Author: Cook, N.M.
Paper Title Page
SUPAF07 High-Fidelity Three-Dimensional Simulations of Thermionic Energy Converters 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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WEPLG03 Theoretical and Computational Modeling of a Plasma Wakefield BBU Instability 341
  • S.D. Webb, D.L. Bruhwiler, N.M. Cook
    RadiaSoft LLC, Boulder, Colorado, USA
  • A.V. Burov, V.A. Lebedev, S. Nagaitsev
    Fermilab, Batavia, Illinois, USA
  Funding: This work was supported in part by the Department of Energy, Office of Science, Office of High Energy Physics, under contract number DE-SC0018718.
Plasma wakefield accelerators achieve accelerating gradients on the order of the wave-breaking limit, m c2 kp/e, so that higher accelerating gradients correspond to shorter plasma wavelengths. Small-scale accelerating structures, such as plasma and dielectric wakefields, are susceptible to the beam break-up instability (BBU), which can be understood from the Panofsky-Wenzel theorem: if the fundamental accelerating mode scales as b-1 for a structure radius b, then the dipole mode must scale as b-3, meaning that high accelerating gradients necessarily come with strong dipole wake fields. Because of this relationship, any plasma-accelerator-based future collider will require detailed study of the trade-offs between extracting the maximum energy from the driver and mitigating the beam break-up instability. Recent theoretical work* predicts the tradeoff between the witness bunch stability and the amount of energy that can be extracted from the drive bunch, a so-called efficiency-instability relation . We will discuss the beam break-up instability and the efficiency-instability relation and the theoretical assumptions made in reaching this conclusion. We will also present preliminary particle-in-cell simulations of a beam-driven plasma wakefield accelerator used to test the domain of validity for the assumptions made in this model.
* V. Lebedev, A. Burov, and S. Nagaitsev, "Efficiency versus
instability in plasma accelerators", Phys. Rev. Acc. Beams 20, 121301
slides icon Slides WEPLG03 [2.234 MB]  
DOI • reference for this paper ※  
About • paper received ※ 01 November 2018       paper accepted ※ 28 January 2019       issue date ※ 26 January 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)