Dayabay Antineutrino Detectors and Aberdeen Neutrino Detector Study

大亞灣微中子震盪實驗位於中國大亞灣, 是一個利用核反應爐所產生的反電子微中子來尋找微中子混合角之一的. 大亞灣的目標是想要找出比現今已知的實驗數據更精確的測量. 探測機制是利用反微中子造成的反衰變中的正子與中子(延遲信號). 因此對於大亞灣實驗中的中子背景的了解是很重要的. 渺子感應中子背景能夠藉由位於香港的香港仔隧道實驗所探知. 香港仔中子探測器能夠探知從宇宙射線中產生的感應中子背景, 其中大多數來源為穿過探測器(或是其附近)的渺子. 香港仔隧道實驗站在大亞灣實驗站不遠的距離, 並且有個相似的地質結構. 因此在香港仔實驗中所觀測到的中子流量是大亞灣實驗中一個重要的參考. 本論文主要討論大亞灣實驗用之壓克力圓桶的設計製造與光學性質. 對於香港仔中子探測器, 將主要討論測試利用基因演算法當作事件重建的核心演算法的表現. 這樣的重建方法也許可以成為大亞灣實驗中的重建方法的一種. 本篇論文也將簡短介紹近期大亞灣和香港仔實驗的近況和展望.Dayabay neutrino experiment in Dayabay, China is a high-precision mea-urement experiment of the reactor anti-electron neutrino flux at Dayabayo search for neutrino mixing angle θ13. The goal of the Dayabay reac-or antineutrino experiment is to determine the unknown mixing angle13 with a sensitivity of 0.01 or better in sin2θ13, an order of magnitudeetter than the current experimental limit.he detection mechanism is to detect both positron (prompt) and neu-ron (delayed) generated from inverse β decay of anti-neutrino. Thus thenderstanding of neutron background in Dayabay neutrino experiments important. Muon-induced neutron background can be detected in theberdeen neutron detecotr in Aberdeen, Hong Kong. Aberdeen neutronetector monitors the induced neutron backgound from the cosmic raysost of which are mouns, nearby or passing through the detector. Ab-rdeen is nearby Dayabay site and with similar geological composition asayabay site. The neutron flux observed by Aberdeen Experiment woulde a important reference of Dayabay Experiment.his thesis focuses on the R&D, construction, and optical property ofcrylic vessel of antineutrino detector for Dayabay Experiment. For theeutron detector of Aberdeen Experiment, the test of generic algorithm foreconstruction is mainly discussed. It is expected this kind of algorithmould be one of the reconstruction algorithm for Dayabay antineutrinoetector. This thesis also briefly introduces the recent milestones of bothhe Dayabay experiment and Abedeen experiment.1 Introduction 1.1 Neutrinos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.1 Neutrino Oscillation, θ13 and Standard Model . . . . . . . . . 2.2 The Dayabay Neutrino Oscillation Experiment . . . . . . . . . . . . . 2.2.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 The Dayabay Anti-neutrino Detectors . . . . . . . . . . . . . . . . . . 5 Aberdeen Neutron Detector 11.1 A experiment at Aberdeen . . . . . . . . . . . . . . . . . . . . . . . . 11.2 The Neutron Detector at Aberdeen . . . . . . . . . . . . . . . . . . . 14.2.1 Design and Signals . . . . . . . . . . . . . . . . . . . . . . . . 14 Acrylic Vessel R&D and Integration 17.1 Overview of A Acrylic Vessel of Dayabay and Aberdeen Experiment . 17.2 Optical QA Instrument and Method . . . . . . . . . . . . . . . . . . 18.2.1 Spectrometer and Integrating sphere . . . . . . . . . . . . . . 18.2.2 Basic Performance . . . . . . . . . . . . . . . . . . . . . . . . 20.2.3 Transmittance Measurement of Acrylics . . . . . . . . . . . . 20.2.4 Reflectance Measurement of Acrylics . . . . . . . . . . . . . . 24.2.5 Sources of Error of Both Transmittance and Reflectance Mea-urement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.2.6 Measurement of Refractive Index and Attenuation Length ofcrylics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.3 Acrylic Optical Property of AD and Neutron Detector . . . . . . . . 30.3.1 Bonding and Aging . . . . . . . . . . . . . . . . . . . . . . . . 35.3.2 Polish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37.3.3 Acrylic Optical Property for Simulations . . . . . . . . . . . . 39.3.4 Summary of Optical Property of Dayabay and Aberdeen Acrylicessels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42.3.5 Dayabay AD Geometry QA . . . . . . . . . . . . . . . . . . . 42.4 Integration of Dayabay Acrylic Vessel . . . . . . . . . . . . . . . . . . 44.4.1 Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44.4.2 Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 Detector Simulation 47.1 Offline Software Overview . . . . . . . . . . . . . . . . . . . . . . . . 47.1.1 G4dyb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47.1.2 NuWa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47.2 The Effect of Optical Property Measurement . . . . . . . . . . . . . . 48.2.1 The Behavior of Optical Photons Passing Through Acrylics . . 48.2.2 The Optical Model . . . . . . . . . . . . . . . . . . . . . . . . 48.2.3 Comparison of Different Acrylic Optical Models . . . . . . . . 51 Event Reconstruction 55.1 Event Reconstruction of Aberdeen Neutron Detector . . . . . . . . . 55.1.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55.1.2 Test of GA for Aberdeen Neutron Detector . . . . . . . . . . . 56.1.3 Fitness Definition . . . . . . . . . . . . . . . . . . . . . . . . . 57.1.4 Comparison of Different Fitness Definitions . . . . . . . . . . . 60.2 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.2.1 Suggested Fitness Definition . . . . . . . . . . . . . . . . . . . 62.2.2 Fitness Definition for Aberdeen Neutron Detector . . . . . . . 65 Data and Analysis 67.1 Dayabay Dry Run . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67.2 Preliminary Aberdeen Calibration . . . . . . . . . . . . . . . . . . . . 67 Summary and Conclusion 73.1 Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73ibliography 7