Kinetic Simulation of Collisional Magnetized Plasmas with Semiimplicit Time Integration
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 weaklycollisional hightemperature 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 semiimplicit additive Runge–Kutta methods in COGENT, a highorder finitevolume gyrokinetic code and test the accuracy, convergence, and computational cost of these semiimplicit methods for test cases with highlycollisional plasmas.
 Authors:

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 Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Center for Applied Scientific Computing
 Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Physics Division
 Publication Date:
 Report Number(s):
 LLNLJRNL735522
Journal ID: ISSN 08857474; 887762
 Grant/Contract Number:
 AC5207NA27344
 Type:
 Accepted Manuscript
 Journal Name:
 Journal of Scientific Computing
 Additional Journal Information:
 Journal Name: Journal of Scientific Computing; Journal ID: ISSN 08857474
 Publisher:
 Springer
 Research Org:
 Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
 Sponsoring Org:
 USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR) (SC21)
 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
 OSTI Identifier:
 1458696
Ghosh, Debojyoti, Dorf, Mikhail A., Dorr, Milo R., and Hittinger, Jeffrey A. F.. Kinetic Simulation of Collisional Magnetized Plasmas with Semiimplicit Time Integration. United States: N. p.,
Web. doi:10.1007/s1091501807266.
Ghosh, Debojyoti, Dorf, Mikhail A., Dorr, Milo R., & Hittinger, Jeffrey A. F.. Kinetic Simulation of Collisional Magnetized Plasmas with Semiimplicit Time Integration. United States. doi:10.1007/s1091501807266.
Ghosh, Debojyoti, Dorf, Mikhail A., Dorr, Milo R., and Hittinger, Jeffrey A. F.. 2018.
"Kinetic Simulation of Collisional Magnetized Plasmas with Semiimplicit Time Integration". United States.
doi:10.1007/s1091501807266.
@article{osti_1458696,
title = {Kinetic Simulation of Collisional Magnetized Plasmas with Semiimplicit 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 weaklycollisional hightemperature 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 semiimplicit additive Runge–Kutta methods in COGENT, a highorder finitevolume gyrokinetic code and test the accuracy, convergence, and computational cost of these semiimplicit methods for test cases with highlycollisional plasmas.},
doi = {10.1007/s1091501807266},
journal = {Journal of Scientific Computing},
number = ,
volume = ,
place = {United States},
year = {2018},
month = {5}
}