Development of 3D microwave imaging reflectometry in LHD (invited)

Abstract

Three-dimensional (3D) microwave imaging reflectometry has been developed in the large helical device to visualize fluctuating reflection surface which is caused by the density fluctuations. The plasma is illuminated by the probe wave with four frequencies, which correspond to four radial positions. The imaging optics makes the image of cut-off surface onto the 2D (7 × 7 channels) horn antenna mixer arrays. Multi-channel receivers have been also developed using micro-strip-line technology to handle many channels at reasonable cost. This system is first applied to observe the edge harmonic oscillation (EHO), which is an MHD mode with many harmonics that appears in the edge plasma. A narrow structure along field lines is observed during EHO.

Dynamical programming based turbulence velocimetry for fast visible imaging of tokamak plasma

“…This path is extrapolated continuously outside of the begin and end lines. (8) The parameter m as well as the width of the strips and spacing is decreased in each subsequent R-Z iteration.…”

“…Turbulence imaging diagnostics have been realized in several forms like the beam emission spectroscopy (BES), 2 fast visible imaging, [3][4][5][6] and microwave reflectometer imaging array. 7,8 Particle Image Velocimetry (PIV) has proven to be an important tool for quantitative estimation of two-dimensional flow structures in experimental fluid mechanics. Application of such a technique to plasma fluctuation images may unveil enormous information of plasma turbulence and flow dynamics.…”

Design and Evaluation of Broad-Band High Pass Filter of Metal Perforated Sheets for Microwave Diagnostics

“…Therefore, we have developed an original broad-band high pass filter. The filter can be also used for c-ECE (correlation ECE) with second heterodyne and microwave imaging reflectometry [3]. The purpose of this study is to design perforated metal sheet type broad-band filters (cut-off frequency is 44 GHz).…”

Development of Microwave Imaging Diagnostics on the HL-2A Tokamak

“…electron cyclotron emission imaging (ECEI) and microwave imaging reflectometry (MIR), with the advantages of local measurements of the plasma temperature and density fluctuations, and lack of plasma perturbations, have attracted intensive interest by physicists [4,5]. Both MIR and ECE systems have been proven to be powerful tools for plasma fluctuation measurements in several machines, including DIII-D, KSTAR, EAST, AUG, and LHD [3,[6][7][8].…”