Measurement of Electron Temperature of Divertor Plasma

由于等离子体在低密度和低温条件下也是黑体，因此利用电子伯恩斯坦波（EBW）进行等离子体加热和等离子体诊断成为近年来的研究热点。本文研究偏滤器等离子体电子温度测量的可能性。由于EBW是一种静电波，因此必须将其转换为电磁波才能从等离子体中出去。在切线方向上，在电子回旋共振层中产生的EBW在上混合共振层中被转换为X模式，并且X模式在截止层处被转换为O模式。然后O模从等离子体中出去，最后到达切向天线。在本研究中，切向天线已安装在铲运机真空容器。在这一年，远程控制设备，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发射之间切换，EBW数据通常不需要专门的机器时间。LHD试验季节通常从9月开始，经过新年假期，到明年2月结束。在这一年中，电子束焊接数据已经采取了各种条件，如斜升电子密度，深穿透弹丸注入和浅穿透弹丸注入。结果表明，当等离子体边缘处电子密度梯度较大时，切向天线接收到的辐射较大，而基波ECE信号很小。频谱取决于电子密度分布。这些现象不能用ECE的多次反射或折射来解释。因此，它可能是电子束焊发射。由于京都大学正在开发用于LHD的EBW射线追踪代码，筑波大学正在开发用于切向方向的全波代码，因此预计不久将对目前的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.