by superconducting radiofrequency photoinjectors (SRF guns) [*]. Since 2007, the free-electron laser FELBE at HZDR successfully operates such a SRF gun under real conditions and equipped with all components [**]. Nevertheless, there are limitations caused by multipacting which should be overcome in order to further improve the gun [***]. One aspect in order to reach this aim lies in studying various modifications of the cathode tip [****]. This contribution will present the effectiveness of isosceles triangular grooves with respect to MP.
* Arnold, et al., NIM A, 593, 57, (2008).
** J. Teichert, et al., 2008 NSS/MIC, Dresden, Germany.
*** J. Teichert, et al., J. Phys.: Conf. Ser. 298(2011), 012008.
**** E. T. Tulu, et al., IPAC2014, p652, Dresden, Germany.

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MOPVA005

Status of the Berlin Energy Recovery Linac Project BERLinPro

gun, linac, booster, cavity

855

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

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

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MOPVA010

Setup and Status of an SRF Photoinjector for Energy-Recovery Linac Applications

gun, laser, cathode, emittance

865

T. Kamps, D. Böhlick, A.B. Büchel, M. Bürger, P. Echevarria, A. Frahm, F. Göbel, S. Heling, A. Jankowiak, S. Keckert, H. Kirschner, G. Klemz, J. Knobloch, G. Kourkafas, J. Kühn, O. Kugeler, A.N. Matveenko, A. Neumann, N. Ohm-Krafft, E. Panofski, F. Pfloksch, S. Rotterdam, M.A.H. Schmeißer, M. Schuster, H. Stein, J. Ullrich, A. Ushakov, J. Völker
HZB, Berlin, Germany
I. Will
MBI, Berlin, Germany

Funding: The work is funded by the Helmholtz-Association, BMBF, the state of Berlin and HZB.
The Superconducting RF (SRF) photoinjector programme for the energy-recovery linac (ERL) test facility BERLinPro sets out to push the brightness and average current limits for ERL electron sources by tackling the main challenges related to beam dynamics of SRF photoinjectors, the incorporation of high quantum efficiency (QE) photocathodes, and suppression of unwanted beam generation. The paper details the experimental layout of the SRF photoinjector and the gun test facility GunLab at Helmholtz-Zentrum Berlin.

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MOPVA036

High Average Brilliance Compact Inverse Compton Light Source

electron, gun, brilliance, laser

932

K.E. Deitrick, J.R. Delayen, G.A. Krafft
ODU, Norfolk, Virginia, USA
J.R. Delayen, G.A. Krafft
JLab, Newport News, Virginia, USA

Funding: Partially authored by Jefferson Science Associates, LLC under U.S. DOE contract NO. DE-AC05-6OR23177.
There exists an increasing demand for compact Inverse Compton Light Sources (ICLS) capable of producing substantial fluxes of narrow-band X-rays. While multiple design proposals have been made, compared to typical bremsstrahlung sources, most of these have comparable fluxes and improve on the brilliance within a 0.1% bandwidth by only a few orders of magnitude. By applying cw superconducting rf beam acceleration and rf focusing to produce a beam of small emittance and magnetic focusing to produce a small spot size on the order of a few microns at collision, the source presented here provides a 12 keV X-ray beam which outperforms other compact designs and bremsstrahlung sources. Compared to a bremsstrahlung source, the flux is improved by at least an order of magnitude and the average brilliance by six orders of magnitude. Surpassing other compact ICLS designs, the source presented here is attractive to a wide variety of potential users.

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MOPVA038

Manufacturing Status of the IFMIF LIPAc SRF Linac

cryomodule, vacuum, cavity, linac

939

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

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

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MOPVA039

Manufacturing and Validation Tests of IFMIF Low-Beta HWRs

cavity, cryomodule, operation, simulation

942

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

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

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MOPVA040

Status of the ESS Elliptical Cryomodules at CEA Saclay

cryomodule, cavity, cryogenics, vacuum

945

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

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

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MOPVA043

Assembly Preparation of the IFMIF SRF Cryomodule

cavity, solenoid, cryomodule, vacuum

954

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

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

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MOPVA046

120kW RF Power Input Couplers for BERLinPro

booster, cavity, coupling, linac

960

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

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

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MOPVA048

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

cavity, simulation, operation, superconducting-RF

968

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

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

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MOPVA049

First Commissioning of an SRF Photo-Injector Module for BERLinPro

cavity, cathode, solenoid, linac

971

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

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

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MOPVA050

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

cavity, niobium, experiment, radio-frequency

975

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

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

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MOPVA052

Study on HOM Power Levels in the BESSY VSR Module

HOM, cavity, operation, resonance

982

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

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

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MOPVA053

The SRF Module Developments for BESSY VSR

HOM, cavity, synchrotron, damping

986

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

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

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MOPVA055

Upgrade of the Capture Section of the S-DALINAC Injector

cavity, electron, operation, accelerating-gradient

993

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

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

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MOPVA057

Structural Investigations of Nitrogen-Doped Niobium for Superconducting RF Cavities

niobium, vacuum, radio-frequency, cavity

996

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

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

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MOPVA062

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

cavity, niobium, diagnostics, radio-frequency

1011

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

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

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MOPVA064

Multipacting Study in INFN-LASA ESS Medium-Beta Cavity

cavity, simulation, site, electron

1019

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

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

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MOPVA074

Fabrication of Superconducting QWR at MHI-MS

cavity, linac, superconducting-RF, niobium

1037

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

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

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MOPVA079

A 166.6 MHz Superconducting RF System for the HEPS Storage Ring

cavity, HOM, LLRF, injection

1049

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

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

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MOPVA082

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

plasma, cavity, accelerating-gradient, electromagnetic-fields

1055

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

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

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MOPVA090

ESS Superconducting RF Collaboration

cryomodule, cavity, linac, proton

1068

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

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

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MOPVA095

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

cavity, monitoring, operation, cryomodule

1077

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

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

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MOPVA097

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

simulation, cryogenics, cavity, distributed

1085

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

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

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MOPVA098

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

operation, vacuum, cryogenics, cavity

1088

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

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

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MOPVA099

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

cavity, klystron, operation, vacuum

1091

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

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

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MOPVA102

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

cavity, simulation, luminosity, klystron

1098

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

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

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MOPVA104

Physical Vapour Deposition of NbTiN Thin Films for Superconducting RF Cavities

cathode, power-supply, target, superconductivity

1102

S. Wilde, B. Chesca
Loughborough University, Loughborough, Leicestershire, United Kingdom
E. Alves
AssociaÃ§Ã£o EURATOM/IST, Instituto de Plasmas e FusÃ£o Nuclear, Lisboa, Portugal
N.P. Barradas
Universidade de Lisboa, Instituto Superior Técnico, Bobadela, Portugal
A.N. Hannah, O.B. Malyshev, N. Pattalwar, S.M. Pattalwar, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G.B.G. Stenning
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

The production of superconducting coatings for radio frequency cavities is a rapidly developing field that should ultimately lead to acceleration gradients greater than those obtained by bulk Nb RF cavities. The use of thin films made from superconductors with thermodynamic critical field, H_C>H_C^Nb, allows the possibility of multilayer superconductor ' insulator ' superconductor (SIS) films and accelerators that could operate at temperatures above the 2 K typically used. SIS films theoretically allow increased acceleration gradient due to magnetic shielding of underlying superconducting layers [1] and higher operating temperature can reduce cost [2]. High impulse magnetron sputtering (HiPIMS) and pulsed DC magnetron sputtering processes were used to deposit NbTiN thin films onto Si(100) substrate. The films were characterised using scanning electron microscopy (SEM), x-ray diffraction (XRD), Rutherford back-scattering spectroscopy (RBS) and a four-point probe.

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MOPVA114

Materials Characterization for SRF Cavities: Gaining Insight Into Nb3Sn

ion, interface, cavity, electron

1111

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

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

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MOPVA115

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

cathode, cavity, niobium, linac

1115

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

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

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MOPVA117

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

cavity, radiation, simulation, pick-up

1123

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

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

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MOPVA119

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

niobium, simulation, cavity, site

1130

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

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

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MOPVA122

Microphonics Studies of the CBETA Linac Cryomodules

cavity, cryomodule, operation, linac

1138

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

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

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MOPVA123

Cornell Sample Host Cavity: Recent Results

cavity, niobium, electron, operation

1142

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

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

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MOPVA124

Effectiveness of Chemical Treatments for Reducing the Surface Roughness of Nb3Sn

niobium, linac, klystron, cavity

1145

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

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

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MOPVA126

Sample Host Cavity Design for Measuring Flux Entry and Quench

cavity, niobium, dipole, klystron

1149

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

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

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MOPVA127

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

cavity, cryomodule, linac, FEL

1152

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

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

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MOPVA128

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

cavity, niobium, operation, accelerating-gradient

1156

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

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

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MOPVA130

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

HOM, cavity, simulation, network

1160

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

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

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MOPVA133

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

linac, cavity, operation, electron

1170

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

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

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MOPVA140

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

cavity, gun, electron, cathode

1180

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

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

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MOPVA144

Post-Processing of Nb3Sn Coated Nb

niobium, superconductivity, cavity, experiment

1190

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

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

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TUPAB027

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

cavity, gun, cathode, niobium

1375

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

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

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TUPAB028

Measuring the Spectral Response of Cs-K-Sb Photocathodes for BERLinPro

cathode, electron, linac, emittance

1378

H. Kirschner, A. Jankowiak, T. Kamps, J. Kühn, M.A.H. Schmeißer
HZB, Berlin, Germany

A spectral response setup was commissioned at the Cs-K-Sb photocathode preparation and analysis system developed for the BERLinPro project. The setup is designed to measure the spectral quantum efficiency from 370 to 700 nm and to monitor the photocurrent during the photocathode growth process and the photocathode lifetime at 515 nm.

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TUPAB029

UHV Photocathode Plug Transfer Chain for the BERLinPro SRF-Photoinjector

vacuum, cathode, cavity, laser

1381

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

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

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TUPAB107

Study of 60 Hz Beam Orbit Fluctuations in the Taiwan Photon Source

vacuum, shielding, photon, insertion-device

1566

C.H. Huang, Y.-S. Cheng, P.C. Chiu, K.T. Hsu, K.H. Hu, C.Y. Liao, C.Y. Wu
NSRRC, Hsinchu, Taiwan

The Taiwan Photon Source is a 3 GeV synchrotron light source at NSRRC. To achieve high quality experimental results, it is important to minimize beam motion. During the installation of insertion devices and front-ends, the beam motion around 60 Hz became significant. The response matrix together with singular value decomposition was used to identify the transmitter of the superconducting radio frequency system as the source for the 60 Hz perturbations. This was subsequently corrected by rerouting the grounding of the mains in the transmitters. Yet, the 60Hz orbit fluctuation became even more serious after the next shutdown. A serious of experiments are performed to dig out that the beam was disturbed by the magnetic field from newly installed fan motors. Shielding the fans with mu-metal and increasing the distance between fan and beam pipe drastically reduced the leakage field and greatly increased beam stability. These errors could be prevented at the design stage in the ideal case. However, these errors happened finally and need to be dug out and eliminated. The method and experiences are summarized in this report. These will benefit others who facing the similar problems.

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TUPIK042

Solenoid Alignment for the SRF Photoinjector of BERLinPro at HZB

solenoid, alignment, software, electron

1778

G. Kourkafas, A. Jankowiak, T. Kamps, J. Li, J. Völker
HZB, Berlin, Germany
M. Schebek
Humboldt University Berlin, Berlin, Germany

The Berlin Energy Recovery Linac Prototype (BERLinPro) at Helmholtz Zentrum Berlin (HZB) aims to deliver a continuous-wave (cw) electron beam of high average current (100 mA) and brilliance (normalized emittance below 1 mm mrad). The achievement of these demanding goals depends significantly on the performance of the electron source, a superconducting RF (SRF) photoinjector. A critical component for the quality of the generated beam is the superconducting solenoid magnet. In order to optimize its operation and minimize parasitic contributions, special attention has been given to the precise alignment of this element using a hexapod mover. Due to the strict limitations inside a cryostat, a complex coupling between the solenoid in vacuum and the hexapod in air has been realized, requiring sophisticated software and hardware mechanisms to prevent collisions. Along with this setup, the developed beam-based alignment procedure and its performance are demonstrated in this article.

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TUPIK107

Upgrade of the Existing PID Controller and Oxygen Detection Alarm System for SRF Modules Operating in the Taiwan Light Source

controls, electronics, status, operation

1968

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

A Cornell-type superconducting RF cavity module was installed in the Taiwan Light Source (TLS) in 2004. New control electronics for the existing SRF modules have been designed, based on the original designs. In addition to the functions for operation, this SRF electronics system in the TLS also provides protection for the SRF modules and cryogenic system. This paper presents the SRF electronics modifications, which will enhance machine protection and make it easy to adjust and optimize operational parameters.

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WEPIK036

ERL Cryomodule Testing and Beam Capabilities

cavity, linac, cryomodule, operation

3010

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

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

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WEPVA048

Particle Generation of CapaciTorr Pumps

vacuum, operation, detector, synchrotron

3363

S. Lederer, L. Lilje
DESY, Hamburg, Germany
E. Maccallini, P. Manini, F. Siviero
SAES Getters S.p.A., Lainate, Italy

Non Evaporable Getter pumps have been used since four decades in various scientific and industrial Ultra High and Extremely Ultra High Vacuum applications. For the majority of applications properties like high pumping speed vs. small size, powerless operation and hydrocarbon cleanliness are main aspects for the usage. In addition to this a growing number of applications nowadays also require particle free systems. In this paper we report on investigations on in-vacuum particle creation during the conditioning and activation process of CapaciTorr pumps.

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WEPVA145

Analysis of Mean Free Path and Field Dependent Surface Resistance

cavity, niobium, electron, radio-frequency

3609

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

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

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THOBB3

ESS SRF Linear Accelerator Components Preliminary Results and Integration

cavity, cryomodule, linac, accelerating-gradient

3666

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

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

Slides THOBB3 [25.611 MB]

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THPAB009

Multi-Objective Optimization of an SRF Photoinjector for ERL and UED Applications

gun, laser, electron, emittance

3704

E. Panofski, A. Jankowiak, T. Kamps, G. Kourkafas
HZB, Berlin, Germany
S. Eisebitt
MBI, Berlin, Germany

Superconducting RF photoinjectors, running in continuous-wave (cw) mode, are able to generate electron beams of high average brightness and ultra-short bunches. Therefore, they satisfy the requirements of future accelerator facilities, such as energy recovery linacs (ERL). Further, SRF guns are able to provide relativistic probe beams for ultrafast electron diffraction (UED). Choosing suitable values for the drive laser, cavity and solenoid settings poses a great challenge for the injector commissioning and operation. Using multi-objective optimization based on an evolutionary algorithm, optimum gun parameter settings are extracted from Pareto-optimum solutions. The development of a universal multi-objective optimization algorithm for SRF photoinjectors as well as first Pareto optimum results for an ERL and UED application of GunLab, the compact SRF gun test facility at Helmholtz-Zentrum Berlin, will be presented.

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THPAB012

Beam Transport Optimization for Applying an SRF Gun at the ELBE Center

electron, gun, linac, radiation

3712

P.N. Lu, A. Arnold, P. Murcek, J. Teichert, H. Vennekate, R. Xiang
HZDR, Dresden, Germany

An SRF gun at the ELBE center has been operated with a magnesium cathode. Electron beams were produced with a maximum bunch charge of 200 pC and an emit-tance of 7.7 μm. Simulations have been conducted with ASTRA and Elegant for applying the SRF gun to ELBE user experiments, including neutron beam generation, positron beam generation, THz radiation and Compton backscattering experiment. Beam transport has been optimized to solve the best beam performance for these user stations at the bunch charge of 200 pC. Simulation results indicate that the SRF gun is potential to benefit the high bunch charge applications at ELBE.

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THPAB087

Emittance Measurements and Simulations in 112 MHz Super-Conducting RF Electron Gun With CsK2Sb Photo-Cathode

emittance, gun, solenoid, electron

3921

K. Mihara
Stony Brook University, Stony Brook, USA
D. Kayran, V. Litvinenko, T.A. Miller, I. Pinayev
BNL, Upton, Long Island, New York, USA

The commissioning of the coherent electron cooling (CeC) proof of principle experiment is under way at Relativistic Heavy Ion Collider (RHIC).. A 112 MHz superconducting radio frequency photo-emission gun is used to generate the electron beam for this experiment. In this paper we report selected results of experimental emittance measurements and compare them with our simulations.

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THPAB104

Engineering Documentation and Asset Management for the European XFEL Accelerator

operation, database, interface, status

3960

L. Hagge, J.A. Dammann, T.T. Hongisto, J. Kreutzkamp, D. Käfer, B. List, S. Rohwedder, S. Sühl, N. Welle
DESY, Hamburg, Germany
A. Frank
European XFEL, Schenefeld, Germany

At the European XFEL, extensive technical documentation has been created during design and construction of the accelerator. It is based on a configuration database (the DESY EDMS), which provides an inventory of major accelerator systems. The configuration database registers components and their used materials, tracks component design and fabrication history, and contains engineering documents and drawings, and work and inspection records. Technical documentation can be accessed through intuitive reports and navigational tree structures, representing specific beamline sections or areas of the facility. Access on mobile devices in the accelerator tunnel is supported by component tags with QR codes. A dedicated front-end has been developed for automatically uploading and cross-linking documents to the configuration database, reducing documentation efforts in the project teams. The configuration database now serves as a foundation for upcoming technical operation and maintenance activities. The paper provides an overview of the available engineering documentation and its access methods, and discusses its expected role and benefits in future maintenance processes.

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THPIK023

Concept of the High Power RF Systems for MESA

cavity, linac, experiment, LLRF

4147

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

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

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THPIK121

Eddy Current Analysis for a 1.495 GHz Injection-Locked Magnetron

interaction-region, cavity, injection, klystron

4383

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

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

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THPIK122

Methods of Phase and Power Control in Magnetron Transmitters for Superconducting Accelerators

controls, injection, power-supply, operation

4386

G.M. Kazakevich, R.P. Johnson, M.L. Neubauer
Muons, Inc, Illinois, USA
V.A. Lebedev, W. Schappert, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Various methods of phase and power control in magnetron RF sources of superconducting accelerators intended for ADS-class projects were recently developed and studied with conventional 2.45 GHz, 1 kW, CW magnetrons operating in pulsed and CW regimes. Magnetron trans-mitters excited by a resonant (injection-locking) phase-modulated signal can provide phase and power control with the rates required for precise stabilization of phase and amplitude of the accelerating field in Superconducting RF (SRF) cavities of the intensity-frontier accelerators. An innovative technique that can significantly increase the magnetron transmitter efficiency at the wide-range power control required for superconducting accelerators was developed and verified with the 2.45 GHz magnetrons operating in CW and pulsed regimes. High efficiency magnetron transmitters of this type can significantly reduce the capital and operation costs of the ADS-class accelerator projects.

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THPVA078

The Beam Quality Assurance of the MedAustron Particle Therapy Accelerator

framework, synchrotron, hardware, software

4634

L.C. Penescu
Abstract Landscapes, Montpellier, France
A. De Franco, F. Farinon, M. Kronberger, C. Kurfürst, S. Myalski, S. Nowak, F. Osmić, M.T.F. Pivi, C. Schmitzer, P. Urschütz, A. Wastl
EBG MedAustron, Wr. Neustadt, Austria
T.K.D. Kulenkampff
CERN, Geneva, Switzerland

The delivery of clinical beams for patient treatment at the MedAustron Ion Therapy Center requires extensive accelerator performance verifications, which are performed in several steps. In first instance, the key parameters of the beam delivered to the irradiation rooms (beam position, spot size, energy and intensity) are verified via measurements performed with beam diagnostic devices distributed along the accelerator. The second verification step consists in testing the full functionality of the therapy accelerator, including the medical frontend: scanning magnets performance, intensity monitoring and safety features. The final verification step is the quality assurance (QA) done by the medical department. An extended set of reference measurements assures the fast identification of the faulty components in case of a performance deviation, and the totality of the accumulated data allows in-depth analysis of the accelerator performance. We present here the trends and correlations observed during the first verification step for the most important parameters, as well as the lessons learned through all the implementation stages of the beam quality assurance.

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FRXCB1

The Energy Efficiency of High Intensity Proton Driver Concepts

proton, linac, cavity, cyclotron

4842

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

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

Slides FRXCB1 [2.964 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-FRXCB1

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