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 spectrome ter employs six flat crystals of mosaic graphite as dispersing element s. Fast rotation of the crystal set allows us to cover a broad band sp ectral range. A stack of three superimposed multi wire proportional ch ambers is used as detector to discriminate the different diffraction o rders. We demonstrate that this instrument can measure both the line a nd continuous spectrum at the same time. A fully digital acquisition s ystem allows us to acquire data with a counting rate exceeding 1 MHz a nd to obtain a good time resolution in the measurements of important p lasma parameters such as electron temperature T-e and the effective ch arge Z(eff).