Keyword: operation
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SUPAF07 High-Fidelity Three-Dimensional Simulations of Thermionic Energy Converters simulation, electron, space-charge, cathode 59
  • N.M. Cook, J.P. Edelen, C.C. Hall, M.V. Keilman, P. Moeller, R. Nagler
    RadiaSoft LLC, Boulder, Colorado, USA
  • J.-L. Vay
    LBNL, Berkeley, California, USA
  Funding: This work is supported the US DOE Office of Science, Office of High Energy Physics: DE-SC0017162.
Thermionic energy converters (TEC) are a class of thermoelectric devices, which promise improvements to the efficiency and cost of both small- and large-scale electricity generation. A TEC is comprised of a narrowly-separated thermionic emitter and an anode. Simple structures are often space-charge limited as operating temperatures produce currents exceeding the Child-Langmuir limit. We present results from 3D simulations of these devices using the particle-in-cell code Warp, developed at Lawrence Berkeley National Lab. We demonstrate improvements to the Warp code permitting high fidelity simulations of complex device geometries. These improvements include modeling of non-conformal geometries using mesh refinement and cut-cells with a dielectric solver. We also consider self-consistent effects to model Schottky emission near the space-charge limit for arrays of shaped emitters. The efficiency of these devices is computed by modeling distinct loss channels, including kinetic losses, radiative losses, and dielectric charging. We demonstrate many of these features within an open-source, browser-based interface for running 3D electrostatic simulations with Warp, including design and analysis tools, as well as streamlined submission to HPC centers.
slides icon Slides SUPAF07 [6.097 MB]  
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About • paper received ※ 01 November 2018       paper accepted ※ 19 November 2018       issue date ※ 26 January 2019  
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TUPAF12 Longitudinal Beam Dynamics With a Higher-Harmonic Cavity for Bunch Lengthening cavity, storage-ring, simulation, synchrotron 202
  • G. Bassi, J. Tagger
    BNL, Upton, Long Island, New York, USA
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy
We discuss the longitudinal beam dynamics in storage rings in the presence of a higher-harmonic cavity (HHC) system for bunch lengthening. We first review the general conditions for HHC operations, either in active or passive mode, assuming the stability of the system. For uniform filling patterns, a distinction is made between operations with a normal-conducting HHC, where optimal conditions for bunch lengthening can be satisfied, and operations with super-conducting HHC, where optimal conditions can be met only approximately. The option to operate the NSLS-II storage ring with a passive, super-conducting third harmonic cavity (3HC) system is discussed next. The stability and performance of the system in the presence of a gap in the uniform filling, which corresponds to the present mode of operation of the NSLS-II storage ring, is investigated with self-consistent Vlasov-Fokker-Planck simulations performed with the code SPACE*.
* G. Bassi, A. Blednykh and V. Smaluk, Phys Rev. Accel. Beams 19, 024401 (2016).
slides icon Slides TUPAF12 [17.562 MB]  
DOI • reference for this paper ※  
About • paper received ※ 20 October 2018       paper accepted ※ 28 January 2019       issue date ※ 26 January 2019  
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WEPAF02 Simulations of Beam Chopping for Potential Upgrades of the SNS LEBT Chopper rfq, simulation, LEBT, gun 325
  • B. Han, S.N. Murray, T.R. Pennisi, V.V. Peplov, M.P. Stockli, R.F. Welton
    ORNL, Oak Ridge, Tennessee, USA
  • R.B. Saethre, C. Stinson
    ORNL RAD, Oak Ridge, Tennessee, USA
  Funding: This work was performed at Oak Ridge National Laboratory, which is managed by UT-Battelle, LLC, under contract number DE-AC05-00OR22725 for the United States Department of Energy.
The LEBT chopper is a critical element of the SNS accelerator system. In this work, the benefit of increasing the chopping voltage amplitude for the present chopping pattern is shown with beam simulations, and an ongoing hardware upgrade of the chopper pulser units is discussed. In addition, with the prospect of higher voltage capability of the new pulser design, two alternative chopping patterns which reduce the switching frequency of the chopper pulsers down to 1/2 or 1/4 of the present chopping pattern, are also explored with beam simulations.
slides icon Slides WEPAF02 [7.431 MB]  
DOI • reference for this paper ※  
About • paper received ※ 31 October 2018       paper accepted ※ 07 December 2018       issue date ※ 26 January 2019  
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