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Title: Kinetic Simulation of Collisional Magnetized Plasmas with Semi-implicit Time Integration

Abstract

Plasmas with varying collisionalities occur in many applications, such as tokamak edge regions, where the flows are characterized by significant variations in density and temperature. While a kinetic model is necessary for weakly-collisional high-temperature plasmas, high collisionality in colder regions render the equations numerically stiff due to disparate time scales. In this study, we propose an implicit–explicit algorithm for such cases, where the collisional term is integrated implicitly in time, while the advective term is integrated explicitly in time, thus allowing time step sizes that are comparable to the advective time scales. This partitioning results in a more efficient algorithm than those using explicit time integrators, where the time step sizes are constrained by the stiff collisional time scales. Finally, we implement semi-implicit additive Runge–Kutta methods in COGENT, a high-order finite-volume gyrokinetic code and test the accuracy, convergence, and computational cost of these semi-implicit methods for test cases with highly-collisional plasmas.

Authors:
ORCiD logo [1];  [2];  [1];  [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Center for Applied Scientific Computing
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Physics Division
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR) (SC-21)
OSTI Identifier:
1458696
Report Number(s):
LLNL-JRNL-735522
Journal ID: ISSN 0885-7474; 887762
Grant/Contract Number:  
AC52-07NA27344
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Scientific Computing
Additional Journal Information:
Journal Name: Journal of Scientific Computing; Journal ID: ISSN 0885-7474
Publisher:
Springer
Country of Publication:
United States
Language:
English
Subject:
97 MATHEMATICS AND COMPUTING; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; IMEX time integration; plasma physics; gyrokinetic simulations; Vlasov–Fokker–Planck equations

Citation Formats

Ghosh, Debojyoti, Dorf, Mikhail A., Dorr, Milo R., and Hittinger, Jeffrey A. F. Kinetic Simulation of Collisional Magnetized Plasmas with Semi-implicit Time Integration. United States: N. p., 2018. Web. doi:10.1007/s10915-018-0726-6.
Ghosh, Debojyoti, Dorf, Mikhail A., Dorr, Milo R., & Hittinger, Jeffrey A. F. Kinetic Simulation of Collisional Magnetized Plasmas with Semi-implicit Time Integration. United States. doi:10.1007/s10915-018-0726-6.
Ghosh, Debojyoti, Dorf, Mikhail A., Dorr, Milo R., and Hittinger, Jeffrey A. F. Sat . "Kinetic Simulation of Collisional Magnetized Plasmas with Semi-implicit Time Integration". United States. doi:10.1007/s10915-018-0726-6.
@article{osti_1458696,
title = {Kinetic Simulation of Collisional Magnetized Plasmas with Semi-implicit Time Integration},
author = {Ghosh, Debojyoti and Dorf, Mikhail A. and Dorr, Milo R. and Hittinger, Jeffrey A. F.},
abstractNote = {Plasmas with varying collisionalities occur in many applications, such as tokamak edge regions, where the flows are characterized by significant variations in density and temperature. While a kinetic model is necessary for weakly-collisional high-temperature plasmas, high collisionality in colder regions render the equations numerically stiff due to disparate time scales. In this study, we propose an implicit–explicit algorithm for such cases, where the collisional term is integrated implicitly in time, while the advective term is integrated explicitly in time, thus allowing time step sizes that are comparable to the advective time scales. This partitioning results in a more efficient algorithm than those using explicit time integrators, where the time step sizes are constrained by the stiff collisional time scales. Finally, we implement semi-implicit additive Runge–Kutta methods in COGENT, a high-order finite-volume gyrokinetic code and test the accuracy, convergence, and computational cost of these semi-implicit methods for test cases with highly-collisional plasmas.},
doi = {10.1007/s10915-018-0726-6},
journal = {Journal of Scientific Computing},
number = ,
volume = ,
place = {United States},
year = {Sat May 12 00:00:00 EDT 2018},
month = {Sat May 12 00:00:00 EDT 2018}
}

Journal Article:
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