Toward large μ-calorimeters X-ray matrices based on Metal-Insulator sensors and HEMTs/SiGe Cryo-Electronics

摘要

The launch of ASTRO-H/ITOMI ,the X-ray Japanese/US mission, in February 2016 with μ-calorimeters based on Metal-Insulator-Sensors (M.I.S) experiment with a 4.5eV spectral resolution, would certainly generate renewed interest on the high impedance M.I.S based on Si P:B. Since 2009 we are involved in a large program to build a camera consisting of a 2×2 mosaic of 32×32 pixel matrices using this sensor type. Since we rely on very similar approach of ASTRO-H/ITOMI design, we have concentred our efforts on the use of collective all-silicon technologies only. We have already presented the building block such as thermometers, sensors and cryo-electronics. Now, thanks to our new 32×32 CAD, we are today in the process of building 4 32×32 matrices per wafer. ASTRO-H/SXS uses degenerated Si as output wiring of the pixel and an HgTe semi-conductor absorber. Thanks to the use of superconducting wiring and composite superconducting Tantalum absorber, we hope to enhance the spectral resolution of this matrix onto that of SXS. Moreover, our development benefits of an ultra low power consumption Cryo-Electronics chain. This chain is based on High Electron Mobility Transistors (HEMTs, with an AsGa/AlAsGa hetero-junction) and SiGe ASICs, and handles 34:1 multiplexing. It has been successfully tested under cryogenic conditions. The composite Tantalum absorber have been tested with 6keV X-rays, and our M.I.S. exhibit good and homogeneous sensitivity. To be compatible with the lμW@50mK thermal budget allowed in present day spatial cryo-coolers, we have also developed new thermal insulation techniques that will allow us to easily handle more than 4000 independent pixels within this tiny power budget.