Development of high spatial resolution detector for characterization of X-ray optics

Abstract

Technological innovations in grazing incidence X-ray optics have been crucial to the advancement of the field of X-ray astronomy. Improvements in X-ray focusing optics translate to higher sensitivity for X-ray telescopes operating in the energy range above 10 keV. Full characterization of the X-ray optics involves measurement of the point spread function, scattering, and reflectivity properties of substrate coatings. This requires a very high spatial resolution, high sensitivity, photon counting and energy discriminating large area detector. In this paper we describe the construction of a detector that is well suited to meet these requirements. A prototype version of this camera was used to calibrate the X-ray focusing optics for the Nuclear Spectroscopic Telescope Array (NuSTAR) mission. Analysis of the data obtained during the ground calibration of the NuSTAR telescopes demonstrated the advantages of such a high resolution 2D detector for hard X-rays (30+ keV); however it showed some limitations for medium energy X-rays (8-30 keV). We present here, alternative methods under investigation to improve performance of the detector for medium energy X-rays such as changing the morphology of the CsI:Tl scintillator, improving light transport from scintillator to EMCCD and using a novel bright scintillator, Ba2CsI5:Eu. © 2011 IOP Publishing Ltd and SISSA.