THE X-RAY SPECTROMETER (XRS) - A MULTISTAGE CRYOGENIC INSTRUMENT FOR THE ASTRO-E X-RAY ASTROPHYSICS MISSION

The XRS cryogenic system has undergone numerous system configuration c hanges since its inception in the early 1980s. The Astro-E XRS is a hi gh precision X-ray spectrometer with better than 20 eV resolution betw een 0.3 and 10 keV. It is a single photon counting solid-state calorim eter with pixel elements cooled to similar to 0.065 K by a unique thre e-stage cooling system. The low temperature is produced by an adiabati c demagnetization refrigerator (ADR) operating between 0.065 K and 1.3 K. The 1.3 K temperature is maintained by a 33 litre helium tank. Gra phite/epoxy straps suspend the helium tank from an outer cryogen tank containing 120 litres of solid neon at similar to 17 K. The neon tank is in turn suspended from the dewar mainshell by low-conductivity stra ps. The system has a minimum design lifetime of 2 years, with a 2.5-ye ar goal. The instrument design is severely constrained by mass limitat ions (less than or equal to 400 kg) and high launch loads. The Astro-E will fly in 2000 on an ISAS M-V solid rocket. The M-V is a new launch vehicle, with the first launch scheduled for 1996.