X-mode Reflectometer

The target of X-mode reflectometer is to measure the fluctuation and its correlation in the core region, especially in the internal transport barrier, ITB, region of high performance plasma.

[Diagnostic Method]
The reflectometer consists of four channels, two of which operate in fixed frequency and the other two channels are tunable. The frequencies of the launched waves are 102 and 117 GHz for the fixed frequency channels, and 109.5 f bank GHz, where f bank = 2.73, 5.28, 6.37, 6.93 and 7.27 GHz, for the variable channels. The tunable channels can step through the five frequencies in each 60 ms. The correlation of the fluctuations is determined from the correlation between fixed and variable frequency channels and the radial profile of the correlations can be measured every 60 ms in a discharge. The polarization of the launched wave is the extraordinary mode, X-mode, in order to obtain a high space resolution and to access the high field side of the magnetic axis. A quadrature phase detection is used, thus we can measure the complex amplitude of the reflected wave.

- Time resolution : 1 micro sec
- Toroidal position : P-5 section, midplane port

K. Shinohara et al, Rev. Sci. Instrum. 70, 4246 (1999)