EAST托卡马克中性气压原位测量实验研究

Experimental Study on the In-Situ Measurement of the Neutral Pressure in EAST Tokamak

偏滤器区域的中性粒子密度及其分布,对研究等离子体与壁相互作用的物理过程具有重要意义。偏滤器区域的强磁场及强电磁干扰导致常规规管难以稳定工作,无法实现对中性粒子密度的原位测量。在EAST托卡马克装置搭建了一套热阴极电离规(快规)诊断系统,并开展了中性气压原位测量研究。利用相敏检测技术,实现强磁场及强电磁场干扰中10 nA-10μA微弱信号的准确测量。在0.35 T磁场条件下完成了1×10^(-3)-1 Pa范围的气压标定,快规输出结果与气压呈现良好的线性关系。实验结果显示相同气压条件下,离子流与灯丝发射电流呈线性关系,强磁场(0.35 T以上)能够显著提高快规灵敏度。在0-1.4 T的实验条件下,快规诊断系统-均能正常工作。快规量程范围覆盖偏滤器区域中性气压变化,满足偏滤器区域中性气压原位测量需求,为EAST及未来聚变堆偏滤器物理研究提供了有力的工具。

The density and distribution of neutral particles in the divertor region are very important for studying plasma physics on plasma-wall interaction.The strong magnetic field and electromagnetic environment in the divertor make it difficult to accurately measure the neutral particles density by the normal gauge.This leads to hard in-situ measurement of neutral particle density.A hot cathode ionization gauge(fast ionization gauge)diagnostic system was employed in EAST Tokamak,and experimental studies of in-situ measurement of neutral pressure were carried out.Phase-sensitive detection technology is used to detect the very weak signal in the range of 10 nA-10μA under a strong electromagnetic environment.The fast ionization gauge was calibrated in the range of 1×10^(-3)-1 Pa under a 0.35 T magnetic field,and it has a good linear relationship with the pressure.The ion current is also proportional to the filament emission current under the same pressure.Moreover,the sensitivity of the fast gauge will be significantly improved at>0.35 T.The results show that the fast ionization gauge diagnostic system works very well in 0-1.4 T magnetic fields,and its measurement covers the neutral pressure range of the divertor region.The fast ionization gauge meets the requirement of in-situ measurement of neutral pressure in the divertor region,which provides a powerful tool for studies on divertor physics in EAST and future fusion reactors.