TY - JOUR
T1 - Production and confinement characteristics of ICRF-accelerated energetic ions in JT-60U negative-shear plasmas
AU - Kusama, Y.
AU - Kimura, H.
AU - Nemoto, M.
AU - Hamamatsu, K.
AU - Tobita, K.
AU - Oikawa, T.
AU - Afanassiev, V. I.
AU - Morioka, A.
AU - Fujita, T.
AU - Koide, Y.
AU - Kondoh, T.
AU - Moriyama, S.
AU - Saigusa, M.
PY - 1999/5
Y1 - 1999/5
N2 - 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$/ resonance in the positive-shear plasma. A larger scale length of pressure profile in the negative-shear plasma compensates for a lower density of tail ions than that in the positive-shear plasma. Accordingly, negative-shear plasmas can contain comparable stored energy of energetic tail ions to positive-shear plasmas.
AB - Characteristics of energetic ion tail formation during the second-harmonic ion cyclotron range of frequency (2ω-CH$/ 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.
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U2 - 10.1088/0741-3335/41/5/305
DO - 10.1088/0741-3335/41/5/305
M3 - Article
AN - SCOPUS:0032628092
SN - 0741-3335
VL - 41
SP - 625
EP - 643
JO - Plasma Physics and Controlled Fusion
JF - Plasma Physics and Controlled Fusion
IS - 5
ER -