Hot-electron-microcalorimeters with 0.25 mm2 area

I present measurements on hot-electron microcalorimeter with a normal-insulator superconductor tunnel-junction thermometer that is used for the detection of X-rays. With an absorber area of 0.5 mm by 0.5 mm, pulses of 20 μs in duration were observed that gave a 30 eV FWHM resolution for 6 keV X-rays and an 18 eV resolution for heat pulses. This detector has sufficient resolution, detector area, and speed to warrant application in materials analysis.