Isotope Effect on Energy Confinement Time and Thermal Transport in Neutral-Beam-Heated Stellarator-Heliotron Plasmas

H. Yamada, K. Tanaka, R. Seki, C. Suzuki, K. Ida, K. Fujii, M. Goto, S. Murakami, M. Osakabe, T. Tokuzawa, M. Yokoyama, M. Yoshinuma, and LHD Experiment Group

Phys. Rev. Lett. 123, 185001 – Published 29 October 2019

Abstract

The isotope effect on energy confinement time and thermal transport has been investigated for plasmas confined by a stellarator-heliotron magnetic field. This is the first detailed assessment of an isotope effect in a stellarator heliotron. Hydrogen and deuterium plasmas heated by neutral beam injection on the Large Helical Device have exhibited no significant dependence on the isotope mass in thermal energy confinement time, which is not consistent with the simple gyro-Bohm model. A comparison of thermal diffusivity for dimensionally similar hydrogen and deuterium plasmas in terms of the gyroradius, collisionality, and thermal pressure has clearly shown robust confinement improvement in deuterium to compensate for the unfavorable mass dependence predicted by the gyro-Bohm model.

Received 2 July 2019
Revised 30 August 2019

DOI:https://doi.org/10.1103/PhysRevLett.123.185001

Physics Subject Headings (PhySH)

Magnetic confinement fusion Plasma fusion Plasma turbulence

Plasma Physics

Authors & Affiliations

H. Yamada ^1,2, K. Tanaka^1,3, R. Seki^1,4, C. Suzuki¹, K. Ida ¹, K. Fujii ⁵, M. Goto^1,4, S. Murakami ⁵, M. Osakabe^1,4, T. Tokuzawa ^1,4, M. Yokoyama ^1,4, M. Yoshinuma ¹, and LHD Experiment Group¹

¹National Institute for Fusion Science, National Institutes of Natural Sciences, Toki, Gifu 509-5292, Japan
²The University of Tokyo, Kashiwa, Chiba 277-8568, Japan
³Kyushu University, Kasuga, Fukuoka 816-8580, Japan
⁴SOKENDAI (The Graduate University for Advanced Studies), Toki, Gifu 509-5292, Japan
⁵Kyoto University, Kyoto 615-8530, Japan