To realize an excitation of electron Bernstein waves （EBW） via mode conversion from X-mode waves injected from the high magnetic field side （HFS）, new inner-vessel mirrors were installed close to a helicM coil in ...To realize an excitation of electron Bernstein waves （EBW） via mode conversion from X-mode waves injected from the high magnetic field side （HFS）, new inner-vessel mirrors were installed close to a helicM coil in the large helicM device （LHD）. 77 GHz electron cyclotron （EC） wave beams injected from an existing EC-wave injection system toward the new mirror are reflected on the mirror so that the beams are injected to plasmas from HFS. Evident increases in the electron temperature at the plasma core region and the plasma stored energy were observed by the HFS beam injection to the plasmas with the line-average electron density of 7.5~ 1019 m-3, which is slightly higher than the plasma cut-off density of 77 GHz EC-waves, 7.35~ 1019 m-3. The heating efficiency evaluated from the changes in the time derivative of the plasma stored energy reached ,,~70%. Although so far it is not clear which is the main cause of the heating effect, the mode-converted EBW or the X-mode wave itself injected from the HFS, an effective heating of high-density plasma over the plasma cut-off of EC-wave was successfully demonstrated.展开更多
Experiments on formation of spherical tokamak (ST) plasmas by electroncyclotron heating (ECH) alone without a central OH solenoid have been carried out on LATE (LowAspect ratio Torus Experiments). By injecting a 2.45 ...Experiments on formation of spherical tokamak (ST) plasmas by electroncyclotron heating (ECH) alone without a central OH solenoid have been carried out on LATE (LowAspect ratio Torus Experiments). By injecting a 2.45 GHz microwave pulse of 6.3 kW for 4 seconds, aplasma current is initiated and ramped up to I_p approx= 3 kA, and finally maintained for 1 secondby adjusting the external vertical field. Magnetic measurements show that closed flux surfaces areformed and the last closed flux surface has an aspect ratio of A ～ 1.3 and an elongation of κ～1.3. The electron density measured by an interferometer is more than 1.5 x 10^(11) cm^(-3) whichexceeds twice of the plasma cut-off density, suggesting that electron cyclotron heating bymode-converted electron Bernstein waves may take place.展开更多
基金supported by KAKENHI (Grant-in-Aid for Scientific Research(C), 21560862) of Japan
文摘To realize an excitation of electron Bernstein waves （EBW） via mode conversion from X-mode waves injected from the high magnetic field side （HFS）, new inner-vessel mirrors were installed close to a helicM coil in the large helicM device （LHD）. 77 GHz electron cyclotron （EC） wave beams injected from an existing EC-wave injection system toward the new mirror are reflected on the mirror so that the beams are injected to plasmas from HFS. Evident increases in the electron temperature at the plasma core region and the plasma stored energy were observed by the HFS beam injection to the plasmas with the line-average electron density of 7.5~ 1019 m-3, which is slightly higher than the plasma cut-off density of 77 GHz EC-waves, 7.35~ 1019 m-3. The heating efficiency evaluated from the changes in the time derivative of the plasma stored energy reached ,,~70%. Although so far it is not clear which is the main cause of the heating effect, the mode-converted EBW or the X-mode wave itself injected from the HFS, an effective heating of high-density plasma over the plasma cut-off of EC-wave was successfully demonstrated.
文摘Experiments on formation of spherical tokamak (ST) plasmas by electroncyclotron heating (ECH) alone without a central OH solenoid have been carried out on LATE (LowAspect ratio Torus Experiments). By injecting a 2.45 GHz microwave pulse of 6.3 kW for 4 seconds, aplasma current is initiated and ramped up to I_p approx= 3 kA, and finally maintained for 1 secondby adjusting the external vertical field. Magnetic measurements show that closed flux surfaces areformed and the last closed flux surface has an aspect ratio of A ～ 1.3 and an elongation of κ～1.3. The electron density measured by an interferometer is more than 1.5 x 10^(11) cm^(-3) whichexceeds twice of the plasma cut-off density, suggesting that electron cyclotron heating bymode-converted electron Bernstein waves may take place.
