Keyword: SRF
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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 icon Slides MOZGBF4 [34.189 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 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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML053  
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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 icon Slides TUYGBE2 [17.348 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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF014  
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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 icon Slides TUZGBE5 [1.363 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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF002  
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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 icon Slides WEYGBF3 [2.386 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
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAK012  
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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.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAK013  
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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.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL005  
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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.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL039  
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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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF036  
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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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF037  
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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 Rs(H) from RF measurements of quality factor Q0 implicitly returns a weighted average of Rs over the surface as a function of peak surface magnetic field H, not the true value of Rs as a function of the local magnitude of H. In this work we present a computational method to convert a measured Q0 vs. Hpeak to a more accurate Rs vs. Hlocal, 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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF047  
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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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF050  
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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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK008  
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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.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML006  
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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.  
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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML067  
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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 icon Slides THXGBD3 [13.552 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THXGBD3  
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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.
 
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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 βopt=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.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL034  
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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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL036  
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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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL039  
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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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL041  
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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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL045  
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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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL076  
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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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL086  
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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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL089  
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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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL104  
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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.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL146  
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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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF017  
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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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF019  
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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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF020  
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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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF021  
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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.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF034  
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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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF038  
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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.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF040  
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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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF063  
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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.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK066  
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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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK144  
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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.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML066  
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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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML068  
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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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML070  
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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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML072  
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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.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML122  
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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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML132  
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