Observation of Electron Density Fluctuations by Using the O-Mode Microwave Imaging Reflectometry (O-MIR) in LHD

Abstract

The O-mode microwave imaging reflectometry (O-MIR) has been developed. The frequency is 26-34 GHz, which corresponds to the cutoff electron density of 0.8-1.5 × 10 19 m −3. Since the local wave of the newly developed horn antenna millimeter wave imaging device (HMID) is fed by coaxial cable, the optical system of O-MIR is significantly simplified. By using O-MIR, the edge electron density fluctuation in an H-mode plasma is observed in LHD. The spectrum in the wave number and the frequency (k-ω) space is obtained by using the two-point correlation analysis. In the H-mode plasma the fluctuation amplitude is higher and the k-ω spectrum has the feature of the drift wave.

Development and application of radar reflectometer using micro to infrared waves

“…An O-mode MIR is applied to LHD plasmas [46,47]. The edge density fluctuation is measured in L-mode and H-mode plasmas.…”

“…The key parameters of fluctuation are the wave number (k) and the frequency (ω). In order to obtain the k-ω spectrum two-point cross-spectrum S ij (ω) is evaluated [46]. The wave numbers between two MIR channels (i, j) which have the distance of d ij can be obtained from The coherence is the normalized cross-power spectrum given by An example of the results is shown in Figure 14.…”

Measurement of Electron Density Fluctuations Using O-Mode Microwave Imaging Reflectometry in a TST-2 Spherical Tokamak

“…the cutoff layer that may represent density fluctuation [3]. MIR has been intensively developed at the National Institute for Fusion Science (NIFS) for the TPE-RX RFP device [3,4] and for the large helical device (LHD) [5][6][7][8]. In the last MIR experiment at LHD [8], a newly developed horn-antenna millimeter-wave imaging detector (HMID) [9,10] was employed.…”

“…MIR has been intensively developed at the National Institute for Fusion Science (NIFS) for the TPE-RX RFP device [3,4] and for the large helical device (LHD) [5][6][7][8]. In the last MIR experiment at LHD [8], a newly developed horn-antenna millimeter-wave imaging detector (HMID) [9,10] was employed. This paper describes the O-mode MIR system (O-MIR), which is installed in the Tokyo Spherical Tokamak 2 (TST-2) [11], and preliminary results on the electron density fluctuation measurements on IRE in TST-2 are presented.…”

Installation of New Electron Cyclotron Emission Imaging in LHD

“…A microwave-imaging reflectometer was employed with ECEI on LHD until 2016 [8][9][10][11][12][13][14]. At the beginning of the D-D plasma experiment of LHD, we refined the receiving antennas called as Horn-antenna Millimeter Imaging Device (HMID) [13], which was originally developed by the LHD group.…”