Plasma and Fusion Research

Volume 14, 2402033 (2019)

Regular Articles

Measurement of End-Loss Ions Originated from Spontaneously Excited High Frequency Waves by Using an MCP Detector on GAMMA 10/PDX
Koki IZUMI, Ryuya IKEZOE1), Makoto ICHIMURA, Mafumi HIRATA, Mizuki SAKAMOTO, Shuhei SUMIDA, Seowon JANG, Atsuto TANAKA, Yushi KUBOTA, Ryo SEKINE, Hiroki KAYANO and Yousuke NAKASHIMA
Plasma Research Center, University of Tsukuba, Tsukuba 305-8577, Japan
1)
Research Institute for Applied Mechanics, Kyushu University, Kasuga 816-8580, Japan
(Received 30 September 2018 / Accepted 9 January 2019 / Published 12 February 2019)

Abstract

Effective ICRF heating creates a high ion-temperature plasma with strong ion-temperature anisotropy in the GAMMA 10/PDX central cell, where several Alfvén-ion-cyclotron (AIC) waves are spontaneously excited. It is clearly measured with a microwave reflectometer installed in the central cell that waves with the difference frequencies of the AIC waves are excited in a core region. In addition, it has been observed with an end-loss high-energy ion detector that high-energy ions of over 6 keV are axially transported along the magnetic field lines with the same frequencies as the difference frequencies of the AIC waves. In this study, in order to understand the related wave-particle interaction, another end-loss high-energy ion detector using a micro-channel plate has been developed. By changing the ion retarding grid voltage, which the new detector equips, it is found that an energy dependence exists in the loss mechanism; some frequencies that the axial transport includes disappear for high-energy ions of over 6 keV while they are significant for low-energy ions. In addition, by changing the radial position of the new detector, a radial localization of the axial transport to a core region, which is consistent with the profile of the difference frequencies waves, is indicated.

Keywords

GAMMA 10/PDX, high-energy ion, Alfvén-ion-cyclotron wave, low-frequency wave, wave-particle interaction

DOI: 10.1585/pfr.14.2402033

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