Various optimizations of TES arrays for X-ray astrophysics

We are developing arrays of superconducting transition-edge sensors (TES) for imaging X-ray spectroscopy telescopes such as the XMS on Constellation-X. While our primary focus has been on arrays that meet the XMS requirements (of which, foremost, are an energy resolution of 2.5 eV at 6 keV and a band pass from ∼0.3 keV to 12 keV), we are also beginning to investigate other optimizations that might be used to extend the XMS capabilities. In one of these optimizations, improved resolution below 1 keV is achieved by reducing the heat capacity. These low-energy pixels can be added to an array with broadband response either as a separate array or interspersed, depending on other factors that include telescope design and science requirements. To explore optimizations for higher count rates, we are also optimizing the design and operating temperature of pixels that are coupled to a solid substrate. We present analysis of the preliminary performance of such variations.