Fast Tangentially Viewed Soft X-Ray Imaging System Based on Image Intensifier with Microchannel Plate Detector on QUEST

Abstract

A two-dimensional (2D) soft X-ray (SXR) imaging system for obtaining tangential views of plasmaproduced SXR has been installed on the QUEST tokamak. The system comprises a chevron micro-channel plate (MCP) and a phosphor screen, which together serve as an SXR detector and image intensifier, along with a high-speed video camera for capturing and storing image data. The system can be used in imaging mode to obtain high spatial- and time-resolution images or in photon counting mode at an ultra-high framing rate of 100 kHz to obtain SXR energy spectra. Here, we propose a method of in situ energy calibration based on the transmission characteristics of a 25-μm Be filter. The proposed method was used to obtain SXR spectra in the energy range 1.5 - 3.5 keV with a core electron temperature in agreement with electron temperatures measured by the Thomson scattering method. Furthermore, oscillations based on the modification of plasma parameters and rapid increases in impurity radiation were detected in imaging mode. This dual-mode-compatible method for obtaining 2D SXR diagnostics is useful for the study of high temperature plasmas.