Benchmark of the bootstrap current simulation in helical plasmas

TL;DR

This paper benchmarks different local drift-kinetic equation solvers to evaluate the impact of parallel momentum conservation on bootstrap current calculations in nonaxisymmetric, helical plasmas, confirming the reliability of ZOW and PENTA models.

Contribution

It extends the ZOW model to include ion parallel mean flow effects and compares it with DKES and PENTA, highlighting the importance of momentum conservation in bootstrap current evaluation.

Findings

ZOW and PENTA models agree well on bootstrap current calculations.

DKES results deviate significantly without parallel momentum conservation.

The study verifies the reliability of ZOW and PENTA models for helical plasmas.

Abstract

The importance of the parallel momentum conservation on the bootstrap current evaluation in nonaxisymmetric systems is demonstrated by the benchmarks among the local drift-kinetic equation solvers, i.e., the Zero-Orbit-width(ZOW), DKES, and PENTA codes. The ZOW model is extended to include the ion parallel mean flow effect on the electron-ion parallel friction. Compared to the DKES model in which only the pitch-angle-scattering term is included in the collision operator, the PENTA model employs the Sugama-Nishimura method to correct the momentum balance. The ZOW and PENTA models agree each other well on the calculations of the bootstrap current. The DKES results without the parallel momentum conservation deviates significantly from those from the ZOW and PENTA models. This work verifies the reliability of the bootstrap current calculation with the ZOW and PENTA models for the helical plasmas.