Alpha emission from actinide impurities in Al is a source of background counting rate in Multi-Grid type detectors of thermal neutrons. The alpha emission rates from samples of radio-purity Al and \mathrm{Al/B_{4}C} composite, used in grid construction, were measured on a large-area, low background spectrometer. Although the alpha emission rate from the composite was a factor \sim280 higher than radio-pure Al, \mathrm{25\:\mu m} Ni plating of the composite reduced the rate by a factor \sim1170. Background counting rates in two Multi-Grid prototypes were compared. They used identical configurations of \mathrm{B_{4}C}-coated, radio-pure Al normal blades for the grids, but the first employed radio-purity Al for the radial blades, while the second used Ni-plated \mathrm{Al/B_{4}C} on the radial blades. The background rate from the second prototype was around 20% of that from the first.
Cite
@article{arxiv.2605.22230,
title = {Alpha Background in Multi-Grid Neutron Detectors},
author = {A. Backis and C. -C. Lai and J. R. M. Annand and K. G. Fissum and G. Zuzel and M. Czubak and K. Livingston},
journal= {arXiv preprint arXiv:2605.22230},
year = {2026}
}