Development of X-ray microcalorimeters for future Japanese X-ray astronomy missions

Abstract

A large format array of transition-edge-sensor (TES) microcalorimeters is a promising detector for high-resolution spectroscopy in X-ray astronomy. Such a detector for future Japanese missions is being developed. In this paper, the recent progress in the work is presented, particularly in the improvement of the energy resolution and the X-ray absorber fabrication. The energy resolution of the single pixel detector was improved to 25 eV (FWHM) at 5.9 keV. This is limited by pulse shape variation and excess noise. The characteristics of these two limiting factors are described, and several possible ways to improve the performance are suggested. As for attaching X-ray absorbers with a high coverage fraction, an electrodeposition method involving a two-layer lift-off process is being proposed. The details of this method are described and the results of the test sample fabricated on a silicon wafer are shown.