1. XEUS Technology Milli-Kelvin Refrigerator for the XEUS Cryogenic Detectors Adiabatic Demagnetisation Refrigerator I Hepburn Mullard Space Science Laboratory

2. Adiabatic Demagnetisation Refrigerator - ADR XEUS Cryogenic Detectors require cooling to milli- Kelvin temperatures –ADR is the ESA system of choice –System to be cooled via space cryo-coolers No liquid helium

3. ESA Engineering Model XEUS ADR End 2001 ESA announced ITT for the XEUS Engineering Model ADR system –Designed for flight (Ariane V qualification) –System to could ultimately be cooled via a space cryo-cooler. –Designed to be accommodated within a spacecraft i.e. complete control of stray magnetic fields –Designed to accommodate both STJ and TES detectors in the magnetically shielded focal plane unit.

4. ESA Engineering Model XEUS ADR Completion of construction due in next few months Mid 2002 MSSL + EADS Astrium (Stevenage) won the contract to build the XEUS EM ADR.

5. MSSL + Astrium XEUS EM ADR First world wide attempt to construct a flight cryogen free (i.e. space cryo-cooler cooled) ADR. –Rational was to identify key developments for the full system. –Driver was to demonstration a working flight system within a short time scale. Expense of mass.

6. MSSL + Astrium XEUS EM ADR Massive system –45kg 1/3 due to magnetic shielding material for large FPU 1/3 due to superconducting magnet wire (300 km of 0.1mm superconducting wire) Rest is the ADR refrigerants and structure.

7. Further work The MSSL + Astrium XEUS EM ADR is a building block for the development of the real XEUS ADR. –Tandem system (comprising two ADR systems) gives continuous operation Reduces mass by factor 5 – 10 –Heat switches To improve cooling power (magnetoresistive heat switch) –Need to work closely with the detector groups Optermisation of system – e.g. provide low mass magnetic shielding for the detector (first attempt = 12 kg due to the require large FPU) –Need to work closely with spacecraft in order to have realistic magnetic shielding for the spacecraft.

8. Conclusion Milli-kelvin cooler in good situation (testing hopefully successful!) –We have a qualified system. More work is required –Reduce the mass –Increase detector operation time (currently modelled to be ~16 hours) to continuous