An X-ray detector using PIN photodiodes for the axion helioscope

An X-ray detector for a solar axion search was developed. The detector is operated in a cryostat of a superconducting magnet. Special care was paid to microphonic noise tolerance and mechanical tightness against thermal contraction. The detector consists of an array of 16 PIN photodiodes and tailor made preamplifiers. The size of each PIN photodiode is 11×11×0.5 mm3. The detector consists of two parts, the front-end part being operated at a temperature of 60 K and the main part at room temperature. Under these circumstances, the detector achieved an energy resolution of 1.0 keV in FWHM, a threshold of 2.5 keV and a background level of 6×10−5 counts s−1 keV−1 cm−2.