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Title: A higher-order finite-element implementation of the nonlinear Fokker–Planck collision operator for charged particle collisions in a low density plasma

Journal Article · · Computer Physics Communications
ORCiD logo [1];  [2];  [3];  [2];  [3];  [4];  [5];  [6]
  1. Tokamak Energy Ltd., Abingdon (United Kingdom); Univ. of Oxford (United Kingdom); United Kingdom Atomic Energy Authority (UKAEA), Abingdon (United Kingdom)
  2. Univ. of Oxford (United Kingdom)
  3. United Kingdom Atomic Energy Authority (UKAEA), Abingdon (United Kingdom)
  4. United Kingdom Atomic Energy Authority (UKAEA), Abingdon (United Kingdom); Univ. of Warwick, Coventry (United Kingdom)
  5. Univ. of Oxford (United Kingdom); Charles Univ., Prague (Czech Republic)
  6. Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)

Collisions between particles in a low density plasma are described by the Fokker–Planck collision operator. In applications, this nonlinear integro-differential operator is often approximated by linearised or ad-hoc model operators due to computational cost and complexity. In this work, we present an implementation of the nonlinear Fokker–Planck collision operator written in terms of Rosenbluth potentials in the Rosenbluth–MacDonald–Judd (RMJ) form. The Rosenbluth potentials may be obtained either by direct integration or by solving partial differential equations (PDEs) similar to Poisson's equation: we optimise for performance and scalability by using sparse matrices to solve the relevant PDEs. We represent the distribution function using a tensor-product continuous-Galerkin finite-element representation and we derive and describe the implementation of the weak form of the collision operator. We present tests demonstrating a successful implementation using an explicit time integrator and we comment on the speed and accuracy of the operator. Finally, we speculate on the potential for applications in the current and next generation of kinetic plasma models.

Research Organization:
Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
Sponsoring Organization:
Engineering and Physical Sciences Research Council (EPSRC); European Union (EU); USDOE
Grant/Contract Number:
AC02-09CH11466
OSTI ID:
2567501
Journal Information:
Computer Physics Communications, Journal Name: Computer Physics Communications Vol. 314; ISSN 0010-4655
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English

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