Abstract:
The contribution to γ-ray background from secondary neutrons, originating from cosmic muon
interactions in Pb-Cu composite shield, has been measured via (n, n
γ) reactions in Cu and Ge. The
minimization of background plays a key role in improving the sensitivity of rare event experimental searches
like neutrinoless double beta decay and neutron background is often a major concern. It is important to
understand secondary neutron production from cosmic muons, especially in materials like Cu and Pb,
which often form a part of the detector or shields. The direct contribution of fast neutrons generated from
cosmic muon interactions to the γ-ray background via (n, n
γ) reactions is investigated for the first time.
Measurements are carried out in the low background HPGe detector setup, TiLES, using Pb-Cu composite
shield as target material for muon interactions. Simulations have been carried out with GEANT4.10.00
and GEANT4.10.05, each with two different Physics lists. The observed intensities of (n, n
γ) for Cu are
significantly under-predicted by GEANT4.10.00, while GEANT4.10.05 shows good agreement with the
experimental data.
