托卡马克等离子体电子逃逸阈值实验研究

Experimental research of the threshold conditions of runaway electron in tokamk

本文采用统计方法分析了HL-2A托卡马克装置上欧姆放电条件下的实验数据,根据硬X射线出现时刻的等离子体环电压、中心线平均等离子体电子密度等参数,计算出电子逃逸的实验阈值,并与初级产生机制下逃逸电子的理论阈值进行对比.实验数据表明逃逸电场阈值明显高于相对论碰撞理论预测,抑制电子逃逸现象的临界电子密度明显比理论预测的低.这与ITPA(International Tokamak Physics Activity)在D3D,TEXTOR,FTU,KSTAR等装置得出的实验结果吻合.针对逃逸现象出现时刻硬X射线增长率的实验研究发现初级产生机制下逃逸电子的增长率与电场强度大小成正比,与中心线平均等离子体电子密度成反比,此现象验证了通过减小环电压或提高等离子体密度的方法可以抑制电子逃逸现象.

The experimental study of onset threshold conditions of runaway electrons was analyzed in ohmic discharge.The plasma loop voltage and line-average electron density of the moment when Hard X-ray appeared were obtained as the runaways threshold.The comparison of the experimental threshold and the theoretical threshold under the primary generation process showed that the threshold electric field is much higher than that predicted by relativistic collisional theory,and the critical electron density of suppressing runaways is significantly lower than the theoretical calculations,which are consistent with the experimental results gotten by ITPA（ International Tokamak Physics Activity） on D3 D,TEXTOR,FTU,KSTAR and so on.It was found that the growth rate of runaways under the Dreicer mechanism grows with the increasing electric field intensity,and decays with the decreasing electron density through the analysis of HXR growth rate in the moment when REs appeared,which demonstrated that the decrease of loop voltage and the increase of electron density could suppress the generation of runaways.