Aberdeen Tunnel Research Articles

Publisher’s Note: Measurement of cosmic-ray muons and muon-induced neutrons in the Aberdeen Tunnel Underground Laboratory [Phys. Rev. D 93 , 072005 (2016)

Received 4 November 2016DOI:https://doi.org/10.1103/PhysRevD.94.099906© 2016 American Physical Society

Measurement of cosmic-ray muons and muon-induced neutrons in the Aberdeen Tunnel Underground Laboratory

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.

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

Muon-induced neutrons are one of the major backgrounds to various underground experiments, such as dark matter searches, low-energy neutrino oscillation experiments and neutrino-less double beta-decay experiments. Previous experiments on the underground production rate of muon-induced neutrons were mostly carried out either at shallow sites or at very deep sites. The Aberdeen Tunnel experiment aims to measure the neutron production rate at a moderate depth of 611 meters water equivalent. Our apparatus comprises of six layers of plastic-scintillator hodoscopes for tracking the incident cosmic-ray muons, and 760 L of gadolinium-doped liquid-scintillator for both neutron production and detection targets. In this paper, we describe the design and the performance of the apparatus. The preliminary result on the measurement of neutron production rate is also presented.

An apparatus for studying spallation neutrons in the Aberdeen Tunnel laboratory

In this paper, we describe the design, construction and performance of an apparatus installed in the Aberdeen Tunnel laboratory in Hong Kong for studying spallation neutrons induced by cosmic-ray muons under a vertical rock overburden of 611m water equivalent (m.w.e.). The apparatus comprises six horizontal layers of plastic-scintillator hodoscopes for determining the direction and position of the incident cosmic-ray muons. Sandwiched between the hodoscope planes is a neutron detector filled with 650kg of liquid scintillator doped with about 0.06% of Gadolinium by weight for improving the efficiency of detecting the spallation neutrons. Performance of the apparatus is also presented.

Overview of the Aberdeen Tunnel Laboratory

An underground laboratory (Aberdeen Tunnel Laboratory) was built inside a traffic tunnel (Aberdeen Tunnel) in the Hong Kong Island in the early 80ʼs for the study of cosmic-ray muon anisotropy. The laboratory has an overburden of about 250 m of rock, which is comparable to those of the detector halls proposed for the Daya Bay Neutrino Experiment in Guangdong Province, China. Given the very similar geographical location, the geology and background radiation to those in Daya Bay, the Aberdeen Tunnel Laboratory is an ideal testing ground for the Daya Bay Experiment. This project aims to study the neutrons initiated from cosmic muons by detecting the neutrons with a 0.5 ton neutron detector comprising of Gd-doped liquid scintillators viewed by PMTs. The events will be triggered by a muon tracker consisting of 3 horizontal layers of crossed stainless steel proportional counters and plastic scintillators, with 2 layers above and 1 layer below the neutron detector. It is hoped that the results will help in understanding and minimizing the neutron background in Gd-doped liquid scintillator based neutrino detectors. This paper presents an overview of the laboratory, the geology and radiation background, and the proposed detectors.

Ground problems at Hong Kong's Aberdeen Tunnel

Ground problems at Hong Kong's Aberdeen Tunnel