Thermal electron cyclotron emission measurement on the Aditya tokamak by radiometers

Thermal electron cyclotron emission (ECE) is measured on a medium size Aditya tokamak by a multi-channel Ka-band radiometer and another multi-channel E-band radiometer. The optically thick second harmonic Ka-band radiometer measured signal is affected by the right-hand cutoff effect beyond ~25 ms. Due to this cutoff, the electron temperature cannot be measured beyond this time. The plasma density is evaluated for the cutoff frequency channel. It is not possible to also determine the electron temperature from the third harmonic optically thin E-band measurements. Yet these measurements are useful to study sawtooth oscillation phenomena. The sawtooth period and amplitude dependence on measurable plasma parameters are determined and new scaling laws are established for Aditya plasma sawtooth. The propagation delays of inverse sawtooth at different radial channels are used to determine thermal diffusivity. The measured diffusivity ( ) is found and compared with , which is determined from power balance of background Aditya plasma. The ratio is 2–3 for the Aditya plasma discharge. This ratio is comparable with a previous study of heat diffusion on medium size tokamaks.