Experimental and numerical modeling of plasma start-up assisted by electron drift injection on J-TEXT

Abstract Start-up is one of the critical phases for tokamak discharge. The electron drift injection (EDI) system has been developed on J-TEXT for start-up studies. The experiment of breakdown with EDI assisted has been conducted, which verified the effect of pre-ionization by EDI to achieve start-up at a lower Ohmic field voltage. A 0-dimensional model has been developed to explain the effect of EDI quantitatively. The comparison between the experiment and simulation verified the credibility of this model. Based on this model, the comparison between pure Ohmic heating start-up and EDI assisted start-up was presented, showing that EDI improved ionization, causing lower delay to the peak of hydrogen ionization and radiation losses and the electron and ion energy to rise more smoothly. This result verified the pre-ionization effect of the EDI to start-up quantitatively. The effects of injecting different currents and electron energy were investigated. The better pre-ionization effect can be realized by improving injected current, which can be a reference to the upgrading of EDI system.