Measurements of ICRF wave-induced density fluctuations in LHD by a microwave reflectometer

作者：Ejiri A^*; Tokuzawa T; Tsujii N; Saito K; Seki T; Kasahara H; Kamio S; Seki R; Mutoh T; Yamada I; Takase Y

来源：Journal of Instrumentation, 2015, 10(12): C12032.

DOI：10.1088/1748-0221/10/12/C12032

• Plasma diagnostics - interferometry, spectroscopy and imaging
• Plasma generation (laser-produced, RF, x ray-produced)

An O-mode microwave reflectometer has been developed to measure ICRFwave induced electron density fluctuations in LHD plasmas. The system has two probing frequencies (28.8 and 30.1 GHz) to measure two spatial points simultaneously. The rms density fluctuation levels are typically 0.01%. The linearity between the measured density fluctuation amplitude and the square root of the RF power is discussed. The decay length of the RF field was estimated to be 1 to 7m under the operational condition investigated. A typical spatial distance between the two measurement points corresponding to the two probing frequencies is a few centimeters, and the fluctuation amplitudes at the two points are similar in amplitude. The phase difference between the two fluctuations show in-phase relationship on average. Out-of phase relationships, which implies a standing wave structure, are often observed when the wave absorption is expected to be poor.

• 出版日期2015-12