Plasma and Fusion Research

Volume 20, 1203049 (2025)

Rapid Communications

Dependence on the Number of Test Fast Ions of Statistical Errors in Neutral Beam Current Drive Calculation
Kazutoshi YASUI, Takaaki FUJITA, Atsushi OKAMOTO, Yuichi KAWACHI
Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
(Received 23 May 2025 / Accepted 10 July 2025 / Published 15 October 2025)

Abstract

The integrated plasma transport code requires acceleration. This study evaluates the computation time and calculation error when the number of test fast ions in the neutral beam deposition calculation is reduced. The statistical error increases approximately in proportion to the inverse square root of the number of test fast ions. A more detailed analysis reveals that the statistical error depends on the number of fast ions newly generated per slowing-down time of the fast ions. The results provide useful guidelines for selecting the number of test fast ions in neutral beam current drive calculations according to the required calculation time and accuracy.

Keywords

TOTAL, neutral beam injection, simulation, optimization, statistical error

DOI: 10.1585/pfr.20.1203049

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