大功率射频负离子源等离子体发光监测系统的研制

Development of plasma light monitoring system for high-power radio frequency negative ion source

基于射频波驱动的负离子源已成为未来中性束注入系统的首选方案。为监测大功率射频负离子源的各个激励器的等离子体放电状态,设计并搭建了基于光电二极管的等离子体发光监测系统。等离子体发光强度与特定碰撞发生次数、碰撞粒子密度、碰撞粒子能量等密切相关。因此,等离子体发光强度能够定性反映出等离子体参数;基于合理的碰撞辐射模型,同时通过分析等离子体特征谱线强度,能够定量地得到等离子体参数。据此,该系统通过实时采集不同位置的等离子体发光强度信息,并以电压信号形式展现并保存下来,用于上位机实时监测和后数据处理。实验结果表明:本系统能够准确、在线地测量射频激励器内的等离子体的激发、维持和熄灭过程,且等离子体发光强度与射频爬坡放电功率具有较好的线性度,并测试了等离子体电流产生的过滤磁场对等离子体发光信号的影响。

[Background]Negative ion sources driven by radio frequency(RF)waves have become the preferred solution for future neutral beam injection systems.[Purpose]This study aims to monitor the plasma discharge state of each exciter of a high power RF negative ion source by developing a plasma luminescence monitoring system based on a photodiode is designed and constructed.[Methods]The intensity of plasma emission was closely related to the number of specific collisions,collision particle density,and collision particle energy.Therefore,the intensity of plasma emission was applied to monitoring plasma parameters qualitatively,and a photodiode-based multichannel plasma luminescence monitoring system was designed and implemented to monitor the plasma discharge state of each exciter of a high power RF negative ion source.Based on a reasonable collision radiation model,plasma parameters were quantitatively obtained by analyzing the intensity of plasma characteristic spectral lines,and the influence of the filtering magnetic field generated by plasma current on plasma emission signals as experimental tested.[Results]Experimental results this monitoring system demonstrate that the real-time intensity information of plasma emission from different positions is successfully collected,and subsequently presented and saved in the form of voltage signals for real-time monitoring and post-data processing by the host computer.The intensity of plasma emission has a good linearity with RF discharge power.[Conclusions]The plasma light monitoring system of this study can accurately and real-time measure the excitation,maintenance,and extinction processes of plasma in the RF exciter.