Measurement of Cosmic-ray Muons and Muon-induced Neutrons in the Aberdeen Tunnel Underground Laboratory

TL;DR

This study measures muon flux and muon-induced neutron production underground, providing key data for understanding background radiation in underground physics experiments.

Contribution

It presents new measurements of muon flux and neutron yield at a specific underground depth, including their energy dependence, using a dedicated detection setup.

Findings

Muon flux measured as (5.7 ± 0.6) × 10^{-6} cm^{-2}s^{-1}sr^{-1}

Muon-induced neutron yield determined as (1.19 ± 0.08 (stat) ± 0.21 (syst)) × 10^{-4} neutrons/(db7gb7cm^{-2})

Neutron yield's energy dependence follows b7E_{b7}^0.76 b1 0.03

Abstract

We have measured the muon flux and production rate of muon-induced neutrons at a depth of 611 m water equivalent. Our apparatus comprises three layers of crossed plastic scintillator hodoscopes for tracking the incident cosmic-ray muons and 760 L of gadolinium-doped liquid scintillator for producing and detecting neutrons. The vertical muon intensity was measured to be $I_{\mu} = (5.7 \pm 0.6) \times 10^{-6}$ cm$^{-2}$s$^{-1}$sr$^{-1}$. The yield of muon-induced neutrons in the liquid scintillator was determined to be $Y_{n} = (1.19 \pm 0.08 (stat) \pm 0.21 (syst)) \times 10^{-4}$ neutrons/($\mu\cdot$g$\cdot$cm$^{-2}$). A fit to the recently measured neutron yields at different depths gave a mean muon energy dependence of $\left\langle E_{\mu} \right\rangle^{0.76 \pm 0.03}$ for liquid-scintillator targets.