Magnet systems for neutron scattering experiments

Recondensing dewars use a cryocooler to capture evaporated gas and turn it back into liquid helium. Using recondensing technology considerably decreases the helium consumption of these magnets while enabling the stringent magnet designs required by neutron scattering applications. These highly complex magnets are good examples of how researchers and industry can work together to push technological boundaries.

The ILL received a 10 T asymmetric split pair coil magnet for their three-axis spectrometers. Dr Eddy Lelièvre-Berna, Advanced Neutron Environment Team Leader at ILL, commented: “With this new design, the superconducting coils are reliably maintained at low temperature within a liquid Helium bath while considerably reducing the boil-off. Compared with dry systems, the absence of room-temperature bore provides a much larger sample space. It also reduces the amount of material in the beam and avoids unwanted neutron absorption and neutrons scattered to the detectors. Together, we have really made a step forward. Among the many topics to be investigated with this magnet are multiferroic properties, quantum phase transitions and excitations in single-molecule magnets. Our satisfaction is such that we have decided to order another magnet for studying the magnetic substrates of our future hard disks.”

The ISIS Neutron Source purchased two recondensing neutron scattering magnets including a 9 T wide angle and 14 T at 4.2 K. These magnets will be used on the Let, Merlin and Wish instruments at ISIS. Dr. Oleg Kirichek, Sample Environment Group Leader at ISIS, Rutherford Appleton Laboratory commented: “Having a recondensing system allows us to considerably reduce our helium cost and health and safety issues. It also provides a homogeneous temperature distribution, which is crucial for optimum magnet performance. With these magnets, we should be able to provide our users with high magnetic field sample environments for neutron scattering experiments in a number of research areas such as high temperature superconductors, quantum magnets, spintronic materials, spin frustrated systems, heavy fermions, nanomagnetic materials and the recently discovered iron-based high-temperature superconductors.”

Dr John Burgoyne, Manager of the Magnets Business Group at Oxford Instruments says: “Working with ILL and ISIS gave us access to some of the world’s leading neutron scientists. Their knowledge and expertise in neutron scattering was crucial to the successful delivery of these innovative systems. It has also enabled us to expand our knowledge and develop a new system that we can offer to other facilities.”