Prototype high resolution multienergy soft x-ray array for NSTX

Abstract

A novel diagnostic design seeks to enhance the capability of multienergy soft x-ray (SXR) detection by using an image intensifier to amplify the signals from a larger set of filtered x-ray profiles. The increased number of profiles and simplified detection system provides a compact diagnostic device for measuring T(e) in addition to contributions from density and impurities. A single-energy prototype system has been implemented on NSTX, comprised of a filtered x-ray pinhole camera, which converts the x-rays to visible light using a CsI:Tl phosphor. SXR profiles have been measured in high performance plasmas at frame rates of up to 10 kHz, and comparisons to the toroidally displaced tangential multi-energy SXR have been made.

Multi-energy soft-x-ray technique for impurity transport measurements in the fusion plasma edge

“…To address the challenge of measuring electron thermal and impurity particle transport within a wide range of plasma temperatures, multi-energy soft-x-ray (ME-SXR) diagnostics have been developed [10][11][12][13]. These instruments provide SXR emissivity measurements with coarse spectral resolution and fine spatial and time resolution.…”

Multi-energy x-ray imaging and sensing for diagnostic and control of the burning plasma

“…This consists simply in imaging the same plasma volume using three or more detector arrays in current-mode, filtered for increasing cutoff energy. [4][5][6][7][8] Our results indicate that the use of three or more energy ranges confers new capabilities compared to the more traditional dual-energy or "two-color" method, such as discriminating the contribution of line and continuum emission and separating the spectral contribution of different impurity charge states. This, in turn, enables more accurate measurements of the electron temperature profile T e (r, t) and, with detailed emission modeling, of the impurity content and transport.…”

“…4 This consists of a thin layer of high-Z scintillator or phosphor deposited on a sealed MCP image intensifier, followed by an efficient and fast image readout system. The multi-energy arrays share the active area of the intensifier as sketched in the inset in Fig.…”

High-performance double-filter soft x-ray diagnostic for measurement of electron temperature structure and dynamics

“…4 The double-foil technique has been used on RFX and NSTX for single-point and radial T e profile measurements. [5][6][7] A SXR diagnostic has been developed for MST that provides multiple SXR measurement capabilities in a single instrument by combining four detectors at different poloidal angles for tomographic reconstruction of emissivity with pairs of sight-lines sharing two different beryllium filters for double-foil temperature measurements. 8 Additionally, the double-foil technique applied to reconstructed emissivities generates a 2D poloidal map of T e .…”