Development of a prototype of ECH system without window for vacuum seal

真空密封窗口是聚变研究用高功率ECH系统研制中的关键问题之一。本项目对一个无窗口真空密封的ECH系统进行了实验研究，设计、制造了一台工作在二次电子回旋谐波的48 GHZ可拆卸回旋管样机，并进行了实验研究。在此基础上，去掉回旋管的真空密封窗口，用4 m长的圆波导将回旋管与WT-3托卡马克真空室直接连接，使回旋管中的压强达到托卡马克等离子体破裂时的最大值。在托卡马克放电间歇后，管内压力恢复到初始值，回旋管运行正常，回旋管与托卡马克同步运行正常，无真空密封窗口的ECH系统可用于聚变研究，系统的维护问题尚不清楚。在像ITER这样的大型装置中，存在着与小型装置不同的问题。将需要进一步调查。

A window for vacuum seal is one of the most serious problems in the development of high power ECH system in fusion research. In this project, we tested an ECH system without windows for vacuum seal.A prototype of 48 GH_z demountable gyrotron operating at the 2nd electron cyclotron harmonics was designed , built and tested. Then the window for vacuum seal of the gyrotron was removed and the gyrotron was directry connected to the vacuum chamber of the WT-3 tokamak with a 4m long circular waveguide.The pressure in the gyrotron tube attains the maximum value when a tokamak plasma is disrupted. After the interval of tokamak discharge, the pressure in the tube is restored at the initial value which is no problem in operating the gyrotron.We confirmed that there is no problem in synchronized operation of the gyrotron and the tokamak.It can be cocluded that the ECH system without windows for vacuum seal can be applicable to fusion research.The problems about maitenance of the system are not clear. They will be clear in use for ECH experiments on the WT-3 tokamak.In a big facility something like ITER, there will be different kind of problems from small facilties. Further investigation will be required.