Divertor Simulation Studies by generating High Heat Flux Plasmas

本研究的目标如下：L。等离子体诊断快速扫描探针系统的建立；2.高热流密度等离子体产生原理的证明；3.偏滤器等离子体与面向等离子体材料界面形成鞘层特性的实验和理论分析。成功构建了用于高热流密度等离子体诊断的快速扫描探头。扫描长度为20厘米，往返时间为0.8秒，起始位置水平方向可改变15厘米，垂直方向可改变10厘米。可每隔2 mm测量一次探头特性。该系统适用于密度高达6×10~(-3)m~(-3)的等离子体。为高热流密度等离子体发生器成功地建立了间接加热的大型实验室、圆盘阴极。使用该阴极组件，在100A的稳态放电下，获得了电流，其中等离子体密度达到5×10~(-1)~(-3)~(-3)，电子温度约为10ev，直径可达12厘米。建立了双电温等离子体的鞘层理论。用热电子发射器在高重复率托卡马克中产生含有两个电子组分的等离子体。实验表明，具有较高二次电子发射系数的材料，如金，对鞘电压有明显的抑制作用，而表面条件对碳、钨、钼的影响较大。

Objectives of this research are as follows : l. Construction of fast scanning probe system for plasma diagnostics ; 2. Proof of principle of generation of high heat flux plasmas ; 3. Experimental and theoretical analysis of sheath characteristics formed at the interface between divertor plasma and plasma facing materials.1. Fast scanning probe is successfully constructed for high heat flux plasma diagnostics. The scanning length is 20cm, its time for go and return is 0.8sec, and the starting position can be changed by 15cm in horizontal direction and by 10cm in vertical one. The probe characteristics can be taken every 2mm. This system was found to be applicable for plasmas whose density is up to 6xlO^<19>m^<-3>.2. Indirectly heated large LaB, , disc cathode is successfully established for high, heat flux plasma generator. Up to 100A steady state discharge, current has been obtained by using the above cathode assembly, in which the plasma density reaches 5xlO^<18>m^<-3> and the electronic temperature is about lOeV with the diameter of as much as 12cm.3. Sheath theory for two electric temperature plasma was established. The plasma with two component of electrons is generated in a high repetition tokamak using a themoelectron emitter. The experiments show that the suppression of sheath voltage is observed for the materials having high secondary electron emission coefficient, like gold, and that the surface conditions are important for carbon, W, and Mo.