Neutron detection capabilities of Water Cherenkov Detectors and others developments

IVAN SIDELNIK; GUARIN, NICOLÁS; ALCALDE BESSIA, FABRICIO; ARNALDI, H.; JOSE LIPOVETZKY; PEREZ, MARTÍN; MIGUEL SOFO HARO; BERISSO, MARIANO GÓMEZ; ASOREY, HERNAN; BLOSTEIN, JUAN JERÓNIMO

S.C de Bariloche

Workshop; 7th International Meeting of Union for Compact Accelerator-driven Neutron Sources; 2018

Departamento de Física de Neutrones (CAB)

In this work we show the neutron detection capabilities of a water Cherenkov detector (WCD). This type of detector is used in different big observatories, such as The Pierre Auger Observatory in Argentina, and the Latin American Giant Observatory (LAGO) across the Andes, for the study of cosmic rays in a very wide energy range. The experiments presented here were performed by using a single and simple, one PMT, WCD and $^{241}$AmBe and $^{252}$Cf neutron sources, using only pure water without additives as the detection volume. Different neutron moderators and shielding configurations and distances have been explored. We show that fast neutrons from the $^{241}$AmBe and $^{252}$Cf sources, as well as thermal neutrons coming from a neutron moderator and exhibiting different spectral characteristics, can be detected and identified over the flux of atmospheric particles background. The characteristic pulse-height histogram shapes are recorded as a clear signature of neutrons with energies lower than $simeq$11,MeV, which is the maximum neutron energy experimentally available with the sources we used. This was verified for different experimental conditions and even with detailed simulations based on Geant4, that corroborate neutron detection capabilities in the energy range from meV to GeV, dependingonly on the geometry of the active detection volume. Using a 1-ton detector, we estimate from our measurements a neutron detection efficiency at the level of (10$pm$5)%.Being the active volume a cheap and easily accessible material, the results obtained in this work are of great interest for the development of large neutron detectors for different applications, at a small fraction of the cost of current technologies. Of special importance are those related with space weather phenomena as well as those for the detection of fissionable or fusionable special nuclear materials.