Vacuum ultraviolet and ultrasoft x-ray diode detectors for tokamak plasmas

Abstract

Ultrasoft x-ray diode (USXRD) arrays have been used on DIII-D and ASDEX to study plasma edge radiation, in the photon energy range from 10 eV to 10 keV. The detectors are extremely useful and versatile due to their simplicity and compactness. Furthermore, absolute quantum efficiencies (QE) of many photocathodes such as vitreous C, Al, Cu, CuI, CsI, and Au have been measured in recent years. With filter technique, broadband resolution, E/ΔE∼1, is possible. Quantum-efficiency comparison of USXRD with semiconductor XRD is also presented to better understand the regions of applicability for each detector.