Keyword: SRF
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MOZB01 Superconducting RF Guns: Emerging Technology for Future Accelerators gun, cathode, cavity, laser 4085
 
  • J. Teichert
    HZDR, Dresden, Germany
  
  This talk should give an overview of Superconducting photo injectors (SRF guns) and focus on the present status of SRF gun development, the technical requirements and the critical issues like cavity design, photocathode integration, and emittance compensation methods.  
slides icon Slides MOZB01 [22.198 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOZB01  
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MOPRO106 Status of the HZB ERL Prototype BERLinPro gun, linac, cavity, booster 340
 
  • M. Abo-Bakr, W. Anders, R. Barday, K.B. Bürkmann-Gehrlein, A. Burrill, V. Dürr, A. Jankowiak, C. Kalus, T. Kamps, G. Klemz, J. Knobloch, J. Kolbe, O. Kugeler, B.C. Kuske, A.N. Matveenko, A. Meseck, A. Neumann, K. Ott, E. Panofski, D. Pflückhahn, J. Rahn, J. Rudolph, M. Schmeißer, S.G. Schubert, O. Schüler, J. Völker, S. Wesch
    HZB, Berlin, Germany
  
  Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association.
The Berlin Energy Recovery Linac Prototype BERLinPro is to be constructed at the Helmholtz Zentrum site in Berlin. The aim of the project is to expand the required accelerator physics and technology knowledge mandatory for the generation of a high current (100 mA), high brilliance (norm. emittance below 1 mm mrad) cw electron beam. Since the funding decision in October 2010 the project has entered a phase of detailed planning. Hardware specifications have been defined and various components have been ordered. Furthermore, extensive tests of principal superconducting accelerator components successfully demonstrated the envisaged hardware performance. A summary of the most recent activities together with the details of the project timeline for the coming years are given in this paper. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRO106  
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MOPRO112 Energy Recovering for Linac RF Injectors cavity, gun, HOM, linac 356
 
  • V. Volkov, Ya.V. Getmanov, O.A. Shevchenko, N. Vinokurov
    BINP SB RAS, Novosibirsk, Russia
  • A.N. Matveenko
    HZB, Berlin, Germany
  
  The article presents a new design of a CW RF high average current superconducting injector cavity. This design allows recovering energy in the injector, improving beam parameters and energy efficiency, reducing injector size, cost, and avoiding high average power coupler problem.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRO112  
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MOPME017 Study of Higher Order Modes in Multi-Cell Cavities for BESSY-VSR Upgrade cavity, HOM, dipole, linac 412
 
  • T. Galek, K. Brackebusch, Sh. Gorgi Zadeh, U. van Rienen
    Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
  
  Funding: Work supported by Federal Ministry for Research and Education BMBF under contract 05K13HR1.
BESSY-VSR is a planned scheme to upgrade the existing BESSY II storage ring to support variable electron pulse lengths. In addition to the present 0.5 GHz energy replenishment cavity, two additional SRF bunch compressing cavities operating at 1.5 GHz (3rd harmonic) and 1.75 GHz (sub-harmonic), will be installed. These cavities are essential to produce short 1.5 ps bunches with current of up to 0.8 mA per bunch. In order to achieve such high beam currents, higher order modes must be damped in the superconducting cavities. In this work we present analysis of higher order modes in cavities with different mid-cell shapes. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPME017  
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MOPME018 Quantification of Geometric Uncertainties in Single Cell Cavities for BESSY VSR using Polynomial Chaos cavity, simulation, HOM, linac 415
 
  • J. Heller, T. Flisgen, C. Schmidt, U. van Rienen
    Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
  
  Funding: Federal Ministry for Research and Education Germany under contract 05K13HR1
The electromagnetic properties of SRF cavities are mostly determined by their shape. Due to fabrication tolerances, tuning and limited resolution of measurement systems, the exact shape remains uncertain. In order to make assessments for the real life behaviour it is important to quantify how these geometrical uncertainties propagate through the mathematical system and influence certain electromagnetic properties, like the resonant frequencies of the structure's eigenmodes. This can be done by using non-intrusive straightforward methods like Monte-Carlo (MC) simulations. However, such simulations require a large number of deterministic problem solutions to obtain a sufficient accuracy. In order to avoid this scaling behaviour, the so-called polynomial chaos (PC) expansion is used. This technique allows for the relatively fast computation of uncertainty propagation for few uncertain parameters in the case of computationally expensive deterministic models. In this paper we use the PC expansion to quantify the propagation of uncertain geometry on the example of single cell cavities used for BESSY VSR as well as to compare the obtained results with the MC simulation. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPME018  
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MOPME067 Kicker Development at the ELBE Facility kicker, positron, gun, electron 520
 
  • G.S. Staats
    FZD, Dresden, Germany
  • A. Arnold, H. Büttig, T. Kirschke, M. Kuntzsch, P. Michel, J. Teichert, H. Vennekate, A. Wagner, R. Xiang
    HZDR, Dresden, Germany
  • R. Krause-Rehberg, A. Müller
    Martin-Luther-Universität, Naturwissenschaftliche Fakultät II, Halle (Saale), Germany
  
  Kicker-devices, also known as choppers, are of great interest for a multi-purpose electron accelerator like the ELBE at HZDR. They serve the following three main tasks: Firstly, they can be used to improve the time resolution for the positron beam line by removing certain parts of the bunch. As a second advantage they enable the machine to run two independent experiments at the same, as a chopper may split the beam into two separate parts. Lastly, a well-positioned kicker can reduce the dark current emitted by the SRF injector of the accelerator. Different designs for structures, deflecting the bunch in the beam line, have been simulated using CST Particle Studio. Here, no big difference to well-known strip line structures do exist. The next step is to design the supply electronics driving the kickers. As the ELBE accelerator runs at a high bunch repetition rate, the kicker has to keep up to this frequencies of up to 13 MHz. Hence, the high power levels needed for the operation may cause additional problems for the driver electronics. The poster is going to present the state of our development for all three tasks and our approaches to solve the corresponding challenges.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPME067  
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MOPRI020 Introducing GunLab – A Compact Test Facility for SRF Photoinjectors gun, electron, laser, cathode 630
 
  • J. Völker, R. Barday, A. Jankowiak, T. Kamps, J. Rudolph, S.G. Schubert, S. Wesch
    HZB, Berlin, Germany
  • A. Ferrarotto, T. Weis
    DELTA, Dortmund, Germany
  • V.I. Shvedunov
    MSU, Moscow, Russia
  • I.Yu. Vladimirov
    MSU SINP, Moscow, Russia
  
  Funding: Work supported by German Bundesministerium für Bildung und Forschung (BMBF contract 05K12CB2 PCHB and 05K10PEA), Land Berlin and grants of Helmholtz Association
Superconducting radio-frequency photoelectron injectors (SRF photoinjectors) are a promising electron source for high brightness accelerators with high average current and short pulse duration like FELs and ERLs. For the upcoming ERL project BERLinPro we want to test and commission different SRF photoinjectors and examine the beam performance of photocathode materials in an independent test facility. Therefore we designed GunLab to characterize the beam parameters from the SRF photoinjectors in a compact diagnostics beamline. In GunLab we want to investigate the complete 6 dimensional phase space as a function of drive laser and RF setup parameters. In this work we present the design and the estimated performance of GunLab. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI020  
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MOPRI023 Simulation of the ELBE SRF Gun II gun, simulation, emittance, laser 636
 
  • P.N. Lu, A. Arnold, U. Lehnert, P. Murcek, J. Teichert, H. Vennekate, R. Xiang
    HZDR, Dresden, Germany
  
  Funding: EuCARD, contract number 227579 German Federal Ministry of Education and Research grant 05 ES4BR1/8 LA³NET, Grant Agreement Number GA-ITN-2011-289191
By combining the code of ASTRA and elegant in a user-friendly interface, a simulation tool is developed for the ELBE SRF Gun II. The photoelectric emission and first acceleration to several MeV in the gun cavity are simulated by ASTRA with a 1D Model, where the space charge effect is considered. The dependence of the beam quality on key parameters is studied, and a compromised optimization for a 77 pC beam is used for further elegant simulation of the beam transport through a dogleg and ELBE Linacs. Proper settings of the magnets and RF phases are the main targets of improving the beam quality. Up to now the best simulation result is an electron bunch with the energy of 47 MeV, energy spread of 66 keV, bunch length of 0.35 ps and transverse emittance of 1.9 μm and 2.7 μm in the two perpendicular directions. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI023  
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MOPRI024 NEA-GaAs (Cs, O) Photocathodes for the ELBE SRF Gun gun, vacuum, cathode, laser 639
 
  • R. Xiang, A. Arnold, P.N. Lu, P. Michel, P. Murcek, J. Teichert, H. Vennekate
    HZDR, Dresden, Germany
  
  Funding: supported by the European Community under the FP7 programme (EuCARD-2, contract number 312453, and LA3NET, contract number 289191), and by the BMBF grant 05K12CR1.
At HZDR a preparation chamber for NEA-GaAs (Cs, O) has been built and commissioned. GaAs is the next photocathode material for the ELBE SRF gun, which has been successfully operated with Cs2Te layer in last years. GaAs At HZDR a preparation chamber for NEA-GaAs (Cs, O) has been built and tested. GaAs is the next photocathode material for the ELBE SRF gun, which has been successfully operated with Cs2Te photocathode in last years. GaAs photocathodes are advantageous because of their high quantum efficiency (QE) with visible light and the extensive experiences of their use in DC guns. Furthermore, GaAs photocathodes provide the possibility to realize a polarized SRF gun in the future. In this presentation we will introduce the new preparation system and the first results of the GaAs tests. The new transfer system under construction will be also presented. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI024  
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MOPRI025 Recent Improvement of Cs2Te Photocathodes at HZDR cathode, gun, vacuum, cavity 642
 
  • R. Xiang, A. Arnold, P.N. Lu, P. Michel, P. Murcek, J. Teichert, H. Vennekate
    HZDR, Dresden, Germany
  
  Funding: Work supported by the European Community-Research Infrastructure Activity (EuCARD, contract number 227579), and the support of the German Federal Ministry of Education and Research grant 05 ES4BR1/8.
The SRF gun has been successfully operated for the radiation source ELBE at HZDR. To achieve higher current and lower beam emittance, a new niobium cavity with superconducting solenoid and a new 13 MHz laser have been recently developed. For this reason, better photocathodes with high quantum efficiency are urgently in demand. In this work we improve the present Cs2Te preparation system for cleaner environment and more precise stoichiometric control than before. A new mask is designed to prevent cesium pollution of the cathode body. Instead of Kapton only alumina ceramics are used for isolation, and the cathode plugs are degassed at higher temperature. New evaporators are installed and tested to obtain an accurate deposition rate. Furthermore, the cathode transfer system is thoroughly cleaned for a better vacuum condition. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI025  
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MOPRI028 Different Countermeasures of Electron Amplification in the Photocathode Unit cathode, electron, gun, simulation 652
 
  • E.T. Tulu, U. van Rienen
    Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
  • A. Arnold
    HZDR, Dresden, Germany
  
  Funding: Federal Ministry for Research and Education BMBF; Project: 05K2013-HOPE
Superconducting radio frequency (SRF) structures may be subjected to electron multipacting (MP). The electrons emitted from one of the structure’s wall under certain conditions are accelerated by the RF field, thereby they may impact the wall again based on the field pattern in the structure. Accordingly the number of electrons increases exponentially caused by secondary electron emission*. The latter depends on the secondary emission coefficient of the surface material and the electron trajectory in the device under study**. This phenomenon limits the accelerating gradient in the cavity, moreover, it might cause an impair of RF components and distortion of the RF signal. Therefore, there should be an efficient countermeasure to suppress MP in order to boost the performance of the SRF gun. In this paper, three techniques of suppression of MP from the vicinity of the cathode, such as DC-bias, geometric modification and the microstructure of the cathode's surface, in the Rossendorf SRF gun are presented. The simulation has been done using CST Microwave Studio® and CST Particle Studio®***. Eventually, the efficient suppression method would be chosen for this particular case.
* H.Padamsee, J. Knobloch and T. Hays, 1998, Ch. 10.
** E. T. Tulu, A. Arnold and U. van Rienen, 16th International Conference on SRF, Paris, France, 2013.
*** CST AG, http://www.cst.com.
 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI028  
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MOPRI059 Fabrication of Alkali Antimonide Photocathode for SRF Gun cathode, laser, gun, vacuum 742
 
  • E. Wang, S.A. Belomestnykh, I. Ben-Zvi, D. Kayran, G.T. McIntyre, T. Rao, J. Smedley, D. Weiss, W. Xu
    BNL, Upton, Long Island, New York, USA
  • I. Ben-Zvi, M. Ruiz-Osés
    Stony Brook University, Stony Brook, USA
  • X. Liang
    SBU, Stony Brook, New York, USA
  • H.M. Xie
    PKU, Beijing, People's Republic of China
  
  Funding: * This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE and DOE grant
The first alkali antimonide photocathode was prepared and inserted into the BNL 704 MHz SRF gun. An excimer laser cleaning system was installed in a cathode deposition chamber and the cleaning technique developed previously was used in the first cathode preparation. We also demonstrated that oxidized cathode can be removed by exposing it to the same excimer laser. In this paper, we show the set up of the incorporated laser cleaning system and the QE enhancement of alkali antimony photocathode. The vacuum evolution at transport cart and QE measurement system are also discussed. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI059  
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MOPRI064 First Test Results from SRF Photoinjector for the R&D ERL at BNL gun, cathode, cavity, electron 748
 
  • D. Kayran, Z. Altinbas, D.R. Beavis, S.A. Belomestnykh, I. Ben-Zvi, J. Dai, S. Deonarine, D.M. Gassner, R.C. Gupta, H. Hahn, L.R. Hammons, C. Ho, J.P. Jamilkowski, P. Kankiya, N. Laloudakis, R.F. Lambiase, V. Litvinenko, G.J. Mahler, L. Masi, G.T. McIntyre, T.A. Miller, D. Phillips, V. Ptitsyn, T. Rao, T. Seda, B. Sheehy, K.S. Smith, A.N. Steszyn, T.N. Tallerico, R. Than, R.J. Todd, E. Wang, D. Weiss, M. Wilinski, W. Xu, A. Zaltsman
    BNL, Upton, Long Island, New York, USA
  • S.A. Belomestnykh, I. Ben-Zvi, J. Dai, L.R. Hammons, V. Litvinenko, V. Ptitsyn
    Stony Brook University, Stony Brook, USA
  
  Funding: This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE and DOE grant at Stony Brook, DE-SC0005713.
An ampere class 20 MeV superconducting Energy Recovery Linac (ERL) is presently under commissioning at Brookhaven National Laboratory (BNL). This facility enables testing of concepts relevant for high-energy coherent electron cooling, electron-ion colliders, and high repetition rate Free-Electron Lasers. The ERL will be capable of providing electron beams with sufficient quality to produce high repetition rate THz and X-ray radiation. When completed the SRF photoinjector will provide 2 MeV energy and 300 mA average beam current. The injector for the R&D ERL was installed in 2012, this includes a 704MHz SRF gun* with multi-alkali photocathode, cryo-system upgrade and a novel emittance preservation zigzag-like low energy merger system. We describe the design and major components of the R&D ERL injector then report the first experimental results and experiences learned in the first stage of beam commissioning of the BNL R&D ERL.
* Wencan Xu et al., “Commissioning SRF gun for the R&D ERL at BNL”, IPAC2013 proceedings, WEPWO085. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI064  
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TUZA02 THz Facility at ELBE: A Versatile Test Facility for Electron Bunch Diagnostics on Quasi-CW Electron Beams electron, diagnostics, operation, linac 933
 
  • M. Gensch, B.W. Green, J. Hauser, S. Kovalev, M. Kuntzsch, U. Lehnert, P. Michel, R. Schurig
    HZDR, Dresden, Germany
  • A. Al-Shemmary, V. B. Asgekar, T. Golz, H. Schlarb, N. Stojanovic, S. Vilcins
    DESY, Hamburg, Germany
  • A.S. Fisher
    SLAC, Menlo Park, California, USA
  • G. Geloni
    XFEL. EU, Hamburg, Germany
  • A.-S. Müller, M. Schwarz
    KIT, Karlsruhe, Germany
  • N.E. Neumann, D. Plettemeier
    TU Dresden, Dresden, Germany
  
  At the Helmholtz-Zentrum Dresden-Rossendorf near Dresden a quasi-cw low-energy electron linear accelerator based on superconducting radiofrequency technology is operated successfully for more than 10 years. The ELBE accelerator is driving several secondary radiation sources including 2 infrared free electron lasers. A new addition will be a THz facility that aims to make use of super-radiant THz radiation. In its final form the THz facility shall consist of one coherent diffraction radiator and one undulator source which provide high-field THz pulses at unprecedented repetition rates. While the medium term goal is to establish a unique user facility for nonlinear THz science, the THz sources are already used as a test facility for novel diagnostic techniques on quasi-cw electron beams. The progress of the developments is reported and an outlook into future challenges and opportunities is given.  
slides icon Slides TUZA02 [3.041 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUZA02  
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TUPME041 The Advanced Superconducting Test Accelerator at Fermilab: Science Program electron, linac, emittance, laser 1447
 
  • P. Piot, E.R. Harms, S. Henderson, J.R. Leibfritz, S. Nagaitsev, V.D. Shiltsev, A. Valishev
    Fermilab, Batavia, Illinois, USA
  
  Funding: This work is supported by DOE contract DE-AC02-07CH11359 to the Fermi Research Alliance LLC
The Advanced Superconducting Test Accelerator (ASTA) currently in commissioning phase at Fermilab is foreseen to support a broad range of beam-based experiments to study fundamental limitations to beam intensity and to develop novel approaches to particle-beam generation, acceleration and manipulation. ASTA incorporates a superconducting radiofrequency (SCRF) linac coupled to a flexible high-brightness photoinjector. The facility also includes a small-circumference storage ring capable of storing electrons or protons. This report summarizes the facility capabilities, and provide an overview of the accelerator-science researches to be enabled. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME041  
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TUPME084 On the Frequency Choice for the eRHIC SRF Linac linac, cavity, HOM, electron 1547
 
  • S.A. Belomestnykh, I. Ben-Zvi, V. Litvinenko, V. Ptitsyn, W. Xu
    BNL, Upton, Long Island, New York, USA
  • S.A. Belomestnykh, I. Ben-Zvi, V. Litvinenko, V. Ptitsyn
    Stony Brook University, Stony Brook, USA
  
  Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
eRHIC is a future electron-hadron collider proposed at BNL. It will collide high-intensity hadron beams from one of the existing rings of RHIC with a 50-mA electron beam from a multi-pass 10-GeV superconducting RF (SRF) Energy Recovery Linac (ERL). A novel approach to the multi-pass ERL utilizing a non-scaling FFAG was recently proposed. It has many advantages over the previous designs including significant cost savings. The current design has 11 passes in two FFAG rings. To mitigate various beam dynamics effects, it was proposed to lower RF frequency of the SRF linac from 704 MHz used in the previous design. In this paper we consider different effects driving the frequency choice of the SRF ERL and present our arguments for choosing lower RF frequency. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME084  
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TUPRI015 Transverse Emittance Compensation for the Rossendorf SRF Gun II gun, solenoid, cavity, electron 1582
 
  • H. Vennekate, A. Arnold, P.N. Lu, P. Murcek, J. Teichert, R. Xiang
    HZDR, Dresden, Germany
  • T. Kamps
    HZB, Berlin, Germany
  • P. Kneisel
    JLab, Newport News, Virginia, USA
  
  Funding: We acknowledge the support of the EU Community-Research Infrastructure Activity under the FP7 program (EuCARD-2, 312453) and of the German Federal Ministry of Education and Research grant 05K12CR1.
Superconducting RF particle sources combine the advantages of normal conducting RF sources and high duty cycle non-RF sources. The Rossendorf SRF gun was the first to demonstrate this injecting electrons into the ELBE accelerator at 13 MHz. Recently, a new 3-1/2-gun cavity has been prepared at Jefferson Lab for its use in an updated injector which is expected to increase the electron energy from 2.4 to 7.5 MeV. Along with this new cavity, a new gun cryostat has been introduced. It combines several minor updates to the setup with the installation of a superconducting solenoid right at the exit of the gun, compensating the emittance growth of the electron bunch at an early stage. The poster is going to conclude the results of the commissioning of the new cryostat including the solenoid and compare it to the prior concept using a normal conducting solenoid outside the cryostat. As it is of great importance to this subject, studies of the magnetic shielding are going to be presented as well. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI015  
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WEIB03 How To Produce 100 Superconducting Modules for the European XFEL in Collaboration and with Industry cavity, vacuum, quadrupole, controls 1923
 
  • H. Weise
    DESY, Hamburg, Germany
  
  European XFEL accelerator module production is in almost full swing by the time of IPAC 2014. This is the first project of this size that includes many partner laboratories and transfer of technology for mass superconducting RF cavity and accelerator module production to industry. This talk will illustrate the organization of the production and the lessons learned, illuminating what one should or would do differently for future projects.  
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEIB03  
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WEPME003 Two Years Experience with the Upgraded ELBE RF System Driven by 20kW Solid State Amplifier Blocks (SSPA) operation, klystron, linac, cavity 2257
 
  • H. Büttig, A. Arnold, A. Büchner, M. Justus, M. Kuntzsch, U. Lehnert, P. Michel, R. Schurig, G.S. Staats, J. Teichert
    HZDR, Dresden, Germany
  
  Since January 2012 the Superconducting CW Linac ELBE is equipped and in permanent operation with four 20 kW Solid State Amplifier Blocks. The poster gives an overview on the design of the new RF system and the experience gained within the first two years of operation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME003  
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WEPME024 Power Coupler Manufacturing and Quality Control at CPI linac, controls, cavity, target 2308
 
  • S.J. Einarson, T.A. Treado
    CPI, Beverley, Massachusetts, USA
  
  CPI has been designing and manufacturing fundamental power couplers for superconducting accelerators for over a dozen years. We have manufactured approximately 200 power couplers of 16 different designs. Power coupler frequencies have ranged from 175 MHz to 3.9 GHz and power levels have ranged from 5 kW to 500 kW average power. We have developed and qualified several key manufacturing processes including a high-RRR copper plating process and a titanium nitride coating process. In addition, we have established uniform quality control and inspection processes which ensure that the power couplers will meet the requirements for the intended use in superconducting accelerators. These processes have been developed, improved and/or qualified in collaboration with colleagues at superconducting accelerator facilities throughout the world. This paper will provide an overview of these critical manufacturing and quality control processes.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME024  
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WEPME058 Development of Thin Films for Superconducting RF Cavities superconductivity, scattering, lattice, power-supply 2406
 
  • S. Wilde, B. Chesca
    Loughborough University, Loughborough, Leicestershire, United Kingdom
  • A.N. Hannah, D.O. Malyshev, O.B. Malyshev, S.M. Pattalwar, R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • G.B.G. Stenning
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  
  Superconducting coatings for superconducting radio frequency (SRF) cavities is an intensively developing field that should ultimately lead to acceleration gradients better than those obtained by bulk Nb RF cavities. ASTeC has built and developed experimental systems for superconducting thin-film deposition, surface analysis and measurement of Residual Resistivity Ratio (RRR). Nb thin-films were deposited by magnetron sputtering in DC or pulsed DC mode (100 to 350 kHz with 50% duty cycle) with powers ranging from 100 to 600 W at various temperatures ranging from room temperature to 800 °C on Si (100) substrates. The first results gave RRR in the range from 2 to 22 with a critical temperature Tc=~9.5 K. Scanning electron microscopy (SEM), x-ray diffraction (XRD), electron back scattering diffraction (EBSD) and DC SQUID magnetometry revealed significant correlations between the film structure, morphology and superconducting properties.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME058  
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WEPRI004 Operational Experience and Upgrades of the SOLEIL Storage Ring RF System cavity, operation, vacuum, cryogenics 2480
 
  • P. Marchand, J.P. Baete, R.C. Cuoq, H.D. Dias, M. Diop, J.L. Labelle, R. Lopes, M. Louvet, C.M. Monnot, L.S. Nadolski, S. Petit, F. Ribeiro, T. Ruan, R. Sreedharan, K. Tavakoli
    SOLEIL, Gif-sur-Yvette, France
  
  In the SOLEIL storage ring, two cryomodules provide to the electron beam an accelerating voltage of 3-4 MV and a power of 575 kW at 352 MHz. Each cryomodule contains a pair of superconducting cavities, cooled with liquid Helium at 4.5 K, which is supplied by a single 350 W cryogenic plant. The RF power is provided by four solid state amplifiers, each delivering up to 180 kW. The parasitic impedances of the high order modes (HOM) are strongly mitigated by means of four coaxial couplers, located on the central pipe connecting the two cavities. Eight years of operational experience with this system, as well as its upgrades, are reported.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI004  
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WEPRI005 Processing and Testing of the SRF Photoinjector Cavity for BERLinPro cavity, operation, electron, niobium 2484
 
  • A. Burrill, W. Anders, A. Frahm, J. Knobloch, A. Neumann
    HZB, Berlin, Germany
  • G. Ciovati, W.A. Clemens, P. Kneisel, L. Turlington
    JLab, Newport News, Virginia, USA
  • E.N. Zaplatin
    FZJ, Jülich, Germany
  
  Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association
The BERLinPro project is a compact, c.w. SRF energy recovery linac (ERL) that is being built to develop the accelerator physics and technology required to operate the next generation of high current ERLs. The machine is designed to produce a 50 MeV 100 mA beam, with better than 1 mm-mrad emittance. The electron source for the ERL will be a SRF photoinjector equipped with a multi-alkali photocathode. In order to produce a SRF photoinjector to operate reliably at this beam current HZB has undertaken a 3 stage photoinjector development program to study the operation of SRF photoinjectors in detail. The 1.4 cell cavity being reported on here is the second stage of this development, and represents the first cavity designed by HZB for use with a high quantum efficiency multi-alkali photocathode. This paper will describe the work done to prepare the cavity for RF testing in the vertical testing dewar at Jefferson Laboratory as well as the results of these RF tests. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI005  
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WEPRI006 High Power RF Input Couplers and Test Stand for the BERLinPro Project cavity, booster, linac, coupling 2487
 
  • V.F. Khan, W. Anders, A. Burrill, J. Knobloch, A. Neumann
    HZB, Berlin, Germany
  
  Funding: Work supported by German Federal Ministry of Education and Research, Land Berlin, and grants of the Helmholtz Association
The BERLinPro project, under construction at HZB, is a 100 mA, 50 MeV superconducting RF (SRF) energy recovery linac (ERL) being built to study the accelerator physics of operating a high current SRF ERL. For this high current operation, coaxial RF power couplers capable of handling 130 kW of power, c.w. at 1.3 GHz are required for both the SRF gun and booster cavities. In order to achieve this power level a coupler has been designed based on the high power coupler currently in use at the KEK-cERL. A key improvement that was made to the coupler was the modification of the coupler tip, termed a golf-tee. This modification is incorporated so as to achieve the desired coupling, Qext ~105, with minimal coupler penetration into the beampipe. Herein, we discuss the RF design and properties of the high-power coaxial coupler for the gun as well as booster cavity of BERLinPro, along with the design of the test stand for conditioning a pair of couplers. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI006  
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WEPRI007 Booster Cavity and Fundamental Power Coupler Design Issues for BERLinPro cavity, booster, emittance, coupling 2490
 
  • A. Neumann, M. Abo-Bakr, W. Anders, A. Burrill, V.F. Khan, J. Knobloch, S. Wesch
    HZB, Berlin, Germany
  
  Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin and grants of Helmholtz Association
HZB has started building the 50MeV, 100mA demonstrator energy-recovery-linac (ERL) facility BERLinPro. The high power injector system needs to deliver this beam at 6.5MeV by combining the energy gain of a 1.4 cell SRF photo-injector and three Cornell style 2-cell booster cavities. One booster cavity will be operated at zero-crossing for bunch energy chirping. Thus two booster cavities have to deliver 2MV each requiring a strong coupling with a loaded Q of 105. To house the two envisaged KEK fundamental power couplers (FPC) with the cavity, the geometry was slightly modified. Further, to increase coupling and reduce transverse kick effects to the beam, a ”golf-tee” antenna tip was designed. This paper summarizes the SRF challenges for the booster cavities, the operational conditions and the modification to the KEK couplers, including tracking calculations to estimate the coupler kick effect to higher order. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI007  
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WEPRI011 Progress of R&D on SRF Cavities at DESY towards the ILC Performance Goal cavity, factory, accelerating-gradient, electron 2499
 
  • A. Navitski
    DESY, Hamburg, Germany
  • A. Prudnikava, Y. Tamashevich
    Uni HH, Hamburg, Germany
  
  Funding: BMBF project 05H12GU9, Alexander von Humboldt Foundation, CRISP (No. 283745) and ”Construction of New Infrastructures-Preparatory Phase” ILC-HiGrade (No. 206711) of the EU 7th FP7/2007-2013 Programme.
The R&D program of the ILC-HiGrade group at DESY aims at a solid understanding and control of the industrial mass-production process of the superconducting radio-frequency accelerating cavities that are being manufactured for the European X-ray Free Electron Laser (EXFEL). This accelerator is currently under construction at DESY. As well as the main production cavities for XFEL, 24 additional cavities are being constructed as part of the ILC-HiGrade program. The goal is to identify the gradient-limiting factors and further refine the cavity-treatment technique to understand how to achieve gradients above 35 MV/m at >90% production yield in an industrial context. Techniques such as 2nd sound and temperature mapping for the quench detection, OBACHT optical inspections, as well as Centrifugal Barrel Polishing (CBP) and Local Grinding repair are foreseen as tools. Actual status, details, and achievements will be reported. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI011  
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WEPRI022 In-house Production of a Large-Grain Single-Cell Cavity at Cavity Fabrication Facility and Results of Performance Tests cavity, accelerating-gradient, radio-frequency, vacuum 2519
 
  • T. Kubo, Y. Ajima, H. Inoue, K. Umemori, Y. Watanabe, M. Yamanaka
    KEK, Ibaraki, Japan
  
  We studied electron beam welding (EBW) conditions for large grain Nb, and fabricated a single cell cavity in Cavity Fabrication Facility (CFF), KEK. Vertical-test results of the cavity made from large grain Nb are also presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI022  
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WEPRI024 Two-Dimensional Models of the Magnetic-Field Enhancement at Pit and Bumps cavity, photon 2525
 
  • T. Kubo
    KEK, Ibaraki, Japan
  
  Analytical models of the magnetic field enhancement at pits were presented at SRF2013 last year*. Other simple models will be addressed in this paper.
* Proceedings of SRF2013, Paris, France (2013), p. 430 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI024  
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WEPRI034 Analysis of BCP Characteristics for SRF Cavities niobium, experiment, ion, cavity 2549
 
  • Y. Jung, H.J. Kim
    IBS, Daejeon, Republic of Korea
  • H.H. Lee, H.C. Yang
    KRICT, Daejoen, Republic of Korea
  
  A chemical polishing process is well-known critical process for improving superconducting cavities such as a quality factor and an acceleration electric filed with additional temperature treatment. Especially, Buffered Chemical Polishing (BCP) has been widely used in SRF (Superconducting Radio Frequency) cavity processing. We performed BCP experiments with 1:1:1 and 1:1:2 of an etchant ratio (HF:HNO3:H3PO4). In fact, BCP experiments were carried out by using both undeformed (as-receoved) and deformed niobium samples. We will report baseline BCP results by analyzing surface states of niobium samples such as optical photographs, etch rates and AFM (Atomic Force Microscopy) depending on temperature and time.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI034  
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WEPRI039 LIPAc SRF Linac Couplers Conditioning vacuum, linac, operation, electron 2562
 
  • D. Regidor, I. Kirpitchev, J. Mollá, P. Méndez, M. Weber, C. de la Morena
    CIEMAT, Madrid, Spain
  • S. Chel, M. Desmons, G. Devanz, H. Jenhani
    CEA/IRFU, Gif-sur-Yvette, France
  • H. Dzitko
    CEA, Pontfaverger-Moronvilliers, France
  
  The LIPAc SRF Linac is a cryomodule with eight superconducting HWR cavities at 175 MHz powered by RF couplers capable of transmitting up to 200 kW in CW. To prepare the couplers for operation, cleaning and high power RF processing are needed. When performed, the couplers will be ready for integration in the cryomodule. The Couplers Test Bench has been designed to perform the RF conditioning by pairs, providing good matching, low losses and the required UHV level. To preserve the cleanliness of the internal surfaces, after the test bench manufacturing, an ISO5 clean room has been used for the vacuum parts assembly. The size and number of particles was carefully controlled during the assembly process. The RF conditioning was performed at the IFMIF-EVEDA RF Integration Facility using the Prototype RF Module in travelling wave and standing wave modes. The process started with short pulses at low power and finished when full power CW was reached. Vacuum, multipacting, arcs and matching were continuously monitored to control the process avoiding damages. An overview of the process applied to the prototypes and the RF conditioning results are presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI039  
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WEPRI042 Nb Coated HIE-ISOLDE QWR Superconducting Accelerating Cavities: From Process Development to Series Production cavity, niobium, cryomodule, cathode 2571
 
  • A. Sublet, I. Aviles Santillana, B. Bártová, S. Calatroni, N.M. Jecklin, I. Mondino, M. Therasse, W. Venturini Delsolaro, P. Zhang
    CERN, Geneva, Switzerland
  • M. Cantoni
    EPFL, Lausanne, Switzerland
  
  The new HIE-ISOLDE accelerator at CERN requires the production of 32 superconducting cavities (20 high-beta and 12 low-beta) in order to increase the energy of the rare isotope beam delivered to the experiments. The Quarter Wave Resonators (QWRs) cavities (0.3m diameter and 0.8m height) are made of OFE 3D-forged copper and are coated by DC-bias diode sputtering with a thin superconducting layer of niobium. Following a preliminary process development phase, the series production of the high-beta cavities has started. An overview of the development phase is presented, describing the key parameters varied to match the HIE-ISOLDE specifications (operation at 4.5 K with an accelerating field of 6 MV/m at 10W RF losses and Q0=4.5x108) and the resulting niobium film characteristics. The first series of cavities, produced using the baseline coating recipe, and their RF performance is reviewed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI042  
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WEPRI051 Results from RF Tests of the First US-built High-gradient Superconducting Cryomodule cavity, cryomodule, cryogenics, linear-collider 2598
 
  • A. Hocker, C.M. Baffes, K. Carlson, B. Chase, D.J. Crawford, E. Cullerton, D.R. Edstrom, E.R. Harms, T. Kubicki, M.J. Kucera, J.R. Leibfritz, J.N. Makara, D. McDowell, O.A. Nezhevenko, D.J. Nicklaus, H. Pfeffer, Y.M. Pischalnikov, P.S. Prieto, J. Reid, W. Schappert, P. Stabile, P. Varghese
    Fermilab, Batavia, Illinois, USA
  
  Funding: United States Department of Energy, Contract No. DE-AC02-07CH11359
Fermilab has built a cryomodule comprised of eight 1.3 GHz superconducting RF cavities for use in its Advanced Superconducting Test Accelerator (ASTA) facility. This cryomodule (RFCA002) was intended to achieve the International Linear Collider (ILC) “S1” goal of demonstrating an average accelerating gradient of 31.5 MV/m, and is the first of its kind built in the United States. The module has been cooled down and operated without beam at ASTA in order to assess its performance. The results from these tests are presented here. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI051  
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WEPRI052 SRF Systems for ASTA at Fermilab cavity, cryomodule, operation, electron 2601
 
  • E.R. Harms, C.M. Baffes, K. Carlson, B. Chase, D.J. Crawford, E. Cullerton, D.R. Edstrom, M. Geynisman, A. Hocker, A.L. Klebaner, M.J. Kucera, J.R. Leibfritz, J.N. Makara, D. McDowell, S. Nagaitsev, O.A. Nezhevenko, D.J. Nicklaus, H. Pfeffer, Y.M. Pischalnikov, P.S. Prieto, J. Reid, W. Schappert, P. Stabile, P. Varghese
    Fermilab, Batavia, Illinois, USA
  
  Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
The Advanced Superconducting Test Accelerator (ASTA) at Fermilab now being commissioned is comprised of a number of superconducting RF systems including single-cavity cryomodules and a TESLA/ILC style 8-cavity cryomodule. Two of them, 'Capture Cavity 2' and 'Cryomodule 2', have been cooled to 2 Kelvin and brought into operation. We provide an overview of the unique characteristics of each of the systems, commissioning experience, and latest results including their respective operating characteristics. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI052  
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WEPRI062 The Joint High Q0 R&D Program for LCLS-II cavity, cryomodule, linac, factory 2627
 
  • M. Liepe, R.G. Eichhorn, F. Furuta, G.M. Ge, D. Gonnella, G.H. Hoffstaetter
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • A.C. Crawford, A. Grassellino, A. Hocker, O.S. Melnychuk, A. Romanenko, A.M. Rowe, D.A. Sergatskov
    Fermilab, Batavia, Illinois, USA
  • R.L. Geng, A.D. Palczewski, C.E. Reece
    JLab, Newport News, Virginia, USA
  • M.C. Ross
    SLAC, Menlo Park, California, USA
  
  The superconducting RF linac for LCLS-II calls for 1.3 GHz 9-cell cavities with an average intrinsic quality factor Q0 of 2.7·1010 at 2K and 16 MV/m accelerating gradient. A collaborative effort between Cornell University, FNAL, and JLab has been set up with the goal of developing and demonstrating a cavity treatment protocol for the LCLS-II cavities meeting these specifications. The high Q0 treatment protocol is based on nitrogen doping of the RF surface layer during a high temperature heat treatment. This novel SRF cavity preparation was recently developed at FNAL and shown to result in SRF cavities of very high Q0 at 2K with an increase in Q0 from low to medium fields. N-doped single cell cavities at Cornell, FNAL, and JLab routinely exceed LCLS-II specification. 9-cell N-doped cavities at FNAL achieve an average Q0(T=2K, 16 MV/m) of ≈ 3.4·1010 with an average quench field of ≈ 19 MV/m, meeting therefore overall with good margin the LCLS-II specification.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI062  
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WEPRI063 Flux Trapping in Nitrogen-Doped and 120 C Baked Cavities cavity, linac, vacuum, niobium 2631
 
  • D. Gonnella, M. Liepe
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Funding: United States Department of Energy
It is well known that external magnetic fields can cause higher residual resistance in superconducting RF cavities if the field is present during cooldown. However, the effect of cavity preparation and surface mean free path on the resulting residual resistance from magnetic field is less well studied. In this paper, we report on recent studies at Cornell in which two SRF cavities (one nitrogen-doped and one 120oC baked) were cooled through Tc in an applied uniform external magnetic field. Trapped flux and residual resistance were measured for a variety of cooldowns and applied magnetic fields. It was found that the residual resistance due to trapped flux in the nitrogen-doped cavity was three times larger than in the 120oC baked cavity. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI063  
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WEPRI064 New Insights into Heat Treatment of SRF Cavities in a Low-pressure Nitrogen Atmosphere cavity, niobium, vacuum, resonance 2634
 
  • D. Gonnella, M. Liepe
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Funding: United States Department of Energy
Recent results from Cornell and FNAL have shown that superconducting RF cavities given a heat treatment in a nitrogen atmosphere of a few mTorr display an increase in Q0 with increasing accelerating field, opposite to the medium field Q slope usually observed. Three cavities was prepared at Cornell using this method and subsequently tested after different amounts of material removal. Cavity performance and material properties were extracted for each cavity and correlated with material removal. This has given new insights into how material properties and the anti-Q slope depend on cavity preparation. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI064  
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WEPRI065 SRF Material Performance Studies using a Sample Host Cavity cavity, niobium, coupling, controls 2638
 
  • D.L. Hall, D. Gonnella, M. Liepe, I.S. Madjarov
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  A sample-host TE-mode cavity developed at Cornell for the purposes of studying novel superconducting materials has undergone further testing using a niobium sample plate. In initial testing the peak field achieved on the sample plate was (45 ± 4.5) mT, although this was limited by the amount of input power available. New tests have been performed using both an improved RF power system and a temperature mapping system for precision measurements of surface resistance as a function of location on the sample plate. Results of the most recent test, in which the cavity achieved a peak sample plate field of (81 ± 4) mT using a high-RRR niobium sample plate, are presented and future work on the cavity is discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI065  
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WEPRI066 Recent Progress in Nb3Sn SRF Cavity Development at Cornell cavity, niobium, accelerating-gradient, cryogenics 2641
 
  • S. Posen, D. Gonnella, M. Liepe
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Nb3Sn coatings on niobium SRF cavities have the potential to significantly reduce cryogenic costs due to their extremely small surface resistance (Rs). In this paper, we present new results showing the repeatability of Cornell's fabrication process, which produces high Q0 cavities that reach medium fields with minimal Q-slope. We also show the results of attempts to smooth RF surfaces and reduce defects via material removal. However, both HF rinsing and centrifugal barrel polishing resulted in strong performance degradation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI066  
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WEPRI069 Reproducibility of High-Q SRF Cavities by High Temperature Heat Treatment cavity, vacuum, induction, niobium 2651
 
  • P. Dhakal, G. Ciovati, P. Kneisel, G.R. Myneni
    JLab, Newport News, Virginia, USA
  
  Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
Recent work on high-temperature (> 600 °C) heat treatment of ingot Nb cavities in a customized vacuum furnace for several hours showed the possibility of achieving Q0-values of up to ~5×1010 at 2.0 K, 1.5 GHz and accelerating gradients of ~20 MV/m. This contribution presents results on further studies of the heat treatment process to produce cavities with high Q0 values for continuous-wave accelerator application. Single-cell cavities of different Nb purity have been processed through few cycles of heat-treatments and chemical etching. Measurements of Q0 as a function of temperature at low RF field and of Q0 as a function of the RF field at or below 2.0 K have been made after each treatment. Measurements by TOF-SIMS of the impurities’ depth profiles were made on samples heat treated with the cavities. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI069  
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WEPRI070 Mechanical Properties of Ingot Nb Cavities cavity, niobium, radio-frequency, network 2654
 
  • G. Ciovati, P. Dhakal, P. Kneisel, J.D. Mammosser, J. Matalevich, G.R. Myneni
    JLab, Newport News, Virginia, USA
  
  Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
This contribution presents the results of measurements of the resonant frequency and of strain along the contour of a single-cell cavity made of ingot Nb subjected to increasing uniform differential pressure, up to 6 atm. The data were used to infer mechanical properties of this material after cavity fabrication, by comparison with the results from simulation calculations done with ANSYS. The objective is to provide useful information about the mechanical properties of ingot Nb cavities which can be used in the design phase of SRF cavities intended to be built with this material. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI070  
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WEPRI072 High Power Co-axial Couplers for SRF Cavities Windows, klystron, simulation, network 2657
 
  • J. Guo, J. Henry, R.A. Rimmer, H. Wang, R.S. Williams
    JLab, Newport News, Virginia, USA
  • A. Dudas, M.L. Neubauer
    Muons, Inc, Illinois, USA
  
  Funding: Work supported by Dept. of Energy grant no. DE-SC0002769
High Power RF couplers are required in a wide range of accelerator projects using superconducting RF cavities. We have proposed a novel robust coax SRF coupler design using two pre-stressed disc windows without the need of additional matching elements. The matching frequency and the power handling capacity can be easily scaled by changing the diameter and the spacing of the windows. In this paper, we will present our latest progress in the fabrication and the testing of the windows. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI072  
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WEPRI074 Status of SRF Facilities at SNS cavity, cryomodule, operation, controls 2663
 
  • J. Saunders, R. Afanador, B. DeGraff, C.J. McMahan
    ORNL RAD, Oak Ridge, Tennessee, USA
  • M.T. Crofford, M. Doleans, M.P. Howell, S.-H. Kim, S.W. Lee, T.S. Neustadt, S.E. Stewart, W.H. Strong
    ORNL, Oak Ridge, Tennessee, USA
  
  Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
As a part or an ongoing process to maintain and improve the performance of its Superconducting Linac (SCL) the Spallation Neutron Source (SNS) is building facilities for processing and testing Superconducting Radio Frequency (SRF) cavities. Recently both a High Pressure Rinse (HPR) tool and a Vertical Test Apparatus (VTA) have been built and commissioned. The HPR is a commercially fabricated piece of equipment which is customized for the SNS application. The VTA was specified, designed and developed by the SNS. This paper will outline the design features as well as the commissioning results for both systems. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI074  
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WEPRI078 Development of a Quarter-wave Coaxial Coupler for 1.3 GHz Superconducting Cavities cavity, coupling, niobium, HOM 2675
 
  • Y. Xie, A. Kanareykin
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • N. Solyak, V.P. Yakovlev
    Fermilab, Batavia, Illinois, USA
  
  Superconducting ILC-type cavities have an rf coupler that is welded on. A detachable coupler will reduce conditioning time (can be conditioned separately), reduce cost and improve reliability. The problem with placing an extra flange in the superconducting cavity is creating a possible quench spot. Euclid Techlabs LLC designed a coupler and optimized its geometry that yielding an area on the surface with zero magnetic field (hence zero surface current). By placing a flange in that area we are able to avoid disturbing surface currents that typically lead to a quench. The coupler is optimized to preserve the axial symmetry of the cavity and rf field. The rf test results of this type coupler with a 1.3 GHz ILC-type single-cell cavity at Fermilab will be reported and discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI078  
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WEPRI081 Mechanical Design of the 704 MHz 5-cell SRF Cavity Cold Mass for CeC PoP Experiment cavity, cryomodule, experiment, electron 2678
 
  • J.C. Brutus, S.A. Belomestnykh, I. Ben-Zvi, Y. Huang, V. Litvinenko, I. Pinayev, J. Skaritka, L. Snydstrup, R. Than, J.E. Tuozzolo, W. Xu
    BNL, Upton, Long Island, New York, USA
  • T.L. Grimm, R. Jecks, J.A. Yancey
    Niowave, Inc., Lansing, Michigan, USA
  
  Funding: * Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
A 5-cell SRF cavity operating at 704 MHz will be used for the Coherent Electron Cooling Proof of Principle (CeC PoP) system under development for the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. The CeC PoP experiment will demonstrate the new technique of cooling proton and ion beams that may increase the beam luminosity in certain cases, by as much as tenfold. The 704 MHz cavity will accelerate 2 MeV electrons from a 112 MHz SRF gun up 22 MeV. Novel mechanical designs, including a super fluid heat exchanger, helium vessel, vacuum vessel and tuner mechanism are presented. Structural and thermal analysis, using ANSYS were performed to confirm the mechanical tuning system structural stability. This paper provides an overview of the design, the project status and schedule of the 704 MHz 5-cell SRF for CeC PoP experiment. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI081  
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THOBB01 Pursuing the Origin and Remediation of Low Q0 observed in the Original CEBAF Cryomodules cryomodule, shielding, cavity, linac 2828
 
  • R.L. Geng, J.F. Fischer, C.E. Reece, A.V. Reilly
    JLab, Newport News, Virginia, USA
  • F.S. He, Y.M. Li
    PKU, Beijing, People's Republic of China
  
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
We report on results of a new investigation into the Q0 degradation phenomenon observed in original CEBAF cavities when assembled into cryomodules. As a result, the RF dissipation losses increased by roughly a factor of two. The origin of the degradation, first observed in 1994, has remained unresolved up to current period, despite much effort. Recently, a new investigation has been launched, taking advantage of the latest cryomodule to undergo refurbishment. Systematic measurements are conducted with respect to the magnetic shielding effects of the double-layer shields and the magnetic properties of various components within the inner shield. This resulted in the new discovery of strongly magnetized strut springs as a major source of remnant magnetic flux near a cavity inside of all magnetic shielding. New springs with superior magnetic properties have been found, evaluated and implemented into the current cryomodule. In this contribution, we will review the data accumulated so far. Options for complete Q0 preservation of assembled cavities and possible Q0 remediation for those 330 cavities already installed in CEBAF will be presented. 		 
slides icon Slides THOBB01 [16.521 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THOBB01  
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THPRO042 Field Emission Studies of Heat Treated Mo Substrates cathode, gun, electron, cavity 2955
 
  • R. Barday, A. Jankowiak, T. Kamps, C. Klimm, J. Knobloch, F. Siewert, A. Varykhalov
    HZB, Berlin, Germany
  • S. Lagotzky, G. Müller
    Bergische Universität Wuppertal, Wuppertal, Germany
  • B. Senkovskiy
    Technische Universität Dresden, Dresden, Germany
  
  Funding: This work was supported by German Bundesministerium für Bildung und Forschung project 05K13PX2, Land Berlin and grants of Helmholtz Association.
Molybdenum can be used as a substrate for the bi-alkali antimonide photocathodes utilized for the generation of high brightness electron beams in a superconducting radio frequency (SRF) photoinjector cavities. Operation at high field strength is required to obtain a low emittance beam, thus increasing the probability of field emission (FE) from the cathode surface. Usually, substrates are heated in situ before alkali de- position to remove oxide layers from the surface. FE on Mo substrates was measured by means of a field emission scanning microscope (FESM). It turned out that in situ heat treatment (HT) of the Mo surface significantly changes the FE behaviour by activation of new emitters. For a better understanding of the mechanism for enhanced emission after in situ heating a witness Mo sample was investigated using x-ray photoelectron spectroscopy. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO042  
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THPRO063 Spin Tune Parametric Resonance Investigation resonance, experiment, dipole, synchrotron 3020
 
  • Y. Senichev, A.N. Ivanov, A. Lehrach, R. Maier, D. Zyuzin
    FZJ, Jülich, Germany
  • S.N. Andrianov
    St. Petersburg State University, St. Petersburg, Russia
  
  The idea of resonant spin oscillation method was modernized and improved in Forschungszentrum Julich in the proposed experiment at the COSY ring. The resonant method is based on spin tune parameterization using transverse RF magnetic or/and electric field. The spin orientation smearing due to the finite spin coherence time (SCT) plays a crucial in the proposed experiment to search for the electric dipole moment. Our analysis is based on the T-BMT differential equations for spin together with shorten motion equations. Using well developed theory of Mathieu's differential equations we have got simplified analytic solution for prediction of spin behavior. In this paper we have numerically evaluated all effects having fundamental contributions from our point of view.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO063  
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THPRO129 Online Modeling of the Rare Isotope Reaccelerator - ReA3 emittance, rfq, linac, diagnostics 3195
 
  • W. Wittmer, D.M. Alt, S.W. Krause, D. Leitner, S. Nash, R. Rencsok, J.A. Rodriguez, M.J. Syphers, X. Wu
    NSCL, East Lansing, Michigan, USA
  
  Funding: Work supported by Michigan State University
With the installation and commissioning of the third accelerating cryomodule in summer of 2014 the first phase of the radioactive ion beams postaccelerator ReA at National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU) will be completed. ReA was integrated in 2013 into the Coupled Cyclotron Facility providing unique low-energy rare isotope beams. After the fast rare isotopes are stopped in a gas stopping system, mass separated and their charge state boosted in an Electron Beam Ion Trap (EBIT), the ions are reaccelerated in a compact superconducting (SC) LINAC. For rare isotope operations, the LINAC is pre-tuned using stable pilot beams with a similar mass to charge ratio as the rare isotope beams and consequently the system is scaled. Scaling steps of up to 5\% are needed to change to the radioactive beams. To preserve the stringent beam characteristic on the experimental end station a precise online model is required. We will present the status of this online model. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO129  
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THPME002 Delta-Phi Method for the IFMIF-LIPAc SRF-Linac Cavity Tuning cavity, linac, simulation, focusing 3205
 
  • M. Valette, N. Chauvin
    CEA/IRFU, Gif-sur-Yvette, France
  • P.A.P. Nghiem, D. Uriot
    CEA/DSM/IRFU, France
  
  In order to achieve the upcoming commissioning of the IFMIF-LIPAc prototype accelerator in Rokkasho, the precision and resolution required for all diagnostics must be determined. These specifications will depend on the precision at which the tuning parameters must be set and finally by the tuning errors that can be tolerated on the beam itself. We will here discuss the use of the ∆φ method to tune the SRF-Linac and the resolution requirements it implies for the BPMs. This method, using a relative time of flight measurement to assess the energy of the beam, has the advantages of allowing setting the beam energy and beam longitudinal focusing at once.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME002  
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THPME039 Requirements for ESS Superconducting Radio Frequency Linac linac, cryomodule, cavity, cryogenics 3311
 
  • C. Darve, M. Eshraqi, D.P. McGinnis, S. Molloy, E. Tanke
    ESS, Lund, Sweden
  
  The European Spallation Source (ESS) is a pan-European project. It will be built by at least 17 European countries, with Sweden and Denmark as host nations. The Superconducting Radio-Frequency (SRF) linac is composed of one section of spoke cavity cryomodules (352.21 MHz) and two sections of elliptical cavity cryomodules (704.42 MHz). These cryomodules contain niobium SRF cavities operating at 2 K. Following a redesign of its accelerator, SRF linac design shall comply with a new set of requirement, like an increase of the beam current from 50 mA to 62.5 mA and an increase of the peak electrical surface field from 40 MV/m to 45 MV/m. Requirements and the main disciplines needed to construct this portion of the linac are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME039  
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THPME042 Preliminary Functional Analysis and Operating Modes of ESS 704 MHz Superconducting Radio-Frequency Linac cryomodule, controls, linac, EPICS 3317
 
  • N. Elias, C. Darve, J. Fydrych, A. Nordt, D.P. Piso
    ESS, Lund, Sweden
  
  The European Spallation Source (ESS) is one of Europe’s largest planned research infrastructures. The project is funded by a collaboration of 17 European countries and is under design and construction in Lund, Sweden. Three families of Superconducting Radio-Frequency (SRF) cavities are being prototyped, counting the spoke resonators with a geometric beta of 0.5, medium-beta elliptical cavities (β=0.67) and high beta elliptical cavities (β=0.86). The ESS linac will produce 2.86 ms long proton pulses with a repetition rate of 14 Hz (4 % duty cycle), a beam current of 62.5 mA and an average beam power of 5 MW. A control system is being developed to operate the different accelerator systems. All operating modes of the superconducting linac shall ensure a safe operation of the accelerator. This paper presents the preliminary functional analysis and the operating modes of the 704 MHz SRF linac.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME042  
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THPME053 Cost Rationales for an SRF Proton Linac cavity, linac, proton, hardware 3349
 
  • F. Marhauser
    Muons, Inc, Illinois, USA
  
  Rationales to assess and minimize costs for a Superconducting Radio Frequency (SRF) proton linac are outlined. Operating frequency, velocity profile and temperature are regarded as variables when applicable. Hardware plus labor costs for cavities and cryomodules as well as expenditures for facility infrastructures including cryogenic systems, conventional facilities, and relevant subsystems are estimated. The focus is on the assessment of a 10 MW, 1 GeV Continuous Wave (CW) linac for an Accelerator Driven Subcritical Reactor (ADSR)  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME053  
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THPME150 Spectrometer for SRF Gun electron, cavity, dipole, simulation 3608
 
  • I.Yu. Vladimirov, V.I. Shvedunov
    MSU, Moscow, Russia
  • T. Kamps, J. Völker
    HZB, Berlin, Germany
  
  We report about the design of a spectrometer for energy spectrum measurements of an electron beam generated by a superconducting radio-frequency photoelectron gun (SRF gun), which is under construction at HZB for BERLinPro. The spectrometer shall provide absolute accuracy of energy measurements of about 0.1% and energy resolution about 0.1%. The spectrometer will be also used for single shot phase space measurements in combination with a transverse deflecting cavity.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME150  
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THPRI113 Spallation Neutron Source Cryogenic Test Facility Horizontal Test Apparatus Operation cavity, cryogenics, plasma, operation 4043
 
  • B. DeGraff, B.S. Hannah, T.S. Neustadt, J. Saunders
    ORNL RAD, Oak Ridge, Tennessee, USA
  • R. Afanador, M. Doleans, M.P. Howell, S.-H. Kim, C.J. McMahan
    ORNL, Oak Ridge, Tennessee, USA
  
  Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
The Spallation Neutron Source (SNS) has built Superconducting Radio Frequency (SRF) processing and testing facilities to support improvement programs and future upgrades. The Cryogenic Test Facility (CTF) system is capable of delivering liquid helium at 4.5K to different test apparatus in support of SRF testing. This paper describes the final stages of fabrication, commissioning and the initial operation of the Horizontal Test Apparatus (HTA). The HTA allows for cold testing of single jacketed medium-beta or high-beta SRF cavities. Heat loads, capacities, and other performance data collected during operation will be presented. Cavity testing lifecycle for plasma processing research and development will be discussed. System changes to allow for 2K helium operation in the HTA will also be addressed. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRI113  
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FRYBA01 Long-term Accelerator R&D as an Independent Research Field laser, electron, plasma, acceleration 4073
 
  • R. Brinkmann
    DESY, Hamburg, Germany
  
  High energy physics projects have been important drivers of accelerator R&D for several decades. The resulting accelerator technology was used to construct frontier accelerators for HEP but was also very successfully applied in accelerators for other science fields, in particular photon science, nuclear physics, medical applications, … Fewer HEP projects and at the same time a growing number of projects in other areas require a modified approach to accelerator R&D. Efforts and progress to perform accelerator R&D as an independent research program with its own, independent funding are described for the example of the Helmholtz ARD program in Germany. Links to efforts in other countries are discussed and an outlook to future accelerator research is given.  
slides icon Slides FRYBA01 [3.581 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-FRYBA01  
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