On coupling fluid plasma and kinetic neutral physics models
Abstract
The coupled fluid plasma and kinetic neutral physics equations are analyzed through theory and simulation of benchmark cases. It is shown that coupling methods that do not treat the coupling rates implicitly are restricted to short time steps for stability. Fast charge exchange, ionization and recombination coupling rates exist, even after constraining the solution by requiring that the neutrals are at equilibrium. For explicit coupling, the present implementation of Monte Carlo correlated sampling techniques does not allow for complete convergence in slab geometry. For the benchmark case, residuals decay with particle number and increase with grid size, indicating that they scale in a manner that is similar to the theoretical prediction for nonlinear bias error. Progress is reported on implementation of a fully implicit Jacobianfree Newton–Krylov coupling scheme. The present block Jacobi preconditioning method is still sensitive to time step and methods that better precondition the coupled system are under investigation.
 Authors:
 Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
 Publication Date:
 Research Org.:
 Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
 Sponsoring Org.:
 USDOE
 OSTI Identifier:
 1347040
 Alternate Identifier(s):
 OSTI ID: 1349230; OSTI ID: 1366930
 Report Number(s):
 LLNLJRNL697766
Journal ID: ISSN 23521791; PII: S2352179116302149
 Grant/Contract Number:
 AC5207NA27344; 15ERD059; AC0209CH11466
 Resource Type:
 Journal Article: Published Article
 Journal Name:
 Nuclear Materials and Energy
 Additional Journal Information:
 Journal Volume: 12; Journal ID: ISSN 23521791
 Publisher:
 Elsevier
 Country of Publication:
 United States
 Language:
 English
 Subject:
 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Divertor modeling; Charge exchange; Ionization; Recombination; Implicit; Newton–Krylov; UEDGE; DEGAS2; EIRENE; SOLPS; 74 ATOMIC AND MOLECULAR PHYSICS; 70 PLASMA PHYSICS AND FUSION
Citation Formats
Joseph, I., Rensink, M. E., Stotler, D. P., Dimits, A. M., LoDestro, L. L., Porter, G. D., Rognlien, T. D., Sjogreen, B., and Umansky, M. V. On coupling fluid plasma and kinetic neutral physics models. United States: N. p., 2017.
Web. doi:10.1016/j.nme.2017.02.021.
Joseph, I., Rensink, M. E., Stotler, D. P., Dimits, A. M., LoDestro, L. L., Porter, G. D., Rognlien, T. D., Sjogreen, B., & Umansky, M. V. On coupling fluid plasma and kinetic neutral physics models. United States. doi:10.1016/j.nme.2017.02.021.
Joseph, I., Rensink, M. E., Stotler, D. P., Dimits, A. M., LoDestro, L. L., Porter, G. D., Rognlien, T. D., Sjogreen, B., and Umansky, M. V. Wed .
"On coupling fluid plasma and kinetic neutral physics models". United States.
doi:10.1016/j.nme.2017.02.021.
@article{osti_1347040,
title = {On coupling fluid plasma and kinetic neutral physics models},
author = {Joseph, I. and Rensink, M. E. and Stotler, D. P. and Dimits, A. M. and LoDestro, L. L. and Porter, G. D. and Rognlien, T. D. and Sjogreen, B. and Umansky, M. V.},
abstractNote = {The coupled fluid plasma and kinetic neutral physics equations are analyzed through theory and simulation of benchmark cases. It is shown that coupling methods that do not treat the coupling rates implicitly are restricted to short time steps for stability. Fast charge exchange, ionization and recombination coupling rates exist, even after constraining the solution by requiring that the neutrals are at equilibrium. For explicit coupling, the present implementation of Monte Carlo correlated sampling techniques does not allow for complete convergence in slab geometry. For the benchmark case, residuals decay with particle number and increase with grid size, indicating that they scale in a manner that is similar to the theoretical prediction for nonlinear bias error. Progress is reported on implementation of a fully implicit Jacobianfree Newton–Krylov coupling scheme. The present block Jacobi preconditioning method is still sensitive to time step and methods that better precondition the coupled system are under investigation.},
doi = {10.1016/j.nme.2017.02.021},
journal = {Nuclear Materials and Energy},
number = ,
volume = 12,
place = {United States},
year = {Wed Mar 01 00:00:00 EST 2017},
month = {Wed Mar 01 00:00:00 EST 2017}
}

The coupled fluid plasma and kinetic neutral physics equations are analyzed through theory and simulation of benchmark cases. It is shown that coupling methods that do not treat the coupling rates implicitly are restricted to short time steps for stability. Fast charge exchange, ionization and recombination coupling rates exist, even after constraining the solution by requiring that the neutrals are at equilibrium. For explicit coupling, the present implementation of Monte Carlo correlated sampling techniques does not allow for complete convergence in slab geometry. For the benchmark case, residuals decay with particle number and increase with grid size, indicating that theymore »

On coupling fluid plasma and kinetic neutral physics models
The coupled fluid plasma and kinetic neutral physics equations are analyzed through theory and simulation of benchmark cases. It is shown that coupling methods that do not treat the coupling rates implicitly are restricted to short time steps for stability. Fast charge exchange, ionization and recombination coupling rates exist, even after constraining the solution by requiring that the neutrals are at equilibrium. For explicit coupling, the present implementation of Monte Carlo correlated sampling techniques does not allow for complete convergence in slab geometry. Furthermore, for the benchmark case, residuals decay with particle number and increase with grid size, indicating thatmore » 
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