PLASMA DIAGNOSTIC-X-RAY TOMOGRAPHY SYSTEM

A radiation-hardened 60-channel x-ray tomography system has been developed to determine the two-dimensional distribution of x-ray emissivity from magnetically confined plasmas. In order to maximize their field of view, the diode arrays are mounted in re-entrant tubes inside the plasma chamber diagnostic ports. Metal foil vacuum windows serve as x-ray filters and permit the diodes and cables to be at atmospheric pressure. Preamplifers are mounted at the outside end of the re-entrant tubes. The diode arrays and preamplifiers are protected from the harsh radiation environment by lead shielding. Image reconstruction is done using the harmonic expansion method or the linear algebraic method. For plasmas with some cylindrical symmetry the harmonic expansion method is superior, but for small discrete objects the Cartesian algebraic method is better. Preliminary data from the Missouri Magnetic Mirror plasma with electron cyclotron resonance heating show evidence of a hot electron ring.