Thermal design issues and performance of microcalorimeter arrays at sub-Kelvin temperatures - Sensors, 2003. Proceedings of IEEE

We have produced 5 x 5 pixel arrays of microcalorimeters using bulk micromachining. Analysis of our data provides the thermal conductivity parameters of SixNy I p m thick membranes at 100 mK. Moreover wefind that the thermal transport at 100 mK in Si beams, with dimensions 1.25 mm x 0.35” x 35pm (length x height x width) is dominated by ballistic phonons with a mean free path of 110 pn. These thermal parameters can be used for modelling fiture 32 x 32 pixel arrays. In addition we operated three pixels in a 5 x 5 array of microcalorimeters andfind that the pixel to pixel reproducibility is very good. When used as an X-ray microcalorimeter individual pixels have a thermal decay time of 200 ps and their energy resolution is behveen 6 and 7 eV for 5.89 keV X-ray photons.