Tam, Yiu Ho = 宇宙射線渺子及其引致中子的研究 / 譚耀豪. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 148-153). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese. / Tam, Yiu Ho = Yu zhou she xian miao zi ji qi yin zhi zhong zi de yan jiu / Tan Yaohao.

Ngan, Sze Yuen = 渺子及其於香港仔隧道實驗室內的綜合研究 / 顏思遠. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 84-85). / Abstracts in English and Chinese. / Ngan, Sze Yuen = Miao zi ji qi yu Xianggangzi sui dao shi yan shi nei de zong he yan jiu / Yan Siyuan. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Cosmic Rays --- p.1 / Chapter 1.2 --- Muons --- p.3 / Chapter 1.3 --- Neutrino Oscillation --- p.5 / Chapter 1.4 --- The Daya Bay Reactor Neutrino Experiment --- p.8 / Chapter 1.4.1 --- Overview --- p.8 / Chapter 1.4.2 --- Detection Mechanism --- p.9 / Chapter 1.5 --- The Aberdeen Tunnel Experiment --- p.11 / Chapter 1.5.1 --- Overview --- p.11 / Chapter 1.5.2 --- Muon Tracker --- p.13 / Chapter 1.5.3 --- Neutron Detector --- p.16 / Chapter 2 --- Underground Muons --- p.18 / Chapter 2.1 --- Muon Simulation in the Daya Bay Experiment --- p.18 / Chapter 2.1.1 --- Gaisser's Formula --- p.20 / Chapter 2.1.2 --- Digitization of the Geographical Profile --- p.23 / Chapter 2.1.3 --- Underground Muon Flux --- p.24 / Chapter 2.2 --- Muon Simulation in the Aberdeen Tunnel Experiment --- p.25 / Chapter 3 --- Muon Behaviors in the Aberdeen Tunnel Laboratory --- p.28 / Chapter 3.1 --- Preparation --- p.29 / Chapter 3.1.1 --- Definition of the Coordinate System --- p.29 / Chapter 3.1.2 --- Generation of Muon Events --- p.30 / Chapter 3.1.3 --- Muon Trajectory --- p.35 / Chapter 3.1.4 --- Muon Energy Dissipation --- p.36 / Chapter 3.2 --- Muon Detection by the ND --- p.38 / Chapter 3.2.1 --- Energy Deposition in Gd-LS --- p.38 / Chapter 3.2.2 --- Experimental Measurements and Comparison --- p.40 / Chapter 3.2.3 --- Energy Deposition in MO --- p.42 / Chapter 3.2.4 --- ND Muon Rate --- p.43 / Chapter 3.2.5 --- Stopping Muons and Muon Decay --- p.44 / Chapter 3.3 --- Muon Detection by the Muon Tracker --- p.46 / Chapter 3.3.1 --- Selection of Top-Bottom Muons --- p.47 / Chapter 3.3.2 --- Selection of Muons which cut the Gd-LS Volume Diagonally --- p.49 / Chapter 4 --- Optimization of the Photomultiplier Tubes --- p.52 / Chapter 4.1 --- Photomultiplier Tube --- p.52 / Chapter 4.2 --- The Earth Field Effect --- p.55 / Chapter 4.2.1 --- FINEMET Magnetic Shield on PMT --- p.56 / Chapter 4.2.2 --- Magnetic Fields Measurement near the PMT Mount --- p.63 / Chapter 4.3 --- p-sec Region Ringing in PMT Signal --- p.65 / Chapter 4.3.1 --- The PMT Body and Simulated PMT Signal --- p.67 / Chapter 4.3.2 --- The Dummy Base --- p.69 / Chapter 4.3.3 --- High Voltage and the PMT Base Design --- p.71 / Chapter 5 --- Summary --- p.81 / Chapter 5.1 --- Underground Muon simulation --- p.81 / Chapter 5.2 --- Optimization of the PMTs in the Daya Bay Experiment --- p.82 / Bibliography --- p.84

Wong, Koon Kei Jackie = 香港仔地底實驗室中的宇宙渺子研究 / 黃冠棋. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 74-76). / Abstracts in English and Chinese. / Wong, Koon Kei Jackie = Xianggangzi di di shi yan shi zhong de yu zhou miao zi yan jiu / Huang Guanqi. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Motivation --- p.1 / Chapter 1.1.1 --- Neutrino Oscillation --- p.1 / Chapter 1.1.2 --- The Daya Bay Reactor Neutrino Experiment --- p.5 / Chapter 1.2 --- Cosmic muons --- p.8 / Chapter 1.2.1 --- Propagation of cosmic muons --- p.10 / Chapter 1.3 --- Aberdeen Tunnel Experiment --- p.11 / Chapter 1.3.1 --- Detection principles of Muon Tracker --- p.13 / Chapter 1.3.2 --- Detection principles of Neutron Detector --- p.16 / Chapter 1.3.3 --- The data acquisition (DAQ) and online monitoring system --- p.17 / Chapter 2 --- Study of Angular distribution of the Expected Muon Flux --- p.20 / Chapter 2.1 --- Determination of muon angular distribution detected by the muon tracker --- p.21 / Chapter 2.2 --- Spherical Harmonics Expansion of muon angular distribution --- p.29 / Chapter 3 --- Hardware Development of the Muon Tracker --- p.35 / Chapter 3.1 --- Front-end electronics board --- p.35 / Chapter 3.1.1 --- The circuit of front-end daughter board --- p.37 / Chapter 3.1.2 --- Test of the front-end daughter board --- p.39 / Chapter 3.2 --- Muon tracker PMT gain calibration --- p.45 / Chapter 4 --- Photomultiplier tubes (PMT) characterization --- p.48 / Chapter 4.1 --- Magnetic field test --- p.49 / Chapter 4.2 --- Nonlinearity test --- p.54 / Chapter 4.2.1 --- Two-LED system --- p.54 / Chapter 4.2.2 --- LED and reference PMT system --- p.56 / Chapter 4.3 --- Optimization of waveform --- p.59 / Chapter 4.4 --- Comparison with Hamamatsu's recommended PMT bases --- p.65 / Chapter 5 --- Summary --- p.71 / Chapter 5.1 --- Calculations about muon angular distribution --- p.71 / Chapter 5.2 --- Front-end electronics tests and PMT measurements --- p.71 / Chapter 5.3 --- Outlook for the Aberdeen Tunnel Experiment --- p.72 / Bibliography --- p.74

Luk, Wing Hong Antony = 地底實驗室的渺子致中子本底研究 / 陸永康. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 74-77). / Abstracts in English and Chinese. / Luk, Wing Hong Antony = Di di shi yan shi de miao zi zhi zhong zi ben di yan jiu / Lu Yongkang. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Muons at Earth´ةs Surface --- p.1 / Chapter 1.2 --- Underground Muons --- p.2 / Chapter 1.2.1 --- Muon Intensity --- p.2 / Chapter 1.2.2 --- Muon Energy --- p.6 / Chapter 1.3 --- Muon-induced Neutrons --- p.7 / Chapter 1.3.1 --- Production of Neutrons from Muons --- p.7 / Chapter 1.3.2 --- The Influence of Muon-induced Neutrons on Underground Experiments --- p.9 / Chapter 1.4 --- Aberdeen Tunnel Laboratory --- p.11 / Chapter 1.4.1 --- Geological Properties --- p.12 / Chapter 1.4.2 --- Detectors Description --- p.14 / Chapter 1.4.3 --- Detection Principles --- p.18 / Chapter 2 --- Simulation of Cosmic Muons for Aberdeen Tunnel Laboratory --- p.22 / Chapter 2.1 --- Muon Spectrum at Sea level --- p.22 / Chapter 2.2 --- Simulation of Muon Propagation through Rock --- p.23 / Chapter 2.3 --- Estimation of Expected Event Rate for the Muon Tracker --- p.28 / Chapter 3 --- Neutron Detector Simulation --- p.30 / Chapter 3.1 --- Simulation Parameters --- p.32 / Chapter 3.2 --- Energy Response --- p.35 / Chapter 3.3 --- Energy Resolution --- p.35 / Chapter 3.4 --- Neutron Drift Distance and Capture Efficiency --- p.40 / Chapter 3.5 --- Neutron Detection Efficiency --- p.42 / Chapter 3.6 --- Photons Arrival Time --- p.45 / Chapter 3.6.1 --- Cobalt-60 Source --- p.45 / Chapter 3.6.2 --- LED --- p.47 / Chapter 4 --- Simulation of Muon-induced Neutron Background --- p.49 / Chapter 4.1 --- Review on Muon-induced Neutron Simulations --- p.50 / Chapter 4.1.1 --- Methodology --- p.50 / Chapter 4.1.2 --- Results in the Literature --- p.52 / Chapter 4.1.3 --- Simulation of Muon-induced Neutrons in GdLS --- p.56 / Chapter 4.2 --- Full Monte Carlo Simulation of Expected Neutron Rate --- p.64 / Chapter 4.2.1 --- Simulation Details --- p.65 / Chapter 4.2.2 --- Results --- p.65 / Chapter 4.3 --- Estimation of the Expected Neutron Rate using Parameterization from Monte Carlo Simulations --- p.68 / Chapter 4.3.1 --- Simulation Details --- p.68 / Chapter 4.3.2 --- Results --- p.69 / Chapter 4.4 --- Summary --- p.71 / Chapter 5 --- Future Work --- p.72 / Chapter 5.1 --- Neutrons from Rock Radioactivity --- p.72 / Chapter 5.2 --- Muon-induced Neutrons from Rock --- p.73 / Chapter 5.3 --- Variation of Muon flux --- p.73 / Bibliography --- p.74

Thesis (M. Phil.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 120-122) Also available in print.

published_or_final_version / Physics / Master / Master of Philosophy

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1990. / Includes bibliographical references (leaves 172-177) / Microfiche. / xiii, 177 leaves, bound ill. 29 cm

The Daya Bay reactor neutrino experiment aims to determine sin2 2θ13 with a sensitivity of 0.01 or better at 90% confidence level. One of the major backgrounds to neutrino measurements is the muon-induced neutrons. An ex- periment had been set up inside the Aberdeen Tunnel laboratory, Hong Kong, to study spallation neutrons induced by cosmic-ray muons in an underground environment similar to the Daya Bay experiment. The Aberdeen Tunnel laboratory is 22 m above sea level at 22:23?N and 114:6?E. The amount of overburden is approximately 235 m of rocks, which is equivalent to 611 m.w.e. Rock compositions in the Aberdeen Tunnel area is similar to that in Daya Bay. MUSIC simulation results showed that in the laboratory the mean energy of muons 〈Eμ〉= 122 GeV and the integrated muon intensity I = 9:64 X10??6 cm??2 s??1. A Bonner Spheres Neutron Spectrometer (BSS) was developed to measure the ambient neutron energy spectrum. The BSS consists of a thermal neutron detector and a set of eight polyethylene spherical shells. The overall detection efficiency of the BSS was (96:7 +3:3 ??13:1)% with a detector background rate of (1:96_0:03)_10??3 s??1. The total neutron fluence rate measured at the Surface Assembly Building (SAB) of the Daya Bay experiment was (5:20 +0:81 ??0:44) _ 10??3 cm??2 s??1, which agreed with the neutron fluence rate measured in the air/ground interface in Taiwan. The unfolded SAB neutron energy spectrum showed a clear thermal-neutron peak around 20 meV and a cascade peak around 100 MeV. Detectable number of neutrons could be seen at 1 GeV. The neutron fluence rate measured at the Aberdeen Tunnel (ABT) laboratory was significantly higher then some other underground laboratories. The unfolded ABT neutron energy spectrum showed a pronounced evaporation peak around 1 MeV, and a sup- pression in the cascade peak. Detections of muon-induced neutrons inside the Aberdeen Tunnel laboratory is achieved by a Muon Tracker and a Neutron Detector. The Muon Tracker consists of three main layers of crossed plastic scintillator hodoscopes capable of determining the incoming direction of muons. The average efficiency for most of the hodoscopes was above 95%. The Neutron Detector consists of about 760 L of gadolinium-doped liquid scintillator and sixteen photomultiplier tubes. The liquid scintillator target is shield by about 1900 L of mineral oil from external radiations. The overall average detection efficiency of muon-induced neutrons was about 16%. The measurement of muon-induced neutrons in the Aberdeen Tunnel lab- oratory started from June 2011, with a total live time of about 30 days. The average rate of the accepted muon events was 0.013 Hz. The muon-induced neutron yield was determined to be Nn = (8:5 _ 0:4(syst.) _ 1:8(stat.)) _ 10??5 neutron/(μg cm??2). This value agreed with the parametrization of FLUKA-1999 simulation results if the muon energy dependence of muon-induced neutron yields was considered. / published_or_final_version / Physics / Doctoral / Doctor of Philosophy

The muon-induced radioactive isotopes, especially neutrons, are dangerous background component for rare-event detection in underground experiments, like neutrino-less double-beta decay and dark matter search. Understanding these cosmogenic backgrounds is crucial for these experiments. An underground experiment aiming at measuring the cosmic-ray muons' flux and their neutron production yield in liquid scintillator through spallation process is being carried out in the Aberdeen Tunnel laboratory located in Hong Kong with a total vertical overburden of 235 m of rocks (611 m.w.e.). The Aberdeen Tunnel detection system is constituted of a Muon Tracker (MT) for muon tagging and a Neutron Detector (ND) for neutron detection. The MT consists of 60 plastic scintillator hodoscopes to determine the incoming muon direction and the ND is a two-zone detector containing 760 L of gadolinium-doped liquid scintillator as target volume and 1900 L of mineral oil as shields. The experiment has been taking data stably since 2012. To obtain reliable results, the detector performance and the stability of the experiment have been studied in this work. Muon-induced fast neutrons can be captured in Gd-LS with characteristic energies released and the capture time follows a characteristic exponential distribution. By using the capture time and energy information, we can select the neutron candidates and thus calculate the neutron production yield. The energy of a neutron capture event is reconstructed from the calibrated photo-multiplier tube signals, while the directions of cosmic-ray muons can be reconstructed from the MT. The mean energy of the incoming muons that pass the selection criteria was estimated by a simulation code MUSIC that transported atmospheric muon spectrum through the mountains to the laboratory, and is found to be 92 GeV. The neutron production yield is calculated to be Yn = (3:28 ±0:12(sta:) ±0:24(sys:)) X 〖10〗^(-4) (n/μ〖gcm〗^(-2)) for both the showering muon and single muon events. This result is about two times higher than the expectation value from previous simulations and experiments. The neutron production yield of the single muons is calculated to be Yn = (1:04 ± 0:08(sta:) ± 0:07(sys:)) X 〖10〗^(-4) (n/μ〖gcm〗^(-2)). This reveals a enhancement of the neutron production from the muons accompanied by showers. / published_or_final_version / Physics / Master / Master of Philosophy

Astrophysical observations give convincing evidence for a vast non-baryonic component, the so-called dark matter, accounting for over 20% of the overall content of our Universe. Direct dark matter search experiments explore the possibility of interactions of these dark matter particles with ordinary baryonic matter via elastic scattering resulting in single nuclear recoils. The ZEPLIN-III detector operated on the basis of a dualphase (liquid/gas) xenon target, recording events in two separate response channels { scintillation and ionisation. These allow discrimination between electron recoils (from background radiation) and the signal expected from Weakly Interacting Massive Particle (WIMP) elastic scatters. Following a productive first exposure, the detector was upgraded with a new array of ultra-low background photomultiplier tubes, reducing the electron recoil background by over an order of magnitude. A second major upgrade to the detector was the incorporation of a tonne-scale active veto detector system, surrounding the WIMP target. Calibration and science data taken in coincidence with ZEPLIN-III showed rejection of up to 30% of the dominant electron recoil background and over 60% of neutron induced nuclear recoils. Data taking for the second science run finished in May 2011 with a total accrued raw fiducial exposure of 1,344 kg days. With this extensive data set, from over 300 days of run time, a limit on the spin-independent WIMP-nucleon cross-section of 4.8 10-8 pb near 50 GeV/c2 WIMP mass with 90% confidence was set. This result combined with the first science run of ZEPLIN-III excludes the scalar cross-section above 3.9 10-8 pb. Studying the background data taken by the veto detector allowed a calculation of the neutron yield induced by high energy cosmic-ray muons in lead of (5.8 0.2) 10-3 neutrons/muon/(g/cm2) for a mean muon energy of 260 GeV. Measurements of this kind are of great importance for large scale direct dark matter search experiments and future rare event searches in general. Finally, this work includes a comprehensive measurement of the energy dependent quenching factor for low energy nuclear recoils in a plastic scintillator, such as from the ZEPLIN-III veto detector, increasing accuracy for future simulation packages featuring large scale plastic scintillator detector systems.