Five horizontal and nine vertical field cryomagnets are available. Most of them are available from the pool on request. Sufficient advance notice to sane(at)ill.fr is required for their reservation and preparation. A very few cryomagnets are assigned to specific instruments. The scientific and technical staff of the instruments concerned are in charge of their upkeep. However major repairs and modifications are carried out in the workshop of the Advanced Neutron Environment team.

The use of the cryomagnets is under the responsibility of the instrument scientists. and local-contacts However, we provide all the necessary equipment and technical support for measuring the magnetic forces and establish the conditions in which each cryomagnet can be used. A set of angular limits and minimum distances is defined from these measurements and added to our Safety section.

New 10T vertical field magnet

We have recently received a new 10T asymmetric split-pair coil cryomagnet for the three-axis spectrometers and some of the diffractometers. This magnet features a new cryogenic system for reducing the liquid helium boil-off. Indeed, there is a standard liquid helium reservoir (about 40l) but it is cooled by a cold head and a 40K jacket attached to the first stage of the 1.5W@4.2K cryocooler. The centre of the cryostat is going to be equipped by ILL with a removable variable temperature insert (VTI) allowing the sample to be maintained at any temperature between 1.5 and 300 K. Temperatures down to 40 mK will be accessible with an ILL dilution insert. presently under construction. It is possible to add a second cryoccoler for recondensing the helium pumped out of the VTI which will further decrease the boil-off.

The access in the horizontal plane is defined by a two-pillar design proposed by ILL and calculated by Oxford Instruments NanoScience. This corresponds to a ±130° horizontal opening angle to Ø38 mm sample + 1 mm for screwing cadmium plates on all sides. The two half-coils suspended in the vacuum shall be kept apart by using two 10 mm thick 5154 aluminium rings capable of withstanding the magnetic attraction between the coils (estimated to be 106.9 kN in the OIS report). With this design, the window thickness is 20 mm radial compared to the 33 mm required in the commonly adopted continuous ring design. In the vertical plane, the neutron access will be ±5° to a sample Ø38 x 30 mm3 (minimum gap of 40 mm).

New 7T vertical field magnet

We have also recently ordered an asymmetric vertical field cryomagnet dedicated to polarised neutron reflectometry (i.e. for ADAM and D17) in collaboration with the Bochum UniversityD17. The access in the horizontal plane will be ±20° to a 20x20 mm2 sample + 1 mm for screwing cadmium plates on all sides. As regards the vertical plane, the neutron access will be ±5°. For reducing diffuse scattering, the outer chamber will feature single-crystalline sapphire windows both at the entrance and the exit of the magnet.

Within the framework of the ILL Millennium Programme, we also anticipate a new horizontal field cryomagnet dedicated to SANS and a vertical field cryomagnet for the IN5 TOF spectrometer.