高频偏置在STOR-M装置中的应用及其效应
Application of high frequency biasing and its effect in STOR-M tokamak
摘要：
研制了一种脉冲振荡功率放大器，用于向STOR-M托卡马克等离子体边缘电极施加高频偏置电压。该功率放大器可在1 kHz-50 kHz的频率范围内提供高达120 V的峰峰值振荡电压和30 A的电流。电极位于赤道面半径$ρ= 0.88$处。施加电压的频率在放电之间变化。观察到等离子体密度和来自等离子体芯区的软X射线强度通常在1 kHz-5 kHz的较低频率区域以及相对较高的频率区域20 kHz-25 kHz增加，但在它们之间很少增加。在两个频率范围内，从实验数据的推导中观察到$τ_{p}$和$τ_{E}$的增加。利用ASTRA模拟程序对STOR-M托卡马克参数进行了输运模拟，以了解高频分支实验观测背后的物理过程。该模型是基于GAM激发共振频率与Ware-pinch由于振荡电场产生的偏置电压，可以抑制异常输运。模拟结果在密度、粒子约束以及能量约束时间演化方面与实验结果吻合较好。所有这些结果表明，高频偏置能够有效地改善约束。
英文摘要：
A pulsed oscillating power amplifier has been developed to apply high frequency biasing voltage to an electrode at the edge of the STOR-M tokamak plasma. The power amplifier can deliver a peak-to-peak oscillating voltage up to 120V and current 30A within the frequency range of 1kHz-50kHz. The electrode is located in the equatorial plane at radius $ρ= 0.88$. The frequency of the applied voltage has been varied between discharges. It is observed that the plasma density and soft x-ray intensity from the plasma core region usually increase at lower frequency regime 1kHz-5kHz as well as relatively higher frequency regime 20kHz-25kHz but seldom increase in between them. Increment of $τ_{p}$ \& $τ_{E}$ have been observed from the derivations of experimental data in both frequency regimes. Transport simulation has been carried out using the ASTRA simulation code for STOR-M tokamak parameters to understand the physical process behind experimental observations at higher frequency branch. The model is based on GAM excitement at resonance frequency associated with Ware-pinch due to oscillating electric field produced by biasing voltage which can suppress anomalous transport. Simulation results reproduce the experiment quite well in terms of the density, particle confinement as well as energy confinement time evolution. All those results indicate high frequency biasing is capable of improving confinement efficiently.
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