The European Spallation Source (ESS), a source of neutrons, will soon be commissioned in Lund, Sweden. It will provide beams nearly 100 times more intense than those from experimental nuclear reactors, most of which are now aging or shut down. However, it is expected to meet only half of the needs for neutron analysis by 2030.

This is why European researchers are studying the feasibility of compact high-intensity neutron sources (HiCAN: High brilliance Compact Accelerator-driven Neutron Source) starting from low-energy proton accelerators. By doing so, they hope to obtain performances approaching those of reactors such as Orphée, at Saclay.

In France, the Source of Neutrons at Thermal Energies (Sonate) project aims to provide pulsed neutron beams from protons at 20 MeV and 50 kW. One of the identified difficulties is the resistance of the target (made of a light element) used to convert protons into neutrons. With this in mind, teams from Iramis (Laboratoire Léon Brillouin) and Irfu have produced a beryllium target that they installed at the exit of the IPHI high-intensity proton injector (3 MeV) at Saclay.

This target was successfully tested between January 26 and February 11, 2022. It was exposed to a 28 kW proton beam (i.e. 93% of the anticipated power) for 100 hours, followed by 31 kW for over 5 hours. During these tests, the researchers performed their first neutron diffraction experiments with this device, named "IPHI-neutrons".

For technical reasons, the measurements were performed with a non-optimized proton pulse duration and repetition rate. With better settings, the duration of the measurements would be reduced from 15 minutes to one or two minutes.

Using proton beams of the same intensity, but with a higher energy (20 MeV instead of 3 MeV), will make it possible to increase the neutron flux by more than a factor of 100. The compact source will then be very competitive with the neutron diffusion study lines from small- and medium-power nuclear reactors.