Plasma and Fusion Research

Volume 16, 2403043 (2021)

Regular Articles

Magnetic Configuration and Heating Location Dependences of Toroidal Torques by Electron Cyclotron Heating in LHD
Yasuhiro YAMAMOTO and Sadayoshi MURAKAMI
Department of Nuclear Engineering, Kyoto University, Kyoto 615-8540, Japan
(Received 17 November 2020 / Accepted 28 January 2021 / Published 19 March 2021)

Abstract

Toroidal torque by electron cyclotron heating (ECH) is investigated in the Large Helical Device (LHD) plasmas, assuming the supra-thermal electrons by ECH generate torques on the plasma through jr × B and collisions. The jr × B torque depends on the radial drift velocity and the fraction of trapped electrons. Therefore, the magnetic configuration and the heating location affects the toroidal torque. We investigate the magnetic configuration and heating location dependences of toroidal torques by ECH in LHD, by considering three typical magnetic configurations: the inward shifted, standard, and outward shifted configurations. As a result, magnetic ripple bottom heating generates larger torque than that of ripple top heating because of the large fraction of trapped electrons. Also, heating at the outer minor radius generates larger toroidal torque than that of heating at the inner radius, and the injection angle can also change the toroidal torque profile. Moreover, ECH generates the largest toroidal torque in the outward shifted configuration. Finally, we evaluate the toroidal flow velocities with the obtained toroidal torques. We obtained the largest flow near the axis in the standard configuration because of its small viscosity and large toroidal torque.

Keywords

toroidal flow, ECH, LHD, magnetic configuration, torque, rotation

DOI: 10.1585/pfr.16.2403043

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