26aE11P
ヘリオトロン J における水素同位体効果解明を目指した密度変調実験
Density modulation experiment for clarification of Hydrogen isotope effects in
Heliotron J
大谷 芳明 1, 田中 謙治 2, 南 貴司 3, 大島 慎介 3, 向井 清史 2, 岸川 英樹 1,
N. Asavathavornvanit1, 秋山 毅志 2, 長崎 百伸 3, 中村 祐司 1, 岡田 浩之 3, 門 信一郎 3,
小林 進二 3, 山本 聡 3, 木島 滋 3, G. M. Weir3, 釼持 尚輝 1, X. Lu1, 小田 大輔 1, 中野 裕一郎 1,
松田 啓嗣 1, 羽田 和慶 1, 村上 弘一郎 1, 神野 洋介 1, 塚崎 僚 1, 水内 亨 3
Y. Ohtani1, K. Tanaka2, T. Minami3, S. Ohshima3, K. Mukai2, et al.
1京大エネ科, 2 核融合研, 3 京大エネ研
1GSES, 2NIFS, 3IAE

Understanding the isotope effects on transport is oneof the important issues to predict the performance offuture DT fusion reactor. In Heliotron J, we studied theisotope effects between hydrogen and deuterium
plasma on particle transport of ECH heated plasma.
The experiment was performed for the line-averaged
density 0.6 × 1019 m-3 with 252 kW 70GHz second
harmonic heating with |B| ≈ 1.3 T. The fueling ratio, which
was defined as nH/(nH+nD), was approximately 10 % in thedeuterium plasma and 80 % in the hydrogen plasma.

The different decay time of the line-averaged density
after turning off the external gas fueling was found. The
decay time is 12.8 ms and 15.9 ms for the hydrogenplasma and the deuterium plasma, respectively. The
longer decay time in the deuterium plasma suggests
better particle confinement than in the hydrogenplasma. However, the different wall recycling cancause the different decay time as well.
Therefore, in order to investigate difference of theparticle transport without recycling effects, density
modulation experiments were performed. From thedensity modulation experiments, the diffusion
coefficient (Dmod) and convection velocity (Vmod) areestimated separately. Also, difference of the particle
source rate does not affect the estimation of Dmod andVmod [1]. Particle balance equation of the modulation
components are solved. Then, the optimized Dmod andVmod are estimated. The estimated Dmod and Vmod
account for the experimental observed modulation
amplitude and phase [2].
Two channels of interferometer were used. One is a
microwave interferometer at = 0.05 and the other is
FIR interferometer at = 0.35 [3]. Three different
modulation frequencies (50, 100 and 125 Hz) wereused in order to increase the constraint to estimate Dmodand Vmod.
Figure 1 shows phase difference and modulation
amplitude ratio between the line-averaged densities
from two channels. In the case of 50 Hz, both themodulation amplitude ratio and the phase difference inthe deuterium plasma were clearly higher than those in
the hydrogen plasma. Figure 2 shows the estimatedDmod and Vmod using three modulation frequencies. Theconvection velocities for both plasmas direct to inward
and the absolute value for the deuterium plasma issmaller than that for the hydrogen plasma. The
diffusion coefficient of the deuterium plasma is smaller
than that of the hydrogen plasma. This suggests particle
confinement is better in deuterium plasma than inhydrogen plasma.
[1] K. W. Gentle Plasma Phys. Control. Fusion 29 1077 (1987)[2] K. Tanaka et al., Plasma Sci. and Tech. Vol. 8, No. 1 (2006) 65[3] Y. Ohtani et al., Plasma Fusion Res. acceptedFig. 1. (a) Amplitude ratio and (b) phase difference
calculated from the experiment.

Fig. 2. First result of particle transport for deuterium
plasma and hydrogen plasma