Microwave Imaging Reflectometry Experiment in TPE-RX

Abstract

Microwave imaging reflectometry (MIR) was developed in TPE-RX, one of the world's largest reversed field pinch (RFP) devices. The system optics are made of aluminum mirrors, Teflon lenses, and Plexiglas plates in order to reduce size. In this system, frequencies are stabilized so that noise can be reduced using narrow bandpass filters. A 4×4 2-D mixer array and phase detection system have also been developed. With this system, density fluctuations in the high-Θ RFP plasma, pulsed poloidal current drive (PPCD) plasma, and quasi-single helicity (QSH) plasma are observed in TPE-RX. This is the first MIR experiment in an RFP device.

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

“…It is hard to make a 2D array of planar antennas, such as bow-tie antenna 7 or dual dipole antenna, 6 because baluns extend from the side of antenna array. A 2D imaging device was firstly used in the MIR experiments 8,9 in the TPE-RX reversed field pinch. In TPE-RX, a stack of four pieces of 1D planar type Yagi-Uda antenna array with mixer diodes 5 were used for the MIR frequency of 20 GHz.…”

Maximum Entropy Analysis of the 2D Density Turbulence Measured by MIR in TPE-RX

“…It is useful for the calibration of the optical aberration of MIR system. Figure 1 shows the schematic diagram of the MIR system in TPE-RX [12]. It consists of a optical system and a 2D receiver system.…”

Investigation of turbulence in reversed field pinch plasma by using microwave imaging reflectometry

“…Details of the MIR system have been reported previously. 12,13 In this system, the plasma is illuminated by the O-mode microwave with the frequency of 20 GHz, which corresponds to the cutoff density of $0.5 Â 10 19 m À 3 . The image of the cutoff surface is made onto the imaging detector by the optical system (M 1 , M 2 ).…”

“…7,8 This paper presents the first fluctuation measurement near the reversal surface by using the microwave imaging reflectometry (MIR). [9][10][11][12][13] In a conventional reflectometer, the reflected signal contains components from multiple fragmented wave fronts caused by turbulence, resulting in a complicated interference pattern at the detector plane, and the assumption of the simple relation between the signal and the density fluctuation fails. In an MIR system, a wide aperture optical system is used to form an image of the reflected surface onto the detector array located at the image plane.…”

“…C > 0 denotes the hollow density profile, and C < 0 denotes the peaked density profile. 13 The 1070-664X/2011/18(10)/102315/4/$30.00 V C 2011 American Institute of Physics 18, 102315-1 normalized cutoff radius (r cut ¼ a cut /a) can be obtained, where a cut is the real cutoff radius and a is the plasma minor radius. The electron density profile is usually flat or hollow in TPE-RX.…”