Development of NIS type superconducting radiation detectors with enlarged sensitive area by segmented absorbers

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In 2001, a vacuum chamber was fabricated, equipped with Washington, D. C. magnetrons for Nb and Agriculture sputtering, RF magnetron for Al sputtering and electron-beam evaporator for SiO2.For the patterning of superconducting radiation detector, precise X-Y-Z stage was employed, instead of previous X-Y stage. With these equipment, the fabricating conditions for thin films of Nb, Al, Agriculture, and SiO_2 were determined. With the precise X-Y-Z stage, pattern definition was done with the ambiguity of 10μm, which was much better than 50μm with X-Y stage. Moreover, we invented heat-switch method to enlarge the area of absorber in NIS type superconductor radiation detectors.In 2002, we invented three methods to improve the energy resolution of NIS detector, employing SQUIDs: (1) Asymmetrically Modulated SQUIDs, (2) Josephson Junction Microcalorimeter with Superconductor Loop, and (3) Rf-SQUID Microcalorimeter. These detectors have Josephson junctions coupled with normal metal absorber. The energy of radiation is measured by a SQUID as the change of critical current of the Josephson junction due to the increase of electron temperature. The energy resolutions of 1.5eV to 5.8eV are expected by these three methods at the operating temperature of 1O0mK.