EAST装置上W波段多道极向相关反射仪的研制

在EAST装置上安装了X模极化W波段多道相关反射仪,用于测量等离子体芯部密度涨落。该诊断利用低损耗(<3dB)多工器将4个不同频率(79.2GHz,85.2GHz,91.8GHz和96GHz)的微波耦合在一起,通过同一个天线发射。反射波由两个极向分离(～5cm)的天线接收,通过下变频技术实现外差测量。通过对两个极向天线接收的信号进行相关分析,获得芯部湍流垂直速度。对2018年低约束模式(L模)放电进行分析发现,在电子回旋共振加热(ECRH)等离子体中,芯部湍流垂直速度在电子逆磁漂移方向。而在注入同向中性束(co-NBI)后,芯部湍流垂直速度变为离子逆磁漂移方向。

Development of a W-band multi-channel poloidal correlation reflectometry on EAST

An X-mode polarized W-band multi-channel correlation reflectometry is installed on EAST tokamak for measuring the density fluctuations in the core of plasma. The diagnostic uses a low loss (<3dB) multiplexer to couple the microwaves of four different frequencies (79.2GHz, 85.2GHz, 91.8GHz and 96GHz) together and then transmit through the same antenna. The reflected wave is received by two antennas separated poloidally with about 5cm, and then heterodyne measurement is achieved by down-conversion technology. The turbulent vertical velocity in the core of plasma can be obtained by doing correlation analysis for the signals received by the two poloidal antennas. Analysis of the 2018 lower confinement mode (L-mode) discharge shows that in plasma heated by the electron cyclotron resonance heating (ECRH), the vertical velocity of the core turbulence is in the direction of the electron diamagnetic drift. The vertical velocity of the core turbulence becomes in the direction of the ion diamagnetic drift after injecting the co-neutral beam.