以大亞灣實驗之中子捕捉信號量測微中子震盪混合角θ13 江門微中子實驗中心探測器之三吋光電倍增管的特性測試

Abstract

本論文分為兩個部分，一部份在於以不同以往的分析信號在大亞灣實驗中量測微中子震盪混合角θ13，另一部份著重在江門微中子觀測站之三吋光電倍增管的建製與測試。 大亞灣微中子震盪實驗在2012 年發表了第一個統計上信心水準大於5 σ 的微中子震盪混合角θ13 量測結果，確信了θ13 非零值。而大亞灣實驗在2018 的最新發表結果依舊是目前最精準之θ13 量測，此量測是依靠逆β 衰變產物中的中子-釓捕捉信號來完成。異於前述分析，本文中的θ13 量測是利用中子-釓, 中子-氫, 及微量中子-碳捕捉信號，而量測結果sin2 2θ13 = 0.077 ± 0.0070(Stat) ± 0.0047(Syst)以9.1 σ 的信心水準再次佐證了θ13 的非零值假設。此結果與日前大亞灣最精準的量測結果差距為1.02 σ, 因此在統計上兩結果具有一致性。 江門微中子震盪實驗計畫在2021 年底開始採計數據，並預期五至六年的數據量能夠以3 到4 σ 的信心水準決定微中子質量順序。論文第二部分介紹26,000 隻已生產之三吋光電倍增管的工廠量測及合作組抽樣結果，其中因後脈衝而導致的抽樣不合格率達到了1%(3% 抽樣率)，而其餘較基本參數所導致的抽樣不合格率約為0.1%(10% 抽樣率)。為了與最終光電倍增管與數據採集電子學系統的整合測試相互對比，我們仍在研究之獨立測試平台目前能成功的測量增益對高壓曲線，量測單光電子解析度，以及單光電子的時間傳遞飄移。對比光電倍增管工廠所給出的出廠參數，測試平台給出的結果並無相互牴觸。

There’re two parts in this thesis, one is using a channel different from the past to analyize neutrino oscillation mixing angle θ13 in DayaBay experiment, the other focus on characterizations of 3 inches photomultiplier tubes in Jiangmen Underground Neutrino Observatory(JUNO) experiment. In 2012, DayaBay collaboration published the first 5 σ measurement of neutrino oscillation mixing angle θ13, which established the truth of non-zero value of θ13. The updated results in 2018 is still the most precise measurement so far, this measurement was done by using inverse β decay followed by neutron-Gadolinium capture signal. Distinct with previous analysis, we’re doing the measurement of θ13 by using the same decay but followed by neutron-Gadolinium, neutron-Hydrogen, and trace neutron-Carbon capture signal, the result sin2 2θ13 = 0.077±0.0070(Stat)±0.0047(Syst) again shows non-zero value of θ13 in 9.1 σ of confidence level. The 1.02 σ difference between our result and current precisest result are consistent with each other in statistics. JUNO experiment plans to start taking data in late 2021, and expects to determine the mass hierarchy in 3 or 4 σ of confidence level with five or six years amount of data. The second part of thesis introduces the vendor qualities and acceptance sampling test of 26,000 3 inches photomultiplier tubes which already been produced. Among the sampling, there’re 1% failure rate due to large after pulses (in 3% sampling rate), and 0.1% failure rate for the other basic quantities (in 10% sampling rate). To cross check the final integration test of tubes and data acquisition electronics combined together, the independent test bench, developed in National Taiwan University, now can successfully measure the gain curve, single photo-electron resolution, and single photo-electron transit time spread. These results are quite promising in compare with the data sheets provided by company.