A dedicated target station for neutron scattering under very high pulsed magnetic fields: Cold source optimization

Neutron scattering in very high pulsed magnetic fields (above 40 T) provides unique insights into the magnetic structure of materials. However, these experiments are often limited by low neutron statistics, primarily due to the mismatch between the high frequency of neutron pulses (14–60 Hz) and the low frequency of magnetic field pulses (approximately one every 5–30 minutes). To overcome this limitation, a dedicated target station specifically optimized for such high pulsed field experiments is recently proposed (Akhyani et al., 2024). In this concept, unlike conventional high-power neutron sources, the source is intended to serve only one single instrument. A key feature is the significantly reduced proton pulse frequency, which enables parallel operation using an existing high-power proton accelerator — such as the one at the European Spallation Source (ESS) — without disrupting other experiments. The lower average thermal and radiation load on the target, made possible by the infrequent proton pulses, allows the neutron guides to be positioned closer to the source and therefore smaller phase space volumes on the moderator. The present work focuses on the optimization of the Target–Moderator–Reflector (TMR) system tailored to the needs of the selected instrument. The source design is evaluated by Monte Carlo (PHITS) simulations, with brightness as the Figure-of-Merit. The gains of minimum 2.2 in a 1 cm 2 area with 1 ° divergence are achieved with optimization of cold moderator cross-sectional geometry. More improvements may be achieved through further optimization of TMR assembly. This study supports the feasibility of constructing a dedicated target station for high pulsed magnetic field applications and highlights its potential to significantly advance experimental capabilities in this area.