Cryogen free high magnetic field sample environment for neutron scattering

Abstract

Cryogenic equipment can be found in the majority of neutron scattering experiments. Recent increases in liquid helium cost caused by global helium supply problems lead to significant concern about affordability of conventional cryogenic equipment. However the latest progress in cryo-cooler technology offers a new generation of cryogenic systems in which the cryogen consumption can be significantly reduced and in some cases completely eliminated. These systems also offer the advantage of operational simplicity, require less space than conventional cryogen-cooled systems and can significantly improve user safety. At the ISIS facility it is possible to substitute conventional cryostats with cryogen free systems. Such systems are based on the pulse tube refrigerator (PTR) which possesses no cold moving parts. Oxford Instruments in collaboration with ISIS have developed new high magnetic field sample environment equipment based on re-condensing technology. This project includes 9T wide angle chopper magnet for spectrometry and 14T magnet for diffraction. The main advantage of these systems is that all magnet operating procedures, for example cooling, running up to the field and quenching remain the same as for a standard magnet in a bath cryostat. This approach also provides a homogeneous temperature distribution, which is crucial for optimum magnet performance.