STUDY OF ENERGETIC ELECTRONS DURING LOWER HYBRID CURRENT DRIVE EXPERIMENTS AT 2.45 GHZ FROM MEASUREMENTS OF SYNCHROTRON RADIATION SPECTRA IN THE PLT TOKAMAK

The spectrum of the synchrotron radiation in the extraordinary mode is measured using a rapid scanning Michelson interferometer during lower hybrid current drive experiments at 2. 45 GHz in the PLT tokamak. The total population of the superthermal electrons scales with plasma density n//e as n//e** minus **1**. **8** plus or minus **0**. **2 for n//e less than equivalent to 1. 5 multiplied by 10**1**3 cm** minus **3. When the input radiofrequency power P//R//F is varied from about 50 kW to 400 kW, the total population of the superthermals increases linearly, from about 8 multiplied by 10**1**5 electrons to 2. 8 multiplied by 10**1**6 electrons; T// PERPEND //m//i//n remains constant at about 80 kev, when P//R//F less than equivalent to 155 kW, and thereafter it decreases almost linearly to about 50 kev, when P//R//F approximately equals 400 kW. The population of the superthermal electrons is found to be maximum for a relative phasing between the waveguides of about 45-60 degree ; the minimum perpendicular temperature is insensitive to the variation of this phasing.