Neutron beam-spot simulation and measurement for various energy bins

During the 2022 maintenance outage, the installation was completed for the new generation of spallation target-moderator-reflector-shield (TMRS), known as Mark-IV for Manuel Lujan Jr. Neutron Scattering Center (Lujan Center) at the Los Alamos Neutron Science Center (LANSCE). This paper discusses the importance of combining various techniques to ensure high-quality beam delivery to nuclear physics experiments. Advanced laser tracker survey technology was used to inform geometry in the Monte Carlo N-Particle Transport (MCNP) code for beam spot simulation. The beam spot was experimentally measured both by active high-speed gated imaging (utilizing a PI-Max4 imaging camera) and passively using image plates.



Experimental beam-spot images acquired by PI-Max4 with various scintillators were analyzed for each energy decade from 1 meV to 1 MeV by our Python scripts. The measured beam-spot distributions agree very well with our prediction by MCNP simulations and so it confirms the alignment importance for one of our flight paths to ensure uniform beam-spot distributions in the full energy range.