MULTILAYER MIRROR BASED LINE EMISSION TOMOGRAPHY FOR SPHERICAL TOKAMAKS

Due to their highly shaped plasma and possible poloidal asymmetry in i mpurity concentration, spherical Tokamaks will require tomographic rec onstruction of local emissivities to assess impurity content and trans port. To collect in an effective manner the data required for such rec onstruction, we develop arrays of high throughput ''mini-monochromator s'' using extreme ultraviolet multilayer mirrors as dispersive element s and filtered surface barrier diodes as detectors. We discuss monochr omator optimization and show that by working at near normal incidence throughput and spectral resolution are simultaneously maximized. A sys tem proposed for tomographic reconstruction of C V and C VI resonance emission at 33.7 and 40.5 Angstrom respectively, achieves 0.9 Angstrom spectral resolution, 2 cm spatial resolution, and 0.2 ms temporal res olution, together with good sensitivity and background rejection. Prel iminary results obtained from CDX-U low aspect ratio tokamak are also presented. (C) 1997 American Institute of Physics.