Studies of GAMMA 10 ECRH Characteristics from the Soft X-Ray Measurement

We examined the difference of the heating characteristic by the injection condition of the ECRH from the measurement of the soft X-rays representing the electron temperature. The line integrated intensity of soft X-ray (IsxL) in X-mode ECRH (the best absorption) increased to 5.8 times of that without ECRH and 3.4 times in O-mode (the worst absorption). The MCP signal ratio of the different absorbers (Pe2/Pe1.5) increased from 0.43 before ECRH to 0.56 during ECRH of X-mode and from 0.47 to 0.52 in O-mode. It is confirmed the electron heating by ECRH qualitatively in both cases. However the ion stored energy decreased in O-mode ECRH. This results show that it is important to maximize the first pass RF absorption at the resonance layer on axis for the efficient electron heating and avoidance of the confinement degradation of plasma.