Microwave imaging reflectometry for KSTAR

Abstract

A microwave imaging reflectometry (MIR) system with two probing frequencies is being developed for 2D measurement of electron density fluctuations for KSTAR plasmas. The two-frequency probe beam enables simultaneous measurement of density fluctuations at two cutoff layers. Laboratory test of two approaches (reflective and refractive optics) has suggested an extreme care is needed in designing the optics considering problems such as aberration issues and standing waves. Currently, an optics based on refractive element is being designed with the minimum number of lens. The detector system consists of array detectors and electronics for the fluctuation phase reconstruction. The two-frequency MIR system will be installed for the 2012 KSTAR campaign and will be expanded to five frequencies by 2014.

Reliability of the two-point measurement of the spatial correlation length from Gaussian-shaped fluctuating signals in fusion-grade plasmas

“…The parallel correlation length of the fluctuations are typically measured using the probes only at the edge of the fusiongrade plasmas [16][17][18]. As the diagnostic systems are being developed, there is a possibility of measuring parallel correlation lengths in the core of KSTAR (Korea Superconducting Tokamak Advanced Research) plasmas with beam emission spectroscopy (BES) [19] and microwave imaging reflectometry [20]. Both systems are 2D (poloidal and radial) but installed at different toroidal locations measuring the same physical quantity-density fluctuations.…”

Trial of Deep Learning for Image Reconstruction of Lens-Less Microwave Holography

“…Plasma turbulence is related to the structure formation of the plasma which determines the overall plasma confinement [1,2]. Various measurement techniques have been studied for the experimental observation of plasma turbulence [3][4][5][6][7]. While the spatial resolution of visible light measurements is generally high, the position identification in the line-of-sight direction is difficult.…”

Three-Dimensional Electromagnetic Field Calculation for Microwave Holography

“…The microwave holography using the multi-channel heterodyne detection to obtain amplitudes and phases of the observed wave is suitable to capture the plasma density structure caused by turbulence. If such a lens-less system is implemented instead of the conventional systems of plasma imaging [4][5][6][7][8], the field of view will be well extended.…”