Measurement of Single Pass Electron Cyclotron (EC) Absorption Using Transmitted Waves in Heliotron J

Single pass absorption of second-harmonic EC waves propagating obliquely to the magnetic field has been studied in Heliotron J. Two orthogonal signals of transmitted high power EC waves are measured to estimate the single pass absorption rate. The experimental results agree well with ray tracing calculation results based on a linear absorption theory under the condition that the refraction effect is not strong, ne/nc < 0.3 (nc is a cut-off density of second-harmonic X-mode), that is, the waves reach the diagnostic port.