Development of a high resolution, high sensitivity cylindrical crystal spectrometer for line shape diagnostics of x-rays emitted from hot plasmas

This report outlines progress towards development of a high resolution, high throughput, curved crystal spectrometer suitable for line shape diagnostics of X-rays emitted from hot plasmas. The instrument is designed to interface with the MIT Tokamak (Alcator) with the initial aim of studying the prominent MoL lines which occur in the X-ray spectrum. However, it will have the versatility to function over an energy range of at least 1.5 keV to 7 keV allowing determination of temperature, charge state and density distributions for important impurity ions. The spectrometer employs a large, cylindrically bent crystal which focuses the dispersed X-rays along the cylinder axis where they are recorded by a position sensitive high resistance anode proportional counter. Thus a wide energy range of the spectrum can be recorded simultaneously and sensitively from a short duration plasma. Computer control of data acquisition and analysis will allow real-time diagnostics. The report includes an analysis and optimization of spectrometer parameters for interface with Alcator and an analysis of monolithic and individual silicon diode arrays as alternative position sensitive detectors. A Si(Li) detector with computer-controlled ADC system has been on line at Alcator providing several time sequenced spectra during each shot. Bremsstrahlung and impurity ion spectra are discussed and results for electron temperatures as a function of time and position in the plasma are presented