The Suzaku High Resolution X-Ray Spectrometer

Abstract

The X-Ray Spectrometer (XRS) has been designed to provide the Suzaku Observatory with non-dispersive, high-resolution X-ray spectroscopy. As designed, the instrument covers the energy range 0.3 to 12 keV, which encompasses the most diagnostically rich part of the X-ray band. The sensor consists of a 32-channel array of X-ray microcalorimeters, each with an energy resolution of about 6 eV. The very low temperature required for operation of the array (60 mK) is provided by a four-stage cooling system containing a single-stage adiabatic demagnetization refrigerator, a superfluid-helium cryostat, a solid-neon dewar, and a single-stage, Stirling-cycle cooler. The Suzaku/XRS is the first orbiting X-ray microcalorimeter spectrometer and was designed to last more than three years in orbit. The early verification phase of the mission demonstrated that the instrument worked properly and that the cryogen consumption rate was low enough to ensure a mission lifetime exceeding 3 years. However, the liquid-He cryogen was completely vaporized two weeks after opening the dewar guard vacuum vent. The problem has been traced to inadequate venting of the dewar He and Ne gases out of the spacecraft and into space. In this paper we present the design and ground testing of the XRS instrument, and then describe the in-flight performance. An energy resolution of 6 eV was achieved during pre-launch tests and a resolution of 7 eV was obtained in orbit. The slight degradation is due to the effects of cosmic rays.

Cooling system for the soft X-ray spectrometer onboard Astro-H

“…This provided a stable 17 K interface temperature and a clean (i.e., no microphonics) environment for the He tank and the detector. Although LHe had evaporated one month after the launch due to a design problem (location of the He vent), initial data suggested very good thermal performance as a cooling system [4]. However, we also found that using two cryogens made the cooling system complicated, and ground operations hard to manage and risky.…”

“…1 and 2. The cooling chain from room temperature to the ADR heat-sink is composed of superfluid liquid 4 He, a 3 He JouleThomson (JT) cryocooler, and double-stage Stirling cryocoolers (hereafter 2ST). The starting point of the SXS cooling system design was that of the XRS.…”

“…A likely candidate is the 3 He JT cryocooler being developed for SPICA [14,15], which has a cooling power of 10 mW at 1.7 K. Currently, a 4 He JT cryocooler has been developed as a flight model for the SMILES instrument onboard the International Space Station and is scheduled to operate in orbit beginning in 2009 [9]. Development of the 3 He JT cryocooler is, however, at the breadboard/engineering model level and is not mature yet to replace the LHe completely.…”

“…The X-Ray Spectrometer (XRS) onboard Suzaku (Astro-E2; launched in 2005) [3] was the first cryogenic X-ray detector in orbit [4]. It achieved 60 mK and energy resolution of 7 eV (FWHM) in orbit.…”

Performance of the helium dewar and the cryocoolers of the Hitomi soft x-ray spectrometer

“…In this section, the design of the SXS cooling system from room temperature to the ADR heat sink, which reflected many improvements resulting from the failure of the Suzaku x-ray spectrometer (XRS) 12 and lessons learned from it, is described. Details are described elsewhere.…”