Initial design of the soft x-ray tomographic diagnostic array system for KSTAR plasmas

A soft x-ray (SXR) tomographic array system is a powerful diagnostic tool for observing inner structure and various physical activities of tokamak plasmas. The SXR diagnostic system for KSTAR is based on the six photodiode detector arrays arranged in a poloidal plane with total of 192 detector channels. The newly developed fast MEM (maximum entropy method) combined with SVD (singular value decomposition) was applied to the tomography test with KSTAR-like emission phantoms. The spatial setup of the components was optimized by geometrical calculation and ray-tracing for accurate SXR analyses. The radiation-resistive AXUV-16ELG detector array was chosen for surviving high dose of radiation during the long pulse operation in KSTAR, and the high-speed ($\sim $600 kHz) in-vacuum preamplifier with high gain ($\sim $10$^{5})$ was developed and tested to observe high speed MHD activities. The spatial optimization of the detector in each array will be adjusted by the miniaturized remote motion-control system, which consists of a small in-vacuum motor and a controllable PXI module. Moreover, in order to maintain the performance of the detector, a controllable thermo-electric cooler and a shutter will be mounted on the array for long-pulse experiments on KSTAR.