05aE31PGAMMA10アンカー部における高周波密度揺動の振る舞いと定量評価に向けた取り組み
Behavior of high-frequency density fluctuation in the GAMMA10 anchor celland a trial toward its quantitative evaluation
岡田拓也1, 池添竜也1, 市村真1, 平田真史1, 横山拓郎1, 飯村拓真1, 齋藤裕希1, 岩本嘉章1
隅田脩平1, 渡邊和征1, 吉川正志1, 小波蔵純子1, 嶋頼子1
OKADA Takuya1, IKEZOE Ryuya1, ICHIMURA Makoto1, HIRATA Mafumi1
YOKOYAMA Takuro 1, IIMURA Takuma1, SAITO Yu-ki1 et al.
筑波大学 プラズマ研究センター1
Plasma Research Center, University of Tsukuba1
ICRF power directly to the anchor cell as shown inFig. 1 (a), the line density increases remarkably andthe AIC mode is spontaneously excited near 9.0
MHz as shown in Fig. 1 (b). To investigate thedetailed character of the AIC mode and thedifference between central and anchor cells, we areaiming at evaluating the electric field intensity of
the AIC modes. We have tried to separate the phasemodulation component from the amplitude
modulation component included in the density
fluctuation of the MHz range by using heterodyne
detection method.
(a)(b)
Frequency (MHz)In the GAMMA10 tandem mirror,ion-cyclotron range of frequency (ICRF) waves
have been used for plasma production, heating andsustainment of MHD stability. In a high power
ICRF experiment on the GAMMA10 tandem mirror,
plasma with beta of a few percentage and strong
temperature-anisotropy is produced in the central
cell. As a result of the heating, the excitation of an
Alfvén-ion-cyclotron (AIC) mode has been
observed. On recent experiments in which anchor
cell plasma was directly heated by an additional
ICRF heating system, the AIC mode was excited
also in the anchor cell, indicating the successfulheating and resultant formation of high-temperatureplasma with anisotropy in the anchor cell.
The frequencies of the AIC modes excited inthe GAMMA10 central cell are between 5.6 MHz –6.0 MHz, just below the frequency of 6.36 MHz
which is used for the ICRF heating on the central
cell. On the other hand, the frequency of the AIC
mode excited in the anchor cell is about 9MHz,
which is outside the frequency range of the AIC
modes in the central cell; it is the ion cyclotron
frequency near the midplane of the anchor cell. In
the frequency spectrum, furthermore, there is adifferent feature between the AIC modes in thecentral cell and the AIC mode in the anchor cell.
While several sharp peaks are observed in thecentral cell, single peak is observed in the anchorcell. (Sometimes two peaks are observed.) Thisdifference may be attributed to the axial width of
the strong temperature-anisotropy region; theanchor cell has narrower mirror field region thanthat of the central cell.
We observed the excitation of the AIC modeby using a reflectometer. Figure 1 shows the line
density of the anchor cell where an additional ICRF
heating was applied and the frequency spectrum ofa reflectometer signal. By applying the additional

10.5
10.0

9.5
9.0

8.5

Externally applied ICRF waves
for heating
AIC mode160

180200Time (ms)Fig. 1. (a) Line density of the anchor cell and (b)the frequency spectrum of a reflectometer signals.
Acknowledgments
This work was partly supported by a Grant-in-Aid for
Scientific Research from JSPS, Japan (No. 25400531)
and by the bidirectional collaborative research
programme of the National Institute for Fusion
Science, Japan (NIFS12KUGM067).