XEUS Technology

Milli-Kelvin Refrigerator for the

XEUS Cryogenic Detectors

Adiabatic Demagnetisation Refrigerator

I HepburnMullard Space Science Laboratory

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

Paramagnetic

Material

Low temperature stage

Magnet

Heat Switch

Liquid Helium Bath

Cold Plate

Low Thermal Conductivity Supports

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.

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.

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.

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.

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.

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