EAST等离子体电子温度涨落特征的初步实验研究

Preliminary experimental study on the characteristics of plasma electron temperature fluctuation in EAST

在EAST上使用相关电子回旋辐射(CECE)诊断系统观测到不同等离子体参数下的电子温度涨落特征,介绍了欧姆放电、L模放电及无ELM的H模放电的三种现象。在欧姆密度爬升等离子体中,电子温度涨落与电子密度之间表现出很强的相关性,即存在电子温度涨落处于较高水平的电子密度的窗口。初步分析表明,电子温度涨落变化是电子密度梯度和电子温度梯度共同影响的结果。不同辅助加热下的L模等离子体中,电子温度涨落的频谱表现出不同的行为。由于电子回旋共振加热(ECRH)的功率有限,其对电子温度的改变很小,而中性束注入(NBI)有较高的注入功率,能够明显提升电子温度,加热方式及加热功率大小引起的电子温度变化与电子温度涨落变化相关。在没有边缘局域模(ELM)的H模期间,可以观测到频率为18kHz的准相干模,其存在于归一化半径ρ=0.71~0.87较宽的径向范围内。

The electron temperature fluctuations under different plasma parameters are measured by a correlation electron cyclotron emission(CECE)diagnostic system in the EAST tokamak.Three kinds of discharge modes are presented in this paper.In the Ohmic density ramp¬-up plasma,there is a strong correlation between the electron temperature fluctuation and the electron density.And there is a density window where the electron temperature fluctuation is at a relatively high level.The preliminary analysis shows that the change of the electron temperature fluctuation is commonly influenced by the electron density and temperature gradients.In L-mode discharges,the frequency spectra of the electron temperature fluctuations show different behaviors under different auxiliary heating conditions.With very limited injected power,the Electron Cyclotron Resonance Heating(ECRH)hardly changes the electron temperature,while the Neutral Beam Injection(NBI)with higher power can significantly increase the electron temperature.The changes of electron temperature caused by different heating methods and heating powers are found to be correlated to the change of electron temperature fluctuations.During H-mode without Edge Localized Mode(ELM),quasi-coherent mode with frequency of 18 kHz can be observed,which exists at a wide range of normalized radiusρfrom 0.71 to 0.87.