0-D modeling of SST-1 plasma break-down & start-up using ECRH assisted pre-ionization

Abstract

Electron cyclotron resonance (ECRH) assisted break-down and start-up is considered as useful tool towards the discharge initiation in superconducting tokamaks, where the vacuum vessels and the cryostats are usually electrically continuous with thick walls. ECH pre-ionizations are known to reduce the required central solenoid swing induced toroidal electric field, E significantly. The Steady state superconducting tokamak (SST-1, R=1.1m, a=0.2m) has achieved successful plasma break-down and subsequent current ramp-up with ECH pre-ionizations in both fundamental mode and second harmonic modes with E∼0.35V/m. This work has discussed an appropriate simulation model and validated its results with experiments for the ECRH assisted breakdown and start-up, for both 1st harmonic ordinary mode (O1) and 2nd harmonic extra-ordinary mode (X2), in SST-1 for hydrogen plasmas, where the loop voltage is limited to 0.35V/m. The simulation model is a zero-dimensional (0-D) model. In this model five temporal equations are solved for spatially-uniform plasma. The primary findings of this investigation has been the determination of the threshold ECRH power for successful pre-ionization of plasma in SST-1 and validations of the results with experimental findings in SST-1