Author: Hoffstaetter, G.H.
Paper Title Page
MOCOWBS01
 CBETA, a 4-turn ERL Based on SRF Linacs: Construction and Commissioning  
 
  • G.H. Hoffstaetter
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  A DC-photo-emitter electron source, a high-power SRF injector linac, a high-current SRF linac for energy recovery, and a permanent-magnet return loop have been assembled to the 4-turn SRF ERL. Because of it’s Fixed-Field Alternating-gradient optics, the single return loop accommodates all 4 beam energies in one vacuum pipe. A collaboration between Cornell and Brookhaven National Laboratory has constructed, and is currently commissioning on the Cornell campus this Cornell-BNL-ERL-Test-Accelerator (CBETA). While the electron sourse and SRF linac were prototyped at Cornell, the strong Halbach-type permanent magnets for the FFA return loop were prototyped at BNL, leading to a strong collaboration. The Electron Ion Collider (EIC) has been determined to be the USA’s highest priority new large accelerator for Nuclear Physics by the National Academy of Sciences. It¿s luminosity relies on electron cooling, and only ERLs can provide the cooling parameters. CBETA therefore provides essential R&D for the EIC. The high-brightness beam with 150 MeV and up to 40 mA will have applications beyond EIC cooling and basic accelerator research, in industry, in nuclear physics, and in X-ray science.  
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TUCOWBS03
 CSR Phase Space Dilution in CBETA  
 
  • W. Lou, G.H. Hoffstaetter, D. Sagan
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • C.E. Mayes
    SLAC, Menlo Park, California, USA
  
  While Energy Recovery Linac (ERLs) give promise to deliver unprecedentedly high beam current with simultaneously small emittance, Coherent Synchrotron Radiation (CSR) can pose detrimental effect on the beam at high bunch charges and short bunch lengths. CBETA, the Cornell BNL ERL Test Accelerator, will be the first multi-turn ERL with SRF accelerating cavities and Fixed Field Alternating gradient (FFA) beamline. To investigate the CSR effects on CBETA, the established simulation code Bmad has been used to track a bunch with different CSR parameters. We found that CSR causes phase space dilution, and the effect becomes more significant as the bunch charge and recirculation pass increase. Convergence tests have been performed for the CSR parameters to validate the observed micro-bunching instability. Potential ways to mitigate the effect involving vacuum chamber shielding and increasing bunch length are also being investigated.  
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TUCOXBS05 Beam Timing and Cavity Phasing 39
 
  • R.M. Koscica, N. Banerjee, G.H. Hoffstaetter, W. Lou, G.T. Premawardhana
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  In a multi-pass Energy Recovery Linac (ERL), each cavity must regain all energy expended from beam acceleration during beam deceleration. The beam should also achieve specific energy targets during each loop that returns it to the linac. To satisfy the energy recovery and loop requirements, one must specify the phase and voltage of cavity fields, and one must control the beam flight times through the return loops. Adequate values for these parameters can be found by using a full scale numerical optimization program. If symmetry is imposed in beam time and energy during acceleration and deceleration, the number of parameters needed decreases, simplifying the optimization. As an example, symmetric models of the Cornell BNL ERL Test Accelerator (CBETA) are considered. Energy recovery results from recent CBETA single-turn tests are presented, as well as multi-turn solutions that satisfy CBETA optimization targets of loop energy and zero cavity loading.  
slides icon Slides TUCOXBS05 [5.186 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-TUCOXBS05  
About • paper received ※ 13 September 2019       paper accepted ※ 01 November 2019       issue date ※ 24 June 2020  
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THCOWBS07
 Passive and Active Control of Microphonics at CBETA and Elsewhere  
 
  • N. Banerjee, G.H. Hoffstaetter, M. Liepe, P. Quigley
    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 (NYSERDA).
Superconducting Radio Frequency (SRF) cavities operating with large loaded quality factors is the natural choice for Energy Recovery Linacs which operate at negligible beam loading. While this leads to lower RF power requirements, the stability of the accelerating field is strongly influenced by peak microphonics detuning. In this talk, I will discuss various methods of passively suppressing vibrations used in various facilities using low bandwidth SRF systems, with special reference to CBETA, a multi-turn SRF ERL being commissioned at Cornell University. I will also describe our active microphonics control system based on a modified narrow band Active Noise Control (ANC) algorithm and compare it with schemes being explored in other machines. 		 
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FRCOWBS04 Essential Instrumentation for the Characterization of ERL Beams 150
 
  • N. Banerjee, A.C. Bartnik, K.E. Deitrick, J. Dobbins, C.M. Gulliford, G.H. Hoffstaetter
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • J.S. Berg, S.J. Brooks, R.J. Michnoff
    BNL, Upton, New York, USA
  
  Funding: This work was performed through the support of New York State Energy Research and Development Agency (NYSERDA).
The typical requirement of Energy Recovery Linacs to produce beams with high repetition rate and high bunch charge presents unique demands on beam diagnostics. ERLs being quite sensitive to time of flight effects necessitate the use of beam arrival time monitors along with typical position detection. Being subjected to a plethora of dynamic effects, both longitudinal and transverse phase space monitoring of the beam becomes quite important. Additionally, beam halo plays an important role determining the overall transmission. Consequently, we also need to characterize halo both directly using sophisticated beam viewers and indirectly using radiation monitors. In this talk, I will describe the instrumentation essential to ERL operation using the Cornell-BNL ERL Test Accelerator (CBETA) as a pertinent example. 		 
slides icon Slides FRCOWBS04 [7.129 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-FRCOWBS04  
About • paper received ※ 19 September 2019       paper accepted ※ 01 November 2019       issue date ※ 24 June 2020  
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FRCOYBS02
 Working Group Summary: ERL Beam Dynamics and Instrumentation  
 
  • G.H. Hoffstaetter
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • P.E. Evtushenko
    HZDR, Dresden, Germany
  
  To be added  
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