Structural analysis of a cryogen-free refrigerator for space

Abstract Future X-ray observatories in space, such as European Space Agency's (ESA) X-ray evolving universe spectroscopy (XEUS) mission, will require cooling to the region 10–100 mK to enable the utilisation of advanced cryogenic photon detectors in cryogenic spectrometer instruments. Such missions are envisaged to be completely cryogen-free, replacing the traditional superfluid liquid helium cryostat with a space worthy mechanically cooled system. As part of the Mullard Space Science Laboratory's (MSSL) adiabatic demagnetisation refrigerator (ADR) development programme, we have investigated the construction of a flight cryostat containing a 10 mK ADR (the MSSL double ADR (dADR)) that can be cooled by a single Astrium (formally Matra Marconi Space (MMS)) 4 K mechanical cooler. A proto-type dADR has been constructed and will be flight proven as part of a sounding rocket payload, where the dADR system will be used to cool an array of superconducting tunnel junction (STJ) detectors at the focus of an X-ray telescope.