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

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