1993 Fiscal Year Final Research Report Summary
Control of Tearing Instability and Disruption by RF
| Project/Area Number |
04452311
|
|---|
| Research Category |
Grant-in-Aid for General Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Research Field |
プラズマ理工学
|
|---|
| Research Institution | KYOTO UNIVERSITY |
|---|
Principal Investigator |
YASUSHI Terumichi Kyoto Unive., Science, Associate Prof., 理学部, 助教授 (50025384)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
NAKAMURA Masahiko Osaka Ins.Tech., Associate Prof., 助教授 (50172440)
HANADA Kazuaki Kyoto Univ., Science, Assistant, 理学部, 教務職員 (30222219)
MAEKAWA Takashi Kyoto Univ., Science, Instructor, 理学部, 助手 (20127137)
|
|---|
| Project Period (FY) |
1992 – 1993
|
| Keywords | Tearing Instability / Plasma Disruption / ECH / LHCD / Tokamak |
|---|
| Research Abstract |
1. Tearing instabilities are steadily observed in the range of the safety factor of qa=2.7-3.1 in Ohmic plasmas in the WT-3 tokamak (R0=65 cm, a=20 cm, Bt=1.75 T). Magnetic measurements show that the frequency is f(〕SY.simeq.〔)10 kHz and the poloidal/toroidal mode numbers are m=2/n=1.
2. We investigate the internal structure of the instability and its dynamic behavior by observing the plasmas with five soft X-ray cameras and reconstructing the image of the instability by making use of computer tomography. The results show that there are two modes, i.e., m=1/n=1 mode at r/a=0.3 and m=2/n=1 at r/a=0.75. The m=1/n=1 mode rotates poloidally to the electoron diamagnetic drift direction with the angular velocity just twice of the m=2/n=1 mode. Relative position of the both modes is such that if the both modes are assumed to be described by the two filament currents, two filaments are dynamically in a stable equilibrium.
3. We control the instability by the electron cyclotron heating at the second harmonic resonance by injecting millimeter waves generated with a gyrotron (56 GHz, 200 KW). The instability is suppressed when the second harmonic resonance layr is located on the q=1, or q=2 surface. When the resonance layr is located between the two surfaces, the instability is somewhat enhanced.
4. We investigate the effect of the lower hybrid current drive on the instability with various power spectrum of lower hybrid waves generating with high power phase shifters. With the phasing of pi/2 for forward injection, the instability is suppressed. While, no suppression is observed with the phasing of -pi/2 for reverse injection.
|
