Fast electron temperature measurements using a 'multicolor'optical soft x-ray array

摘要

A fast (≤0.1 ms) and compact "multicolor" scintillator-based optical soft x-ray (OSXR) array has been developed for time- and space-resolved measurements of the electron temperature [T_e{R,t)] profiles in magnetically confined fusion plasmas. The 48-channel tangential multicolor OSXR prototype was tested on the National Spherical Torus Experiment. Each sight line views the same plasma volume at the midplane (0≤r/a≤1), in three distinct energy ranges determined by beryllium foils with different thicknesses. A tangential view of the toroidally (circular) symmetric plasma allows an Abel inversion of the line-integrated SXR brightness to obtain the x-ray emissivity profiles which are then used to constrain the reconstruction of the fast T_e(R,t). The first assessment of the electron temperature is obtained by modeling the slope of the continuum radiation with the ideal double-foil method using both the line-integrated intensity measurements as well as the inverted SXR emissivity profiles.