HIGH COUNTING RATE SOFT-X-RAY SPECTROMETER FOR TOKAMAK PLASMA DIAGNOSTICS

We describe a high counting rate spectrometer designed to measure the soft X-ray emission spectrum in magnetic fusion devices. The spectrometer employs six flat crystals of mosaic graphite as dispersing elements. Fast rotation of the crystal set allows us to cover a broad band spectral range. A stack of three superimposed multi wire proportional chambers is used as detector to discriminate the different diffraction orders. We demonstrate that this instrument can measure both the line and continuous spectrum at the same time. A fully digital acquisition system allows us to acquire data with a counting rate exceeding 1 MHz and to obtain a good time resolution in the measurements of important plasma parameters such as electron temperature T-e and the effective charge Z(eff).