Development of arrays of transition edge sensors for application in X-ray astronomy

The development of an array of voltage biased superconducting transition edge microcalorimeters is described. This work is directed to an application in future X-ray Astronomy missions, such as Constellation-X (USA) and the X-ray Evolving Universe Spectroscopy Mission (XEUS, Europe). After several years of very successful development of single pixel microcalorimeters (SRON showed a record energy resolution ΔEFWHM=3.9 eV for 5.9 keV photons, combined with an effective time constant of 150 μs and high X-ray absorption efficiency (94%)) work towards an array of 32×32 pixels has started. Aiming at a prototype of 5×5 pixels, several options for fabrication, using micromachining techniques are under study, both experimentally and theoretically. Measurement of thermal transport in detector support structures at sub-Kelvin temperatures indicates ballistic phonon transport. The detector development is accompanied by finite element modeling.