Higher harmonic ECE spectrum and its change during ECRH in LHD

The calculation of the electron cyclotron emission (ECE) spectrum with the non thermal electron component is enabled solving the radiation transfer equation along the line of sight including the bi-Maxwellian distribution function. Such calculated ECE spectra are compared with the experimental ones during the high power electron cyclotron heated low density plasma where the high energy electrons in the range up to 100 keV are observed by the hard X-ray pulse height analysis. It is indicated that the ECE intensity lies in the thermal level due to the reabsorption at optically thick region, but becomes non-thermal from the relativistic down shifted emission at optically thin region. These results show that non-thermal ECE can be used to estimate the high energy electrons produced by the high power electron cyclotron heating. (author)