HT-7托卡马克等离子体slide-away放电研究

Investigation of slide-away discharges in HT-7 tokamak

在HT-7托卡马克上,只在等离子体放电击穿阶段充气,击穿后关闭充气阀门,让装置内真空室器壁的出气维持放电的进行,通过密度衰减实现了slide-away放电.实验分析了不同等离子体电流平台下的slide-away放电模式的密度阈值,以及相同充气量的条件下放电等离子体电流对实现slide-away放电的影响.研究了slide-away放电模式下密度提升对等离子体放电状态的影响.结果发现,slide-away放电模式下的密度提升使得Ha线辐射强度增强,等离子体中超热电子的约束性能变差,等离子体芯部的超热电子减少,高能逃逸电子厚靶轫致辐射增加.

In tokamak plasmas,the discharge will turn into＂runaway＂discharge if the density decays to a critical one. The discharge will enter into ＂slide-away ＂ discharge if the density reaches a lower level. The slide-away discharge is characterized by high confinement of superthermal electrons which constitute a large part of plasma current. In HT-7 Tokamak,the slide-away discharge is achieved by reducing the plasma density. The relationship between plasma current and critical density of slide-away discharge is investigated. It is also find that the increase of density in slide-away discharge can make the confinement of superthermal electrons poor and lots of superthermal electrons lost from the vacuum chamber.