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Modelling Gap Closure Within Pulsed Power Machines

Kirk, Grace and Oblapenko, Georgii and Goldstein, David and Varghese, Philip and Sirajuddin, David and Moore, Christopher (2023) Modelling Gap Closure Within Pulsed Power Machines. In: DSMC23 Conference. DSMC23 Conference 2023, 2023-09-24 - 2023-09-27, Santa Fe, New Mexico, USA.

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Official URL: https://www.sandia.gov/dsmc/


Gap closure is a process where expanding electrode plasmas close the anode-cathode gaps of the vacuum transmission lines used in TW pulsed-power machines, affecting power flow, and ultimately limiting operating performance [1]. Simulating the formation of plasma is therefore a critical modeling need for characterizing high-current diodes in machines such as the Saturn accelerator, and to assess the power delivered in Sandia's next-generation pulsed power (NGPP) machine; however, our ability to simulate this process is limited due to the enormous computational cost. Full PIC-DSMC simulations of gap closure are limited by huge variability in length and time scales necessary to resolve the physics. In order to preserve the solution stability, while accurately capturing the electron velocity distribution function and collisions, the time step needs to be less than a picosecond with grid spacing on the order of nanometers. Running a full simulation through the ~100 ns pulse thus requires tens of millions of time steps. One way to speed up the solution while keeping time steps and spatial grids unaffected is to use event splitting to allow for fewer macroparticles necessary for better statistics. This is done by taking the classic variable weight technique a step further by splitting a particle into multiple particles upon collision, with individual weights determined by the probability of each possible collision outcome. Event splitting enhances the ability of the DSMC technique to model low-probability processes, such as for the relatively rare ionization collisions that drive the formation of the plasma [2]. We will discuss the superiority of event splitting over standard 1D DSMC in terms of computational costs and level of stochastic noise [3]; this will be shown by comparing multiple simulations of gap closure run by both standard DSMC and the event splitting technique.

Item URL in elib:https://elib.dlr.de/196169/
Document Type:Conference or Workshop Item (Speech)
Title:Modelling Gap Closure Within Pulsed Power Machines
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Kirk, GraceUniversity of Texas at AustinUNSPECIFIEDUNSPECIFIED
Oblapenko, GeorgiiUNSPECIFIEDhttps://orcid.org/0000-0002-1434-7166UNSPECIFIED
Goldstein, DavidUniversity of Texas at AustinUNSPECIFIEDUNSPECIFIED
Varghese, PhilipUniversity of Texas at AustinUNSPECIFIEDUNSPECIFIED
Sirajuddin, DavidSandia National LaboratoriesUNSPECIFIEDUNSPECIFIED
Moore, ChristopherSandia National LaboratoriesUNSPECIFIEDUNSPECIFIED
Date:September 2023
Journal or Publication Title:DSMC23 Conference
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:No
Keywords:PIC-DSMC, plasma flow
Event Title:DSMC23 Conference 2023
Event Location:Santa Fe, New Mexico, USA
Event Type:international Conference
Event Start Date:24 September 2023
Event End Date:27 September 2023
Organizer:Sandia National Laboratories
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Transportation
DLR - Research area:Raumfahrt
DLR - Program:R RP - Space Transportation
DLR - Research theme (Project):R - Reusable Space Systems and Propulsion Technology
Location: Göttingen
Institutes and Institutions:Institute for Aerodynamics and Flow Technology > Spacecraft, GO
Deposited By: Hannemann, Dr.rer.nat. Volker
Deposited On:08 Dec 2023 10:51
Last Modified:24 Apr 2024 20:56

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