WEZBA —  Wednesday Parallel Session 5   (04-Sep-19   14:00—16:00)
Chair: M.A. Palmer, BNL, Upton, New York, USA
Paper Title Page
WEZBA1
Status and Future Directions for High Power Neutron Production Targets  
 
  • C.N. Barbier
    ORNL, Oak Ridge, Tennessee, USA
 
  Development of megawatt class targets for neutron production remains one of the largest engineering challenges in the field of accelerator science. This talk will review state of the art in neutron target capabilities and ongoing R&D of next generation targets.  
slides icon Slides WEZBA1 [14.128 MB]  
 
WEZBA2
Experience and Lessons in FRIB Superconducting Quarter-Wave Resonator RF Commissioning  
 
  • S.H. Kim, H. Ao, F. Casagrande, W. Chang, C. Compton, A. Facco, V. Ganni, W. Hartung, P. Knudsen, T. Larter, H. Maniar, S.J. Miller, D.G. Morris, P.N. Ostroumov, A.S. Plastun, J.T. Popielarski, L. Popielarski, H.T. Ren, K. Saito, M. Thrush, D.R. Victory, J. Wei, M. Xu, T. Xu, Y. Yamazaki, C. Zhang, S. Zhao
    FRIB, East Lansing, Michigan, USA
 
  The superconducting (SC) linac for the Facility for Rare Isotope Beams (FRIB) has one quarter-wave resonator (QWR) segment and two half-wave resonator (HWR) segments. Linac Segment 1 contains twelve β = 0.041 and ninety-two β = 0.085 QWRs operating at 80.5 MHz, and thirty-nine SC solenoid packages. RF commissioning and beam commissioning of Segment 1 was completed in April 2019. The design accelerating gradients (5.1 MV/m for β = 0.041 and 5.6 MV/m for β = 0.085) were achieved in all of the cavities with no multipacting or field emission issues. The amplitude and phase stability of the cavity field met the design goals, peak-to-peak stability of ± 1% and ± 1 degree, respectively. We achieved 20.3 MeV per nucleon beams of Ar, Kr, Ne, and Xe beams with Segment 1. In this talk, we will discuss lessons learned from the RF commissioning of the cryomodules, including mitigation of microphonics in QWRs operated at 4.5 K and methods developed for efficient testing, conditioning, and commissioning of more than 100 SC cavities, each with its own independent RF system.  
slides icon Slides WEZBA2 [2.823 MB]  
 
WEZBA3 No Beam-Loss Quadrupole Scan for Transverse Phase Space Measurements -1
 
  • K. Fukushima, T. Maruta, P.N. Ostroumov, T. Yoshimoto
    FRIB, East Lansing, Michigan, USA
 
  Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661, the State of Michigan and Michigan State University.
Facility for Rare Isotope Beams (FRIB) at Michigan State University is based on a high power heavy ion linac and beam commissioning is under way. For evaluation of beam Twiss parameters and rms emittance, we routinely use multiple profile measurements while the strength of an upstream quadrupole is varied. The change of the quadrupole strength results in a beam mismatch downstream of the profile monitor which can cause beam losses. This is not acceptable in a high energy beamline. To avoid this transverse mismatch, we developed a beam matching procedure by optimization of quadrupoles’ setting downstream of the profile monitor. Using this procedure we were able to eliminate beam losses during the quadrupole scan, and evaluate beam Twiss parameters and rms emittance. Examples of using this procedure in the folding segment of the FRIB linac will be reported.
 
slides icon Slides WEZBA3 [8.017 MB]  
 
WEZBA4
Characterization and Analysis of Nanocrystalline Diamond as Stripper Foils  
 
  • L.V. Saturday, P.D. Rack
    University of Tennessee, Knoxville, USA
  • D.P. Briggs, P.D. Rack, S.T. Retterer
    CNMS, Oak Ridge, USA
  • N.J. Evans, C.F. Luck
    ORNL RAD, Oak Ridge, Tennessee, USA
  • L.L. Wilson
    ORNL, Oak Ridge, Tennessee, USA
 
  Funding: This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy.
The 1.4 MW Spallation Neutron Source (SNS) uses nanocrystalline diamond (NCD) foils to strip 1 GeV H ions to protons during injection into the accumulator ring. The SNS Proton Power Upgrade will double the power deposited into the NCD foils by increasing the beam current by 50% and linac energy by 30%. This makes understanding the failure modes of the NCD foils increasingly important. In this work we report on experiments using a 30 keV, 5 mA electron gun capable of simulating SNS PPU time structure and energy deposition in NCD foils. We analyze changes to the foil with an RGA, FLIR camera, faraday cup, high definition photography, SEM, and Raman spectroscopy. We examine failure mechanisms for foils subjected to equivalent PPU conditions. Preliminary results have shown characteristic signs of foil thinning and different failure mechanisms between the electron gun and SNS beam line. Additionally, membrane cantilever structures have been synthesized and characterized to understand the material properties of the NCD. Finally, finite element thermal simulations of the suspended diamond foils have been performed, which will be used to assess and direct future foil modifications.
 
slides icon Slides WEZBA4 [9.989 MB]  
 
WEZBA5 Development of a Marx Modulator for FNAL Linac -1
WEPLM45   use link to see paper's listing under its alternate paper code  
 
  • T.A. Butler, F.G. Garcia, M.R. Kufer, K.S. Martin, H. Pfeffer
    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.
A Marx-topology modulator has been designed and developed at the Fermi National Accelerator Laboratory under the Proton Improvement Plan (PIP). This modulator replaces the previous triode hard-tube design, increasing reliability, lowering operational costs, and maintaining waveform accuracy. The Marx modulator supplies the anode of the 7835 VHF power triode tube with a 35 kV, 375 Amp, 460 µs pulse at 15 Hz. It consists of 54 individual Marx cells, each containing a 639 µF capacitor charged to 900 Volts, combined in series with IGBT switches to create the desired output waveform. This requires variable rise and fall times, flattening of capacitive droop, and feedforward beam loading compensation. All five 201.25 MHz RF systems have been upgraded to Marx modulators to ensure continued operation of the linear accelerator.
 
poster icon Poster WEZBA5 [3.034 MB]  
 
WEZBA6 A 100 kW 1.3 GHz Magnetron System with Amplitude and Phase Control -1
 
  • M.E. Read, T. Bui, G. Collins, R.L. Ivespresenter
    CCR, San Mateo, California, USA
  • B.E. Chase, J. Reid
    Fermilab, Batavia, Illinois, USA
  • J.R. Conant, C.M. Walker
    CPI, Beverley, Massachusetts, USA
 
  Funding: United States Department of Energy Grant No. DE-SC0011229.
Calabazas Creek Research, Inc., Fermilab, and Communications & Power Industries, LLC, developed a 100 kW peak, 10 kW average, 1.3 GHz, magnetron-based, RF system for driving accelerators. Efficiency varied between 81% and 87%. Phase locking uses a novel approach that provides fast amplitude and phase control when coupled into a superconducting accelerator cavity [1]. The system was successfully tested at Fermilab and produced 100 kW in 1.5 ms pulses at a repetition rate of 2 pps. A locking bandwidth of 0.9 MHz was achieved with a drive signal of 269 W injected through a 4 port circulator. The phase locking signal was 25 dB below the magnetron output power. The spectrum of the phase locked magnetron was suitable for driving accelerator cavities. Phase modulation was demonstrated to 50 kHz (the limit of the available driver source). The average power was limited by available conditioning time. Scaling indicates 42 kW of average power should be achievable. Estimated cost is less than $1/Watt of delivered RF power, exclusive of power supplies or modulators. System design and performance measurements will be presented.
[1] B. Chase, R. Pasquinelli, E. Cullerton, P. Varghese, "Precision Vector Control of a Superconducting RF Cavity driven by an Injection Locked Magnetron," Jou. of Instrumentation, Vol. 10 March 2015.
 
slides icon Slides WEZBA6 [2.661 MB]