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Influence of Nitrogen Ratio on Plasma Detachment during Combined Seeding with Hydrogen on Divertor Simulation Experiment of GAMMA 10/PDX

Hiroki GAMO, Naomichi EZUMI, Tsukasa SUGIYAMA, Kunpei NOJIRI, Ayane KONDO, Mafumi HIRATA, Junko KOHAGURA, Masayuki YOSHIKAWA, Yousuke NAKASHIMA, Dogyun HWANGBO, Mizuki SAKAMOTO, Renato PERILLO¹⁾, Tatsuya KUWABARA²⁾, Hirohiko TANAKA²⁾, Noriyasu OHNO²⁾, Keiji SAWADA³⁾, Akira TONEGAWA⁴⁾ and Suguru MASUZAKI⁵⁾

Plasma Research Center, University of Tsukuba, Tsukuba, Ibaraki 305-8577, Japan

1)

University of California San Diego, California 92093-0411, USA

2)

Graduate School of Engineering, Nagoya University, Nagoya, Aichi 464-8603, Japan

3)

Faculty of Engineering, Shinshu University, Nagano 380-8553, Japan

4)

Graduate School of Science, Tokai University, Hiratsuka, Kanagawa 259-1292, Japan

5)

National Institute for Fusion Science, Toki, Gifu 509-5292, Japan

(Received 27 November 2020 / Accepted 25 January 2021 / Published 19 March 2021)

Abstract

Influences of nitrogen ratio on plasma detachment and molecular activated recombination (MAR) processes during combined seeding with hydrogen have been investigated utilizing end-loss plasma in the GAMMA 10/PDX tandem mirror. Additional gases were injected under the condition that hydrogen partial pressure was fixed and nitrogen partial pressure was changed from 0% - 10% compared to that of hydrogen. Electron density and ion flux further decrease with increasing nitrogen ratio. In addition, it is suggested that the hydrogen-MAR process that begins with dissociative attachment is suppressed during combined seeding of nitrogen and hydrogen. Observed emission spectrum of NH radicals suggests that the density of NH increases as nitrogen ratio increases and nitrogen-induced MAR efficiently contributes to the reduction of particle flux.

Copyright (c) 2021 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

divertor, detached plasma, nitrogen, MAR, GAMMA 10/PDX

DOI: 10.1585/pfr.16.2402041

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