Production and confinement characteristics of ICRF-accelerated energetic ions in JT-60U negative-shear plasmas

Y. Kusama, H. Kimura, M. Nemoto, K. Hamamatsu, K. Tobita, T. Oikawa, V. I. Afanassiev, A. Morioka, T. Fujita, Y. Koide, T. Kondoh, S. Moriyama, M. Saigusa

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

Abstract

Characteristics of energetic ion tail formation during the second-harmonic ion cyclotron range of frequency (2ω-CH$/ ICRF) heating and confinement of tail ions were investigated in negative magnetic shear plasmas on JT-60U. Charge-exchange neutral particle measurements show significantly lower tail temperature in negative-shear plasmas than those in positive-shear plasmas. The tail temperature in negative-shear plasmas increases with plasma current and shows improvement of energetic ion confinement. Charge-exchange neutral fluxes are also lower in negative-shear plasmas than in positive-shear plasmas. Meanwhile, tail ion stored energy is comparable between negative- and positive-shear plasmas. In order to understand these experimental results, simple modelled calculations were carried out with an orbit-following Monte Carlo (OFMC) code. The model calculations suggest that the ICRF power absorption is dominant near the 2ω-CH$/ resonance in the negative-shear plasma and in the low-field side away from the 2ω-CH$/ resonance in the positive-shear plasma. A larger scale length of pressure profile in the negative-shear plasma compensates for a lower density of tail ions than that in the positive-shear plasma. Accordingly, negative-shear plasmas can contain comparable stored energy of energetic tail ions to positive-shear plasmas.

Original languageEnglish
Pages (from-to)625-643
Number of pages19
JournalPlasma Physics and Controlled Fusion
Volume41
Issue number5
DOIs
Publication statusPublished - 1999 May 1
Externally publishedYes

ASJC Scopus subject areas

  • Nuclear Energy and Engineering
  • Condensed Matter Physics

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