X-ray microcalorimeters using metallic magnetic sensors show great promise for use in astronomical x-ray spectroscopy. In the last year, magnetic microcalorimeters demonstrated their potential in high resolution spectroscopy when an energy resolution of 3.4 eV (FWHM) was achieved for 6 keV X-rays in single pixels with a 5 micron thick, 160 micron square gold absorber attached to a magnetic sensor. We have recently formed a collaboration to develop arrays of magnetic microcalorimeters suitable for future X-ray astronomy missions.
This collaboration includes scientists from the University of Heidelberg, Brown University, NIST, SAO, PTB-Berlin, IPHT Jena and GSFC. We are developing array construction techniques for building arrays of magnetic calorimeters with mushroom absorbers. We are studying different alternatives for the circuit that couples the signal from the detector to the SQUID amplifier. We are developing magnetic calorimeter multiplexing capabilities using time division multiplexing similar to that used for transition edge sensors. On behalf of the collaboration, in this paper I will review the measured performance of magnetic microcalorimeters achieved so far and then focus on the present status of our array technology development.