IPAC2018 - List of Keywords (SRF)

Paper	Title	Other Keywords	Page
MOZGBF4	Evolution of the Superconducting Linac Output Energy at the Spallation Neutron Source	cavity, cryomodule, operation, linac	73
	S.-H. Kim, D.E. Anderson, M.T. Crofford, M. Doleans, J. Galambos, S.W. Gold, M.P. Howell, M.A. Plum, D.J. Vandygriff ORNL, Oak Ridge, Tennessee, USA R. Afanador, D.L. Barnhart, B. DeGraff, J.D. Mammosser, C.J. McMahan, T.S. Neustadt, C.C. Peters, J. Saunders, D.M. Vandygriff ORNL RAD, Oak Ridge, Tennessee, USA
	Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE. The SNS linac output energy has increased since the start of neutron production in FY2007. The various improvements that contributed to the increase of the linac output energy are LLRF/control system improvement, high voltage converter modulator system improvement, high-power RF system improvement, cryomodule repairs, spare cryomodule development and accelerating gradient improvement through in-situ plasma processing. In this paper, the history of the SNS SCL output energy is reported, and plans for the near-term future and for the Proton Power Upgrade (PPU) project are also presented.
	Slides MOZGBF4 [34.185 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOZGBF4
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MOPMF072	On the Feasibility of a Pulsed 14 TeV C.M.E. Muon Collider in the LHC Tunnel	collider, luminosity, proton, acceleration	296
	V.D. Shiltsev, D.V. Neuffer Fermilab, Batavia, Illinois, USA
	We will consider technical feasibility, key machine parameters and major challenges of the recently proposed 14 TeV c.m.e. muon-muon collider in the LHC tunnel.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF072
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MOPML034	Development Status of Superconducting RF Transmission Electron Microscope	cavity, acceleration, LLRF, gun	481
	N. Higashi, A. Enomoto, Y. Funahashi, T. Furuya, X.J. Jin, Y. Kamiya, S. Michizono, F. Qiu, M. Yamamoto KEK, Ibaraki, Japan S. Yamashita University of Tokyo, Tokyo, Japan
	Now we are developing a new type of transmission electron microscope (TEM) employing the accelerator technologies. In place of a DC thermal gun generally used in conventional TEMs, we apply a photocathode gun and a special-shaped superconducting cavity, named two-mode cavity. The two-mode cavity has two resonant modes of TM010 (1.3 GHz) and TM020 (2.6 GHz). To superimpose these, we can suppress the increase of the energy spread, which is needed for the high-spatial-resolution TEMs. We have already developed some prototypes of the photocathode gun and two-mode cavity, and now in the middle of the performance tests. In this presentation, we will show the latest status of the development.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML034
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MOPML053	Mu*STAR Accelerator-Driven Subcritical Reactors Burning Spent Nuclear Fuel at Light-Water-Reactor Sites	target, site, neutron, operation	524
	R.P. Johnson, R.J. Abrams, M.A. Cummings, T.J. Roberts Muons, Inc, Illinois, USA
	This project will use modeling and simulation tools to optimize many aspects of the MuSTAR design and begin to explore accident scenarios. At present we have a conceptual design of the accelerator, the reactor, the spallation target, and the fractional distillation to separate volatile fission products. Our GAIN project with ORNL is preparing a design of the Fuel Processing Plant that will convert spent nuclear fuel into the molten-salt fuel for MuSTAR. This includes all of the nuclear components, but not such things as the turbine and generator, physical plant, control and monitoring systems, etc. We currently have basic simulations of the reactor neutronics, and a start at calculating the fuel evolution. These have used MCNP and ORIGEN, and initial results have been reported1. This project will support the use of additional neutronics and multi-physics codes, enabling a much more thorough analysis of the system.
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TUYGBE2	CBETA, the 4-Turn ERL with SRF and Single Return Loop	electron, linac, gun, cryomodule	635
	G.H. Hoffstaetter, N. Banerjee, J. Barley, A.C. Bartnik, I.V. Bazarov, D.C. Burke, J.A. Crittenden, L. Cultrera, J. Dobbins, S.J. Full, F. Furuta, R.E. Gallagher, M. Ge, C.M. Gulliford, B.K. Heltsley, R.P.K. Kaplan, V.O. Kostroun, Y. Li, M. Liepe, W. Lou, C.E. Mayes, J.R. Patterson, P. Quigley, D.M. Sabol, D. Sagan, J. Sears, C.H. Shore, E.N. Smith, K.W. Smolenski, V. Veshcherevich, D. Widger Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA J.S. Berg, S.J. Brooks, C. Liu, G.J. Mahler, F. Méot, R.J. Michnoff, M.G. Minty, S. Peggs, V. Ptitsyn, T. Roser, P. Thieberger, D. Trbojevic, N. Tsoupas, J.E. Tuozzolo, F.J. Willeke, H. Witte BNL, Upton, Long Island, New York, USA D. Douglas JLab, Newport News, Virginia, USA J.K. Jones Cockcroft Institute, Warrington, Cheshire, United Kingdom D. Jusic Cornell University, Ithaca, New York, USA D.J. Kelliher STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom B.C. Kuske, M. McAteer, J. Völker HZB, Berlin, Germany
	Funding: Supported by NSF award DMR-0807731, DOE grant DE-AC02-76SF00515, and NYSERDA. A collaboration between Cornell University and Brookhaven National Laboratory has designed and is constructing CBETA, the Cornell-BNL ERL Test Accelerator on the Cornell campus. The ERL technology that has been prototyped at Cornell for many years is being used for this new accelerator, including a DC electron source and an SRF injector Linac with world-record current and normalized brightness in a bunch train, a high-current linac cryomodule optimized for ERLs, a high-power beam stop, and several diagnostics tools for high-current and high-brightness beams. BNL has designed multi-turn ERLs for several purpose, dominantly for the electron beam of eRHIC, its Electron Ion Collider (EIC) project and for the associated fast electron cooling system. Also in JLEIC, the EIC designed at JLAB, an ERL is envisioned to be used for electron cooling. The number of transport lines in an ERL is minimized by using return arcs that are comprised of a Fixed Field Alternating-gradient (FFA) design. This technique will be tested in CBETA, which has a single return for the 4-beam energies with strongly-focusing permanent magnets of Halbach type. The high-brightness beam with 150~MeV and up to 40~mA will have applications beyond accelerator research, in industry, in nuclear physics, and in X-ray science. Low current electron beam has already been sent through the most relevant parts of CBETA, from the DC gun through both cryomodules, through one of the 8 similar separator lines, and through one of the 27 similar FFA structures. Further construction is envisioned to lead to a commissioning start for the full system early in 2019.
	Slides TUYGBE2 [17.343 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUYGBE2
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TUPAF014	Beam Dynamics Studies For the IFMIF-DONES SRF-Linac	linac, cryomodule, cavity, solenoid	687
	L. Du, N. Bazin, N. Chauvin, S. Chel, J. Plouin CEA/IRFU, Gif-sur-Yvette, France
	The DONES (DEMO oriented neutron source) project is aimed at constructing a DEMO of IFMIF to provide sufficient material damage [1]. In the SRF-Linac of this project, losses can cause harmful material activation and must be maintained much less than 1W/m. It's a challenge to keep losses at such a low level with high beam power and high space charge. This paper presents two designs of the DONES SRF-Linac, one with 4 cryomodules and another with 5 cryomodules. The design details to reduce the losses and the multi-particle simulation results will be shown. The errors studies for these results will also be discussed.
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TUPAF076	Design of PIP-II Medium Energy Beam Transport	vacuum, linac, kicker, cryomodule	905
	A. Saini, C.M. Baffes, A.Z. Chen, V.A. Lebedev, L.R. Prost, A.V. Shemyakin Fermilab, Batavia, Illinois, USA
	Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics The Proton Improvement Plan-II (PIP-II) is a proposed upgrade for the accelerator complex at Fermilab. The central piece of PIP-II is a superconducting radio frequency (SRF) 800 MeV linac capable of operating in both CW and pulse regimes. The PIP-II linac comprises a warm front-end that includes a H⁻ ion source capable of delivering 15-mA, 30-keV DC or pulsed beam, a Low Energy Beam Transport (LEBT), a 162.5 MHz, CW Radio-Frequency Quadrupole (RFQ) accelerating the ions to 2.1 MeV and, a 14-m Medium Energy Beam Transport (MEBT) before beam is injected into SRF part of the linac. This paper presents the PIP-II MEBT design and, discusses operational features and considerations that lead to existing optics design such as bunch by bunch chopping system, minimization of radiation coming to the warm front-end from the SRF linac using a concrete wall, a robust vacuum protection system etc.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF076
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TUZGBE5	A Combined Temperature and Magnetic Field Mapping System for SRF Cavities	cavity, operation, niobium, experiment	1228
	J.M. Köszegi, K. Alomari, J. Knobloch, O. Kugeler, B. Schmitz HZB, Berlin, Germany
	In the past decade, a significant improvement of SRF cavity performance has been achieved, yet a number of performance limiting mechanisms, such as magnetic flux trapping, still exist. We present a diagnostics tool which combines flux expulsion measurement during the superconducting phase transition with temperature mapping during operation. This system has a time resolution for both temperature and magnetic field mapping of 2 ms for full cavity coverage, so that short-lived events, including cavity quenches, can easily be resolved.
	Slides TUZGBE5 [1.358 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUZGBE5
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TUPMF002	A Cu Photocathode for the Superconducting RF Photoinjector of BERLinPro	cathode, gun, cavity, laser	1247
	J. Kühn, M. Bürger, A. Frahm, A. Jankowiak, T. Kamps, G. Klemz, G. Kourkafas, A. Neumann, N. Ohm, M. Schmeißer, M. Schuster, J. Völker HZB, Berlin, Germany P. Murcek, J. Teichert HZDR, Dresden, Germany
	The initial commissioning of the Superconducting RF (SRF) photoinjector is done with a Cu photocathode due to its robustness with regard to interactions with the SRF cavity of the injector. Here we present the preparation and characterization of a Cu photocathode plug and the diagnostics to insert the photocathode in the back wall of the SRF cavity. A polycrystalline bulk Cu plug was polished, particle free cleaned and characterized by x-ray photoelectron spectroscopy. During the transfer of the photocathode insert into the gun module the whole process was controlled by several diagnostic tools monitoring the insert position as well as RF, vacuum and cryogenic signals. We discuss the challenges of the photocathode transfer into an SRF cavity and how they can be tackled.
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TUPML053	The BERLinPro SRF Photoinjector System - From First RF Commissioning to First Beam	cathode, cavity, operation, solenoid	1660
	A. Neumann, D. Böhlick, M. Bürger, P. Echevarria, A. Frahm, H.-W. Glock, F. Göbel, S. Heling, K. Janke, A. Jankowiak, T. Kamps, S. Klauke, G. Klemz, J. Knobloch, G. Kourkafas, J. Kühn, O. Kugeler, N. Leuschner, N. Ohm, E. Panofski, H. Plötz, S. Rotterdam, M.A.H. Schmeißer, M. Schuster, H. Stein, Y. Tamashevich, J. Ullrich, A. Ushakov, J. Völker HZB, Berlin, Germany
	Funding: The work is funded by the Helmholtz-Association, BMBF, the state of Berlin and HZB. Helmholtz-Zentrum Berlin (HZB) is currently constructing a high average current superconducting (SC) ERL as a prototype to demonstrate low normalized beam emittance of 1 mm-mrad at 100 mA and short pulses of about 2 ps. To attain the required beam properties, an SRF based photo-injector system was developed and during the past year underwent RF commissioning and was setup within a dedicated diagnostics beamline called Gunlab to analyze beam dynamics of both, a copper cathode and a Cs2KSb cathode as well as their quantum efficiency at UV and green light respectively. The medium power prototype - a first stage towards the final high power 100 mA design - 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 and up to 3.5 MeV kinetic energy, limited by the modified twin TTF-III fundamental power couplers. In this contribution, the first RF commissioning results of the photo-injector module will be presented including dark current analysis as well as measured beam properties with an initially installed Copper cathode.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML053
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WEYGBF3	Nb3Sn Multicell Cavity Coating at JLab	cavity, niobium, factory, superconductivity	1798
	U. Pudasaini, M.J. Kelley The College of William and Mary, Williamsburg, Virginia, USA G. Ciovati, G.V. Eremeev, M.J. Kelley, C.E. Reece JLab, Newport News, Virginia, USA M.J. Kelley Virginia Polytechnic Institute and State University, Blacksburg, USA I.P. Parajuli, MNS. Sayeed ODU, Norfolk, Virginia, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics. Following encouraging results with Nb3Sn-coated R&D cavities, the existing coating system was upgraded to allow for Nb3Sn coating of CEBAF accelerator cavities. The upgrade was designed to allow Nb3Sn coating of original CEBAF 5-cell cavities with the vapor diffusion technique. Several CEBAF cavities were coated in the upgraded system to investigate vapor diffusion coatings on extended structures. Witness samples coated along with the cavities were characterized with material science techniques, while coated cavities were measured at 4 and 2 K. The progress, lessons learned, and the pathforward are discussed.
	Slides WEYGBF3 [2.381 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEYGBF3
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WEPAK012	Developing Kalman Filter Based Detuning Control with a Digital SRF CW Cavity Simulator	cavity, controls, FPGA, LLRF	2114
	A. Ushakov, P. Echevarria, A. Neumann HZB, Berlin, Germany
	Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of the Helmholtz Association Continuous wave operated superconducting cavities experiencing small net beam loading and thus operate potentially at narrow bandwidth require precise detuning control to reach the high stability requirements for RF fields within facilities as FEL or ERL based photon sources. Especially microphonics compensation down to sub-hertz detuning regime besides improving stability reduces the risk of rise of Lorentz force detuning driven ponderomotive instabilities. Usually the complex and second order nature of the mechanical to RF detuning transfer functions of cavity and cavity-tuner system require for more advanced control schemes. In this paper we will show the application of a Kalman filter based detuning estimator algorithm first introduced during IPAC2017 [1] to the SRF cavity simulator developed at Helmholtz Zentrum Berlin [2]. Results using the algorithm in observer mode to detuning compensation attempts in closed loop mode are presented. * A. Ushakov, P. Echevarria, A. Neumann, Proc. of IPAC 2017, Copenhagen, Denmark
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WEPAK013	SRF Cavity Simulator for LLRF Algorithms Debugging	cavity, controls, LLRF, FPGA	2118
	P. Echevarria, J. Knobloch, A. Neumann, A. Ushakov HZB, Berlin, Germany E. Aldekoa, J. Jugo University of the Basque Country, Faculty of Science and Technology, Bilbao, Spain
	Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association The availability of niobium superconducting cavities, ei-ther due to a lack of a real cavity or due to the time needed for the experiment set up (vacuum, cryogenics, cabling, etc.), is limited, and thus it can block or delay the develop-ment of new algorithms such as low level RF control. Hardware-in-the-loop simulations, where an actual cavity is replaced by an electronics system, can help to solve this issue. In this paper we present a Cavity Simulator imple-mented in a National Instruments PXI equipped with an FPGA module. This module operates with one intermedi-ate frequency input which is IQ-demodulated and fed to the electrical cavity's model, where the transmitted and re-flected voltages are calculated and IQ-modulated to gener-ate two intermediate frequency outputs. Some more ad-vanced features such as mechanical vibration modes driven by Lorentz-force detuning or external microphonics have also been implemented. This Cavity Simulator is planned to be connected to an mTCA chassis to close the loop with a LLRF control system.
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WEPAL005	Beam Size Measurement and PSF Evaluate of KB Mirror Monitor at SSRF	storage-ring, optics, electron, photon	2151
	D.C. Zhu, J.S. Cao, Y.F. Sui, J.H. Yue IHEP, Beijing, People's Republic of China
	Funding: Work supported by National Nature Science Foundation of China(11605213) A Kirkpatrick Baez mirror imaging system was designed and installed to measure the transverse beam size and emittance of SSRF storage ring. Two crossed cylindrical mirrors are used to image the dipole source point in the horizontal and vertical direction. Both mirrors could be moved in and out in order to interchangeable with an original X-ray pinhole system. Hard X-ray with peak energy of 20.5 keV was focused at the X-ray scintillator camera. Aberration and point spread function which would cause image blur were evaluated. System commissioning and optimization have been done. PSF measurement was acquired using beam based calibration scheme by varying the beam images with different quadrupole settings and fitting them with the corresponding theoretical beam sizes.
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WEPAL039	LCLS-II Gun/Buncher LLRF System Design	gun, LLRF, cavity, controls	2258
	G. Huang, K.S. Campbell, L.R. Doolittle, J.A. Jones, Q. Qiang, C. Serrano LBNL, Berkeley, California, USA S. Babel, A.L. Benwell, M. Boyes, G.W. Brown, D. Cha, J.H. De Long, J.A. Diaz Cruz, B. Hong, A. McCollough, A. Ratti, C.H. Rivetta, D. Rogind, F. Zhou SLAC, Menlo Park, California, USA R. Bachimanchi, C. Hovater, D.J. Seidman JLab, Newport News, Virginia, USA B.E. Chase, E. Cullerton, J. Einstein-Curtis, D.W. Klepec Fermilab, Batavia, Illinois, USA J.A. Diaz Cruz CSU, Fort Collins, Colorado, USA
	Funding: This work was supported by the LCLS-II Project and the U.S. Department of Energy, Contract n. DE-AC02-05CH11231. For a free electron laser, the stability of injector is critical to the final electron beam parameters, e.g., beam energy, beam arrival time, and eventually it determines the photon quality. The LCLS-II project's injector contains a VHF copper cavity as the gun and a two-cell L-band copper cavity as its buncher. The cavity designs are inherited from the APEX design, but requires more field stability than demonstrated in APEX operation. The gun LLRF system design uses a connectorized RF front end and low noise digitizer, together with the same general purpose FPGA carrier board used in the LCLS-II SRF LLRF system. The buncher LLRF system directly adopts the SRF LLRF chassis design, but programs the controller to run the normal conducting cavities. In this paper, we describe the gun/buncher LLRF system design, including the hardware design, the firmware design and bench test.
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WEPAL055	TPS Beam Trip Analysis and Dose Distribution	radiation, kicker, neutron, storage-ring	2302
	B.Y. Chen, F.Y. Chang, S. Fann, C.S. Huang, C.H. Kuo, T.Y. Lee, C.C. Liang, W.Y. Lin, Y.C. Lin, Y.-C. Liu NSRRC, Hsinchu, Taiwan
	Failure analysis during TPS users operation is im-portant to improve the performance of the TPS storage ring. In this report, we discuss the particular radiation dose patterns, relevant to different beam trips, and the development of a tool to help us analyse this dose distri-bution. We will use this analysing tool to train our ability for future failure analysis to shorten the time it takes to find the problem.
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WEPMF012	Power Requirement and Preliminary Coupler Design for the eRHIC Crab Cavity System	cavity, operation, proton, electron	2394
	S. Verdú-Andrés, I. Ben-Zvi, D. Holmes, Q. Wu BNL, Upton, Long Island, New York, USA I. Ben-Zvi Stony Brook University, Stony Brook, USA
	Funding: Work supported by Brookhaven Science Associates LLC under contract no. DE-SC0012704 with the U.S. Department of Energy. Crab cavities are deflecting cavities operated in such a way that the bunch center is in synchronism with the zero-crossing kick voltage. In that case, beam loading is zero for an on-axis beam. The crab cavity system of the future electron-ion collider eRHIC will manipulate 275 GeV proton beams. At high energies, the beam offset can be as large as 2 mm (including mechanical and electrical offset tolerances). The beam loading resulting from such offset can greatly incur in large power requirements to the RF amplifier. The choice of external Q for the Fundamental Power Coupler (FPC) is critical to limit the power requirement to practical values. The loaded Q of the eRHIC crab cavities is mainly governed by the external Q of the FPC, so the external Q will also define the cavity bandwidth and thus the tuning requirements to counteract frequency transients from external perturbations. This paper discusses the choice of external Q for the FPC of the eRHIC crab cavities and introduces the design of a preliminary FPC antenna concept that would provide the appropriate external Q.
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WEPMF036	RF Test Result of a BNL N-Doped 500 MHz B-Cell Cavity at Cornell	cavity, vacuum, superconducting-cavity, niobium	2440
	F. Furuta, M. Ge, T. Gruber, J.J. Kaufman, M. Liepe, J.T. Maniscalco, J. Sears Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA F. Gao, J. Rose BNL, Upton, Long Island, New York, USA
	Cornell's SRF group has collaborated with Brookhaven National Laboratory (BNL) on one 500 MHz CESR type SRF "B-cell" cavity (BNL B-cell) for the National Synchrotron Light Source II. Cornell has been responsible for RF surface preparation, vertical testing, and short cavity string assembly. As a state-of-the-art surface preparation protocol, Cornell selected Nitrogen doping for the BNL B-cell. N-doping has been well demonstrated and established to push the cavity quality factor (Q0) higher in 1.3GHz SRF cavities at many laboratories. Cornell calculated that N-doping could also be beneficial on a 500MHz SRF cavity, with a potential to increase its Q0 by a factor of two compared with the traditional chemical polishing based surface preparation protocol. Here we report on the detailed surface preparation and vertical test result of the BNL B-cell.
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WEPMF037	HF Free Bipolar Electro-Polishing Studies on Niobium SRF Cavities at Cornell With Faraday Technology	cavity, niobium, MMI, radio-frequency	2443
	F. Furuta, M. Ge, T. Gruber, J.J. Kaufman, P.N. Koufalis, M. Liepe, J. Sears Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA T.D. Hall, M.E. Inman, R. Radhakrishnan, S.T. Snyder, E.J. Taylor Faraday Technology, Inc., Clayton, Ohio, USA
	Cornell's SRF group and Faraday Technology have been collaborating on two phase-II SBIR projects. One of them is the development and commissioning of a 9-cell scale HF free Bipolar Electro-Polishing (BEP) system. Faraday Technology has upgraded their 1.3 GHz single-cell BEP system for hosting 9-cell cavities. Initial commissioning of the new system was done with a three single-cell cavity string, and high a gradient of 40MV/m was demonstrated during the RF tests at Cornell. After this success with the test string, the 9-cell cavity was processed with the new system at Faraday and RF test was performed at Cornell. Here we report detailed results from these 9-cell scale HF free BEP studies.
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WEPMF038	Microphonics Suppression in the CBETA Linac Cryomodules	cavity, linac, cryomodule, controls	2447
	N. Banerjee, J. Dobbins, F. Furuta, G.H. Hoffstaetter, R.P.K. Kaplan, 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 New York State Energy Research and Development Agency. The linac cryomodules were constructed with funding from the National Science Foundation. The Cornell-BNL ERL Test Accelerator (CBETA) is a new multi-turn energy recovery linac currently under construction at Cornell University. It uses two superconducting linacs, both of which are susceptible to microphonics detuning. The high-current injector accelerates electrons to 6 MeV and the main linac accelerates and decelerates electrons by 36 MeV. In this paper, we discuss various measures taken to reduce vibrations caused by instabilities and flow transients in the cryogenic system of the main linac cryomodule. We further describe the use of a Least Mean Square algorithm in establishing a stable Active Microphonics Compensation system for operation of the main linac cavities.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF038
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WEPMF042	A Computational Method for More Accurate Measurements of the Surface Resistance in SRF Cavities	cavity, operation, niobium, radio-frequency	2458
	J.T. Maniscalco, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	The principal loss mechanism for superconducting RF cavities in normal operation is Ohmic heating due to the microwave surface resistance in the superconducting surface. The typical method for calculating this field-dependent surface resistance R_s(H) from RF measurements of quality factor Q₀ implicitly returns a weighted average of R_s over the surface as a function of peak surface magnetic field H, not the true value of R_s as a function of the local magnitude of H. In this work we present a computational method to convert a measured Q₀ vs. H_peak to a more accurate R_s vs. H_local, given knowledge about cavity geometry and field distribution.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF042
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WEPMF044	Updates on the DC Field Dependence Cavity	cavity, niobium, multipactoring, simulation	2465
	J.T. Maniscalco, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Work at Cornell has demonstrated good agreement between a theoretical model by A. Gurevich of the anti-Q-slope (a field-dependent decrease of the microwave surface resistance) and experimental results from impurity-doped niobium. As a corollary, the model predicts that a strong DC magnetic field applied parallel to the RF surface will produce a similar decrease in surface resistance. In order to explore this prediction for many materials, we have designed a new coaxial cavity with a strong, uniform DC field superimposed over a weak RF field on a removable and replaceable niobium sample. Here we present updates on the progress of this new cavity.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF044
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WEPMF045	Performance of the Prototype SRF Half-Wave-Resonators Tested at Cornell for the RAON Project	cavity, multipactoring, pick-up, radiation	2468
	M. Ge, F. Furuta, T. Gruber, S.W. Hartman, M. Liepe, J.T. Maniscalco, 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
	Two prototype superconducting half-wave-resonator (162.5 MHz and β=0.12) for the RAON project have been successfully tested at Cornell University. Detailed vertical performance testing included (1) test of the bare cavity without the helium tank, and (2) test of the dressed cavity with a helium tank. In this paper, we report on the development of the test infrastructure, test results, and performance data analysis, showing that the specifications for RAON were met.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF045
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WEPMF046	Modeling of the Frequency and Field Dependence of the Surface Resistance of Impurity-Doped Niobium	cavity, niobium, experiment, ECR	2471
	J.T. Maniscalco, P.N. Koufalis, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	The anti-Q-slope, a field-dependent decrease in surface resistance observed in impurity-doped niobium, has been investigated extensively in 1.3 GHz cavities. New early research into this effect has recently been performed at higher and lower frequencies, revealing an additional dependence on frequency: the anti-Q-slope is stronger at higher frequencies and weaker at lower frequencies. Several models have been proposed to explain the anti-Q-slope, with varying success in this new frequency-dependent regime. In this work, we analyze recent experimental data from a low-temperature-doped 1.3 GHz cavity and a high-temperature nitrogen-doped 2.6 GHz cavity and discuss the implications of these results on the proposed models.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF046
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WEPMF047	Performance of Samples With Novel SRF Materials and Growth Techniques	cavity, superconducting-RF, niobium, site	2475
	T.E. Oseroff, M. Ge, M. Liepe, J.T. Maniscalco, R.D. Porter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA S.R. McNeal Ultramet, Pacoima, California, USA M.J. Sowa Veeco-CNT, Medford, USA
	Novel materials are currently being studied in an attempt to push accelerating superconducting RF cavities to support higher accelerating fields and to operate with lower power loss. Growing layers of these materials of the quality necessary has proven to be difficult. In this work, we present the SRF performance of planar samples of the promising materials, NbN and Nb¬3Sn, grown using atomic layer deposition (ALD) and chemical vapor deposition (CVD) respectively. Results are promising.
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WEPMF050	Update on Nb3Sn Progress at Cornell University	cavity, niobium, accelerating-gradient, site	2479
	R.D. Porter, J. Ding, D.L. Hall, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA T.A. Arias, P. Cueva, D.A. Muller, N. Sitaraman Cornell University, Ithaca, New York, USA
	Niobium-3 Tin (Nb3Sn) is the most promising alternative material for SRF accelerator cavities. The material can achieve higher quality factors, higher temperature operation and potentially higher accelerating gradients compared to conventional niobium. Cornell University has a leading program to produce 2 - 3 micrometer thick coatings of Nb3Sn on Nb for SRF applications using vapor diffusion. This program has been the first to produce quality factors higher than achievable with conventional Nb at usable accelerating gradients. Here we present an update on progress at Cornell University, including studies of the formation of the Nb3Sn layer, density functional theory calculations of Nb3Sn growth, and designs for a sample host cavity for measuring the quench field of Nb3Sn.
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WEPMK008	In-Depth Analysis of the Vertical Test Results of the Third-Harmonic Cavities for the E-XFEL Injector	cavity, FEL, experiment, feedback	2644
	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 C.G. Maiano, P. Pierini ESS, Lund, Sweden C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy
	The results of the vertical tests performed at LASA on the 3.9 GHz third-harmonic cavities for the E-XFEL injector are here discussed. Analysis of experimental data allows to confirm that such high frequency cavity, prepared with standard BCP treatment and 800°C annealing treatment, suffers an intrinsic performance limitation at around 22 MV/m (@ 2 K) due to a global thermal dissipation mechanism. A quantitative interpretation of the high field Q slope is also presented according to the latest theoretical models of field-dependent surface resistance.
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WEPMK009	Status of the ESRF-EBS Magnets	quadrupole, dipole, sextupole, octupole	2648
	C. Benabderrahmane, J.C. Biasci, J-F. B. Bouteille, J. Chavanne, L. Eybert, L. Goirand, G. Le Bec, L. Lefebvre, S.M. Liuzzo, D. Martin, C. Penel, P. Raimondi, J.-L. Revol, F. Villar, S.M. White ESRF, Grenoble, France
	The ESRF-EBS (Extremely Brilliant Source) is an upgrade project planned at the European Synchrotron Radiation Facility (ESRF) in the period 2015-2022. A new storage ring will be built, aiming to decrease the horizontal emittance and to improve the brilliance and coherence of the X-ray beams. The lattice of the new storage ring relies on magnets with demanding specifications: dipoles with longitudinal gradient (field ranging from 0.17 T up to 0.67 T), strong quadrupoles (up to 90 T/m), combined function dipole-quadrupoles with high gradient (0.57 T and 37 T/m), strong sextupoles and octupoles. The design of these magnets is based on innovative solutions; in particular, the longitudinal gradient dipoles are permanent magnets and the combined dipole-quadrupoles are single-sided devices. The longitudinal gradient dipoles have been assembled and measured in house. The design of the magnets, production status and magnetic measurement results will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK009
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WEPMK012	Update on Plasma Processing R&D for LCLS-II	plasma, cavity, HOM, experiment	2656
	P. Berrutti, A. Grassellino, T.N. Khabiboulline, M. Martinello Fermilab, Batavia, Illinois, USA M. Doleans, S.-H. Kim, K.E. Tippey ORNL, Oak Ridge, Tennessee, USA D. Gonnella, G. Lanza, M.C. Ross SLAC, Menlo Park, California, USA
	Funding: Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the U.S. DOE SRF cavities performance preservation is crucial, from vertical test to accelerator operation. Field emission is still one of the main problems to overcome and plasma cleaning has been proven successful by SNS, in cleaning field emitters and increasing the work function of Nb. A collaboration has been established between FNAL, SLAC and ORNL with the purpose of applying plasma processing to LCLS-II cavities, in order to minimize and overcome field emission without affecting the high Q of N-doped cavities. The recipe will follow the neon-oxygen active plasma adopted at SNS, allowing in-situ processing of cavities and cryomodules from hydrocarbon contaminants. A novel method for plasma ignition has been developed at FNAL: a plasma glow discharge is ignited using high order modes to overcome limitations imposed by the fundamental power coupler. The results of experiments on 9-cell LCLS-II cavity are presented, along with plasma ignition studies. In addition the RF system is shown and N-doped Nb samples studies are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK012
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WEPMK014	A New Design for the Hilumi Radio-Frequency Dipole Bare Cavity	cavity, niobium, GUI, resonance	2659
	M. Parise, P. Berrutti, L. Ristori Fermilab, Batavia, Illinois, USA
	Crabbing cavities are one of the technological landmark that will allow the LHC to optimize its per-formance and maximize its integrated luminosity by allowing a head-on collision between the bunches despite the non-zero crossing angle. A total of 8 crab cavities will be installed in the interaction region of each of the two experiments, ATLAS and CMS. In the last years, the two types of crab cavities were de-signed, built and tested under the US-LARP R&D pro-gram. Horizontal crabbing is obtained with a radio-frequency dipole cavity (RFD) designed by Old Do-minion University (ODU), SLAC and Fermilab (FNAL). In this paper a new mechanical design, that uses passive stiffeners, is presented. This design leads to a decrease of the Lorentz Force Detuning frequency shift, satisfy the requirements on pressure sensitivity, validate the structural integrity and increase the tuner sensitivity and the maximum elastic tuning range. Furthermore, it will be possible to greatly simplify the shape of the magnetic shield and Helium vessel with respect to the current design.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK014
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WEPMK015	Optimization of Vertical Electro-Polishing Process: Experiments with Updated Cathode on Single-Cell Cavity and Performance Achieved in Vertical Test	cavity, cathode, linac, superconductivity	2662
	F. Éozénou, L. Maurice CEA/DSM/IRFU, France P. Carbonnier, C. Madec, Th. Proslier, C. Servouin CEA/DRF/IRFU, Gif-sur-Yvette, France V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi MGH, Hyogo-ken, Japan H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe KEK, Ibaraki, Japan
	Marui Galvanizing Co.Ltd., and CEA have been studying Vertical Electro-Polishing (VEP) on Nb single-cell accelerating superconducting accelerator cavity with the goal of mass-production and cost-reduction, in collaboration with KEK within TYL-FJPPL Particle Physics Laboratory. Marui has invented and patented a rotative cathode called ‘i-Ninja'. The version 5 has been tested for the first time in Europe at CEA Saclay. The four wings of the cathode remove efficiently, bubbles of hydrogen, and the chosen parameters make it possible to achieve better surface and uniform material removal compared to VEP with a fixed cathode. The effect of the temperature of the cavity walls on current oscillations has been precisely studied. Two single-cell cavities have been electro-polished and tested at 2 K in vertical cryostat and the results will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK015
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WEPMK016	New Insight on Nitrogen Infusion Revealed by Successive Nanometric Material Removal	cavity, accelerating-gradient, factory, niobium	2665
	M. Checchin, A. Grassellino, M. Martinello, O.S. Melnychuk, S. Posen, A.S. Romanenko, D.A. Sergatskov Fermilab, Batavia, Illinois, USA
	In this study we present new insight on low temperature nitrogen infusion on bulk niobium superconducting radio-frequency (SRF) cavities. Nitrogen infusion is a thermal treatment recently discovered at Fermilab that allows to reach high accelerating gradients, of the order of 45MV/m, with high Q-factors, of the order of 2 · 10¹⁰. Detailed depth dependent RF studies (by means of subsequent HF rinses) and comparisonwith SIMS results pinpointed interstitial nitrogen as the responsible for the improved performance and uncovered the extension of its profile inside the material.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK016
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WEPML003	Precision Q0 Measurement of an SRF Cavity with a Digital RF Techniques	cavity, coupling, impedance, GUI	2674
	J.P. Holzbauer, B.M. Hanna, Y.M. Pischalnikov, W. Schappert, D.A. Sergatskov, A.I. Sukhanov Fermilab, Batavia, Illinois, USA
	Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. Direct measurement of the quality factor of SRF cavity using traditional RF techniques is essential for cavity production and development. Systematic effects of the measurement can contribute significant amounts of error to these measurements if not accounted for. This paper will present measurements taken at Fermilab using a digital RF system to characterize and correct for these systematic effects and directly measure the quality factor versus gradient curve for a single spoke resonator in the Spoke Test Cryostat at Fermilab. These measurements will be compared to traditional calorimetric measurements, and a discussion of improving/extending these techniques to other testing situations will be included.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML003
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WEPML004	Production Tuner Testing for LCLS-II Cryomodule Production	cavity, cryomodule, LLRF, interface	2678
	J.P. Holzbauer, Y.M. Pischalnikov, W. Schappert, J.C. Yun Fermilab, Batavia, Illinois, USA C. Contreras-Martinez FRIB, East Lansing, USA
	Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. LCLS-II 1.3 GHz cryomodule production is well underway at Fermilab. Several dozen cavity/tuner systems have been tested, including tuning to 1.3 GHz, cold landing frequency, range/sensitivity of the slow tuner, and range/sensitivity of the fast tuner. All this testing information as well as lessons learned from tuner installation will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML004
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WEPML005	Testing of SSR1 Production Tuner for PIP-II	cavity, linac, niobium, cryomodule	2681
	J.P. Holzbauer, D. Passarelli, Y.M. Pischalnikov Fermilab, Batavia, Illinois, USA
	Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. The PIP-II project at Fermilab is a proton driver linac calling for the use of five different, novel cavity geometries. Prototyping at Fermilab is in the advanced stages for the low-beta single-spoke resonator (SSR1) and associated technologies. A production tuner design has been fabricated and tested, both warm and cold in the Spoke Test Cryostat (STC). This paper will present the detailed studies on this tuner, including slow motor/piezoelectric tuner range and hysteresis as well as dynamic mechanical system characterization.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML005
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WEPML006	Modified Slow Tuner Design for Cavity 1 Inside LCLS II Cryomodules	cavity, cryomodule, interface, simulation	2684
	Y.M. Pischalnikov, T.T. Arkan, S. Cheban, J.P. Holzbauer, J.A. Kaluzny, Y.O. Orlov, J.C. Yun Fermilab, Batavia, Illinois, USA
	Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. Initial LCLS-II cryomodule testing at Fermilab showed microphonics on the furthest upstream cavity (number 1) at least factor 2 larger than on the rest of the cavities. Testing indicated that this was a difference in the mechanical support of cavity 1, not a local acoustic source. Further investigation pointed to the upstream beam-pipe of the cavity 1. The upstream cavity flange has a solid spool piece connection to the beamline gate valve unlike the other cavities, which all connect through bellows. The gate valve's weight is supported by sliding system (free in z-axis) connected to large diameter Helium gas return pipe. The tuner design was modified to transform interface between cavity#1 and gate valve. Arms of the tuner for cavity 1 were extended and became the support structure for gate valve, eliminating the connection to the helium return pipe. Modification of the tuner design and results in microphonics mitigations will be presented.
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WEPML008	Tuner Testing of a Dressed 3.9 GHz Cavity for LCLS-II at Fermilab	cavity, operation, background, FEL	2690
	J.P. Holzbauer, S. Aderhold, T.N. Khabiboulline, Y.M. Pischalnikov, W. Schappert, J.C. Yun Fermilab, Batavia, Illinois, USA C. Contreras-Martinez FRIB, East Lansing, USA
	Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. Fermilab is responsible for the design of the 3.9 GHz cryomodule for LCLS-II. Integrated acceptance testing of a dressed 3.9 GHz cavity for the LCLS-II project has been done at the Fermilab Horizontal Test Stand. This test included a slim blade tuner (based on INFN & XFEL designs) with integrated piezoelectric fast/fine tuner. This paper will present results of the mechanical setup, cold testing, and cold function of this tuner including fast and slow tuner range, sensitivity, and hysteresis.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML008
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WEPML010	Operation Regime Analysis of Conduction Cooled Cavities Through Multi-Physics Simulation	cavity, operation, simulation, niobium	2697
	R.A. Kostin, R. Dhuley, M.G. Geelhoed, R.D. Kephart, T.K. Kroc, O.V. Prokofiev, J.C.T. Thangaraj Fermilab, Batavia, Illinois, USA A. Kanareykin Euclid TechLabs, LLC, Solon, Ohio, USA
	Funding: Department of Energy Euclid Techlabs in collaboration with Fermilab IARC (Batavia, IL) is developing industrial superconducting 10MeV electron linac. Conduction cooling is used for cooling instead of liquid helium bath to simplify linac maintenance. The cavity linked to commercially available cryo-cooler cold head through highly conductive aluminium strips. However, this solution raises a problem of contact thermal resistance. This paper shows some results of Comsol multyphysics simulations of the cavity cooling by AL strips. Some insight was obtained on the acceptable range of contact resistance. Operation regimes were obtained at different accelerating gradients and cavity temperatures. The results of simulation are presented and discussed.
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WEPML013	Anti-Q-slope enhancement in high-frequency niobium cavities	cavity, ECR, niobium, experiment	2707
	M. Martinello, S. Aderhold, S.K. Chandrasekaran, M. Checchin, A. Grassellino, O.S. Melnychuk, S. Posen, A.S. Romanenko, D.A. Sergatskov Fermilab, Batavia, Illinois, USA
	N-doped 1.3 GHz niobium cavities showed for the first time the so-called anti-Q-slope, i.e. the increasing of the Q-factor as a function of the accelerating field. It was verified that the anti-Q-slope is consequence of the decreasing of the temperature-dependent component of the surface resistance as a function of the field. This trend is opposite compared to the increasing of the surface resistance previously observed in 1.3 GHz standard (EP, BCP, 120 C baked) niobium cavities. The effect of the different state-of-the-art surface treatments on the field dependence of the surface resistance is studied for 650 MHz, 1.3 GHz, 2.6 GHz and 3.9 Ghz cavities. This proceeding shows that the field dependence of the temperature-dependent component of the surface resistance has a strong frequency dependence and that the anti-Q-slope may appear even in clean niobium cavities if the resonant frequency is high enough, suggesting new routes toward the understanding of the anti-Q-slope effect.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML013
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WEPML016	Development of Nb3Sn Coatings for Superconducting RF Cavities at Fermilab	cavity, factory, superconductivity, network	2718
	S. Posen, S.K. Chandrasekaran, O.S. Melnychuk, D.A. Sergatskov, B. Tennis, Y. Trenikhina Fermilab, Batavia, Illinois, USA J. Lee NU, Evanston, Illinois, USA
	Nb3Sn films are a promising alternative material for su-perconducting RF cavities, with proven high quality factors at medium fields and predictions for increased superheating field as well. In this contribution, we de-scribe the latest results from the Fermilab Nb3Sn SRF program. Early experiments have been focused on single cell 1.3 GHz cavities. We briefly review efforts to bring the parameters used in the coating process into a range where they produce uniform surfaces without regions showing signs of excess tin or thin/uncoated areas. We then present the latest cavity results, after modifications to the coating recipe based on feedback from film appear-ance and RF performance. These results show high Q0 at medium fields and a maximum field of ~18 MV/m.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML016
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WEPML040	Further Tests on the Final State of the SC 325 MHz CH-Cavity and Coupler Test Bench Update	cavity, linac, heavy-ion, framework	2783
	M. Busch, M. Basten, J. List, P. Müller, H. Podlech, M. Schwarz IAP, Frankfurt am Main, Germany W.A. Barth, J. List GSI, Darmstadt, Germany W.A. Barth HIM, Mainz, Germany W.A. Barth MEPhI, Moscow, Russia
	Funding: Work supported by BMBF Contr. No. 05P15RFBA At the Institute for Applied Physics, Goethe-University Frankfurt, a sc 325 MHz CH-cavity has been developed and successfully tested up to 14.1 mV/m and has now reached the final production stage with the helium vessel welded to the frontal joints of the cavity and final processing steps have been performed. Further tests in a vertical and horizontal environment are being prepared for intensive studies. This cavity is a prototype for envisaged beam tests with a pulsed ion beam at 11.4 AMeV. In this contribution the results of the performed RF tests are being presented. Furthermore, first measurements of the recently installed 217 MHz coupler test bench are shown.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML040
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WEPML045	Infrastructure for Superconducting CH-Cavity Preparation at HIM	cavity, linac, vacuum, heavy-ion	2796
	T. Kürzeder, K. Aulenbacher, W.A. Barth, F.D. Dziuba, V. Gettmann, M. Miski-Oglu, E. Riehn HIM, Mainz, Germany K. Aulenbacher, R.G. Heine, T. Stengler IKP, Mainz, Germany W.A. Barth, S. Yaramyshev GSI, Darmstadt, Germany F. Hug KPH, Mainz, Germany
	A superconducting cw LINAC for heavy ions is currently under development at GSI in Darmstadt and HIM in Mainz. This Linac is based on 217 MHz multigap bulk niobium Crossbar H-mode RF-cavities. In order to treat and prepare RF-cavities with such a complex geometry a new cleanroom facility has been already built at the Helmholtz-Institut in Mainz. All tools and machines inside the cleanroom can handle cavities with up to 800 mm in diameter and with up to 1300 mm in length. In its ISO-class 6 and 4 zones, respectively it features a large ultrasonic and conductance rinsing bath, a high pressure rinsing (HPR) cabinet and a vacuum oven. The HPR cabinet has an inside clearance of 1.4 m. The large cavities sit on a rotating table, while the rising wand moves vertically up and down. Due to the crossbar structure of the RF-cavities the HPR device allows for off axis-rinsing in their quadrants. For RF testing a 52 m² (4 m x 13 m) concrete shielded area with sufficient liquid helium and nitrogen supply is located next to the cleanroom and the cryo-module assembly area. We will report on the new SRF infrastructure in Mainz and the commissioning of the new high pressure rinsing cabinet.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML045
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WEPML047	Study on RF Coupler Kicks of SRF Cavities in the BESSY VSR Module	cavity, storage-ring, HOM, GUI	2804
	A.V. Tsakanian, T. Mertens Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany H.-W. Glock, J. Knobloch, M. Ries, A.V. Vélez HZB, Berlin, Germany
	The BESSY VSR upgrade of the BESSY II light source represents a novel approach to simultaneously store long (ca. 15ps) and short (ca. 1.7ps) bunches in the storage ring with the standard user optics. This challenging goal requires installation of four new SRF multi-cell cavities (2x1.5GHz and 2x1.75GHz) equipped with strong waveguide HOM dampers ensuring tolerable beam coupling impedance, necessary for stable operation. These cavities will operate at high 20MV/m in CW mode and at the zero-crossing phase according to the accelerating voltage. Consequently the transverse voltages will be maximum and can impact the transverse beam dynamics. The asymmetric character of those transverse kicks are caused by cavity fundamental power couplers (FPC) with strong monopole terms, introducing transverse kick to on-axis particles. Different FPC orientations were analyzed to optimize the net coupler kick from the four cavity chain. The coupler kick strength of each cavity is estimated taking into account accelerating mode amplitudes and phases required for operation in VSR mode.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML047
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WEPML048	HOM Power Levels in the BESSY VSR Cold String	HOM, cavity, simulation, GUI	2808
	A.V. Tsakanian, T. Flisgen Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany 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 long (ca. 15ps) and short (ca. 1.7ps) bunches in the storage ring. This challenging goal requires installation of four new SRF cavities (2x1.5 GHz and 2x1.75 GHz) in one module for installation in a single straight. These cavities are equipped with strong waveguide HOM dampers necessary for stable operation. The expected HOM power and spectrum has been analyzed for the complete cold string. The cold string is a combination of various elements such as SRF cavities, bellows with and without shielding, warm HOM beampipe absorbers and UHV pumping domes. The presented study is performed for various BESSY VSR bunch filling patterns with 300 mA beam current. The contribution of each component to the total HOM power is presented. In addition the optimization of different cavity arrangements in the module is performed in order to reach the optimal operation conditions with equally distributed power levels along the string and tolerable beam coupling impedance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML048
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WEPML049	The Challenge to Measure nΩ Surface Resistance on SRF Samples	quadrupole, pick-up, cavity, simulation	2812
	S. Keckert, T. Junginger, J. Knobloch, O. Kugeler HZB, Berlin, Germany T. Junginger Lancaster University, Lancaster, United Kingdom
	Systematic research on fundamental limits of superconducting materials for SRF applications and their intrinsic material properties relevant for use in an accelerator requires studies in a wide parameter space of temperature, RF field and frequency. The Quadrupole Resonator at HZB enables precision measurements on planar samples at temperatures of 1.8 K to >20 K, RF fields of up to 120 mT, and frequencies of 420 MHz, 850 MHz and 1285 MHz. In the past years the capabilities of the setup were studied intensively and developed further. Sources of systematic errors, such as microphonics or misalignment have been identified and eliminated. In this contribution the current status of the QPR and its systematic limitations are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML049
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WEPML053	Availability of the TiN Coating-Free Ceramic in the STF-type Power Coupler for ILC	electron, vacuum, cryomodule, GUI	2819
	Y. Yamamoto, E. Kako, T. Matsumoto, S. Michizono, A. Yamamoto KEK, Ibaraki, Japan M. Irikura, M. Ishibashi, H. Yasutake Toshiba Electron Tubes & Devices Co., Ltd (TETD), Tochigi, Japan C. Julie, E. Montesinos CERN, Geneva, Switzerland
	In the Superconducting RF Test Facility (STF) in KEK, the research and development for the power coupler with the TiN coating-free ceramic has been done from 2014. In 2016, the high power test at the test bench was stopped due to the worse vacuum level by the unusual heating around the RF window with the TiN coating-free ceramic and the coaxial tapered section, which was caused by the enormous emission of the secondary electrons from the ceramic. And, the situation was never also changed by the ultrapure water rinsing for the power couplers several times. However, in 2017, the ultrasonic rinsing was done for the power couplers for the first time by the collaboration between KEK and TETD. After that, the situation was drastically improved, and the secondary electron emission almost disappeared even in the higher RF duty. This shows that the TiN coating-free ceramic is the prospective item for the cost reduction in ILC. In this report, the recent result for the power coupler with the TiN coating-free ceramic will be presented in detailed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML053
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WEPML067	Second Sound Quench Detection on Superconducting Cavities	cavity, detector, site, superconducting-cavity	2843
	Z.C. Liu, S. Bai, J. Gao, F.S. He, H.Y. Lin, P. Zhang IHEP, Beijing, People's Republic of China
	Second sound is an effective way to detect the quench position on superconducting cavity. A second sound quench site detection system is under developing for the PAPS. High gradient is very important for superconducting cavity, however it may be limited by quench on the cavity high field region. Quench can be caused by various reasons. To locate the position is the key to reveal the mysteries of quench. Now we are developing the quench position detection system by RTD sensors such as Cernox and OST sensors.
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WEPML078	Development of a Superconducting Double-Spoke Cavity at IMP	cavity, accelerating-gradient, ion-source, niobium	2869
	T.C. Jiang, H. Guo, Y. He, C.L. Li, L.B. Liu, T. Tan, P.R. Xiong, Z.M. You, W.M. Yue, S.H. Zhang, S.X. Zhang IMP/CAS, Lanzhou, People's Republic of China
	Superconducting multi-spoke cavities are well-known optional choice for acceleration of heavy ions in medium velocity regimes. The paper describes the design, fabrication and test results of the superconducting double-spoke cavity developed at IMP. After Buffered Chemical Polishing and High pressure Rinsing, one cavity has undergone high gradient RF testing at 4 K in the Vertical Test Stand. We present measurements of the quality factor as a function of accelerating field and maximum field on the surface. Accelerating gradient of more than 15 MV/m is reached with peak electric field of 61 MV/m, and peak magnetic field of 118 mT.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML078
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THXGBD3	Status of the ESRF-Extremely Brilliant Source Project	vacuum, operation, injection, dipole	2882
	J.-L. Revol, C. Benabderrahmane, P. Berkvens, J.C. Biasci, J-F. B. Bouteille, T. Brochard, N. Carmignani, J.M. Chaize, J. Chavanne, F. Cianciosi, A. D'Elia, R.D. Dimper, M. Dubrulle, D. Einfeld, F. Ewald, L. Eybert, G. Gautier, L. Goirand, L. Hardy, J. Jacob, B. Joly, M.L. Langlois, G. Le Bec, I. Leconte, S.M. Liuzzo, C. Maccarrone, T.R. Mairs, T. Marchial, H.P. Marques, D. Martin, J.M. Mercier, A. Meunier, M. Morati, J. Pasquaud, T.P. Perron, E. Plouviez, E. Rabeuf, P. Raimondi, P. Renaud, B. Roche, K.B. Scheidt, V. Serrière, P. Van Vaerenbergh, R. Versteegen, S.M. White ESRF, Grenoble, France
	The ESRF - the European Synchrotron Radiation Facility - is a user facility in Grenoble, France, and the source of intense high-energy (6 GeV) X-rays. In 2019, the existing storage ring will be removed and a new lattice will be installed in its place, dramatically reducing the equilibrium horizontal emittance. This 'fourth-generation' synchrotron will produce an X-ray beam 100 times more brilliant and coherent than the ESRF source today. The Extremely Brilliant Source (EBS) project was launched in 2015 and is now well underway, on track for its scheduled completion in 2020. The design is completed, the procurement in full swing, the assembly has started, and critical installation activities are being prepared. The current status, three years into the project, will be revealed, along with the expected performance of the accelerator and the technical challenges involved. This paper will focus on the implementation of the project.
	Slides THXGBD3 [13.547 MB]
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THPAF028	Multi-Objectives Genetic Algorithms (MOGA) Optimization of PETRA IV Scenarios	lattice, injection, sextupole, dynamic-aperture	3015
	X.N. Gavaldà, J. Keil, R. Wanzenberg DESY, Hamburg, Germany
	This paper reports the application of Multi-Objective Genetic Algorithms (MOGA) to optimize the linear and nonlinear beam dynamics of the different PETRA IV scenarios to transform PETRA III storage ring in a diffracted limited one. As it is well known, the dynamic aperture and momentum acceptance of these kinds of lattices are dramatically reduced due to the increase of the sextupoles strengths to compensate its strong focusing. The reduction of the dynamic aperture jeopardizes the current off-axis injection system and lower beam lifetimes increase the beam instabilities and the radiation safety concerns of the storage ring. MOGA searches the best settings of quadrupoles and sextupoles in a multi-dimensional parameter space taking into account the dynamic properties and the natural emittance as objectives at the level of ten picometers. The lattices studied are the so-called 'Twist lattice' based in a phase space exchange lattice, a solution based in the ESRF-Hybrid Multi-bend Achromat (HMA) design and finally the 'double 'I' lattice combining a non-interleaved sextupoles cell with an ESRF-HMA cell.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF028
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THPAF084	Impact of RF Coupler Kicks on Beam Dynamics in BESSY VSR	cavity, simulation, kicker, lattice	3182
	T. Mertens Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany T. Atkinson, F. Glöckner, A. Jankowiak, M. Ries, A.V. Tsakanian HZB, Berlin, Germany
	The expected BESSY II upgrade to BESSY VSR requires the installation of a superconducting RF system, consisting of four cavities. Two cavities will operate at 1.5 GHz and two at 1.75 GHz. Each of them is equipped with a Fundamental Power Coupler and with Higher Order Mode (HOM) damping waveguide couplers. Dedicated simulations of these cavities and couplers have shown that at the location of the FPC the beam will see a transverse kick [], perturbing the closed orbit and affecting transverse beam dynamics. We present the results of simulations and experiments of the impact on transverse beam dynamics of these coupler induced kicks for different FPC orientations. [] Study on RF Coupler Kicks of SRF Cavities in the BESSY VSR Module A. Tsakanian#, H.-W. Glock, T. Mertens, M. Ries, A. Velez, J. Knobloch IPAC18
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF084
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THPAK076	Development and Benchmarking of the IMPACT-T Code	rfq, linac, simulation, space-charge	3408
	H.P. Li, M.J. Easton, Y.R. Lu, Z. Wang PKU, Beijing, People's Republic of China J. Qiang LBNL, Berkeley, California, USA
	The multi-particle tracking code IMPACT-T is widely used to calculate the particle motion in high intensity linacs. The code is a self-consistent three-dimensional beam dynamics simulation toolbox that utilizes the particle-in-cell method in the time domain. In the collaboration between PKU and LBNL, an RFQ module was implemented to the IMPACT-T code, which enables simulations of the accelerator front-end. In order to benchmark the newly developed module in the IMPACT-T code, we have simulated the beam transport in Beijing Isotope Separation On-Line (BISOL) high intensity deuteron driver linac. It consists of a 3 MeV RFQ and 40 MeV superconducting HWR linac with five cryomodules. After comparing the simulation results with PARMTEQM, TraceWin and Toutatis, we obtained a very good agreement, which represents the validation of the new code.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK076
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THPAL007	Upgrade of PIAVE Superconducting RFQs at INFN-Legnaro	rfq, operation, cavity, superconducting-RF	3623
	G. Bisoffi, E. Bissiato, D. Bortolato, F. Chiurlotto, T. Contran, E. Fagotti, A. Minarello, P. Modanese, E. Munaron, D. Scarpa INFN/LNL, Legnaro (PD), Italy V. Andreev ITEP, Moscow, Russia A. Bosotti, R. Paparella INFN/LASA, Segrate (MI), Italy L.M.A. Ferreira CERN, Geneva, Switzerland K. Kasprzak IFJ-PAN, Kraków, Poland R.C. Pardo ANL, Argonne, Illinois, USA
	Superconducting RFQs (SRFQs), the first SC RFQs ever made operational for users, have been operated on the PIAVE SC heavy ion linac injector at INFN-Legnaro since 2006. The structure is split into two resonators and is limited to the accelerating RFQ sections. The resonators had never exceeded 80% of the design accelerating fields. In 2015, an upgrade plan started, aimed at increasing the accelerating fields, while improving their slow and fast tuning systems, repairing degraded components, imple-menting a LASER alignment method. The upgrade plan was successfully concluded in summer 2017. The resona-tors were kept stably locked for days at a field larger than the nominal one. Eventually, a test beam was accelerated successfully for 72 hours, with negligible locking issues. SRFQs entered once again routine operation in December 2017. The new features will allow to accelerate heavy ions with an A/q value as high as 8.5 (versus a former maximum A/q=7.5), allowing operation of the very first accelerated uranium beams at INFN-LNL, after the relat-ed authorizations shall have been issued.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL007
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THPAL012	Soft Chemical Polishing and Surface Analysis of Niobium Samples	cavity, niobium, linac, operation	3641
	J. Conrad, L. Alff, M. Arnold, S. Flege, R. Grewe, M. Major, N. Pietralla TU Darmstadt, Darmstadt, Germany F. Hug IKP, Mainz, Germany
	Funding: Work supported by the German Federal Ministry for Education and Research (BMBF) under Grant No. 05H15RDRBA The Superconducting Darmstadt Linear Accelerator S-DALINAC uses twelve Niobium Cavities with a RRR of 280 which are operated at 2 K. The operating frequency is 3 GHz; the design value of the accelerating gradient is 5 MV/m. To achieve the target value of 3 x 10˄9 for Q0, different surface preparation methods were applied and systematically tested using a vertical 2 K cryostat. A well-established technique is the so called Darmstadt Soft Chemical Polishing, which consists of an ultrasonic cleaning of the cavity with ultrapure water followed by oxidizing the inner surface with nitric acid. After rinsing with water the niobium oxide layer is removed with hydrofluoric acid in a separate second step. Finally the structure is rinsed and then dried by a nitrogen flow. Until now each cavity in operation was chemically treated with a proven record of success. In order to understand and to optimize the process on the niobium surface, systematic tests with samples were performed and analyzed using material science techniques like SEM, SIMS and EDX. We will report on the results of our research and we will give a review on our experiences with varied chemical procedures.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL012
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THPAL015	Evaluation of superconducting characteristics on the thin-film structure by NbN and Insulator coatings on pure Nb substrate	cavity, embedded, radio-frequency, electromagnetic-fields	3653
	R. Katayama, Y. Iwashita, H. Tongu Kyoto ICR, Uji, Kyoto, Japan C.Z. Antoine CEA/IRFU, Gif-sur-Yvette, France A. Four CEA/DRF/IRFU, Gif-sur-Yvette, France H. Hayano, T. Kubo, T. Saeki KEK, Ibaraki, Japan H. Ito Sokendai, Ibaraki, Japan R. Ito, T. Nagata ULVAC, Inc, Chiba, Japan H. Oikawa Utsunomiya University, Utsunomiya, Japan
	Funding: The work is supported by JSPS KAKENHI Grant Numbers JP17H04839, JP26600142 and the Collaborative Research Program of ICR Kyoto University (grant 2016-8, 2017-8, 2017-9). In recent years, it is pointed out that the maximum accelerating gradient of a superconducting RF cavity can be pushed up by coating the inner surface of cavity with a multilayer thin-film structure that consists of alternate insulator and superconductive layers. In this structure, the principal parameter that limits the performance of the cavity is the critical magnetic field or effective Hc1 at which vortices start penetrate into the first superconductor layer. We made a sample that has NbN/SiO2 thin-film structure on pure Nb substrate by DC magnetron sputtering method. In this paper, we will report the measurement results of effective Hc1 of the sample by the third-harmonic voltage method.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL015
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THPAL034	Dynamic Tuner Development for Medium β Superconducting Elliptical Cavities	cavity, linac, operation, superconducting-RF	3709
	C. Contreras-Martinez, P.N. Ostroumov FRIB, East Lansing, USA E. Borissov, S. Cheban, Y.M. Pischalnikov, V.P. Yakovlev, J.C. Yun Fermilab, Batavia, Illinois, USA
	Funding: Work supported by U.S. DOE SCGSR program under contract number DE-SC0014664, Michigan State University, and Fermi Research Alliance under contract N. DEAC02-07CH11959 with the U.S. DOE The Facility for Rare Isotope Beams (FRIB) is developing a 5-cell 644 MHz β_opt=0.65 elliptical cavity for a future linac energy upgrade to 400 MeV/u for the heaviest uranium ions. Superconducting elliptical cavities operated in continuous wave, such as the ones for FRIB, are prone to microphonics which can excite mechanical modes of the cavities. It has been shown that the detuning due to microphonics can be mitigated with the use of piezo actuators (fast tuner) as opposed to the costly option of increasing the input RF power. The FRIB slow/fast dynamic tuner will be based on the Fermilab experience with similar tuners like those developed for the linac coherent light source (LCLS) II and proton improvement plan (PIP) II. This paper will present the results of tuner properties on the bench.
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THPAL036	Nb3Sn Thin Films for the Production of Higher Gradient SRF Cavities at Reduced Cost	cavity, niobium, superconductivity, site	3716
	S.A. Kahn, M.A. Cummings Muons, Inc, Illinois, USA E.Z. Barzi, D. Turrioni Fermilab, Batavia, Illinois, USA S. Falletta Politecnico di Torino, Torino, Italy A. Kikuchi NIMS, Tsukuba, Ibaraki, Japan
	High gradient superconducting cavities (SRF) will be needed for future accelerators. The higher gradient can achieve the high energy with fewer cavities. However the accelerating field of niobium cavities is limited by the peak magnetic field on the cavity surface. Cavities coated with Nb3Sn have a significantly larger Hc2 allowing the cavity to achieve a larger gradient. Measurements of Nb3Sn coated cavities have achieved about half the theoretical predicted gradient. It is possible to improve Nb3Sn plated cavity performance.
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THPAL039	Improved Magnetron Stability and Reduced Noise in Efficient Transmitters for Superconducting Accelerators	controls, cavity, feedback, experiment	3726
	G.M. Kazakevich, R.P. Johnson Muons, Inc, Illinois, USA V.A. Lebedev, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	State of the art high-current superconducting accelerators require efficient RF sources with a fast dynamic phase and power control. This allows for compensation of the phase and amplitude deviations of the accelerating volt-age in the Superconducting RF (SRF) cavities caused by microphonics, etc. Efficient magnetron transmitters with fast phase and power control are attractive RF sources for this application. They are more cost effective than traditional RF sources such as klystrons, IOTs and solid-state amplifiers used with large scale accelerator projects. However, unlike traditional RF sources, controlled magnetrons operate as forced oscillators. Study of the impact of the controlling signal on magnetron stability, noise and efficiency is therefore important. This paper discusses experiments with 2.45 GHz, 1 kW tubes and verifies our analytical model which is based on the charge drift approximation.
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THPAL041	Power Coupler Design for the LUCRECE Project	cavity, simulation, coupling, linac	3732
	H. Guler, D. Auguste, J. Bonis, O. Bouras, M. El Khaldi, W. Kaabi, P. Lepercq LAL, Orsay, France
	The LUCRECE project aims at developing an elementary RF system (cavity, power source, LLRF and controls) suitable for continuous (CW) operation at 1.3 GHz. This effort is made in the framework of the advanced and compact FEL project LUNEX5 (free electron Laser Using a New accelerator for the Exploitation of X-ray radiation of 5th generation), using superconducting linac technology for high repetition rate and multi-user operation (www.lunex5.com). In this context, based on its large experience on coupler design and RF conditioning, LAL Laboratory is in charge of the design and the fabrication of RF couplers that could operate at up to 15-20 kW in CW mode. For this purpose, geometry based on CORNELL 65kW CW couplers will me modified to fulfil the LCLS2 type cavity with the high necessary coupling level. Electromagnetic simulations and optimisation and associated thermal heating will be discussed. Methods to decrease the thermal impact, and strategy for RF conditioning will be considered.
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THPAL045	Determination of the Electron Bunch Length With Third Harmonic Cavity for the Taiwan Photon Source	cavity, operation, simulation, electron	3745
	Z.K. Liu, F.Y. Chang, L.-H. Chang, M.H. Chang, S.W. Chang, L.J. Chen, F.-T. Chung, M.-C. Lin, C.H. Lo, Ch. Wang, M.-S. Yeh, T.-C. Yu NSRRC, Hsinchu, Taiwan
	The Taiwan Photon Source (TPS) is a modern 3 GeV low emittance light source with RMS bunch lengths of about 3 mm at a beam current of 500 mA and operating gap voltage of 3.2 MV. With a higher harmonic cavity, we could increase the Touschek lifetime and lower the heat load of in-vacuum undulators by lengthening the bunch lengths. Preliminary studies show that for full and uni-form fill patterns, the bunch lengths could be increased by a factor of four. However, this calculation ignores phase transient effects and may overestimate the effect of harmonic cavities. A multi-bunch, multi-particle tracking method has been developed to determine the bunch lengths for non-uniform fill patterns, which also takes phase transient effects into account and the expected maximum bunch lengthening factor for different TPS operation conditions are discussed.
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THPAL065	Improving the Work Function of Nitrogen-Doped Niobium Surfaces for SRF Cavities by Plasma Processing	plasma, cavity, niobium, accelerating-gradient	3802
	K.E. Tippey, R. Afanador, M. Doleans, S.-H. Kim, J.D. Mammosser, C.J. McMahan ORNL, Oak Ridge, Tennessee, USA M. Martinello Fermilab, Batavia, Illinois, USA
	Funding: DOE research grant FWP-ERKCSA2; DOE contract DE-AC05-00OR22725 Work function and surface chemistries of SiC-polished, electropolished, and nitrogen-doped niobium coupons were analyzed before and after plasma processing using a neon-oxygen gas mixture. These studies represent an initial enquiry into the feasibility of applying the plasma processing technique designed at ORNL for the Spallation Neutron Source (SNS) to the nitrogen-doped Nb cavities for the Coherent Light Source II (LCLS-II). Work function of all measured samples was increased after plasma processing, which indicates the strong potential of the plasma processing technique as a tool for increasing the accelerating gradient of nitrogen-doped cavities.
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THPAL076	Experimental Methods for the Assessment of NEG Pumps Working in Dust-Sensitive Environments	vacuum, cavity, experiment, background	3828
	T. Porcelli, E. Maccallini, P. Manini, M. Mura, M.F. Urbano SAES Getters S.p.A., Lainate, Italy
	NEG pumps have been widely adopted by many accelerator facilities since decades. However, their use in dust-sensitive areas - such as superconductive radio frequency (SRF) cavities - has always been limited by concerns about accidental dust emission, which could induce detrimental field emission. As future machines will necessarily rely on highly-efficient SRF cavities, able to supply very high accelerating gradients, requirements in terms of particle release from vacuum components (e.g., pumps and valves) are becoming more and more stringent. At the same time, achieving stable ultra-high vacuum conditions is crucial, as condensed residual gas might also be a potential source of field emission. At present, a unified standard procedure to assess dust generation and propagation along a machine is still missing and discussions are ongoing in the vacuum community. Recent experimental measurements demonstrated the compatibility of sintered NEG pumps with ultra-clean environments, due to their intrinsic very low dust release. In parallel, in-situ tests performed at different accelerator facilities showed absence of dust contamination from NEGs and no impact on cavities efficiency.
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THPAL080	Parallel-Feed SRF Accelerator Structures	cavity, coupling, simulation, impedance	3835
	P.B. Welander, Z. Li, M.H. Nasr, S.G. Tantawi SLAC, Menlo Park, California, USA
	Funding: This work is supported by the Department of Energy, Laboratory Directed Research and Development program at SLAC National Accelerator Laboratory, under contract DE-AC02-76SF00515. Development of SRF accelerator technology that enables both higher gradient and higher efficiency is crucial for future machines. While much of the recent R&D focus has been on materials and surface science, our aim is to optimize the cavity geometry to maximize performance with current materials. The recent demonstration of a highly efficient parallel-feed NCRF structure at SLAC has served as a proof-of-concept. Applied to SRF, such a structure could dramatically reduce power consumption while boosting the achievable gradient. Instead of coupled elliptical cells, our structure employs isolated reentrant cells. To feed RF power to the cavities, each cell is directly coupled to an integrated manifold. The structure is made in two parts, split along the beam axis, which are then joined. Such a structure has been fabricated from bulk Cu and tested at SLAC - designed for X-band, it operates at a record gradient of 150 MV/m. Adapting to SRF at 1.3 GHz and fabricating from Nb, such a cavity could achieve more than 50% lower RF loss and 40% higher gradient compared to the TESLA cavity. We will describe our simulations and propose an experimental roadmap for demonstrating this technology.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL080
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THPAL081	A 3 GHz SRF Reduced-beta Cavity for the S-DALINAC	cavity, linac, operation, electron	3838
	D.B. Bazyl, H. De Gersem, W.F.O. Müller TEMF, TU Darmstadt, Darmstadt, Germany J. Enders, S. Weih TU Darmstadt, Darmstadt, Germany
	Funding: Work supported by DFG through GRK 2128 In order to reduce the energy spread and to be able to use a 200 keV spin-polarized electron source, the initial part of the injector linac of the superconducting Darmstadt electron linear accelerator S-DALINAC needs to be upgraded. The decisions on the cavity type, number of cells and value of geometric beta are motivated. The main part of this work is dedicated to the mechanical design of the cavity. A precise evaluation of the mechanical characteristics of an SRF cavity is necessary during the design stage. The dependence of the resonant frequency of the fundamental mode on external mechanical loads needs to be investigated for developing the tuning procedures. The results of the multiphysics simulations and of the optimization of the mechanical design are presented.
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THPAL086	Superconducting Thin Film RF Measurements	cavity, vacuum, niobium, operation	3856
	P. Goudket, L. Bizel-Bizellot, L. Gurran, O.B. Malyshev, S.M. Pattalwar, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom G. Burt, L. Gurran Cockcroft Institute, Lancaster University, Lancaster, United Kingdom P. Goudket, T. Junginger, O.B. Malyshev, S.M. Pattalwar, R. Valizadeh Cockcroft Institute, Warrington, Cheshire, United Kingdom L. Gurran, T. Junginger Lancaster University, Lancaster, United Kingdom
	As part of an ongoing programme of SRF Thin Films development, a radiofrequency (RF) cavity and cryostat dedicated to the measurement of superconducting coatings at GHz frequencies was designed to evaluate surface resistive losses on a flat sample. The resonator has now been used for measurements on Thin Film samples. Results from a test on a sample previously tested at Cornell University are presented. In order to simplify the measurements and achieve a faster turnaround, the experiment will be moved to a new cryostat fitted with a cryocooler. This will limit the measurements to low power only, but will allow a much faster sorting of samples to identify those that would benefit from further investigation. A description of the system and initial results will be presented.
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THPAL089	Design, Assembly and Commissioning of a New Cryogenic Facility for Complex Superconducting Thin Film Testing	experiment, site, cavity, operation	3859
	O.B. Malyshev, L. Bizel-Bizellot, K.D. Dumbell, P. Goudket, N. Pattalwar, S.M. Pattalwar, P. Pizzol, P.A. Smith, R. Valizadeh, S. Wilde STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom P. Pizzol The University of Liverpool, Liverpool, United Kingdom
	An ongoing study on the superconducting thin films for future superconducting RF cavities requires an intense testing of various superconducting properties. We have designed, built and tested a new facility for complex superconducting thin film testing that includes: (1) RRR measurement with and without magnetic field, (2) planar and (3) tubular magnetic field penetration experiments, (4) a superconducting coaxial resonator for bulk niobium and superconducting thin film characterisation. The system is based on a closed cycle refrigerator, eliminating the need for liquid helium, thus making it simple and safe to operate. The details of the design and commissioning will be presented at the conference.
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THPAL092	Test Particle Monte Carlo Simulation of NEG Coated Narrow Tubular Samples	vacuum, ECR, experiment, simulation	3862
	O. Seify, A.N. Hannah, O.B. Malyshev, Sirvinskaite, R. Sirvinskaite, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom Sirvinskaite, R. Sirvinskaite Loughborough University, Loughborough, Leicestershire, United Kingdom
	The pumping properties of the NEG coated vacuum chambers play an important role in the efficiency of vac-uum system of accelerators. The sticking probability of the NEG films is one the most important parameters to characterise the pumping properties of the NEG coated vacuum chambers. In order to investigate the NEG film sticking probability, Test Particle Monte-Carlo (TPMC) models were used. The models were based on the design of the installed experimental setup in ASTeC Vacuum Science group laboratory at Daresbury Laboratory (DL). The results of the simulations have been used for inter-preting the results of the measurements in the experi-mental setup.
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THPAL104	The Magnetic Field Measurement Systems for a Cryogenic Undulator and a Superconducting Undulator at SSRF	cryogenics, undulator, GUI, vacuum	3878
	H.F. Wang SSRF, Shanghai, People's Republic of China M.F. Qian, W. Zhang, Q.G. Zhou SINAP, Shanghai, People's Republic of China
	Two cryogenic permanent magnet undulators (CPMU) have been developed and assembled into storage ring at SSRF，in order to reach larger magnetic field and to produce higher brilliance in the hard X rays domain. Lowering the temperature of permanent magnets increases the magnetic produced field about by 15%. A set of magnetic measurement system and a suitable magnetic field optimization method have been developed. The design of a magnetic measurement bench based on a Hall probe to perform low temperature measurement has been finished. In addition, a 50-period superconducting undulator prototype with 16mm period length is also being developed for more photons with some specific photon characteristic. And a special hall probe system has been built in order to characterize the magnetic field distribution of the SCU prototype.
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THPAL105	Lower Critical Field Measurement System of Thin Film Superconductor	controls, experiment, simulation, embedded	3882
	H. Ito Sokendai, Ibaraki, Japan C.Z. Antoine CEA/IRFU, Gif-sur-Yvette, France A. Four CEA/DRF/IRFU, Gif-sur-Yvette, France H. Hayano, T. Kubo, T. Saeki KEK, Ibaraki, Japan R. Ito, T. Nagata ULVAC, Inc, Chiba, Japan Y. Iwashita, R. Katayama, H. Tongu Kyoto ICR, Uji, Kyoto, Japan H. Oikawa Utsunomiya University, Utsunomiya, Japan
	Funding: The work is supported by Japan Society for the Promotion of Science Grant-in-Aid for Young Scientist (A) No.17H04839. Superconducting thin film is the promising technology to increase the performance of SRF cavities. The lower critical field Hc1, which is one of the important physical parameters characterizing a superconducting material, will be enhanced by coating Nb with thin film superconductor such as NbN. To investigate the performance of thin film, we developed the Hc1 measurement system using the third harmonic response of applied AC magnetic field. The measurement system consists of helium cryostat with two of GM refrigerators, sample Cu stage, solenoid coil Cu mount, solenoid coil, temperature sensors, and liquid helium level meter. AC magnetic field is produced by a coil which is driven by function generator and power amplifier at around 1 kHz. In order to control the temperature of the sample stage and coil mount, the depth of thermal anchors attached to the stage and the mount can be moved by the motor. By this temperature control the sample state can be easily transferred from Meissner state to mixed state. So that the measurement is repeated for various applied magnetic field, and the transition curve can be made. In this report, performance of the measurement system is described.
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THPAL120	Cryogenics Infrastructure at TRIUMF's Particle Accelerator Facilities	cryogenics, TRIUMF, ISAC, operation	3925
	A.N. Koveshnikov, Y. Bylinskii, G.W. Hodgson, D. Kishi, R.E. Laxdal, R.R. Nagimov, D. Yosifov TRIUMF, Vancouver, Canada
	Funding: TRIUMF receives federal funding via a contribution agreement with the National Research Council of Canada. Cryogenic infrastructure is an indispensable part of TRIUMF accelerator facilities. At the moment TRIUMF operates three helium cryogenic systems supporting operation of three major accelerator systems: 520 MeV proton cyclotron, superconductive radio-frequency (SRF) heavy ion linear accelerator at the Rare Isotope Beams (RIB) facility, and SRF electron linear accelerator (e-linac) at Advanced Rare IsotopE Laboratory (ARIEL). Applications of cryogenic thermal loads vary from cryogenic absorption pumping of the cyclotron vacuum tank to cryogenic cooling of superconducting (SC) RF cavities of production accelerators and support of research and development at SRF department. Wide range of production techniques for cryogenic refrigeration includes helium refrigerators based on both piston and turbine expansion coldboxes for both 4 K and 2 K temperature cryogenic loads. This paper presents the details of TRIUMF cryogenic systems as well as operational experience of various cryogenic installations.
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THPAL126	Nitrogen Bake-out Procedures at the Vertical High-Temperature UHV-Furnace of the S-DALINAC	cavity, vacuum, niobium, linac	3937
	R. Grewe, L. Alff, M. Arnold, J. Conrad, S. Flege, M. Major, N. Pietralla TU Darmstadt, Darmstadt, Germany F. Hug IKP, Mainz, Germany
	Funding: Work supported by the Federal Ministry of Education and Research through grant No. 05H15RDRBA. As the performance limits of bulk Nb srf cavities are reached, our research is focused on materials with superior srf properties like Nb3Sn and NbN. Research on NbN resulted in the "nitrogen-doping" process used for increasing the quality factors of srf cavities for the LCLS-II project. This process leads to delta-phase Nb-N, a phase with higher critical sc parameters than bulk Nb. This phase is formed at temperatures of 800°C in nitrogen atmospheres of 10^-2 mbar. Other crystalline phases of NbN have even better sc parameters. We concentrate our research on applicability of delta-phase NbN for cavities. The delta-phase forms at temperatures of above 1300°C, which is more than most of the furnaces at accelerator facilites are capable of. Since 2005 the Institute for Nuclear Physics at the Technische Universität Darmstadt operates a high temperature vacuum furnace which has been upgraded to allow temperatures of up to 1750°C and bakeouts of niobium samples and cavities in nitrogen atmospheres. We will report on the current status of our research on nitrogen bake-out procedures on Nb samples. The samples have been analyzed at the Material Science Departement with SIMS, REM and XRD.
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THPAL129	Magnetron Sputtering of Nb3Sn for SRF Cavities	cavity, site, target, controls	3946
	MNS. Sayeed, H. Elsayed-Ali ODU, Norfolk, Virginia, USA G.V. Eremeev, M.J. Kelley, C.E. Reece JLab, Newport News, Virginia, USA M.J. Kelley, U. Pudasaini The College of William and Mary, Williamsburg, Virginia, USA M.J. Kelley Virginia Polytechnic Institute and State University, Blacksburg, USA
	Nb3Sn is a potential candidate for surface material of SRF cavities since it can enable the cavity to operate at higher temperatures with high quality factor and at an increased accelerating gradient. Nb-Sn films were deposited using magnetron sputtering of individual Nb and Sn targets onto Nb and sapphire substrates. The as-deposited films were annealed at 1200 °C for 3 hours. The films were characterized for their structure by X-ray Diffraction (XRD), morphology by Field Emission Scanning Electron Microscopy (FESEM), and composition by Energy Dispersive X-ray Spectroscopy (EDS) and Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS). The surface resistivity was measured down to cryogenic temperature to determine the superconducting transition temperature and its width. The composition of the multilayered films was controlled by varying the thickness of the Nb and Sn layers. The films showed crystalline Nb3Sn phases with Tc up to 17.6 K.
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THPAL130	Effect of Deposition Temperature and Duration on Nb3Sn Diffusion Coating	cavity, niobium, experiment, superconductivity	3950
	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: Partially authored by Jefferson Science Associates under contract no. DE¬AC05¬06OR23177. Work at College of William & Mary supported by Office of High Energy Physics under grant SC0014475. Nb3Sn is a potential candidate to replace Nb in SRF accelerator cavities to reduce cost and advance perfor-mance. Tin vapor diffusion is the preferred technique to realize such cavities by growing a few microns thick Nb3Sn coating on the interior surface of the niobium cavity. The coating process typically uses temperatures of 1100-1200 °C for 3-6 hours. It is important to better understand the coating process, and optimize the coating parameters to overcome the current limitation on the performance of Nb3Sn coated SRF cavities. We investi-gate Nb3Sn coatings prepared in the temperature range of 900-1200 °C and duration of 3 - 12 hours using various material characterization tools. Variation of these pa-rameters appears to have notable effect on microstructure and topography of the obtained surface.
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THPAL131	Studies of Electropolishing and Oxypolishing Treated Diffusion Coated Nb3Sn Surfaces	cavity, niobium, experiment, superconductivity	3954
	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
	The Nb3Sn-coated cavities aim to enhance perfor-mance and significantly reduce cost. Their fabrication involves tin vapor diffusion coating of Nb3Sn on the interior surface of a Nb cavity. Controlled removal of first few layers to obtain a smoother and cleaner surface could be desirable to improve the high field RF perfor-mance. Our first results from the application of elec-tropolishing and oxypolishing techniques on Nb3Sn-coated surfaces indicated reduced surface roughness, and the surface composition appeared nominally unchanged. Systematic studies explore the effect of different polish-ing parameters into the roughness and composition. We present the latest results from SEM/EDS and AFM studies of Nb3Sn-coated samples treated with electropolishing and oxypolishing.
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THPAL142	Surface Characterization of NbTiN Films for Accelerator Applications	site, FEL, detector, lattice	3975
	D.R. Beverstock, M.J. Kelley, C.E. Reece, J.K. Spradlin, A-M. Valente-Feliciano JLab, Newport News, Virginia, USA
	Funding: Work supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The development of next-generation SRF cavities requires the deployment of innovative material solutions with RF performance beyond bulk Nb. Theoretical interest has stimulated efforts to grow and characterize thin multi-layer superconductor/insulator/superconductor (SIS) structures for their potential capability of supporting otherwise inaccessible surface magnetic fields in SRF cavities . The ternary B1-compound NbTiN is among the candidate superconducting materials for SIS structures. Single crystal NbTiN films with thicknesses below 15 nm are also of interest for the development of high resolution, high sensitivity (SNSPD) detectors for particle physics application. Using DC reactive magnetron sputtering, NbTiN can be deposited with nominal superconducting parameters. This contribution presents the on-going material surface and superconducting properties characterization in order to optimize the NbTiN films for each application. A Gurevich, "Maximum screening fields of superconducting multilayer structures", AIP ADVANCES 5, 017112 (2015)
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THPAL143	Commissioning of JLab Vertical Cavity Processing System for SRF Nb Single Cell and Multicell Cavity With HF-Free Pulse-Reverse Electopolishing	cavity, controls, niobium, MMI	3978
	H. Tian, M. Lester, J. Musson, H.L. Phillips, C.E. Reece, C. Seaton JLab, Newport News, Virginia, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177 Pulse reversed electropolishing of niobium SRF cavities, using a dilute aqueous H2SO4 electrolyte without HF yields equivalent RF performance with traditional EP. Comparing with present EP process for Nb SRF cavity which uses 1:10 volume ratio of HF (49%) and H2SO4 (98%), pulse reverse EP (also known as bipolar EP (BPEP)) is ecologically friendly and uses relatively benign electrolyte options for cavity processing. In this study, we report the commissioning of a new vertical cavity processing system for SRF Nb single cell and multi-cell cavities with HF-free pulse-reverse electropolishing at Jefferson Lab, together with RF test of cavities being processed. We report the scale-up challenges and interpretations from process R&D to implementation.
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THPAL144	952.6 MHz SRF Cavity Development for JLEIC	cavity, HOM, damping, electron	3982
	R.A. Rimmer, W.A. Clemens, F. Fors, J. Guo, F.E. Hannon, J. Henry, F. Marhauser, L. Turlington, H. Wang, S. Wang JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 JLab is developing new SRF cavity designs at 952.6 MHz for the proposed Jefferson Lab Electron-Ion Collider (JLEIC). New cavities will be required for the ion ring, cooler ERL and booster and eventually for an upgrade of the electron ring to allow the highest possible bunch collision rate. The challenges include the need for high fundamental mode power couplers and strong HOM damping, with high HOM power capability. Initial focus is on the cooler ERL 5-cell cavity as this is a critical component for the strong, high energy, bunched-beam cooling concept. 1-cell and 5-cell Nb prototype cavities have been designed and fabricated. Details concerning the cavity fabrication and test results will be presented.
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THPAL145	Magnetron R&D toward the Amplitude Modulation Control for SRF Accelerator	injection, controls, cavity, simulation	3986
	R.A. Rimmer, T. E. Plawski, H. Wang JLab, Newport News, Virginia, USA A. Dudas, S.A. Kahn, M.L. Neubauer Muons, Inc, Illinois, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and SBIR grant DE-SC0013203 The scheme of using a high efficiency magnetron to drive a superconducting radio frequency (SRF) accelerator cavity needs not only the injection phase locking but also the amplitude modulation to compensate the cavity's microphomics caused cavity voltage change and the beam loading variation. To be able to do a fast and efficient modulation, the magnetron's magnetic field has to be trimmed by an external coil to compensate the frequency pushing effect due to the anode current change [1]. A low eddy current magnetron body has been designed and built [2]. This paper will present the analytical prediction, simulation and experimental results on the 2.45 GHz magnetron test stand with the modulation frequency up to 1 kHz. In addition, the progresses on the injection lock to a copper cavity, new 1497 MHz magnetron prototype, 13 kW high power magnetron test stand development and newly built low level RF (LLRF) controller for the amplitude modulation will be reported. [1] M. Neubauer et al, THPIK123, Proceedings of IPAC 2017, Copenhagen, Denmark [2] S. A. Kahn et al, THPIK121, Proceedings of IPAC 2017, Copenhagen, Denmark
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THPAL146	802 MHz ERL Cavity Design and Development	cavity, collider, electron, hadron	3990
	F. Marhauser, S. Castagnola, W.A. Clemens, J.G. Dail, P. Dhakal, F. Fors, J. Henry, R.A. Rimmer, L. Turlington, R.S. Williams JLab, Newport News, Virginia, USA R. Calaga, K.M. Dr. Schirm, E. Jensen CERN, Geneva, Switzerland
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177, and CERN Contract NR. KE3080/ATS In the framework of a collaboration between CERN and JLab, an SRF accelerating cavity for energy recovery linacs operating at 802 MHz was developed in the context of the CERN's Large Hadron electron Collider (LHeC) design study. A single-cell and a five-cell cavity from fine grain high RRR niobium were built at JLab to validate the basic RF design in vertical tests. Two copper single-cell cavities were produced in parallel for R&D purposes at CERN. The cavity design has since been adapted as baseline for the main linac cavities in the proposed Powerful Energy Recovery Linac Experiment facility (PERLE) at Orsay. Details concerning the cavity fabrication and test results for the Nb cavities are presented.
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THPMF017	Operation Improvements and Emittance Reduction of the ESRF Booster	emittance, booster, operation, quadrupole	4077
	N. Carmignani, N. Benoist, J-F. B. Bouteille, M.G. Di Vito, F. Ewald, L. Farvacque, A. Franchi, O. Goudard, J.M. Koch, S. Lagarde, S.M. Liuzzo, B. Ogier, T.P. Perron, P. Raimondi, D. Robinson, F. Taoutaou, E.T. Taurel, P.V. Verdier, R. Versteegen, P. Vidal, S.M. White ESRF, Grenoble, France
	The ESRF storage ring will be replaced by the Extremely Brilliant Source (EBS) in 2020 and the equilibrium emittance will decrease from the present 4 nmrad to 134 pmrad. The current injector system, composed by a linac and a synchrotron booster, will be used to inject into the new storage ring. To increase the injection efficiency in the new storage ring, three methods to reduce the horizontal emittance of the booster have been considered and tested. This paper presents the studies and achievements in terms of operation improvements and emittance reduction.
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THPMF019	ESRF-EBS Lattice Model with Canted Beamlines	lattice, optics, MMI, quadrupole	4081
	S.M. Liuzzo, N. Carmignani, J. Chavanne, L. Farvacque, T.P. Perron, P. Raimondi, S.M. White ESRF, Grenoble, France
	The ESRF Extremely Brilliant Source (ESRF-EBS) lattice model is updated to include three canted beamlines. The cells are modified where necessary to include 3-Pole Wiggler (3PW), 2-Pole Wiggler (2PW) and Short Bending Magnet (SBM) sources. Several lattices are obtained for the different stages that will bring from commissioning to operation with users. A scheme for tune modification keeping key optics knobs unchanged is proposed.
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THPMF020	A 4th Generation Light Source for South-East Europe	lattice, emittance, storage-ring, synchrotron	4084
	H. Ghasem, R. Bartolini DLS, Oxfordshire, United Kingdom D. Einfeld ESRF, Grenoble, France
	In Europe, most of the Synchrotron Light Sources are located in the middle, west and northern regions while the south-east is still lacking any major project. Hence a new initiative has been set up to propose the construction of a 4th Generation Light Source in that region. Design requirements limit the beam energy between 2.5 GeV to 3 GeV, the circumference is limited to 350 m, the emittance should be smaller than 250 pm rad and at least 14 to 16 straights have to be available for the users. Several mag-net configurations have been investigated and the results revealed that the HMBA lattice can fully meets the requirements and is therefore proposed for the Light Source in the SEE-region of Europe. These studies show that for a 4th Generation Light Source with energies up to 3 GeV a circumferences of 350 m will be adequate.
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THPMF021	ESRF Operation Status	injection, operation, power-supply, booster	4088
	J.-L. Revol, J.C. Biasci, N. Carmignani, A. D'Elia, A. Franchi, L. Hardy, J. Jacob, I. Leconte, S.M. Liuzzo, H.P. Marques, T.P. Perron, E. Plouviez, P. Raimondi, B. Roche, K.B. Scheidt, L. Torino, S.M. White ESRF, Grenoble, France
	The European Synchrotron Radiation Facility (ESRF) is undergoing the second phase (2015-2022) of an Up-grade which concerns its infrastructure, beamlines and X-ray source. This paper reports on the present operational source performance, highlighting the most recent developments, and the preparation of the Extremely Brilliant Source project. The renovation of the injector and the recent operation in top-up mode are also detailed.

Paper

Title

Other Keywords

Page

MOZGBF4

Evolution of the Superconducting Linac Output Energy at the Spallation Neutron Source

cavity, cryomodule, operation, linac

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S.-H. Kim, D.E. Anderson, M.T. Crofford, M. Doleans, J. Galambos, S.W. Gold, M.P. Howell, M.A. Plum, D.J. Vandygriff
ORNL, Oak Ridge, Tennessee, USA
R. Afanador, D.L. Barnhart, B. DeGraff, J.D. Mammosser, C.J. McMahan, T.S. Neustadt, C.C. Peters, J. Saunders, D.M. Vandygriff
ORNL RAD, Oak Ridge, Tennessee, USA

Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
The SNS linac output energy has increased since the start of neutron production in FY2007. The various improvements that contributed to the increase of the linac output energy are LLRF/control system improvement, high voltage converter modulator system improvement, high-power RF system improvement, cryomodule repairs, spare cryomodule development and accelerating gradient improvement through in-situ plasma processing. In this paper, the history of the SNS SCL output energy is reported, and plans for the near-term future and for the Proton Power Upgrade (PPU) project are also presented.

Slides MOZGBF4 [34.185 MB]

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MOPMF072

On the Feasibility of a Pulsed 14 TeV C.M.E. Muon Collider in the LHC Tunnel

collider, luminosity, proton, acceleration

296

V.D. Shiltsev, D.V. Neuffer
Fermilab, Batavia, Illinois, USA

We will consider technical feasibility, key machine parameters and major challenges of the recently proposed 14 TeV c.m.e. muon-muon collider in the LHC tunnel.

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MOPML034

Development Status of Superconducting RF Transmission Electron Microscope

cavity, acceleration, LLRF, gun

481

N. Higashi, A. Enomoto, Y. Funahashi, T. Furuya, X.J. Jin, Y. Kamiya, S. Michizono, F. Qiu, M. Yamamoto
KEK, Ibaraki, Japan
S. Yamashita
University of Tokyo, Tokyo, Japan

Now we are developing a new type of transmission electron microscope (TEM) employing the accelerator technologies. In place of a DC thermal gun generally used in conventional TEMs, we apply a photocathode gun and a special-shaped superconducting cavity, named two-mode cavity. The two-mode cavity has two resonant modes of TM010 (1.3 GHz) and TM020 (2.6 GHz). To superimpose these, we can suppress the increase of the energy spread, which is needed for the high-spatial-resolution TEMs. We have already developed some prototypes of the photocathode gun and two-mode cavity, and now in the middle of the performance tests. In this presentation, we will show the latest status of the development.

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MOPML053

Mu*STAR Accelerator-Driven Subcritical Reactors Burning Spent Nuclear Fuel at Light-Water-Reactor Sites

target, site, neutron, operation

524

R.P. Johnson, R.J. Abrams, M.A. Cummings, T.J. Roberts
Muons, Inc, Illinois, USA

This project will use modeling and simulation tools to optimize many aspects of the Mu*STAR design and begin to explore accident scenarios. At present we have a conceptual design of the accelerator, the reactor, the spallation target, and the fractional distillation to separate volatile fission products. Our GAIN project with ORNL is preparing a design of the Fuel Processing Plant that will convert spent nuclear fuel into the molten-salt fuel for Mu*STAR. This includes all of the nuclear components, but not such things as the turbine and generator, physical plant, control and monitoring systems, etc. We currently have basic simulations of the reactor neutronics, and a start at calculating the fuel evolution. These have used MCNP and ORIGEN, and initial results have been reported1. This project will support the use of additional neutronics and multi-physics codes, enabling a much more thorough analysis of the system.

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TUYGBE2

CBETA, the 4-Turn ERL with SRF and Single Return Loop

electron, linac, gun, cryomodule

635

G.H. Hoffstaetter, N. Banerjee, J. Barley, A.C. Bartnik, I.V. Bazarov, D.C. Burke, J.A. Crittenden, L. Cultrera, J. Dobbins, S.J. Full, F. Furuta, R.E. Gallagher, M. Ge, C.M. Gulliford, B.K. Heltsley, R.P.K. Kaplan, V.O. Kostroun, Y. Li, M. Liepe, W. Lou, C.E. Mayes, J.R. Patterson, P. Quigley, D.M. Sabol, D. Sagan, J. Sears, C.H. Shore, E.N. Smith, K.W. Smolenski, V. Veshcherevich, D. Widger
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
J.S. Berg, S.J. Brooks, C. Liu, G.J. Mahler, F. Méot, R.J. Michnoff, M.G. Minty, S. Peggs, V. Ptitsyn, T. Roser, P. Thieberger, D. Trbojevic, N. Tsoupas, J.E. Tuozzolo, F.J. Willeke, H. Witte
BNL, Upton, Long Island, New York, USA
D. Douglas
JLab, Newport News, Virginia, USA
J.K. Jones
Cockcroft Institute, Warrington, Cheshire, United Kingdom
D. Jusic
Cornell University, Ithaca, New York, USA
D.J. Kelliher
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
B.C. Kuske, M. McAteer, J. Völker
HZB, Berlin, Germany

Funding: Supported by NSF award DMR-0807731, DOE grant DE-AC02-76SF00515, and NYSERDA.
A collaboration between Cornell University and Brookhaven National Laboratory has designed and is constructing CBETA, the Cornell-BNL ERL Test Accelerator on the Cornell campus. The ERL technology that has been prototyped at Cornell for many years is being used for this new accelerator, including a DC electron source and an SRF injector Linac with world-record current and normalized brightness in a bunch train, a high-current linac cryomodule optimized for ERLs, a high-power beam stop, and several diagnostics tools for high-current and high-brightness beams. BNL has designed multi-turn ERLs for several purpose, dominantly for the electron beam of eRHIC, its Electron Ion Collider (EIC) project and for the associated fast electron cooling system. Also in JLEIC, the EIC designed at JLAB, an ERL is envisioned to be used for electron cooling. The number of transport lines in an ERL is minimized by using return arcs that are comprised of a Fixed Field Alternating-gradient (FFA) design. This technique will be tested in CBETA, which has a single return for the 4-beam energies with strongly-focusing permanent magnets of Halbach type. The high-brightness beam with 150~MeV and up to 40~mA will have applications beyond accelerator research, in industry, in nuclear physics, and in X-ray science. Low current electron beam has already been sent through the most relevant parts of CBETA, from the DC gun through both cryomodules, through one of the 8 similar separator lines, and through one of the 27 similar FFA structures. Further construction is envisioned to lead to a commissioning start for the full system early in 2019.

Slides TUYGBE2 [17.343 MB]

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TUPAF014

Beam Dynamics Studies For the IFMIF-DONES SRF-Linac

linac, cryomodule, cavity, solenoid

687

L. Du, N. Bazin, N. Chauvin, S. Chel, J. Plouin
CEA/IRFU, Gif-sur-Yvette, France

The DONES (DEMO oriented neutron source) project is aimed at constructing a DEMO of IFMIF to provide sufficient material damage [1]. In the SRF-Linac of this project, losses can cause harmful material activation and must be maintained much less than 1W/m. It's a challenge to keep losses at such a low level with high beam power and high space charge. This paper presents two designs of the DONES SRF-Linac, one with 4 cryomodules and another with 5 cryomodules. The design details to reduce the losses and the multi-particle simulation results will be shown. The errors studies for these results will also be discussed.

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TUPAF076

Design of PIP-II Medium Energy Beam Transport

vacuum, linac, kicker, cryomodule

905

A. Saini, C.M. Baffes, A.Z. Chen, V.A. Lebedev, L.R. Prost, A.V. Shemyakin
Fermilab, Batavia, Illinois, USA

Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics
The Proton Improvement Plan-II (PIP-II) is a proposed upgrade for the accelerator complex at Fermilab. The central piece of PIP-II is a superconducting radio frequency (SRF) 800 MeV linac capable of operating in both CW and pulse regimes. The PIP-II linac comprises a warm front-end that includes a H⁻ ion source capable of delivering 15-mA, 30-keV DC or pulsed beam, a Low Energy Beam Transport (LEBT), a 162.5 MHz, CW Radio-Frequency Quadrupole (RFQ) accelerating the ions to 2.1 MeV and, a 14-m Medium Energy Beam Transport (MEBT) before beam is injected into SRF part of the linac. This paper presents the PIP-II MEBT design and, discusses operational features and considerations that lead to existing optics design such as bunch by bunch chopping system, minimization of radiation coming to the warm front-end from the SRF linac using a concrete wall, a robust vacuum protection system etc.

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TUZGBE5

A Combined Temperature and Magnetic Field Mapping System for SRF Cavities

cavity, operation, niobium, experiment

1228

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

In the past decade, a significant improvement of SRF cavity performance has been achieved, yet a number of performance limiting mechanisms, such as magnetic flux trapping, still exist. We present a diagnostics tool which combines flux expulsion measurement during the superconducting phase transition with temperature mapping during operation. This system has a time resolution for both temperature and magnetic field mapping of 2 ms for full cavity coverage, so that short-lived events, including cavity quenches, can easily be resolved.

Slides TUZGBE5 [1.358 MB]

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TUPMF002

A Cu Photocathode for the Superconducting RF Photoinjector of BERLinPro

cathode, gun, cavity, laser

1247

J. Kühn, M. Bürger, A. Frahm, A. Jankowiak, T. Kamps, G. Klemz, G. Kourkafas, A. Neumann, N. Ohm, M. Schmeißer, M. Schuster, J. Völker
HZB, Berlin, Germany
P. Murcek, J. Teichert
HZDR, Dresden, Germany

The initial commissioning of the Superconducting RF (SRF) photoinjector is done with a Cu photocathode due to its robustness with regard to interactions with the SRF cavity of the injector. Here we present the preparation and characterization of a Cu photocathode plug and the diagnostics to insert the photocathode in the back wall of the SRF cavity. A polycrystalline bulk Cu plug was polished, particle free cleaned and characterized by x-ray photoelectron spectroscopy. During the transfer of the photocathode insert into the gun module the whole process was controlled by several diagnostic tools monitoring the insert position as well as RF, vacuum and cryogenic signals. We discuss the challenges of the photocathode transfer into an SRF cavity and how they can be tackled.

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TUPML053

The BERLinPro SRF Photoinjector System - From First RF Commissioning to First Beam

cathode, cavity, operation, solenoid

1660

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

Funding: The work is funded by the Helmholtz-Association, BMBF, the state of Berlin and HZB.
Helmholtz-Zentrum Berlin (HZB) is currently constructing a high average current superconducting (SC) ERL as a prototype to demonstrate low normalized beam emittance of 1 mm-mrad at 100 mA and short pulses of about 2 ps. To attain the required beam properties, an SRF based photo-injector system was developed and during the past year underwent RF commissioning and was setup within a dedicated diagnostics beamline called Gunlab to analyze beam dynamics of both, a copper cathode and a Cs2KSb cathode as well as their quantum efficiency at UV and green light respectively. The medium power prototype - a first stage towards the final high power 100 mA design - 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 and up to 3.5 MeV kinetic energy, limited by the modified twin TTF-III fundamental power couplers. In this contribution, the first RF commissioning results of the photo-injector module will be presented including dark current analysis as well as measured beam properties with an initially installed Copper cathode.

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WEYGBF3

Nb3Sn Multicell Cavity Coating at JLab

cavity, niobium, factory, superconductivity

1798

U. Pudasaini, M.J. Kelley
The College of William and Mary, Williamsburg, Virginia, USA
G. Ciovati, G.V. Eremeev, M.J. Kelley, C.E. Reece
JLab, Newport News, Virginia, USA
M.J. Kelley
Virginia Polytechnic Institute and State University, Blacksburg, USA
I.P. Parajuli, MNS. Sayeed
ODU, Norfolk, Virginia, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics.
Following encouraging results with Nb3Sn-coated R&D cavities, the existing coating system was upgraded to allow for Nb3Sn coating of CEBAF accelerator cavities. The upgrade was designed to allow Nb3Sn coating of original CEBAF 5-cell cavities with the vapor diffusion technique. Several CEBAF cavities were coated in the upgraded system to investigate vapor diffusion coatings on extended structures. Witness samples coated along with the cavities were characterized with material science techniques, while coated cavities were measured at 4 and 2 K. The progress, lessons learned, and the pathforward are discussed.

Slides WEYGBF3 [2.381 MB]

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WEPAK012

Developing Kalman Filter Based Detuning Control with a Digital SRF CW Cavity Simulator

cavity, controls, FPGA, LLRF

2114

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

Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of the Helmholtz Association
Continuous wave operated superconducting cavities experiencing small net beam loading and thus operate potentially at narrow bandwidth require precise detuning control to reach the high stability requirements for RF fields within facilities as FEL or ERL based photon sources. Especially microphonics compensation down to sub-hertz detuning regime besides improving stability reduces the risk of rise of Lorentz force detuning driven ponderomotive instabilities. Usually the complex and second order nature of the mechanical to RF detuning transfer functions of cavity and cavity-tuner system require for more advanced control schemes. In this paper we will show the application of a Kalman filter based detuning estimator algorithm first introduced during IPAC2017 [1] to the SRF cavity simulator developed at Helmholtz Zentrum Berlin [2]. Results using the algorithm in observer mode to detuning compensation attempts in closed loop mode are presented.
* A. Ushakov, P. Echevarria, A. Neumann, Proc. of IPAC 2017, Copenhagen, Denmark

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WEPAK013

SRF Cavity Simulator for LLRF Algorithms Debugging

cavity, controls, LLRF, FPGA

2118

P. Echevarria, J. Knobloch, A. Neumann, A. Ushakov
HZB, Berlin, Germany
E. Aldekoa, J. Jugo
University of the Basque Country, Faculty of Science and Technology, Bilbao, Spain

Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association
The availability of niobium superconducting cavities, ei-ther due to a lack of a real cavity or due to the time needed for the experiment set up (vacuum, cryogenics, cabling, etc.), is limited, and thus it can block or delay the develop-ment of new algorithms such as low level RF control. Hardware-in-the-loop simulations, where an actual cavity is replaced by an electronics system, can help to solve this issue. In this paper we present a Cavity Simulator imple-mented in a National Instruments PXI equipped with an FPGA module. This module operates with one intermedi-ate frequency input which is IQ-demodulated and fed to the electrical cavity's model, where the transmitted and re-flected voltages are calculated and IQ-modulated to gener-ate two intermediate frequency outputs. Some more ad-vanced features such as mechanical vibration modes driven by Lorentz-force detuning or external microphonics have also been implemented. This Cavity Simulator is planned to be connected to an mTCA chassis to close the loop with a LLRF control system.

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WEPAL005

Beam Size Measurement and PSF Evaluate of KB Mirror Monitor at SSRF

storage-ring, optics, electron, photon

2151

D.C. Zhu, J.S. Cao, Y.F. Sui, J.H. Yue
IHEP, Beijing, People's Republic of China

Funding: Work supported by National Nature Science Foundation of China(11605213)
A Kirkpatrick Baez mirror imaging system was designed and installed to measure the transverse beam size and emittance of SSRF storage ring. Two crossed cylindrical mirrors are used to image the dipole source point in the horizontal and vertical direction. Both mirrors could be moved in and out in order to interchangeable with an original X-ray pinhole system. Hard X-ray with peak energy of 20.5 keV was focused at the X-ray scintillator camera. Aberration and point spread function which would cause image blur were evaluated. System commissioning and optimization have been done. PSF measurement was acquired using beam based calibration scheme by varying the beam images with different quadrupole settings and fitting them with the corresponding theoretical beam sizes.

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WEPAL039

LCLS-II Gun/Buncher LLRF System Design

gun, LLRF, cavity, controls

2258

G. Huang, K.S. Campbell, L.R. Doolittle, J.A. Jones, Q. Qiang, C. Serrano
LBNL, Berkeley, California, USA
S. Babel, A.L. Benwell, M. Boyes, G.W. Brown, D. Cha, J.H. De Long, J.A. Diaz Cruz, B. Hong, A. McCollough, A. Ratti, C.H. Rivetta, D. Rogind, F. Zhou
SLAC, Menlo Park, California, USA
R. Bachimanchi, C. Hovater, D.J. Seidman
JLab, Newport News, Virginia, USA
B.E. Chase, E. Cullerton, J. Einstein-Curtis, D.W. Klepec
Fermilab, Batavia, Illinois, USA
J.A. Diaz Cruz
CSU, Fort Collins, Colorado, USA

Funding: This work was supported by the LCLS-II Project and the U.S. Department of Energy, Contract n. DE-AC02-05CH11231.
For a free electron laser, the stability of injector is critical to the final electron beam parameters, e.g., beam energy, beam arrival time, and eventually it determines the photon quality. The LCLS-II project's injector contains a VHF copper cavity as the gun and a two-cell L-band copper cavity as its buncher. The cavity designs are inherited from the APEX design, but requires more field stability than demonstrated in APEX operation. The gun LLRF system design uses a connectorized RF front end and low noise digitizer, together with the same general purpose FPGA carrier board used in the LCLS-II SRF LLRF system. The buncher LLRF system directly adopts the SRF LLRF chassis design, but programs the controller to run the normal conducting cavities. In this paper, we describe the gun/buncher LLRF system design, including the hardware design, the firmware design and bench test.

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WEPAL055

TPS Beam Trip Analysis and Dose Distribution

radiation, kicker, neutron, storage-ring

2302

B.Y. Chen, F.Y. Chang, S. Fann, C.S. Huang, C.H. Kuo, T.Y. Lee, C.C. Liang, W.Y. Lin, Y.C. Lin, Y.-C. Liu
NSRRC, Hsinchu, Taiwan

Failure analysis during TPS users operation is im-portant to improve the performance of the TPS storage ring. In this report, we discuss the particular radiation dose patterns, relevant to different beam trips, and the development of a tool to help us analyse this dose distri-bution. We will use this analysing tool to train our ability for future failure analysis to shorten the time it takes to find the problem.

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WEPMF012

Power Requirement and Preliminary Coupler Design for the eRHIC Crab Cavity System

cavity, operation, proton, electron

2394

S. Verdú-Andrés, I. Ben-Zvi, D. Holmes, Q. Wu
BNL, Upton, Long Island, New York, USA
I. Ben-Zvi
Stony Brook University, Stony Brook, USA

Funding: Work supported by Brookhaven Science Associates LLC under contract no. DE-SC0012704 with the U.S. Department of Energy.
Crab cavities are deflecting cavities operated in such a way that the bunch center is in synchronism with the zero-crossing kick voltage. In that case, beam loading is zero for an on-axis beam. The crab cavity system of the future electron-ion collider eRHIC will manipulate 275 GeV proton beams. At high energies, the beam offset can be as large as 2 mm (including mechanical and electrical offset tolerances). The beam loading resulting from such offset can greatly incur in large power requirements to the RF amplifier. The choice of external Q for the Fundamental Power Coupler (FPC) is critical to limit the power requirement to practical values. The loaded Q of the eRHIC crab cavities is mainly governed by the external Q of the FPC, so the external Q will also define the cavity bandwidth and thus the tuning requirements to counteract frequency transients from external perturbations. This paper discusses the choice of external Q for the FPC of the eRHIC crab cavities and introduces the design of a preliminary FPC antenna concept that would provide the appropriate external Q.

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WEPMF036

RF Test Result of a BNL N-Doped 500 MHz B-Cell Cavity at Cornell

cavity, vacuum, superconducting-cavity, niobium

2440

F. Furuta, M. Ge, T. Gruber, J.J. Kaufman, M. Liepe, J.T. Maniscalco, J. Sears
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
F. Gao, J. Rose
BNL, Upton, Long Island, New York, USA

Cornell's SRF group has collaborated with Brookhaven National Laboratory (BNL) on one 500 MHz CESR type SRF "B-cell" cavity (BNL B-cell) for the National Synchrotron Light Source II. Cornell has been responsible for RF surface preparation, vertical testing, and short cavity string assembly. As a state-of-the-art surface preparation protocol, Cornell selected Nitrogen doping for the BNL B-cell. N-doping has been well demonstrated and established to push the cavity quality factor (Q0) higher in 1.3GHz SRF cavities at many laboratories. Cornell calculated that N-doping could also be beneficial on a 500MHz SRF cavity, with a potential to increase its Q0 by a factor of two compared with the traditional chemical polishing based surface preparation protocol. Here we report on the detailed surface preparation and vertical test result of the BNL B-cell.

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WEPMF037

HF Free Bipolar Electro-Polishing Studies on Niobium SRF Cavities at Cornell With Faraday Technology

cavity, niobium, MMI, radio-frequency

2443

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

Cornell's SRF group and Faraday Technology have been collaborating on two phase-II SBIR projects. One of them is the development and commissioning of a 9-cell scale HF free Bipolar Electro-Polishing (BEP) system. Faraday Technology has upgraded their 1.3 GHz single-cell BEP system for hosting 9-cell cavities. Initial commissioning of the new system was done with a three single-cell cavity string, and high a gradient of 40MV/m was demonstrated during the RF tests at Cornell. After this success with the test string, the 9-cell cavity was processed with the new system at Faraday and RF test was performed at Cornell. Here we report detailed results from these 9-cell scale HF free BEP studies.

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WEPMF038

Microphonics Suppression in the CBETA Linac Cryomodules

cavity, linac, cryomodule, controls

2447

N. Banerjee, J. Dobbins, F. Furuta, G.H. Hoffstaetter, R.P.K. Kaplan, 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 New York State Energy Research and Development Agency. The linac cryomodules were constructed with funding from the National Science Foundation.
The Cornell-BNL ERL Test Accelerator (CBETA) is a new multi-turn energy recovery linac currently under construction at Cornell University. It uses two superconducting linacs, both of which are susceptible to microphonics detuning. The high-current injector accelerates electrons to 6 MeV and the main linac accelerates and decelerates electrons by 36 MeV. In this paper, we discuss various measures taken to reduce vibrations caused by instabilities and flow transients in the cryogenic system of the main linac cryomodule. We further describe the use of a Least Mean Square algorithm in establishing a stable Active Microphonics Compensation system for operation of the main linac cavities.

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WEPMF042

A Computational Method for More Accurate Measurements of the Surface Resistance in SRF Cavities

cavity, operation, niobium, radio-frequency

2458

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

The principal loss mechanism for superconducting RF cavities in normal operation is Ohmic heating due to the microwave surface resistance in the superconducting surface. The typical method for calculating this field-dependent surface resistance R_s(H) from RF measurements of quality factor Q₀ implicitly returns a weighted average of R_s over the surface as a function of peak surface magnetic field H, not the true value of R_s as a function of the local magnitude of H. In this work we present a computational method to convert a measured Q₀ vs. H_peak to a more accurate R_s vs. H_local, given knowledge about cavity geometry and field distribution.

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WEPMF044

Updates on the DC Field Dependence Cavity

cavity, niobium, multipactoring, simulation

2465

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

Work at Cornell has demonstrated good agreement between a theoretical model by A. Gurevich of the anti-Q-slope (a field-dependent decrease of the microwave surface resistance) and experimental results from impurity-doped niobium. As a corollary, the model predicts that a strong DC magnetic field applied parallel to the RF surface will produce a similar decrease in surface resistance. In order to explore this prediction for many materials, we have designed a new coaxial cavity with a strong, uniform DC field superimposed over a weak RF field on a removable and replaceable niobium sample. Here we present updates on the progress of this new cavity.

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WEPMF045

Performance of the Prototype SRF Half-Wave-Resonators Tested at Cornell for the RAON Project

cavity, multipactoring, pick-up, radiation

2468

M. Ge, F. Furuta, T. Gruber, S.W. Hartman, M. Liepe, J.T. Maniscalco, 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

Two prototype superconducting half-wave-resonator (162.5 MHz and β=0.12) for the RAON project have been successfully tested at Cornell University. Detailed vertical performance testing included (1) test of the bare cavity without the helium tank, and (2) test of the dressed cavity with a helium tank. In this paper, we report on the development of the test infrastructure, test results, and performance data analysis, showing that the specifications for RAON were met.

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WEPMF046

Modeling of the Frequency and Field Dependence of the Surface Resistance of Impurity-Doped Niobium

cavity, niobium, experiment, ECR

2471

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

The anti-Q-slope, a field-dependent decrease in surface resistance observed in impurity-doped niobium, has been investigated extensively in 1.3 GHz cavities. New early research into this effect has recently been performed at higher and lower frequencies, revealing an additional dependence on frequency: the anti-Q-slope is stronger at higher frequencies and weaker at lower frequencies. Several models have been proposed to explain the anti-Q-slope, with varying success in this new frequency-dependent regime. In this work, we analyze recent experimental data from a low-temperature-doped 1.3 GHz cavity and a high-temperature nitrogen-doped 2.6 GHz cavity and discuss the implications of these results on the proposed models.

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WEPMF047

Performance of Samples With Novel SRF Materials and Growth Techniques

cavity, superconducting-RF, niobium, site

2475

T.E. Oseroff, M. Ge, M. Liepe, J.T. Maniscalco, R.D. Porter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
S.R. McNeal
Ultramet, Pacoima, California, USA
M.J. Sowa
Veeco-CNT, Medford, USA

Novel materials are currently being studied in an attempt to push accelerating superconducting RF cavities to support higher accelerating fields and to operate with lower power loss. Growing layers of these materials of the quality necessary has proven to be difficult. In this work, we present the SRF performance of planar samples of the promising materials, NbN and Nb¬3Sn, grown using atomic layer deposition (ALD) and chemical vapor deposition (CVD) respectively. Results are promising.

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WEPMF050

Update on Nb3Sn Progress at Cornell University

cavity, niobium, accelerating-gradient, site

2479

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

Niobium-3 Tin (Nb3Sn) is the most promising alternative material for SRF accelerator cavities. The material can achieve higher quality factors, higher temperature operation and potentially higher accelerating gradients compared to conventional niobium. Cornell University has a leading program to produce 2 - 3 micrometer thick coatings of Nb3Sn on Nb for SRF applications using vapor diffusion. This program has been the first to produce quality factors higher than achievable with conventional Nb at usable accelerating gradients. Here we present an update on progress at Cornell University, including studies of the formation of the Nb3Sn layer, density functional theory calculations of Nb3Sn growth, and designs for a sample host cavity for measuring the quench field of Nb3Sn.

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WEPMK008

In-Depth Analysis of the Vertical Test Results of the Third-Harmonic Cavities for the E-XFEL Injector

cavity, FEL, experiment, feedback

2644

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
C.G. Maiano, P. Pierini
ESS, Lund, Sweden
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy

The results of the vertical tests performed at LASA on the 3.9 GHz third-harmonic cavities for the E-XFEL injector are here discussed. Analysis of experimental data allows to confirm that such high frequency cavity, prepared with standard BCP treatment and 800°C annealing treatment, suffers an intrinsic performance limitation at around 22 MV/m (@ 2 K) due to a global thermal dissipation mechanism. A quantitative interpretation of the high field Q slope is also presented according to the latest theoretical models of field-dependent surface resistance.

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WEPMK009

Status of the ESRF-EBS Magnets

quadrupole, dipole, sextupole, octupole

2648

C. Benabderrahmane, J.C. Biasci, J-F. B. Bouteille, J. Chavanne, L. Eybert, L. Goirand, G. Le Bec, L. Lefebvre, S.M. Liuzzo, D. Martin, C. Penel, P. Raimondi, J.-L. Revol, F. Villar, S.M. White
ESRF, Grenoble, France

The ESRF-EBS (Extremely Brilliant Source) is an upgrade project planned at the European Synchrotron Radiation Facility (ESRF) in the period 2015-2022. A new storage ring will be built, aiming to decrease the horizontal emittance and to improve the brilliance and coherence of the X-ray beams. The lattice of the new storage ring relies on magnets with demanding specifications: dipoles with longitudinal gradient (field ranging from 0.17 T up to 0.67 T), strong quadrupoles (up to 90 T/m), combined function dipole-quadrupoles with high gradient (0.57 T and 37 T/m), strong sextupoles and octupoles. The design of these magnets is based on innovative solutions; in particular, the longitudinal gradient dipoles are permanent magnets and the combined dipole-quadrupoles are single-sided devices. The longitudinal gradient dipoles have been assembled and measured in house. The design of the magnets, production status and magnetic measurement results will be presented.

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WEPMK012

Update on Plasma Processing R&D for LCLS-II

plasma, cavity, HOM, experiment

2656

P. Berrutti, A. Grassellino, T.N. Khabiboulline, M. Martinello
Fermilab, Batavia, Illinois, USA
M. Doleans, S.-H. Kim, K.E. Tippey
ORNL, Oak Ridge, Tennessee, USA
D. Gonnella, G. Lanza, M.C. Ross
SLAC, Menlo Park, California, USA

Funding: Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the U.S. DOE
SRF cavities performance preservation is crucial, from vertical test to accelerator operation. Field emission is still one of the main problems to overcome and plasma cleaning has been proven successful by SNS, in cleaning field emitters and increasing the work function of Nb. A collaboration has been established between FNAL, SLAC and ORNL with the purpose of applying plasma processing to LCLS-II cavities, in order to minimize and overcome field emission without affecting the high Q of N-doped cavities. The recipe will follow the neon-oxygen active plasma adopted at SNS, allowing in-situ processing of cavities and cryomodules from hydrocarbon contaminants. A novel method for plasma ignition has been developed at FNAL: a plasma glow discharge is ignited using high order modes to overcome limitations imposed by the fundamental power coupler. The results of experiments on 9-cell LCLS-II cavity are presented, along with plasma ignition studies. In addition the RF system is shown and N-doped Nb samples studies are discussed.

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WEPMK014

A New Design for the Hilumi Radio-Frequency Dipole Bare Cavity

cavity, niobium, GUI, resonance

2659

M. Parise, P. Berrutti, L. Ristori
Fermilab, Batavia, Illinois, USA

Crabbing cavities are one of the technological landmark that will allow the LHC to optimize its per-formance and maximize its integrated luminosity by allowing a head-on collision between the bunches despite the non-zero crossing angle. A total of 8 crab cavities will be installed in the interaction region of each of the two experiments, ATLAS and CMS. In the last years, the two types of crab cavities were de-signed, built and tested under the US-LARP R&D pro-gram. Horizontal crabbing is obtained with a radio-frequency dipole cavity (RFD) designed by Old Do-minion University (ODU), SLAC and Fermilab (FNAL). In this paper a new mechanical design, that uses passive stiffeners, is presented. This design leads to a decrease of the Lorentz Force Detuning frequency shift, satisfy the requirements on pressure sensitivity, validate the structural integrity and increase the tuner sensitivity and the maximum elastic tuning range. Furthermore, it will be possible to greatly simplify the shape of the magnetic shield and Helium vessel with respect to the current design.

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WEPMK015

Optimization of Vertical Electro-Polishing Process: Experiments with Updated Cathode on Single-Cell Cavity and Performance Achieved in Vertical Test

cavity, cathode, linac, superconductivity

2662

F. Éozénou, L. Maurice
CEA/DSM/IRFU, France
P. Carbonnier, C. Madec, Th. Proslier, C. Servouin
CEA/DRF/IRFU, Gif-sur-Yvette, France
V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi
MGH, Hyogo-ken, Japan
H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe
KEK, Ibaraki, Japan

Marui Galvanizing Co.Ltd., and CEA have been studying Vertical Electro-Polishing (VEP) on Nb single-cell accelerating superconducting accelerator cavity with the goal of mass-production and cost-reduction, in collaboration with KEK within TYL-FJPPL Particle Physics Laboratory. Marui has invented and patented a rotative cathode called ‘i-Ninja'. The version 5 has been tested for the first time in Europe at CEA Saclay. The four wings of the cathode remove efficiently, bubbles of hydrogen, and the chosen parameters make it possible to achieve better surface and uniform material removal compared to VEP with a fixed cathode. The effect of the temperature of the cavity walls on current oscillations has been precisely studied. Two single-cell cavities have been electro-polished and tested at 2 K in vertical cryostat and the results will be presented.

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WEPMK016

New Insight on Nitrogen Infusion Revealed by Successive Nanometric Material Removal

cavity, accelerating-gradient, factory, niobium

2665

M. Checchin, A. Grassellino, M. Martinello, O.S. Melnychuk, S. Posen, A.S. Romanenko, D.A. Sergatskov
Fermilab, Batavia, Illinois, USA

In this study we present new insight on low temperature nitrogen infusion on bulk niobium superconducting radio-frequency (SRF) cavities. Nitrogen infusion is a thermal treatment recently discovered at Fermilab that allows to reach high accelerating gradients, of the order of 45MV/m, with high Q-factors, of the order of 2 · 10¹⁰. Detailed depth dependent RF studies (by means of subsequent HF rinses) and comparisonwith SIMS results pinpointed interstitial nitrogen as the responsible for the improved performance and uncovered the extension of its profile inside the material.

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WEPML003

Precision Q0 Measurement of an SRF Cavity with a Digital RF Techniques

cavity, coupling, impedance, GUI

2674

J.P. Holzbauer, B.M. Hanna, Y.M. Pischalnikov, W. Schappert, D.A. Sergatskov, A.I. Sukhanov
Fermilab, Batavia, Illinois, USA

Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
Direct measurement of the quality factor of SRF cavity using traditional RF techniques is essential for cavity production and development. Systematic effects of the measurement can contribute significant amounts of error to these measurements if not accounted for. This paper will present measurements taken at Fermilab using a digital RF system to characterize and correct for these systematic effects and directly measure the quality factor versus gradient curve for a single spoke resonator in the Spoke Test Cryostat at Fermilab. These measurements will be compared to traditional calorimetric measurements, and a discussion of improving/extending these techniques to other testing situations will be included.

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WEPML004

Production Tuner Testing for LCLS-II Cryomodule Production

cavity, cryomodule, LLRF, interface

2678

J.P. Holzbauer, Y.M. Pischalnikov, W. Schappert, J.C. Yun
Fermilab, Batavia, Illinois, USA
C. Contreras-Martinez
FRIB, East Lansing, USA

Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
LCLS-II 1.3 GHz cryomodule production is well underway at Fermilab. Several dozen cavity/tuner systems have been tested, including tuning to 1.3 GHz, cold landing frequency, range/sensitivity of the slow tuner, and range/sensitivity of the fast tuner. All this testing information as well as lessons learned from tuner installation will be presented.

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WEPML005

Testing of SSR1 Production Tuner for PIP-II

cavity, linac, niobium, cryomodule

2681

J.P. Holzbauer, D. Passarelli, Y.M. Pischalnikov
Fermilab, Batavia, Illinois, USA

Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
The PIP-II project at Fermilab is a proton driver linac calling for the use of five different, novel cavity geometries. Prototyping at Fermilab is in the advanced stages for the low-beta single-spoke resonator (SSR1) and associated technologies. A production tuner design has been fabricated and tested, both warm and cold in the Spoke Test Cryostat (STC). This paper will present the detailed studies on this tuner, including slow motor/piezoelectric tuner range and hysteresis as well as dynamic mechanical system characterization.

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WEPML006

Modified Slow Tuner Design for Cavity 1 Inside LCLS II Cryomodules

cavity, cryomodule, interface, simulation

2684

Y.M. Pischalnikov, T.T. Arkan, S. Cheban, J.P. Holzbauer, J.A. Kaluzny, Y.O. Orlov, J.C. Yun
Fermilab, Batavia, Illinois, USA

Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
Initial LCLS-II cryomodule testing at Fermilab showed microphonics on the furthest upstream cavity (number 1) at least factor 2 larger than on the rest of the cavities. Testing indicated that this was a difference in the mechanical support of cavity 1, not a local acoustic source. Further investigation pointed to the upstream beam-pipe of the cavity 1. The upstream cavity flange has a solid spool piece connection to the beamline gate valve unlike the other cavities, which all connect through bellows. The gate valve's weight is supported by sliding system (free in z-axis) connected to large diameter Helium gas return pipe. The tuner design was modified to transform interface between cavity#1 and gate valve. Arms of the tuner for cavity 1 were extended and became the support structure for gate valve, eliminating the connection to the helium return pipe. Modification of the tuner design and results in microphonics mitigations will be presented.

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WEPML008

Tuner Testing of a Dressed 3.9 GHz Cavity for LCLS-II at Fermilab

cavity, operation, background, FEL

2690

J.P. Holzbauer, S. Aderhold, T.N. Khabiboulline, Y.M. Pischalnikov, W. Schappert, J.C. Yun
Fermilab, Batavia, Illinois, USA
C. Contreras-Martinez
FRIB, East Lansing, USA

Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
Fermilab is responsible for the design of the 3.9 GHz cryomodule for LCLS-II. Integrated acceptance testing of a dressed 3.9 GHz cavity for the LCLS-II project has been done at the Fermilab Horizontal Test Stand. This test included a slim blade tuner (based on INFN & XFEL designs) with integrated piezoelectric fast/fine tuner. This paper will present results of the mechanical setup, cold testing, and cold function of this tuner including fast and slow tuner range, sensitivity, and hysteresis.

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WEPML010

Operation Regime Analysis of Conduction Cooled Cavities Through Multi-Physics Simulation

cavity, operation, simulation, niobium

2697

R.A. Kostin, R. Dhuley, M.G. Geelhoed, R.D. Kephart, T.K. Kroc, O.V. Prokofiev, J.C.T. Thangaraj
Fermilab, Batavia, Illinois, USA
A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA

Funding: Department of Energy
Euclid Techlabs in collaboration with Fermilab IARC (Batavia, IL) is developing industrial superconducting 10MeV electron linac. Conduction cooling is used for cooling instead of liquid helium bath to simplify linac maintenance. The cavity linked to commercially available cryo-cooler cold head through highly conductive aluminium strips. However, this solution raises a problem of contact thermal resistance. This paper shows some results of Comsol multyphysics simulations of the cavity cooling by AL strips. Some insight was obtained on the acceptable range of contact resistance. Operation regimes were obtained at different accelerating gradients and cavity temperatures. The results of simulation are presented and discussed.

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WEPML013

Anti-Q-slope enhancement in high-frequency niobium cavities

cavity, ECR, niobium, experiment

2707

M. Martinello, S. Aderhold, S.K. Chandrasekaran, M. Checchin, A. Grassellino, O.S. Melnychuk, S. Posen, A.S. Romanenko, D.A. Sergatskov
Fermilab, Batavia, Illinois, USA

N-doped 1.3 GHz niobium cavities showed for the first time the so-called anti-Q-slope, i.e. the increasing of the Q-factor as a function of the accelerating field. It was verified that the anti-Q-slope is consequence of the decreasing of the temperature-dependent component of the surface resistance as a function of the field. This trend is opposite compared to the increasing of the surface resistance previously observed in 1.3 GHz standard (EP, BCP, 120 C baked) niobium cavities. The effect of the different state-of-the-art surface treatments on the field dependence of the surface resistance is studied for 650 MHz, 1.3 GHz, 2.6 GHz and 3.9 Ghz cavities. This proceeding shows that the field dependence of the temperature-dependent component of the surface resistance has a strong frequency dependence and that the anti-Q-slope may appear even in clean niobium cavities if the resonant frequency is high enough, suggesting new routes toward the understanding of the anti-Q-slope effect.

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WEPML016

Development of Nb3Sn Coatings for Superconducting RF Cavities at Fermilab

cavity, factory, superconductivity, network

2718

S. Posen, S.K. Chandrasekaran, O.S. Melnychuk, D.A. Sergatskov, B. Tennis, Y. Trenikhina
Fermilab, Batavia, Illinois, USA
J. Lee
NU, Evanston, Illinois, USA

Nb3Sn films are a promising alternative material for su-perconducting RF cavities, with proven high quality factors at medium fields and predictions for increased superheating field as well. In this contribution, we de-scribe the latest results from the Fermilab Nb3Sn SRF program. Early experiments have been focused on single cell 1.3 GHz cavities. We briefly review efforts to bring the parameters used in the coating process into a range where they produce uniform surfaces without regions showing signs of excess tin or thin/uncoated areas. We then present the latest cavity results, after modifications to the coating recipe based on feedback from film appear-ance and RF performance. These results show high Q0 at medium fields and a maximum field of ~18 MV/m.

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WEPML040

Further Tests on the Final State of the SC 325 MHz CH-Cavity and Coupler Test Bench Update

cavity, linac, heavy-ion, framework

2783

M. Busch, M. Basten, J. List, P. Müller, H. Podlech, M. Schwarz
IAP, Frankfurt am Main, Germany
W.A. Barth, J. List
GSI, Darmstadt, Germany
W.A. Barth
HIM, Mainz, Germany
W.A. Barth
MEPhI, Moscow, Russia

Funding: Work supported by BMBF Contr. No. 05P15RFBA
At the Institute for Applied Physics, Goethe-University Frankfurt, a sc 325 MHz CH-cavity has been developed and successfully tested up to 14.1 mV/m and has now reached the final production stage with the helium vessel welded to the frontal joints of the cavity and final processing steps have been performed. Further tests in a vertical and horizontal environment are being prepared for intensive studies. This cavity is a prototype for envisaged beam tests with a pulsed ion beam at 11.4 AMeV. In this contribution the results of the performed RF tests are being presented. Furthermore, first measurements of the recently installed 217 MHz coupler test bench are shown.

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WEPML045

Infrastructure for Superconducting CH-Cavity Preparation at HIM

cavity, linac, vacuum, heavy-ion

2796

T. Kürzeder, K. Aulenbacher, W.A. Barth, F.D. Dziuba, V. Gettmann, M. Miski-Oglu, E. Riehn
HIM, Mainz, Germany
K. Aulenbacher, R.G. Heine, T. Stengler
IKP, Mainz, Germany
W.A. Barth, S. Yaramyshev
GSI, Darmstadt, Germany
F. Hug
KPH, Mainz, Germany

A superconducting cw LINAC for heavy ions is currently under development at GSI in Darmstadt and HIM in Mainz. This Linac is based on 217 MHz multigap bulk niobium Crossbar H-mode RF-cavities. In order to treat and prepare RF-cavities with such a complex geometry a new cleanroom facility has been already built at the Helmholtz-Institut in Mainz. All tools and machines inside the cleanroom can handle cavities with up to 800 mm in diameter and with up to 1300 mm in length. In its ISO-class 6 and 4 zones, respectively it features a large ultrasonic and conductance rinsing bath, a high pressure rinsing (HPR) cabinet and a vacuum oven. The HPR cabinet has an inside clearance of 1.4 m. The large cavities sit on a rotating table, while the rising wand moves vertically up and down. Due to the crossbar structure of the RF-cavities the HPR device allows for off axis-rinsing in their quadrants. For RF testing a 52 m² (4 m x 13 m) concrete shielded area with sufficient liquid helium and nitrogen supply is located next to the cleanroom and the cryo-module assembly area. We will report on the new SRF infrastructure in Mainz and the commissioning of the new high pressure rinsing cabinet.

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WEPML047

Study on RF Coupler Kicks of SRF Cavities in the BESSY VSR Module

cavity, storage-ring, HOM, GUI

2804

A.V. Tsakanian, T. Mertens
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany
H.-W. Glock, J. Knobloch, M. Ries, A.V. Vélez
HZB, Berlin, Germany

The BESSY VSR upgrade of the BESSY II light source represents a novel approach to simultaneously store long (ca. 15ps) and short (ca. 1.7ps) bunches in the storage ring with the standard user optics. This challenging goal requires installation of four new SRF multi-cell cavities (2x1.5GHz and 2x1.75GHz) equipped with strong waveguide HOM dampers ensuring tolerable beam coupling impedance, necessary for stable operation. These cavities will operate at high 20MV/m in CW mode and at the zero-crossing phase according to the accelerating voltage. Consequently the transverse voltages will be maximum and can impact the transverse beam dynamics. The asymmetric character of those transverse kicks are caused by cavity fundamental power couplers (FPC) with strong monopole terms, introducing transverse kick to on-axis particles. Different FPC orientations were analyzed to optimize the net coupler kick from the four cavity chain. The coupler kick strength of each cavity is estimated taking into account accelerating mode amplitudes and phases required for operation in VSR mode.

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WEPML048

HOM Power Levels in the BESSY VSR Cold String

HOM, cavity, simulation, GUI

2808

A.V. Tsakanian, T. Flisgen
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany
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 long (ca. 15ps) and short (ca. 1.7ps) bunches in the storage ring. This challenging goal requires installation of four new SRF cavities (2x1.5 GHz and 2x1.75 GHz) in one module for installation in a single straight. These cavities are equipped with strong waveguide HOM dampers necessary for stable operation. The expected HOM power and spectrum has been analyzed for the complete cold string. The cold string is a combination of various elements such as SRF cavities, bellows with and without shielding, warm HOM beampipe absorbers and UHV pumping domes. The presented study is performed for various BESSY VSR bunch filling patterns with 300 mA beam current. The contribution of each component to the total HOM power is presented. In addition the optimization of different cavity arrangements in the module is performed in order to reach the optimal operation conditions with equally distributed power levels along the string and tolerable beam coupling impedance.

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WEPML049

The Challenge to Measure nΩ Surface Resistance on SRF Samples

quadrupole, pick-up, cavity, simulation

2812

S. Keckert, T. Junginger, J. Knobloch, O. Kugeler
HZB, Berlin, Germany
T. Junginger
Lancaster University, Lancaster, United Kingdom

Systematic research on fundamental limits of superconducting materials for SRF applications and their intrinsic material properties relevant for use in an accelerator requires studies in a wide parameter space of temperature, RF field and frequency. The Quadrupole Resonator at HZB enables precision measurements on planar samples at temperatures of 1.8 K to >20 K, RF fields of up to 120 mT, and frequencies of 420 MHz, 850 MHz and 1285 MHz. In the past years the capabilities of the setup were studied intensively and developed further. Sources of systematic errors, such as microphonics or misalignment have been identified and eliminated. In this contribution the current status of the QPR and its systematic limitations are discussed.

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WEPML053

Availability of the TiN Coating-Free Ceramic in the STF-type Power Coupler for ILC

electron, vacuum, cryomodule, GUI

2819

Y. Yamamoto, E. Kako, T. Matsumoto, S. Michizono, A. Yamamoto
KEK, Ibaraki, Japan
M. Irikura, M. Ishibashi, H. Yasutake
Toshiba Electron Tubes & Devices Co., Ltd (TETD), Tochigi, Japan
C. Julie, E. Montesinos
CERN, Geneva, Switzerland

In the Superconducting RF Test Facility (STF) in KEK, the research and development for the power coupler with the TiN coating-free ceramic has been done from 2014. In 2016, the high power test at the test bench was stopped due to the worse vacuum level by the unusual heating around the RF window with the TiN coating-free ceramic and the coaxial tapered section, which was caused by the enormous emission of the secondary electrons from the ceramic. And, the situation was never also changed by the ultrapure water rinsing for the power couplers several times. However, in 2017, the ultrasonic rinsing was done for the power couplers for the first time by the collaboration between KEK and TETD. After that, the situation was drastically improved, and the secondary electron emission almost disappeared even in the higher RF duty. This shows that the TiN coating-free ceramic is the prospective item for the cost reduction in ILC. In this report, the recent result for the power coupler with the TiN coating-free ceramic will be presented in detailed.

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WEPML067

Second Sound Quench Detection on Superconducting Cavities

cavity, detector, site, superconducting-cavity

2843

Z.C. Liu, S. Bai, J. Gao, F.S. He, H.Y. Lin, P. Zhang
IHEP, Beijing, People's Republic of China

Second sound is an effective way to detect the quench position on superconducting cavity. A second sound quench site detection system is under developing for the PAPS. High gradient is very important for superconducting cavity, however it may be limited by quench on the cavity high field region. Quench can be caused by various reasons. To locate the position is the key to reveal the mysteries of quench. Now we are developing the quench position detection system by RTD sensors such as Cernox and OST sensors.

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WEPML078

Development of a Superconducting Double-Spoke Cavity at IMP

cavity, accelerating-gradient, ion-source, niobium

2869

T.C. Jiang, H. Guo, Y. He, C.L. Li, L.B. Liu, T. Tan, P.R. Xiong, Z.M. You, W.M. Yue, S.H. Zhang, S.X. Zhang
IMP/CAS, Lanzhou, People's Republic of China

Superconducting multi-spoke cavities are well-known optional choice for acceleration of heavy ions in medium velocity regimes. The paper describes the design, fabrication and test results of the superconducting double-spoke cavity developed at IMP. After Buffered Chemical Polishing and High pressure Rinsing, one cavity has undergone high gradient RF testing at 4 K in the Vertical Test Stand. We present measurements of the quality factor as a function of accelerating field and maximum field on the surface. Accelerating gradient of more than 15 MV/m is reached with peak electric field of 61 MV/m, and peak magnetic field of 118 mT.

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THXGBD3

Status of the ESRF-Extremely Brilliant Source Project

vacuum, operation, injection, dipole

2882

J.-L. Revol, C. Benabderrahmane, P. Berkvens, J.C. Biasci, J-F. B. Bouteille, T. Brochard, N. Carmignani, J.M. Chaize, J. Chavanne, F. Cianciosi, A. D'Elia, R.D. Dimper, M. Dubrulle, D. Einfeld, F. Ewald, L. Eybert, G. Gautier, L. Goirand, L. Hardy, J. Jacob, B. Joly, M.L. Langlois, G. Le Bec, I. Leconte, S.M. Liuzzo, C. Maccarrone, T.R. Mairs, T. Marchial, H.P. Marques, D. Martin, J.M. Mercier, A. Meunier, M. Morati, J. Pasquaud, T.P. Perron, E. Plouviez, E. Rabeuf, P. Raimondi, P. Renaud, B. Roche, K.B. Scheidt, V. Serrière, P. Van Vaerenbergh, R. Versteegen, S.M. White
ESRF, Grenoble, France

The ESRF - the European Synchrotron Radiation Facility - is a user facility in Grenoble, France, and the source of intense high-energy (6 GeV) X-rays. In 2019, the existing storage ring will be removed and a new lattice will be installed in its place, dramatically reducing the equilibrium horizontal emittance. This 'fourth-generation' synchrotron will produce an X-ray beam 100 times more brilliant and coherent than the ESRF source today. The Extremely Brilliant Source (EBS) project was launched in 2015 and is now well underway, on track for its scheduled completion in 2020. The design is completed, the procurement in full swing, the assembly has started, and critical installation activities are being prepared. The current status, three years into the project, will be revealed, along with the expected performance of the accelerator and the technical challenges involved. This paper will focus on the implementation of the project.

Slides THXGBD3 [13.547 MB]

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THPAF028

Multi-Objectives Genetic Algorithms (MOGA) Optimization of PETRA IV Scenarios

lattice, injection, sextupole, dynamic-aperture

3015

X.N. Gavaldà, J. Keil, R. Wanzenberg
DESY, Hamburg, Germany

This paper reports the application of Multi-Objective Genetic Algorithms (MOGA) to optimize the linear and nonlinear beam dynamics of the different PETRA IV scenarios to transform PETRA III storage ring in a diffracted limited one. As it is well known, the dynamic aperture and momentum acceptance of these kinds of lattices are dramatically reduced due to the increase of the sextupoles strengths to compensate its strong focusing. The reduction of the dynamic aperture jeopardizes the current off-axis injection system and lower beam lifetimes increase the beam instabilities and the radiation safety concerns of the storage ring. MOGA searches the best settings of quadrupoles and sextupoles in a multi-dimensional parameter space taking into account the dynamic properties and the natural emittance as objectives at the level of ten picometers. The lattices studied are the so-called 'Twist lattice' based in a phase space exchange lattice, a solution based in the ESRF-Hybrid Multi-bend Achromat (HMA) design and finally the 'double 'I' lattice combining a non-interleaved sextupoles cell with an ESRF-HMA cell.

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THPAF084

Impact of RF Coupler Kicks on Beam Dynamics in BESSY VSR

cavity, simulation, kicker, lattice

3182

T. Mertens
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany
T. Atkinson, F. Glöckner, A. Jankowiak, M. Ries, A.V. Tsakanian
HZB, Berlin, Germany

The expected BESSY II upgrade to BESSY VSR requires the installation of a superconducting RF system, consisting of four cavities. Two cavities will operate at 1.5 GHz and two at 1.75 GHz. Each of them is equipped with a Fundamental Power Coupler and with Higher Order Mode (HOM) damping waveguide couplers. Dedicated simulations of these cavities and couplers have shown that at the location of the FPC the beam will see a transverse kick [*], perturbing the closed orbit and affecting transverse beam dynamics. We present the results of simulations and experiments of the impact on transverse beam dynamics of these coupler induced kicks for different FPC orientations.
[*] Study on RF Coupler Kicks of SRF Cavities in the BESSY VSR Module
A. Tsakanian#, H.-W. Glock, T. Mertens, M. Ries, A. Velez, J. Knobloch
IPAC18

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THPAK076

Development and Benchmarking of the IMPACT-T Code

rfq, linac, simulation, space-charge

3408

H.P. Li, M.J. Easton, Y.R. Lu, Z. Wang
PKU, Beijing, People's Republic of China
J. Qiang
LBNL, Berkeley, California, USA

The multi-particle tracking code IMPACT-T is widely used to calculate the particle motion in high intensity linacs. The code is a self-consistent three-dimensional beam dynamics simulation toolbox that utilizes the particle-in-cell method in the time domain. In the collaboration between PKU and LBNL, an RFQ module was implemented to the IMPACT-T code, which enables simulations of the accelerator front-end. In order to benchmark the newly developed module in the IMPACT-T code, we have simulated the beam transport in Beijing Isotope Separation On-Line (BISOL) high intensity deuteron driver linac. It consists of a 3 MeV RFQ and 40 MeV superconducting HWR linac with five cryomodules. After comparing the simulation results with PARMTEQM, TraceWin and Toutatis, we obtained a very good agreement, which represents the validation of the new code.

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THPAL007

Upgrade of PIAVE Superconducting RFQs at INFN-Legnaro

rfq, operation, cavity, superconducting-RF

3623

G. Bisoffi, E. Bissiato, D. Bortolato, F. Chiurlotto, T. Contran, E. Fagotti, A. Minarello, P. Modanese, E. Munaron, D. Scarpa
INFN/LNL, Legnaro (PD), Italy
V. Andreev
ITEP, Moscow, Russia
A. Bosotti, R. Paparella
INFN/LASA, Segrate (MI), Italy
L.M.A. Ferreira
CERN, Geneva, Switzerland
K. Kasprzak
IFJ-PAN, Kraków, Poland
R.C. Pardo
ANL, Argonne, Illinois, USA

Superconducting RFQs (SRFQs), the first SC RFQs ever made operational for users, have been operated on the PIAVE SC heavy ion linac injector at INFN-Legnaro since 2006. The structure is split into two resonators and is limited to the accelerating RFQ sections. The resonators had never exceeded 80% of the design accelerating fields. In 2015, an upgrade plan started, aimed at increasing the accelerating fields, while improving their slow and fast tuning systems, repairing degraded components, imple-menting a LASER alignment method. The upgrade plan was successfully concluded in summer 2017. The resona-tors were kept stably locked for days at a field larger than the nominal one. Eventually, a test beam was accelerated successfully for 72 hours, with negligible locking issues. SRFQs entered once again routine operation in December 2017. The new features will allow to accelerate heavy ions with an A/q value as high as 8.5 (versus a former maximum A/q=7.5), allowing operation of the very first accelerated uranium beams at INFN-LNL, after the relat-ed authorizations shall have been issued.

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THPAL012

Soft Chemical Polishing and Surface Analysis of Niobium Samples

cavity, niobium, linac, operation

3641

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

Funding: Work supported by the German Federal Ministry for Education and Research (BMBF) under Grant No. 05H15RDRBA
The Superconducting Darmstadt Linear Accelerator S-DALINAC uses twelve Niobium Cavities with a RRR of 280 which are operated at 2 K. The operating frequency is 3 GHz; the design value of the accelerating gradient is 5 MV/m. To achieve the target value of 3 x 10˄9 for Q0, different surface preparation methods were applied and systematically tested using a vertical 2 K cryostat. A well-established technique is the so called Darmstadt Soft Chemical Polishing, which consists of an ultrasonic cleaning of the cavity with ultrapure water followed by oxidizing the inner surface with nitric acid. After rinsing with water the niobium oxide layer is removed with hydrofluoric acid in a separate second step. Finally the structure is rinsed and then dried by a nitrogen flow. Until now each cavity in operation was chemically treated with a proven record of success. In order to understand and to optimize the process on the niobium surface, systematic tests with samples were performed and analyzed using material science techniques like SEM, SIMS and EDX. We will report on the results of our research and we will give a review on our experiences with varied chemical procedures.

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THPAL015

Evaluation of superconducting characteristics on the thin-film structure by NbN and Insulator coatings on pure Nb substrate

cavity, embedded, radio-frequency, electromagnetic-fields

3653

R. Katayama, Y. Iwashita, H. Tongu
Kyoto ICR, Uji, Kyoto, Japan
C.Z. Antoine
CEA/IRFU, Gif-sur-Yvette, France
A. Four
CEA/DRF/IRFU, Gif-sur-Yvette, France
H. Hayano, T. Kubo, T. Saeki
KEK, Ibaraki, Japan
H. Ito
Sokendai, Ibaraki, Japan
R. Ito, T. Nagata
ULVAC, Inc, Chiba, Japan
H. Oikawa
Utsunomiya University, Utsunomiya, Japan

Funding: The work is supported by JSPS KAKENHI Grant Numbers JP17H04839, JP26600142 and the Collaborative Research Program of ICR Kyoto University (grant 2016-8, 2017-8, 2017-9).
In recent years, it is pointed out that the maximum accelerating gradient of a superconducting RF cavity can be pushed up by coating the inner surface of cavity with a multilayer thin-film structure that consists of alternate insulator and superconductive layers. In this structure, the principal parameter that limits the performance of the cavity is the critical magnetic field or effective Hc1 at which vortices start penetrate into the first superconductor layer. We made a sample that has NbN/SiO2 thin-film structure on pure Nb substrate by DC magnetron sputtering method. In this paper, we will report the measurement results of effective Hc1 of the sample by the third-harmonic voltage method.

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THPAL034

Dynamic Tuner Development for Medium β Superconducting Elliptical Cavities

cavity, linac, operation, superconducting-RF

3709

C. Contreras-Martinez, P.N. Ostroumov
FRIB, East Lansing, USA
E. Borissov, S. Cheban, Y.M. Pischalnikov, V.P. Yakovlev, J.C. Yun
Fermilab, Batavia, Illinois, USA

Funding: Work supported by U.S. DOE SCGSR program under contract number DE-SC0014664, Michigan State University, and Fermi Research Alliance under contract N. DEAC02-07CH11959 with the U.S. DOE
The Facility for Rare Isotope Beams (FRIB) is developing a 5-cell 644 MHz β_opt=0.65 elliptical cavity for a future linac energy upgrade to 400 MeV/u for the heaviest uranium ions. Superconducting elliptical cavities operated in continuous wave, such as the ones for FRIB, are prone to microphonics which can excite mechanical modes of the cavities. It has been shown that the detuning due to microphonics can be mitigated with the use of piezo actuators (fast tuner) as opposed to the costly option of increasing the input RF power. The FRIB slow/fast dynamic tuner will be based on the Fermilab experience with similar tuners like those developed for the linac coherent light source (LCLS) II and proton improvement plan (PIP) II. This paper will present the results of tuner properties on the bench.

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THPAL036

Nb3Sn Thin Films for the Production of Higher Gradient SRF Cavities at Reduced Cost

cavity, niobium, superconductivity, site

3716

S.A. Kahn, M.A. Cummings
Muons, Inc, Illinois, USA
E.Z. Barzi, D. Turrioni
Fermilab, Batavia, Illinois, USA
S. Falletta
Politecnico di Torino, Torino, Italy
A. Kikuchi
NIMS, Tsukuba, Ibaraki, Japan

High gradient superconducting cavities (SRF) will be needed for future accelerators. The higher gradient can achieve the high energy with fewer cavities. However the accelerating field of niobium cavities is limited by the peak magnetic field on the cavity surface. Cavities coated with Nb3Sn have a significantly larger Hc2 allowing the cavity to achieve a larger gradient. Measurements of Nb3Sn coated cavities have achieved about half the theoretical predicted gradient. It is possible to improve Nb3Sn plated cavity performance.

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THPAL039

Improved Magnetron Stability and Reduced Noise in Efficient Transmitters for Superconducting Accelerators

controls, cavity, feedback, experiment

3726

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

State of the art high-current superconducting accelerators require efficient RF sources with a fast dynamic phase and power control. This allows for compensation of the phase and amplitude deviations of the accelerating volt-age in the Superconducting RF (SRF) cavities caused by microphonics, etc. Efficient magnetron transmitters with fast phase and power control are attractive RF sources for this application. They are more cost effective than traditional RF sources such as klystrons, IOTs and solid-state amplifiers used with large scale accelerator projects. However, unlike traditional RF sources, controlled magnetrons operate as forced oscillators. Study of the impact of the controlling signal on magnetron stability, noise and efficiency is therefore important. This paper discusses experiments with 2.45 GHz, 1 kW tubes and verifies our analytical model which is based on the charge drift approximation.

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THPAL041

Power Coupler Design for the LUCRECE Project

cavity, simulation, coupling, linac

3732

H. Guler, D. Auguste, J. Bonis, O. Bouras, M. El Khaldi, W. Kaabi, P. Lepercq
LAL, Orsay, France

The LUCRECE project aims at developing an elementary RF system (cavity, power source, LLRF and controls) suitable for continuous (CW) operation at 1.3 GHz. This effort is made in the framework of the advanced and compact FEL project LUNEX5 (free electron Laser Using a New accelerator for the Exploitation of X-ray radiation of 5th generation), using superconducting linac technology for high repetition rate and multi-user operation (www.lunex5.com). In this context, based on its large experience on coupler design and RF conditioning, LAL Laboratory is in charge of the design and the fabrication of RF couplers that could operate at up to 15-20 kW in CW mode. For this purpose, geometry based on CORNELL 65kW CW couplers will me modified to fulfil the LCLS2 type cavity with the high necessary coupling level. Electromagnetic simulations and optimisation and associated thermal heating will be discussed. Methods to decrease the thermal impact, and strategy for RF conditioning will be considered.

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THPAL045

Determination of the Electron Bunch Length With Third Harmonic Cavity for the Taiwan Photon Source

cavity, operation, simulation, electron

3745

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

The Taiwan Photon Source (TPS) is a modern 3 GeV low emittance light source with RMS bunch lengths of about 3 mm at a beam current of 500 mA and operating gap voltage of 3.2 MV. With a higher harmonic cavity, we could increase the Touschek lifetime and lower the heat load of in-vacuum undulators by lengthening the bunch lengths. Preliminary studies show that for full and uni-form fill patterns, the bunch lengths could be increased by a factor of four. However, this calculation ignores phase transient effects and may overestimate the effect of harmonic cavities. A multi-bunch, multi-particle tracking method has been developed to determine the bunch lengths for non-uniform fill patterns, which also takes phase transient effects into account and the expected maximum bunch lengthening factor for different TPS operation conditions are discussed.

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THPAL065

Improving the Work Function of Nitrogen-Doped Niobium Surfaces for SRF Cavities by Plasma Processing

plasma, cavity, niobium, accelerating-gradient

3802

K.E. Tippey, R. Afanador, M. Doleans, S.-H. Kim, J.D. Mammosser, C.J. McMahan
ORNL, Oak Ridge, Tennessee, USA
M. Martinello
Fermilab, Batavia, Illinois, USA

Funding: DOE research grant FWP-ERKCSA2; DOE contract DE-AC05-00OR22725
Work function and surface chemistries of SiC-polished, electropolished, and nitrogen-doped niobium coupons were analyzed before and after plasma processing using a neon-oxygen gas mixture. These studies represent an initial enquiry into the feasibility of applying the plasma processing technique designed at ORNL for the Spallation Neutron Source (SNS) to the nitrogen-doped Nb cavities for the Coherent Light Source II (LCLS-II). Work function of all measured samples was increased after plasma processing, which indicates the strong potential of the plasma processing technique as a tool for increasing the accelerating gradient of nitrogen-doped cavities.

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THPAL076

Experimental Methods for the Assessment of NEG Pumps Working in Dust-Sensitive Environments

vacuum, cavity, experiment, background

3828

T. Porcelli, E. Maccallini, P. Manini, M. Mura, M.F. Urbano
SAES Getters S.p.A., Lainate, Italy

NEG pumps have been widely adopted by many accelerator facilities since decades. However, their use in dust-sensitive areas - such as superconductive radio frequency (SRF) cavities - has always been limited by concerns about accidental dust emission, which could induce detrimental field emission. As future machines will necessarily rely on highly-efficient SRF cavities, able to supply very high accelerating gradients, requirements in terms of particle release from vacuum components (e.g., pumps and valves) are becoming more and more stringent. At the same time, achieving stable ultra-high vacuum conditions is crucial, as condensed residual gas might also be a potential source of field emission. At present, a unified standard procedure to assess dust generation and propagation along a machine is still missing and discussions are ongoing in the vacuum community. Recent experimental measurements demonstrated the compatibility of sintered NEG pumps with ultra-clean environments, due to their intrinsic very low dust release. In parallel, in-situ tests performed at different accelerator facilities showed absence of dust contamination from NEGs and no impact on cavities efficiency.

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THPAL080

Parallel-Feed SRF Accelerator Structures

cavity, coupling, simulation, impedance

3835

P.B. Welander, Z. Li, M.H. Nasr, S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: This work is supported by the Department of Energy, Laboratory Directed Research and Development program at SLAC National Accelerator Laboratory, under contract DE-AC02-76SF00515.
Development of SRF accelerator technology that enables both higher gradient and higher efficiency is crucial for future machines. While much of the recent R&D focus has been on materials and surface science, our aim is to optimize the cavity geometry to maximize performance with current materials. The recent demonstration of a highly efficient parallel-feed NCRF structure at SLAC has served as a proof-of-concept. Applied to SRF, such a structure could dramatically reduce power consumption while boosting the achievable gradient. Instead of coupled elliptical cells, our structure employs isolated reentrant cells. To feed RF power to the cavities, each cell is directly coupled to an integrated manifold. The structure is made in two parts, split along the beam axis, which are then joined. Such a structure has been fabricated from bulk Cu and tested at SLAC - designed for X-band, it operates at a record gradient of 150 MV/m. Adapting to SRF at 1.3 GHz and fabricating from Nb, such a cavity could achieve more than 50% lower RF loss and 40% higher gradient compared to the TESLA cavity. We will describe our simulations and propose an experimental roadmap for demonstrating this technology.

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THPAL081

A 3 GHz SRF Reduced-beta Cavity for the S-DALINAC

cavity, linac, operation, electron

3838

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

Funding: Work supported by DFG through GRK 2128
In order to reduce the energy spread and to be able to use a 200 keV spin-polarized electron source, the initial part of the injector linac of the superconducting Darmstadt electron linear accelerator S-DALINAC needs to be upgraded. The decisions on the cavity type, number of cells and value of geometric beta are motivated. The main part of this work is dedicated to the mechanical design of the cavity. A precise evaluation of the mechanical characteristics of an SRF cavity is necessary during the design stage. The dependence of the resonant frequency of the fundamental mode on external mechanical loads needs to be investigated for developing the tuning procedures. The results of the multiphysics simulations and of the optimization of the mechanical design are presented.

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THPAL086

Superconducting Thin Film RF Measurements

cavity, vacuum, niobium, operation

3856

P. Goudket, L. Bizel-Bizellot, L. Gurran, O.B. Malyshev, S.M. Pattalwar, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G. Burt, L. Gurran
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
P. Goudket, T. Junginger, O.B. Malyshev, S.M. Pattalwar, R. Valizadeh
Cockcroft Institute, Warrington, Cheshire, United Kingdom
L. Gurran, T. Junginger
Lancaster University, Lancaster, United Kingdom

As part of an ongoing programme of SRF Thin Films development, a radiofrequency (RF) cavity and cryostat dedicated to the measurement of superconducting coatings at GHz frequencies was designed to evaluate surface resistive losses on a flat sample. The resonator has now been used for measurements on Thin Film samples. Results from a test on a sample previously tested at Cornell University are presented. In order to simplify the measurements and achieve a faster turnaround, the experiment will be moved to a new cryostat fitted with a cryocooler. This will limit the measurements to low power only, but will allow a much faster sorting of samples to identify those that would benefit from further investigation. A description of the system and initial results will be presented.

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THPAL089

Design, Assembly and Commissioning of a New Cryogenic Facility for Complex Superconducting Thin Film Testing

experiment, site, cavity, operation

3859

O.B. Malyshev, L. Bizel-Bizellot, K.D. Dumbell, P. Goudket, N. Pattalwar, S.M. Pattalwar, P. Pizzol, P.A. Smith, R. Valizadeh, S. Wilde
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
P. Pizzol
The University of Liverpool, Liverpool, United Kingdom

An ongoing study on the superconducting thin films for future superconducting RF cavities requires an intense testing of various superconducting properties. We have designed, built and tested a new facility for complex superconducting thin film testing that includes: (1) RRR measurement with and without magnetic field, (2) planar and (3) tubular magnetic field penetration experiments, (4) a superconducting coaxial resonator for bulk niobium and superconducting thin film characterisation. The system is based on a closed cycle refrigerator, eliminating the need for liquid helium, thus making it simple and safe to operate. The details of the design and commissioning will be presented at the conference.

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THPAL092

Test Particle Monte Carlo Simulation of NEG Coated Narrow Tubular Samples

vacuum, ECR, experiment, simulation

3862

O. Seify, A.N. Hannah, O.B. Malyshev, Sirvinskaite, R. Sirvinskaite, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
Sirvinskaite, R. Sirvinskaite
Loughborough University, Loughborough, Leicestershire, United Kingdom

The pumping properties of the NEG coated vacuum chambers play an important role in the efficiency of vac-uum system of accelerators. The sticking probability of the NEG films is one the most important parameters to characterise the pumping properties of the NEG coated vacuum chambers. In order to investigate the NEG film sticking probability, Test Particle Monte-Carlo (TPMC) models were used. The models were based on the design of the installed experimental setup in ASTeC Vacuum Science group laboratory at Daresbury Laboratory (DL). The results of the simulations have been used for inter-preting the results of the measurements in the experi-mental setup.

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THPAL104

The Magnetic Field Measurement Systems for a Cryogenic Undulator and a Superconducting Undulator at SSRF

cryogenics, undulator, GUI, vacuum

3878

H.F. Wang
SSRF, Shanghai, People's Republic of China
M.F. Qian, W. Zhang, Q.G. Zhou
SINAP, Shanghai, People's Republic of China

Two cryogenic permanent magnet undulators (CPMU) have been developed and assembled into storage ring at SSRF，in order to reach larger magnetic field and to produce higher brilliance in the hard X rays domain. Lowering the temperature of permanent magnets increases the magnetic produced field about by 15%. A set of magnetic measurement system and a suitable magnetic field optimization method have been developed. The design of a magnetic measurement bench based on a Hall probe to perform low temperature measurement has been finished. In addition, a 50-period superconducting undulator prototype with 16mm period length is also being developed for more photons with some specific photon characteristic. And a special hall probe system has been built in order to characterize the magnetic field distribution of the SCU prototype.

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THPAL105

Lower Critical Field Measurement System of Thin Film Superconductor

controls, experiment, simulation, embedded

3882

H. Ito
Sokendai, Ibaraki, Japan
C.Z. Antoine
CEA/IRFU, Gif-sur-Yvette, France
A. Four
CEA/DRF/IRFU, Gif-sur-Yvette, France
H. Hayano, T. Kubo, T. Saeki
KEK, Ibaraki, Japan
R. Ito, T. Nagata
ULVAC, Inc, Chiba, Japan
Y. Iwashita, R. Katayama, H. Tongu
Kyoto ICR, Uji, Kyoto, Japan
H. Oikawa
Utsunomiya University, Utsunomiya, Japan

Funding: The work is supported by Japan Society for the Promotion of Science Grant-in-Aid for Young Scientist (A) No.17H04839.
Superconducting thin film is the promising technology to increase the performance of SRF cavities. The lower critical field Hc1, which is one of the important physical parameters characterizing a superconducting material, will be enhanced by coating Nb with thin film superconductor such as NbN. To investigate the performance of thin film, we developed the Hc1 measurement system using the third harmonic response of applied AC magnetic field. The measurement system consists of helium cryostat with two of GM refrigerators, sample Cu stage, solenoid coil Cu mount, solenoid coil, temperature sensors, and liquid helium level meter. AC magnetic field is produced by a coil which is driven by function generator and power amplifier at around 1 kHz. In order to control the temperature of the sample stage and coil mount, the depth of thermal anchors attached to the stage and the mount can be moved by the motor. By this temperature control the sample state can be easily transferred from Meissner state to mixed state. So that the measurement is repeated for various applied magnetic field, and the transition curve can be made. In this report, performance of the measurement system is described.

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THPAL120

Cryogenics Infrastructure at TRIUMF's Particle Accelerator Facilities

cryogenics, TRIUMF, ISAC, operation

3925

A.N. Koveshnikov, Y. Bylinskii, G.W. Hodgson, D. Kishi, R.E. Laxdal, R.R. Nagimov, D. Yosifov
TRIUMF, Vancouver, Canada

Funding: TRIUMF receives federal funding via a contribution agreement with the National Research Council of Canada.
Cryogenic infrastructure is an indispensable part of TRIUMF accelerator facilities. At the moment TRIUMF operates three helium cryogenic systems supporting operation of three major accelerator systems: 520 MeV proton cyclotron, superconductive radio-frequency (SRF) heavy ion linear accelerator at the Rare Isotope Beams (RIB) facility, and SRF electron linear accelerator (e-linac) at Advanced Rare IsotopE Laboratory (ARIEL). Applications of cryogenic thermal loads vary from cryogenic absorption pumping of the cyclotron vacuum tank to cryogenic cooling of superconducting (SC) RF cavities of production accelerators and support of research and development at SRF department. Wide range of production techniques for cryogenic refrigeration includes helium refrigerators based on both piston and turbine expansion coldboxes for both 4 K and 2 K temperature cryogenic loads. This paper presents the details of TRIUMF cryogenic systems as well as operational experience of various cryogenic installations.

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THPAL126

Nitrogen Bake-out Procedures at the Vertical High-Temperature UHV-Furnace of the S-DALINAC

cavity, vacuum, niobium, linac

3937

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

Funding: Work supported by the Federal Ministry of Education and Research through grant No. 05H15RDRBA.
As the performance limits of bulk Nb srf cavities are reached, our research is focused on materials with superior srf properties like Nb3Sn and NbN. Research on NbN resulted in the "nitrogen-doping" process used for increasing the quality factors of srf cavities for the LCLS-II project. This process leads to delta-phase Nb-N, a phase with higher critical sc parameters than bulk Nb. This phase is formed at temperatures of 800°C in nitrogen atmospheres of 10^-2 mbar. Other crystalline phases of NbN have even better sc parameters. We concentrate our research on applicability of delta-phase NbN for cavities. The delta-phase forms at temperatures of above 1300°C, which is more than most of the furnaces at accelerator facilites are capable of. Since 2005 the Institute for Nuclear Physics at the Technische Universität Darmstadt operates a high temperature vacuum furnace which has been upgraded to allow temperatures of up to 1750°C and bakeouts of niobium samples and cavities in nitrogen atmospheres. We will report on the current status of our research on nitrogen bake-out procedures on Nb samples. The samples have been analyzed at the Material Science Departement with SIMS, REM and XRD.

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THPAL129

Magnetron Sputtering of Nb3Sn for SRF Cavities

cavity, site, target, controls

3946

MNS. Sayeed, H. Elsayed-Ali
ODU, Norfolk, Virginia, USA
G.V. Eremeev, M.J. Kelley, C.E. Reece
JLab, Newport News, Virginia, USA
M.J. Kelley, U. Pudasaini
The College of William and Mary, Williamsburg, Virginia, USA
M.J. Kelley
Virginia Polytechnic Institute and State University, Blacksburg, USA

Nb3Sn is a potential candidate for surface material of SRF cavities since it can enable the cavity to operate at higher temperatures with high quality factor and at an increased accelerating gradient. Nb-Sn films were deposited using magnetron sputtering of individual Nb and Sn targets onto Nb and sapphire substrates. The as-deposited films were annealed at 1200 °C for 3 hours. The films were characterized for their structure by X-ray Diffraction (XRD), morphology by Field Emission Scanning Electron Microscopy (FESEM), and composition by Energy Dispersive X-ray Spectroscopy (EDS) and Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS). The surface resistivity was measured down to cryogenic temperature to determine the superconducting transition temperature and its width. The composition of the multilayered films was controlled by varying the thickness of the Nb and Sn layers. The films showed crystalline Nb3Sn phases with Tc up to 17.6 K.

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THPAL130

Effect of Deposition Temperature and Duration on Nb3Sn Diffusion Coating

cavity, niobium, experiment, superconductivity

3950

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: Partially authored by Jefferson Science Associates under contract no. DE¬AC05¬06OR23177. Work at College of William & Mary supported by Office of High Energy Physics under grant SC0014475.
Nb3Sn is a potential candidate to replace Nb in SRF accelerator cavities to reduce cost and advance perfor-mance. Tin vapor diffusion is the preferred technique to realize such cavities by growing a few microns thick Nb3Sn coating on the interior surface of the niobium cavity. The coating process typically uses temperatures of 1100-1200 °C for 3-6 hours. It is important to better understand the coating process, and optimize the coating parameters to overcome the current limitation on the performance of Nb3Sn coated SRF cavities. We investi-gate Nb3Sn coatings prepared in the temperature range of 900-1200 °C and duration of 3 - 12 hours using various material characterization tools. Variation of these pa-rameters appears to have notable effect on microstructure and topography of the obtained surface.

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THPAL131

Studies of Electropolishing and Oxypolishing Treated Diffusion Coated Nb3Sn Surfaces

cavity, niobium, experiment, superconductivity

3954

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

The Nb3Sn-coated cavities aim to enhance perfor-mance and significantly reduce cost. Their fabrication involves tin vapor diffusion coating of Nb3Sn on the interior surface of a Nb cavity. Controlled removal of first few layers to obtain a smoother and cleaner surface could be desirable to improve the high field RF perfor-mance. Our first results from the application of elec-tropolishing and oxypolishing techniques on Nb3Sn-coated surfaces indicated reduced surface roughness, and the surface composition appeared nominally unchanged. Systematic studies explore the effect of different polish-ing parameters into the roughness and composition. We present the latest results from SEM/EDS and AFM studies of Nb3Sn-coated samples treated with electropolishing and oxypolishing.

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THPAL142

Surface Characterization of NbTiN Films for Accelerator Applications

site, FEL, detector, lattice

3975

D.R. Beverstock, M.J. Kelley, C.E. Reece, J.K. Spradlin, A-M. Valente-Feliciano
JLab, Newport News, Virginia, USA

Funding: Work supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The development of next-generation SRF cavities requires the deployment of innovative material solutions with RF performance beyond bulk Nb. Theoretical interest has stimulated efforts to grow and characterize thin multi-layer superconductor/insulator/superconductor (SIS) structures for their potential capability of supporting otherwise inaccessible surface magnetic fields in SRF cavities *. The ternary B1-compound NbTiN is among the candidate superconducting materials for SIS structures. Single crystal NbTiN films with thicknesses below 15 nm are also of interest for the development of high resolution, high sensitivity (SNSPD) detectors for particle physics application. Using DC reactive magnetron sputtering, NbTiN can be deposited with nominal superconducting parameters. This contribution presents the on-going material surface and superconducting properties characterization in order to optimize the NbTiN films for each application.
* A Gurevich, "Maximum screening fields of superconducting multilayer structures", AIP ADVANCES 5, 017112 (2015)

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THPAL143

Commissioning of JLab Vertical Cavity Processing System for SRF Nb Single Cell and Multicell Cavity With HF-Free Pulse-Reverse Electopolishing

cavity, controls, niobium, MMI

3978

H. Tian, M. Lester, J. Musson, H.L. Phillips, C.E. Reece, C. Seaton
JLab, Newport News, Virginia, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177
Pulse reversed electropolishing of niobium SRF cavities, using a dilute aqueous H2SO4 electrolyte without HF yields equivalent RF performance with traditional EP. Comparing with present EP process for Nb SRF cavity which uses 1:10 volume ratio of HF (49%) and H2SO4 (98%), pulse reverse EP (also known as bipolar EP (BPEP)) is ecologically friendly and uses relatively benign electrolyte options for cavity processing. In this study, we report the commissioning of a new vertical cavity processing system for SRF Nb single cell and multi-cell cavities with HF-free pulse-reverse electropolishing at Jefferson Lab, together with RF test of cavities being processed. We report the scale-up challenges and interpretations from process R&D to implementation.

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THPAL144

952.6 MHz SRF Cavity Development for JLEIC

cavity, HOM, damping, electron

3982

R.A. Rimmer, W.A. Clemens, F. Fors, J. Guo, F.E. Hannon, J. Henry, F. Marhauser, L. Turlington, H. Wang, S. Wang
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
JLab is developing new SRF cavity designs at 952.6 MHz for the proposed Jefferson Lab Electron-Ion Collider (JLEIC). New cavities will be required for the ion ring, cooler ERL and booster and eventually for an upgrade of the electron ring to allow the highest possible bunch collision rate. The challenges include the need for high fundamental mode power couplers and strong HOM damping, with high HOM power capability. Initial focus is on the cooler ERL 5-cell cavity as this is a critical component for the strong, high energy, bunched-beam cooling concept. 1-cell and 5-cell Nb prototype cavities have been designed and fabricated. Details concerning the cavity fabrication and test results will be presented.

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THPAL145

Magnetron R&D toward the Amplitude Modulation Control for SRF Accelerator

injection, controls, cavity, simulation

3986

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

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and SBIR grant DE-SC0013203
The scheme of using a high efficiency magnetron to drive a superconducting radio frequency (SRF) accelerator cavity needs not only the injection phase locking but also the amplitude modulation to compensate the cavity's microphomics caused cavity voltage change and the beam loading variation. To be able to do a fast and efficient modulation, the magnetron's magnetic field has to be trimmed by an external coil to compensate the frequency pushing effect due to the anode current change [1]. A low eddy current magnetron body has been designed and built [2]. This paper will present the analytical prediction, simulation and experimental results on the 2.45 GHz magnetron test stand with the modulation frequency up to 1 kHz. In addition, the progresses on the injection lock to a copper cavity, new 1497 MHz magnetron prototype, 13 kW high power magnetron test stand development and newly built low level RF (LLRF) controller for the amplitude modulation will be reported.
[1] M. Neubauer et al, THPIK123, Proceedings of IPAC 2017, Copenhagen, Denmark
[2] S. A. Kahn et al, THPIK121, Proceedings of IPAC 2017, Copenhagen, Denmark

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THPAL146

802 MHz ERL Cavity Design and Development

cavity, collider, electron, hadron

3990

F. Marhauser, S. Castagnola, W.A. Clemens, J.G. Dail, P. Dhakal, F. Fors, J. Henry, R.A. Rimmer, L. Turlington, R.S. Williams
JLab, Newport News, Virginia, USA
R. Calaga, K.M. Dr. Schirm, E. Jensen
CERN, Geneva, Switzerland

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177, and CERN Contract NR. KE3080/ATS
In the framework of a collaboration between CERN and JLab, an SRF accelerating cavity for energy recovery linacs operating at 802 MHz was developed in the context of the CERN's Large Hadron electron Collider (LHeC) design study. A single-cell and a five-cell cavity from fine grain high RRR niobium were built at JLab to validate the basic RF design in vertical tests. Two copper single-cell cavities were produced in parallel for R&D purposes at CERN. The cavity design has since been adapted as baseline for the main linac cavities in the proposed Powerful Energy Recovery Linac Experiment facility (PERLE) at Orsay. Details concerning the cavity fabrication and test results for the Nb cavities are presented.

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THPMF017

Operation Improvements and Emittance Reduction of the ESRF Booster

emittance, booster, operation, quadrupole

4077

N. Carmignani, N. Benoist, J-F. B. Bouteille, M.G. Di Vito, F. Ewald, L. Farvacque, A. Franchi, O. Goudard, J.M. Koch, S. Lagarde, S.M. Liuzzo, B. Ogier, T.P. Perron, P. Raimondi, D. Robinson, F. Taoutaou, E.T. Taurel, P.V. Verdier, R. Versteegen, P. Vidal, S.M. White
ESRF, Grenoble, France

The ESRF storage ring will be replaced by the Extremely Brilliant Source (EBS) in 2020 and the equilibrium emittance will decrease from the present 4 nmrad to 134 pmrad. The current injector system, composed by a linac and a synchrotron booster, will be used to inject into the new storage ring. To increase the injection efficiency in the new storage ring, three methods to reduce the horizontal emittance of the booster have been considered and tested. This paper presents the studies and achievements in terms of operation improvements and emittance reduction.

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THPMF019

ESRF-EBS Lattice Model with Canted Beamlines

lattice, optics, MMI, quadrupole

4081

S.M. Liuzzo, N. Carmignani, J. Chavanne, L. Farvacque, T.P. Perron, P. Raimondi, S.M. White
ESRF, Grenoble, France

The ESRF Extremely Brilliant Source (ESRF-EBS) lattice model is updated to include three canted beamlines. The cells are modified where necessary to include 3-Pole Wiggler (3PW), 2-Pole Wiggler (2PW) and Short Bending Magnet (SBM) sources. Several lattices are obtained for the different stages that will bring from commissioning to operation with users. A scheme for tune modification keeping key optics knobs unchanged is proposed.

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THPMF020

A 4th Generation Light Source for South-East Europe

lattice, emittance, storage-ring, synchrotron

4084

H. Ghasem, R. Bartolini
DLS, Oxfordshire, United Kingdom
D. Einfeld
ESRF, Grenoble, France

In Europe, most of the Synchrotron Light Sources are located in the middle, west and northern regions while the south-east is still lacking any major project. Hence a new initiative has been set up to propose the construction of a 4th Generation Light Source in that region. Design requirements limit the beam energy between 2.5 GeV to 3 GeV, the circumference is limited to 350 m, the emittance should be smaller than 250 pm rad and at least 14 to 16 straights have to be available for the users. Several mag-net configurations have been investigated and the results revealed that the HMBA lattice can fully meets the requirements and is therefore proposed for the Light Source in the SEE-region of Europe. These studies show that for a 4th Generation Light Source with energies up to 3 GeV a circumferences of 350 m will be adequate.

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THPMF021

ESRF Operation Status

injection, operation, power-supply, booster

4088

J.-L. Revol, J.C. Biasci, N. Carmignani, A. D'Elia, A. Franchi, L. Hardy, J. Jacob, I. Leconte, S.M. Liuzzo, H.P. Marques, T.P. Perron, E. Plouviez, P. Raimondi, B. Roche, K.B. Scheidt, L. Torino, S.M. White
ESRF, Grenoble, France

The European Synchrotron Radiation Facility (ESRF) is undergoing the second phase (2015-2022) of an Up-grade which concerns its infrastructure, beamlines and X-ray source. This paper reports on the present operational source performance, highlighting the most recent developments, and the preparation of the Extremely Brilliant Source project. The renovation of the injector and the recent operation in top-up mode are also detailed.

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THPMF034

Status Report of the Berlin Energy Recovery Linac Project BERLinPro

gun, cathode, vacuum, cavity

4127

M. Abo-Bakr, W. Anders, Y. Bergmann, 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. Knobloch, J. Kolbe, G. Kourkafas, J. Kühn, B.C. Kuske, J. Kuszynski, A.N. Matveenko, M. McAteer, A. Meseck, R. Müller, A. Neumann, N. Ohm, K. Ott, E. Panofski, F. Pflocksch, L. Pichl, J. Rahn, M.A.H. Schmeißer, O. Schüler, M. Schuster, J. Ullrich, A. Ushakov, J. Völker
HZB, Berlin, Germany
A. Bundels
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany

Funding: Work supported by the 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 last year's progress, including the comissioning of the gun module as the first SRF component to be installed in BERLinPro.

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THPMF038

Status of the BESSY VSR Project

cavity, vacuum, operation, electron

4138

P. Schnizer, W. Anders, Y. Bergmann, P. Goslawski, H. Hartmut, A. Jankowiak, J. Knobloch, A. Neumann, K. Ott, M. Ries, A. Schälicke, A.V. Vélez
HZB, Berlin, Germany

BESSY VSR is set out to provide a variable pulse pattern to the BESSY II users. This project is now fully funded and heading into its implementation phase. The pulse pattern, consisting of long and short pulses, require inserting cavities providing a 3rd and a 3.5th harmonic of the fundamental harmonic of the ring. Therefore 1.5 and 1.75 GHz cavities are developed with appropriate higher order mode damping spectrum. Similarly the BESSY II ring and injector chain has to be upgraded to provide appropriate diagnostics and increase the injection efficiency. In this paper we give the current status of the project and give an overview of scientific challenges currently being tackled.

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THPMF039

Study of Magnesium Photocathodes for Superconducting RF Photoinjectors

laser, gun, cathode, cavity

4142

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

Funding: The work is supported by the German Federal Ministry of Education and Research (BMBF) grant 05K12CR1.
The superconducting RF photoinjector (SRF Gun II) has successfully served for the ELBE user facility at HZDR. Nevertheless, the quality of photocathodes is one of the most critical issues in improving the stability and reliability for its application. Magnesium has a comparably low work function (3.6 eV) and shows a quantum efficiency up to 0.3% after laser cleaning. However, the present cleaning process with a high intensity laser beam is time consuming and produces unwanted surface roughness, which leads to a higher thermal emittance. Thermal treatment and Excimer laser cleaning for Mg cathodes are investigated as alternative methods. In this work, the new cleaning procedures are tested and optimized, and the quantum efficiency of Mg samples with different microstructure, composition and suppliers are compared.

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THPMF040

Experiences with the SRF Gun II for User Operation at the ELBE Radiation Source

gun, radiation, undulator, electron

4145

J. Teichert, A. Arnold, M. Bawatna, P.E. Evtushenko, M. Gensch, B.W. Green, S. Kovalev, U. Lehnert, P.N. Lu, P. Michel, P. Murcek, H. Vennekate, R. Xiang
HZDR, Dresden, Germany

Funding: The work is supported by the German Federal Ministry of Education and Research (BMBF) grant 05K12CR1.
The second version of the superconducting RF pho-toinjector (SRF Gun II) was successfully commissioned at the ELBE radiation source in 2014. The gun features an improved 3.5-cell niobium cavity combined with a super-conducting solenoid integrated in the cryostat. With a Mg photocathode the SRF Gun II is able to generate bunches with up to 200 pC and with sub-ps length in CW mode with 100 kHz pulse frequency for the THz radiation fa-cility at ELBE. In the ELBE linac, the beam is accelerat-ed, gets a proper correlated energy spread, and is com-pressed in a magnetic chicane. Sub-ps pulses are obtained producing coherent diffraction radiation and superradiant undulator radiation.

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THPMF063

The MESA 15 kW cw 1.3 GHz Solid State Power Amplifier Prototype

operation, experiment, linac, cavity

4216

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

The Mainz Energy recovering Superconducting Accelerator MESA is a multi-turn energy recovery linac with beam energies in the 100 MeV regime currently designed and build at Institut für Kernphysik (KPH) of Johannes Gutenberg-Universität Mainz. The main accelerator consists of two superconducting Rossendorf type modules, while the injector MAMBO (MilliAMpere BOoster) relies on normal conducting technolgy. The high power RF system is planned completely in solid state technology. With the high power demands of the normal conducting RF cavities up-to-date transistor technology with increased power density has to be used. A 15 kW CW power ampifier prototype with the new technology has been developed by Sigma Phi Electronics and deliverd to KPH. In this paper we will present the results of the performance measurements of the amplifier.

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THPMK066

Cryogenic Permanent Magnet Undulator of SSRF

permanent-magnet, undulator, cryogenics, vacuum

4449

Y.Z. He, M.F. Qian, H.F. Wang, W. Zhang, Q.G. Zhou
SINAP, Shanghai, People's Republic of China

Funding: Work supported by the State Key Lab of Advanced Metals and Materials (2016-Z03) and the Youth Innovation Promotion Association of CAS (Grant No: 2017305)
The two Cryogenic Permanent Magnet Undulators (CPMU18 with PrFeB magnets P46H and CPMU20 with NdFeB magnets N48H) were designed and developed in SSRF in the past few years (2014-2017).This paper introduces magnetic performance of the permanent magnets, design parameters of the two CPMUs, cryogenic cooling and magnetic field of the two CPMUs and so on. When gap of the two CPMUs is about 6.0 mm, the measurement results showed that the effective magnetic field peak of CPMU18 at 300 K and 77 K was 0.82 T, 0.92T, respectively, and the magnetic field phase error is about 3 degrees and 5 degrees respectively. The effective magnetic field peak of CPMU20 at 300 K and 140 K was 0.94T and 1.03T, respectively, and the magnetic field phase error was 3 degrees and 3.5 degrees respectively.

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THPMK106

Architectural Considerations for Recirculated and Energy-Recovered Hard XFEL Drivers

FEL, linac, recirculation, operation

4560

D. Douglas, S.V. Benson, T. Powers, Y. Roblin, T. Satogata, C. Tennant
JLab, Newport News, Virginia, USA
D. Angal-Kalinin, N. Thompson, A.E. Wheelhouse, P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
T.K. Charles
CERN, Geneva, Switzerland
R.C. York
FRIB, East Lansing, Michigan, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
A confluence of events motivates discussion of design options for hard XFEL driver accelerators. Firstly, multiple superconducting radio-frequency (SRF) driven systems are now online (European XFEL), in construction (LCLS-II), or in design (MARIE); these provide increasing evidence of the transformational potential they offer for fundamental science with its concomitant benefits. Secondly, operation of 12 GeV CEBAF* validates use of recirculation in high energy SRF linacs. Thirdly, advances in the analysis and control of effects such as coherent synchrotron radiation (CSR) and the microbunching instability (uBI) have been recently achieved. Collectively, these developments offer insights providing extended facility science reach, reduced costs, multiplicity (i.e., support of numerous FELs operating over a range of wavelengths), and enhanced scalability and upgradability (to higher powers and energies). We will discuss the relationship amongst the various threads, and indicate how they inform design choices for the system architecture of an option for the UK-XFEL** - that of a staged multi-user X-ray FEL and nuclear physics facility based on a multi-pass recirculating SRF CW linac.
*M. Spata, "12 GeV CEBAF Initial Operations and Challenges", these proceedings.
**P. Williams et al., Proc. FLS2018, Shanghai, China (March 2018).

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THPMK144

Lattices for a 4th-Generation Synchrotron Light Source

lattice, synchrotron, emittance, radiation

4639

G. K. Shamuilov
Uppsala University, Uppsala, Sweden

Inspired by the ESRF upgrade (Extremely Brilliant Source, EBS), I present some modern lattices for a medium-sized 4th-generation synchrotron radiation source. They incorporate new elements, such as anti-bend magnets. The composed lattices are optimized using a simple double-objective algorithm. Its goal is to minimize the natural emittance and absolute chromaticities simultaneously. Then, the lattices are analyzed and compared to a version of the ESRF-EBS lattice scaled down in size. The design is performed to meet the needs of the user community of the Siberian Synchrotron and Terahertz Radiation Centre under the umbrella of the Budker Institute of Nuclear Physics.

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THPML066

Filling Pattern Measurement System Upgrade in SSRF*

operation, storage-ring, synchrotron, injection

4791

N. Zhang, F.Z. Chen, Y.M. Zhou
SSRF, Shanghai, People's Republic of China

Funding: Work supported by National Natural Science Foundation of China (No.11575282 No.11375255 No.11305253)
Filling pattern affects various operation performance of a synchrotron light source. A new diagnostic beam charge monitor (BCM) with high bandwidth multi-channels digitizer was developed to perform bunch-by-bunch charge measurement and record filling pattern for SSRF storage ring. Signals picked up from button elec-trodes were sampled synchronously with RF frequency, and IQ (In-phase and Quadrature phase) sampling meth-od was employed for noise-filtering and phase independ-ence calibration. Layout and evaluation experiment of the system are presented in this paper.

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THPML068

Upgrade of Bunch Phase Monitor at SSRF Storage Ring

injection, storage-ring, pick-up, experiment

4797

Y.M. Zhou, Y.B. Leng, T. Wu, N. Zhang
SSRF, Shanghai, People's Republic of China

Beam instability is a serious problem for physics in beam diagnosis technology. With regard to the evaluation of longitudinal phase oscillations during the transient injection process, bunch-by-bunch phase measurement is a useful tool for studying the behavior of the refilled bunches. A new upgraded beam phase monitor system with 1.2GHz bandwidth PXI waveform digitizer has been developed at Shanghai synchrotron radiation source (SSRF). Bunch-by-bunch phase information, retrieved from button pickup signals, is calculated by the zero-crossing detection method with the best phase resolution of 0.4ps. The refilled bunches can be separated from the stored ones, and the longitudinal offset of each refilled bunch has been measured. Several groups of experiments have been performed to verify the repeatability of bunch-by-bunch phase measurement, and some results regarding refilled bunches will be discussed in this paper.

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THPML070

Point Spread Function Study of Quasi-Monochromatic X-Ray Pinhole Camera at SSRF

simulation, photon, experiment, synchrotron

4803

B. Gao, H.J. Chen
SINAP, Shanghai, People's Republic of China
J. Chen, Y.B. Leng
SSRF, Shanghai, People's Republic of China

Since 2009 an X-ray pinhole camera that has been used to present the transverse beam size and emittance on diagnostic beam line of the storage ring at SSRF. The real beam size is a function of the image size of the CCD camera and point spread function (PSF) of the system. The performance of the measurement of the transverse electron beam size is given by the width of the PSF of X-ray pinhole camera. The contributions to the PSF width are the PSF of pinhole itself due to diffraction, and the PSF of the screen and camera. An X-ray monochromatic system has been established to measure the PSF accurately, and decrease the variation in the beam size between the theoretical values and the measured ones at SSRF. In this article, both calculated and measured PSF of quasi-monochromatic X-ray pinhole camera will be presented in detail.

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THPML072

Injection Comparison using Bunch-by-Bunch Beam Size Measurement System at SSRF

injection, damping, storage-ring, betatron

4811

H.J. Chen, J. Chen, B. Gao, Y.B. Leng
SINAP, Shanghai, People's Republic of China

Injection transient process happens every 5-10 minutes in storage ring during normal top-up operating mode at SSRF, which is a proper window for machine status and injection performance evaluation. In the recent year, a bunch-by-bunch beam size measurement system has been implemented at SSRF, which has the capability to offer transverse bunch-by-bunch position and size information and is a powerful tool for injection study. In this paper, we summarize three injection study results from July 2017 to April 2018, including betatron oscillation amplitude, spectrum, horizontal tune and damping time comparison. The oscillation amplitude and temporal behavior of recent injection are all better than results before contributed to the injection optimization work during maintenance in 2018 winter. In addition, the principal component analysis method is also applied to further study the injection behavior in turn-by-turn or bunch-by-bunch direction to the refilled bucket.

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THPML122

Beta-SRF - A New Facility to Characterize SRF Materials near Fundamental Limits

cavity, TRIUMF, linac, accelerating-gradient

4961

E. Thoeng
UBC & TRIUMF, Vancouver, British Columbia, Canada
R.A. Baartman, R.E. Laxdal, B. Matheson, G. Morris, N. Muller, S. Saminathan
TRIUMF, Vancouver, Canada
A. Chen
UBC, Vancouver, Canada
T. Junginger
Lancaster University, Lancaster, United Kingdom

Funding: Natural Sciences and Engineering Research Council of Canada (NSERC) & UBC (NSERC) IsoSiM Program
Demands of CW high-power LINAC require SRF cavities operating at the frontier of high accelerating gradient and low RF power dissipation, i.e. high quality factor (Q₀). This requirement poses a challenge for standard surface treatment recipes of SRF cavities. In a recent breakthrough, elliptical SRF cavities doped with Nitrogen have been shown to improve Q₀ by a factor of 3, close to the fundamental SRF limit. The fundamental mechanisms at microscopic level and optimum doping recipe, however, have still not fully been understood. Materials other than Nb have also been proposed for SRF cavities to overcome the fundamental limit already reached with Nitrogen doping, e.g. Nb₃Sn, MgB₂, and Nb-SIS multilayer. At TRIUMF, a unique experimental facility is currently being developed to address these issues. This facility will be able to probe local surface magnetic field in the order of the London Penetration Depth (several tens of nm) via \beta decay detection of a low-energy radioactive ion-beam. This allows depth-resolution and layer-by-layer measurement of magnetic field shielding effectiveness of different SRF materials at high-parallel field (up to 200 mT). Design and current development of this facility will be presented here, as well as commissioning and future measurements strategies for new SRF materials.

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THPML132

Cryogenic Performance of an SRF Deflecting Cavity Fabricated Using Alternative Techniques for the ARIEL eLinac

cavity, linac, niobium, cryogenics

4992

D.W. Storey
Victoria University, Victoria, B.C., Canada
R.E. Laxdal, Z.Y. Yao
TRIUMF, Vancouver, Canada

A 650 MHz SRF deflecting mode cavity has been built and tested for use as a three-way beam separator in the ARIEL eLinac. The cavity operates in a TE-like mode, and has been optimized for high shunt impedance with minimal longitudinal footprint. The device is the first SRF cavity to be fully fabricated in house at TRIUMF. The requirements of the cavity allowed for the development of low cost manufacturing techniques, including the use of Reactor grade niobium and atmospheric pressure TIG welding. The cavity has been fabricated and tested at 4 K and 2 K, obtaining a 4 K Qo of 4·10⁸ at the operating voltage of 0.3 MV, surpassing the goal voltage and quality factor required for operation. Results of the cryogenic tests of the cavity will be presented here.

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