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Contribution of Hydrogen Molecular Activated Recombination to Plasma Particle Loss in DT-ALPHA

Keigo YOSHIMURA¹⁾, Hiroyuki TAKAHASHI¹⁾, Ryota NISHIMURA¹⁾, Tomoya HARA¹⁾, Shigetaka KAGAYA¹⁾, Tetsutarou OISHI¹⁾, Akinobu MATSUYAMA²⁾, Kenji TOBITA¹⁾

1)

Department of Quantum Science and Energy Engineering, Tohoku University, Sendai 980-8579, Japan

2)

Graduate School of Energy Science, Kyoto University, Uji 611-0011, Japan

(Received 17 July 2024 / Accepted 2 December 2024 / Published 21 February 2025)

Abstract

A hydrogen secondary gas feeding experiment was conducted with hydrogen plasma. A rollover of the electron density and a monotonic decrease in the electron temperature were observed as the amount of the secondary gas increased. The vibrational distribution and temperature of ground electronic hydrogen molecules were evaluated based on the Fulcher-α band spectroscopy. To analyze the contribution of molecular activated recombination (MAR) to plasma particle loss, the reaction rates of the dissociative attachment (DA) and ion conversion (IC) of vibrationally excited hydrogen molecules were calculated. The reaction rate of IC was approximately two orders of magnitude greater than that of DA and significantly increased with the onset of the density rollover. The IC reaction rate remained high even as the electron density decreased. This analysis is limited to the first reactions of MAR; however, the significance of IC-MAR is strongly indicated.

Copyright (c) 2025 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

molecular activated recombination, ion conversion, detached divertor, radio-frequency plasma, DT-ALPHA

DOI: 10.1585/pfr.20.1401015

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