Optimization of transition-edge calorimeter performance

Calorimeters that exploit the superconducting-to-normal transition are used to detect individual photons from near-infrared to γ-ray wavelengths. Across this wide range, absorption efficiency, speed, and energy resolution are key performance parameters. Here, we describe recent improvements in the resolution of X-ray and γ-ray transition-edge sensors (TESs). Using the measured dependencies of the high-frequency unexplained noise in TESs, we have optimized the design of our TES X-ray sensors and achieved FWHM energy resolutions of 2.4 eV at 5.9 keV in Constellation-X style sensors and ∼2.9 eV at 5.9 keV in larger sensors suitable for materials analysis. We have also achieved a FWHM energy resolution of 42 eV at 103 keV in a TES calorimeter optimized for the detection of hard X-rays and γ-rays.