Low-cost, robust, filtered spectrometer for absolute intensity measurements in the soft x-ray region

We have developed a low-cost, robust, multifoil-filtered spectrometer to pr ovide absolute measurements of low-Z impurity concentrations in the Madison Symmetric Torus reversed-field pinch. The spectrometer utilizes an array o f six thin-film coated soft x-ray diodes. Each multilayered coating is spec ifically tailored to isolate the K-shell emission lines of H- and He-like o xygen, carbon, and aluminum. With calibrations obtained via a synchrotron s ource, absolute measurements of photon flux have been made. We address the technical aspects of this diagnostic and present impurity data from both st andard and high-confinement plasma discharges. (C) 2001 American Institute of Physics.