Frequency Shift of Submm Waues with a Super Rotating Grating

1.在<IF>转速为43200 rpm的涡轮分子泵转子顶部制作了旋转光栅，对337 μ mHCN激光束获得了ω_（1/2 π）= 1.45MHz的频移。（超级旋转光栅）。频移比通常的旋转光栅高一个数量级。利用它作为局部光束，可以用单个远红外激光器外差探测等离子体中的低频微湍流以及高时间分辨率的干涉测量.频移后的光束经过轻微的频率调制（调制指数M_f <similar or equal>1.2），其周期等于光栅的旋转周期。这种频率调制对这些诊断没有损害。3.用热释电探测器测得的SRG的功率转换效率为0.20和0.25的晶体石英窗口。我们将在今后的工作中提高效率。然而，由于337 μ m HCN激光器产生大的功率，因此目前的效率可以足以执行具有10个或更多个通道数的多通道检测。我们打算用SRG制作一台高时间分辨率的多通道干涉仪和一台带有外差探测系统的散射装置，并研究托卡马克等离子体中的输运现象，如微扰振荡和低频微扰。

1. Frequency shift of omega_<IF>/2pi=1.45 MHz is obtained for 337 mum HCN laser beam by use of a rotating grating fabricated on the top of the rotor of a turbo-molecular pump with a high rotating speed of 43200 rpm. (Super Rotating Grating). The frequency shift is one order higher than those with usual rotating gratings. Using this as a local beam, heterodyne detection of low frequency microturbulence as well as high time resolution interferometry in plasmas becomes possible with a single FIR laser.2. The frequency-shifted beam is slightly frequency-modulated (modulation index M_f<similar or equal>1.2) with a period equal to the rotation period of the grating. This frequency modulation does no harm to these diagnostics.3. The power conversion efficiency of the SRG measured with a pyroelectric detector is 0.2 for a teflon window and 0.25 for a crystal quartz window. We will increase the efficiency in a future work. The present efficiency may be, however, sufficient to carry out multichannel detection with a channel number of 10 or more, since 337 mum HCN lasers generate a large power.4. We intend to make a multi-channel interferometer of high time resolution as well as a scattering apparatus with heterodyne detection system by using the SRG and to study transport phenomena such as sawtooth oscillations and low frequency microtubulences in tokamak plasmas.