<title>Application Of Computerized Tomography Techniques To Tokamak Diagnostics</title>

Abstract

The methods of computerized tomography (CT), developed for medical X-ray applications, can be adapted for use in studying plasma X-ray emissivity distributions in tokamaks and other magnetic confinement devices. Current generation CT scanners reconstruct maps of X-ray absorptivity on body cross sections by processing transmission data from a number of fan-shaped beams of X-rays. Analogous fan beam emission data can be obtained from confined plasmas by collimating emitted soft X-rays with a pin hole or slit and detecting them with a linear array of solid state detectors. Data from a number of such one-dimensional views of the plasma can be used to reconstruct a two-dimensional photograph of the absolute X-ray emission in cross section. No a priori assumptions about the nature of the emissivity distribution are necessary. In this paper we demonstrate the feasibility of the technique by reconstructing test patterns with data simulated for a number of different types of detector arrangements. We also use the technique with real data to reconstruct a rotating emissivity feature on a cross section of Massachusetts Institute of Technology's Alcator A tokamak.