We are developing X-ray calorimeters to meet the specifications of the Constellation-X
mission. Each calorimeter consists of a transition-edge-sensor (TES) thermometer, which is
suspended on a silicon-nitride membrane. Our TES thermometers are Mo/Au bilayer films
that are biased in the sharp phase transition between the superconducting and normal-
metal states. These calorimeters have demonstrated very good energy resolutions: 2.4 eV at
1.5 keV and 3.7 eV at 3.3 keV. The energy resolutions are limited by thermal noise and …