WG4: Superconducting RF
Paper Title Page
MOICCC001
Power Couplers & HOM Dampers at CERN  
 
  • E. Montesinos
    CERN, Geneva, Switzerland
 
  Abstract not submitted at print time.  
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MOICCC002
Coaxial Couplers  
 
  • Q. Wu
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy
The method of couple power into and out of an RF resonator tends to be based on either waveguide or coaxial couplers. Coaxial couplers are widely used due to multiple merits, such as compactness, easy fabrication, less heat leak, easy to compress multipacting, etc.. However, the coaxial couplers also encounter cooling and power handling problems at high power transmission scenarios. We will discuss the characteristics of the coaxial coupler designs and their application in various projects.
 
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MOICCC003
Resonance Control at the Compact ERL in KEK  
 
  • T. Miura, D.A. Arakawa, M. Egi, K. Enami, T. Furuya, E. Kako, H. Katagiri, T. Konomi, T. Matsumoto, S. Michizono, F. Qiu, H. Sakai, K. Umemori
    KEK, Ibaraki, Japan
  • N. Liu
    Sokendai, Ibaraki, Japan
  • M. Sawamura
    QST, Tokai, Japan
 
  The compact energy recovery linac (cERL) in KEK is a test facility for the future 3-GeV ERL light source. The 1.3 GHz superconducting cavities are used in the injector linac cryomodule and the main linac cryomodule. The slide-jack tuner with stepper motor is used for coarse tuning of the resonant frequency, and piezo tuner is used for fine tuning. The digital tuner feedback system based on micro-TCA standard has been employed. The frequency band of the tuner feedback has been set lower than the mechanical resonance frequency. The rf field fluctuation caused by the Michrophonics is compensated by the rf feedback. In the injector linac, one rf source drives two cavities with vector-sum control. The vector-sum calibration error affected the beam energy jitter, but that has been improved after adopting the high gain parameter in resonant frequency feedback in order to keep the field balance of the cavities.  
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TUICCC001
High-Q R&D at FNAL  
 
  • M. Checchin
    Fermilab, Batavia, Illinois, USA
 
  Modern projects of accelerators for High Energy Physics and FEL accelerators (PIP II, LCLS II, etc.) demand operation of the SRF cavities in CW regime. In this situation, low cryogenic losses are essential. Decrease of the losses or, thus, increase of the cavity unloaded quality factor Q0 allows great savings in capital and operational cost. The new N-doping technique for the SRF cavity processing in order to achieve high Q0 is described, which is now a ready-to-use technology for SRF accelerators. The current implementation of this technique for the LCLS-II cavity production, allow us to present how ultra-high Q-factors can be maintained from the vertical to the horizontal test. In particular, efficient cooling and optimization of shielding design will be discussed to address potential Q degradation from the remnant magnetic fields in the cryomodule. The talk will go through the physics and fundamental studies performed at FNAL that allowed us a) to define the best nitrogen doping treatment which minimizes the Q sensitivity to trapped magnetic field, b) to maximize magnetic flux expulsion based on cavity treatment.  
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TUICCC002
Twin-Axis Elliptical Cavity  
 
  • F. Marhauser, A. Hutton
    JLab, Newport News, Virginia, USA
  • S.U. De Silva, J.R. Delayen, H. Park, L. Sweat
    ODU, Norfolk, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Energy Recovery Linacs (ERLs) use superconducting RF cavities to accelerate the primary electron beam while the spent electron beam is decelerated in the same cavities to recover the energy. Using separate beam pipes for the accelerated and decelerated beams allows for independent focusing and better merging of the beam from the injector into the ERL. In the frame of a DoE accelerator stewardship program we have designed and built a prototype 1.5 GHz twin-axis single-cell cavity as a proof of principle. Experiences on fabrication techniques and lessons learned will be reported prior to the vertical RF testing.
 
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TUICCC003
Cornell ERL CM Performance  
 
  • F. Furuta, J. Dobbins, R.G. Eichhorn, M. Ge, G.H. Hoffstaetter, M. Liepe, T.I. O'Connell, P. Quigley, D.M. Sabol, J. Sears, E.N. Smith, V. Veshcherevich
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • D. Gonnella
    SLAC, Menlo Park, California, USA
 
  The main linac prototype cryomodule (MLC) is a key component for the Cornell-BNL ERL Test Accelerator (CBETA) project, which is a 4-turn FFAG ERL under construction at Cornell University. This novel cryomodule is the first SRF module ever to be fully optimized simultaneously for high efficient SRF cavity operation and for supporting very high CW beam currents. After the success of the initial MLC testing, the MLC had been moved into the final location for the first MLC beam test. Cornell ERL high voltage DC gun and Injector Cryomodule were connected to MLC via the entry beam line; the beam stop assembly was also installed as the exit line. In this paper, we summarize the performance of this novel ERL cryomodule including the results of the first beam test and the additional tests focused on RF field stability and cavity microphonics.  
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TUICCC004
The Potential of Nb/Cu Technology for High Beam Current Applications  
 
  • S. Aull
    CERN, Geneva, Switzerland
 
  Particle accelerators with high beam current require not only robust fundamental power couplers that can deliver high power to the accelerating cavities but also thorough handling of losses due to higher order modes induced by the particle beam. Both favour low frequency superconducting RF cavities with big apertures. We present the advantages and limitations of niobium coated copper cavities in comparison to the well-established bulk niobium technology and its potential for high beam current applications such as energy recovery linacs.  
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THIBCC001
Resonance Control of the PIP-II SC Cavities  
 
  • W. Schappert
    Fermilab, Batavia, Illinois, USA
 
  Abstract not submitted at print time.  
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THIBCC002
Microphonics Analysis of ERL Cryomodule  
 
  • F. Furuta, N. Banerjee, J. Dobbins, R.G. Eichhorn, M. Ge, G.H. Hoffstaetter, M. Liepe, P. Quigley, J. Sears, V. Veshcherevich
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  The main linac prototype cryomodule (MLC) is a key component for the Cornell-BNL ERL Test Accelerator (CBETA) project, which is a 4-turn FFAG ERL under construction at Cornell University. After the success of the initial MLC test, the MLC has been moved into the final location for the initial beam test into the MLC. The levels of microphonic in the MLC cavities without fast tuner compensation were measured at the initial and the final location, confirming that these should not limit the CBETA requirement of a nominal energy gain of 36 MeV per pass. Nevertheless, a further reduction of microphonics is desirable for improved energy stability and reduced RF power demand. The cryogenic gas line to the MLC was optimized to reduce vibrations. A piezoelectric-driven fast tuner is installed on each MLC cavity, and its usefulness in compensating cavity microphonics was studied. Here we report details from these tests and summarize results.  
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THIBCC005 Development of an ERL RF Control System 70
MOPSPP002   use link to see paper's listing under its alternate paper code  
 
  • S. Orth, D. Domont-Yankulova, H. Klingbeil
    TEMF, TU Darmstadt, Darmstadt, Germany
 
  Funding: Work supported by Deutsche Forschungsgemeinschaft (DFG): GRK 2128 "AccelencE"
The Mainz Energy-recovering Superconducting Accelerator (MESA), currently under construction at Johannes Gutenberg-Universität Mainz, requires a newly designed digital low-level radio frequency (LLRF) system. Challenging requirements have to be fulfilled to ensure high beam quality and beam parameter stability. First, the layout with two recirculations and the requirements will be shown from an LLRF point of view. Afterwards, different options for the control system are presented. This includes the generator-driven system, the self-excited loop and classical PID controller as well as more sophisticated solutions.
 
slides icon Slides THIBCC005 [4.062 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2017-THIBCC005  
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FRIBCC004 ERL17 Workshop, WG4 Summary: Superconducting RF 81
 
  • F. Gerigk
    CERN, Geneva, Switzerland
  • I. Ben-Zvi
    BNL, Upton, Long Island, New York, USA
 
  Working Group 4 consisted of 10 talks, which were split into three sessions around four main themes. These themes will be listed and summarized in the following along with a summary of the discussion session.  
slides icon Slides FRIBCC004 [0.592 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2017-FRIBCC004  
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