Measurement of Electron Temperature of Divertor Plasma

近年来，等离子体加热和利用电子伯恩斯坦波（EBW）进行等离子体诊断得到了深入的研究，因为即使是低密度和/或低温的等离子体也是EBW的黑体。本研究的目的是探讨分流等离子体电子温度测量的可能性。由于EBW是一种静电波，它必须转换成电磁波才能从等离子体中出去。切向上，电子回旋共振层产生的EBW在上层杂化共振层转换为x模式，在截止层转换为o模式。然后o模式从等离子体发出，最后到达切向天线。在本研究中，在LHD真空容器中安装了切向天线。在这一年，一个远程控制装置以连接ECE测量系统。因此，EBW接收器和ECE接收器可以在等离子体射击之间切换，EBW数据的采集通常不需要特殊的机器时间。LHD实验的季节通常从9月开始，经过新年假期，到明年2月结束。今年，EBW数据被用于各种条件，如电子密度上升、深穿透颗粒注入和浅穿透颗粒注入。结果表明，当等离子体边缘的电子密度梯度较大时，切向天线接收到较大的发射，而基频ECE信号很小。频谱取决于电子密度分布。这些现象既不能用ECE的多反射也不能用ECE的折射来解释。所以，它可能是电子束辐射。由于京都大学正在开发用于LHD的EBW射线追踪代码，筑波大学正在开发切向的完整波代码，因此预计很快就会对目前的EBW实验结果有进一步的了解。

Recently plasma heating and plasma diagnostics using the electron Bernstein wave (EBW) have been intensively investigated, since plasma is black body for EBW even if it is low density and/or low temperature. Present research is aimed to investigate possibility of the electron temperature measurement of divertor plasma. Since EBW is an electrostatic wave, it has to be converted to a electromagnetic wave in order to go out from the plasma. In the tangential direction, EBW, which is generated in the electron cyclotron resonance layer, is converted to the X-mode in the upper-hybrid resonance layer, and the X-mode is converted to the O-mode at the cut-off layer. Then the O-mode goes out from the plasma, and finally it reaches the tangential antenna. In the present research, a tangential antenna has been installed in the LHD vacuum vessel. In this year, a remote controlled device in order to connect the ECE measurement system. So, the EBW receiver and the ECE receiver can be switched between plasma shots, EBW data have been often taken without taking special machine time. The season of LHD experiment starts in September, passes new year holidays and finishes in next February, usually. In this year, EBW data have been taken for various conditions, such as ramping-up electron density, deeply penetrating pellet injection and shallow penetrating pellet injection. As the result, when the electron density gradient is large at the plasma edge, a large emission is received with tangential antenna while fundamental ECE signal is very small. The frequency spectrum depends on the electron density profile. These phenomena cannot be explained by the multi-reflection nor the refraction of ECE. So, it may be EBW emission. Since, an EBW ray tracing code for LHD is under development in Kyoto University, and a full wave code for tangential direction is being developed in Tsukuba University, further understanding is expected for the present EBW experimental result, soon.