A Michelson type interfermeter using two different wave-length, 10.6 μm (Co2 laser), 0.633 μm (He Ne laser), has been investigated for plasma density measurement of STP-2 apparatus. It is demonstrated that the two different beams enable to cancel effects of mechanical oscillations which appear between the optical paths. Consequently, fringe shifts due to plasma density variation up to 1/100 can be discriminated.
Recent studies on electron cyclotron radiation from toroidal plasma are summarized, laying emphasis on plasma dispersion effects. The spectra of electron cyclotron radiation are computed for high density tokamaks, using a correct absorption coefficient. The present new theory of the perpendicular propergation for the second harmonic extraordinary mode is based on the relativistic dispersion relation which has not been treated in the existed theoretical papers.