学术报告第158期—张俊利 高远论文投稿报告

时间：2022年3月23日  周三  14:30

地点：313会议室

论文投稿报告

报告人：张俊利  研究生

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

摘要：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 experiment and simulation verified the credibility of this model. Based on this model, the comparison between pure Ohmic heating startup 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 current 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.

报告人：高远 研究生

题目：Investigation of Electron Cyclotron Resonance Heating effect on Sawtooth Instability on J-TEXT

摘要：Localized electron heating produced by electron cyclotron resonance heating (ECRH) system has been proven to be an effective method to control sawtooth instabilities. In this paper, we present the experimental results carried out on J-TEXT tokamak with regard to sawtooth control via ECRH. Systematic ECRH vertical deposition scans from inside to outside the q=1 surface have been performed in two experiment cases with ne = (1-1.5) × 1019m-3, PECRH ~ 200 kW or ne = (2-2.6) × 1019m-3, PECRH ~ 400 kW, respectively. In the former low-density case, it found that the sawtooth is stabilized (characterized by prolonged sawtooth period) whether ECRH deposited inside or outside the q=1 surface. In the latter high-density case, it is found that the sawtooth is destabilized (characterized by reduced sawtooth period) when ECRH deposited inside q=1 surface, and is stabilized when ECRH deposited outside q=1 surface. For both two cases, the maximum sawtooth period is gotten as ECRH deposition around q=1 surface. The pressure gradient, current density profile with various ECRH deposition and the stabilization effect of fast electron on sawtooth are thought to determine the evolution of sawtooth period. Moreover, sawtooth instabilities are accompanied by dual flux tubes when ECRH is deposited inside the q=1 surface, and behave as partial collapse and multi-flux structure when deposited near or just outside the q=1 surface.