Plasma Scattering Measurement Using a Frequency Tunable, Submillimeter Wave Gyrotron as a Power Source

目的：研制一种工作在亚毫米波范围内的高功率源（- 100w）高频回旋管，将其输出转换成高质量的光束，并将其应用于等离子体散射测量。研究结果：1。在脉冲时间为0.6 s的情况下，将回旋加速器的振荡稳定在第二回旋谐波（f=353 GHz, p=110 W）为输出功率的10%以内。这种振荡对散射测量是足够稳定的。为了获得高频率输出，我们利用12 T超导磁体研制了一种新型回旋加速器，并成功地在二次回旋加速器谐波下实现了单模振荡（f=595 GHz, p=220 W）。目前达到的最大频率为636ghz。我们制作了一种准光学天线，将回旋管输出转换成线性偏振的二维聚焦光束。天线产生的准直光束达到了衍射效应的程度。为了提高光束的聚焦和模式纯度，我们正在制作一种由多镜组成的新型传输线，将回旋管输出转换成高斯光束并耦合到等离子体上。利用回旋管作为电源的等离子体散射测量我们构建了一个由回旋管和准光学天线组成的散射测量系统，并成功地观测了美国国家聚变科学研究所CHS （Compact Helical system in National Institute for Fusion Science）等离子体中的漂移波。在不久的将来，我们将改进散射测量系统，用新的传输线代替准光学天线，并观测等离子体加热的外部激发波。

Objectives: Development of a high frequency gyrotron for high power source (-100 W) operating in the submillimeter wave range, conversion of the output into a high quality beam and its application to plasma scattering measurement.The results :1. Development of a submillimeter wave gyrotron as a power source for scattering measurement We stabilized the gyrotron oscillation at the second cyclotron harmonic (f=353 GHz, p=110 W) within 10% of output power during a pulse of 0.6 s. This oscillation is stable enough for scattering measurement. In order to get high frequency output, we have developed a new gyrotron using a 12 T superconducting magnet and succeeded in a single mode oscillation (f=595 GHz, p=220 W) at the second cyclotron harmonic. The maxim frequency attained up to now is 636 GHz.2. Production of a high quality beam We have made a quasi-optical antenna to converting a gyrotron output into a linearly-polarized, two dimensionally focusing beam. The antenna produces a well collimated beam to the extent of a diffraction effect. In order to improve the focusing and the mode purity of beam, we are making a new transmission line consisting of multi-mirrors, which converts a gyrotron output into a Gaussian beam and couples it to plasma.3. Plasma scattering measurement using a gyrotron as a power source We have constructed a scattering measurement system consisting of a gyrotron and a quasi-optical antenna and succeeded in observing drift waves in CHS (Compact Helical System in National Institute for Fusion Science) plasma. In the near future, we will improve a scattering measurement system by replacing the quasi-optical antenna with the new transmission line and will observe externally excited wave for plasma heating.