本文選題：宇宙線 + 大型高海拔空氣簇射觀測站　； 參考：《中國科學(xué)技術(shù)大學(xué)》2014年博士論文

【摘要】：宇宙線自發(fā)現(xiàn)以來就成為了人類探索宇宙的重要媒介。在過去的100多年的時間中,科學(xué)家逐漸了解了宇宙線的許多信息,包括宇宙線的成分、能譜等,但宇宙線仍然存在著許多未解之謎。 尋找宇宙線的起源是宇宙線物理的核心問題。為了探索和研究這一問題,我國科學(xué)家提出了在我國的高海拔地區(qū)建設(shè)一個大型的宇宙線觀測站——大型高海拔空氣簇射觀測站(Large High Altitude Air Shower Observatory,LHAASO)。 LHAASO的核心科學(xué)目標(biāo)是探索高能宇宙線起源,研究相關(guān)天體演化和暗物質(zhì)等。LHAASO由四個探測器陣列組成,包括占地一平方公里的粒子簇射地面陣列(Kilometer-square Array, KM2A)、水切倫科夫探測器陣列(Water Cherenkov Detector Array,WCDA)、廣角切倫科夫望遠(yuǎn)鏡陣列(Wide Field of View Cherenkov Telescope Array,WFCTA)、簇射芯探測器(Shower Core Detector Array, SCDA)。 WCDA是LHAASO的重要組成部分,其探測目標(biāo)是巡天掃描北半球的甚高能1,射線源。WCDA的總面積達到90000平方米,由四個同樣大小的水池組成。每個水池被分成了900路5m×5m的單元探測器。每單元探測器需要一支八英寸半球形光電倍增管,光陰極朝上,用于記錄水中產(chǎn)生的切倫科夫光的電荷和時間信息。物理模擬結(jié)果表明WCDA信號讀出要求滿足的性能指標(biāo)包括：信號增益約為2.5×106,單光電子譜的峰谷比2.0,暗噪聲計數(shù)率5kHz,信號上升時間4ns,渡越時間分散4ns,線性動態(tài)范圍達到1-4000光電子。 LHAASO WCDA研制的關(guān)鍵問題是要解決光電倍增管的大動態(tài)讀出性能,難度在于在較高的增益水平下,必須保持很大的線性動態(tài)范圍,同時還需要具備良好的單光電子分辨能力以及時間性能。由于常規(guī)的PMT信號讀出設(shè)計方案很難同時滿足這些需求,因此需要研究如何改進和優(yōu)化光電倍增管的分壓及讀出電路。 論文首先對宇宙線物理進行了論述,包括宇宙線的成分、能譜、起源、傳播和加速機制、探測手段等。詳細(xì)調(diào)研了國內(nèi)外一些大型的水切倫科夫探測器,以及這些探測器所使用的光電倍增管的性能指標(biāo)。詳細(xì)的論述了水切倫科夫探測器和WCDA的工作機制以及實驗要求。 論文研究的主要課題是針對WCDA的具體實驗要求,對大面積光電倍增管(Hamamatsu R5912)的讀出電路進行設(shè)計和改進,并通過大量的實驗研究提出一種滿足WCDA實驗要求的PMT分壓和信號讀出設(shè)計方案。測試的結(jié)果表明,在1000V的工作電壓下,光電倍增管的增益能夠達到2.5×106,單光電子譜的峰谷比為2.4,脈沖信號上升時間約為4ns,單光子渡越時間分散為3.67ns,暗噪聲計數(shù)率在工作增益下為l kHz左右,陽極和第十打拿極的線性動態(tài)范圍最大能夠達到3500個光電子,第八打拿極的線性動態(tài)范圍能夠達到6000個光電子以上,這是R5912首次在該增益下能夠達到如此大的線性動態(tài)范圍,解決了WCDA研制和PMT讀出設(shè)計的關(guān)鍵問題。文中詳細(xì)論述了這些性能參數(shù)的具體測試方法,以及為開展此項研究,所建立的PMT性能測試系統(tǒng)。 由于WCDA有3600路單元探測器,因而一共有3600個光電倍增管需要進行性能測試。因此,需要建立起一套裝置以實現(xiàn)批量測試。我們在單個PMT性能測試基礎(chǔ)上,完成批量測試裝置研究。該測試裝置包括暗箱、分光器、光纖、電子學(xué)、數(shù)據(jù)獲取系統(tǒng)等。該裝置進行測試結(jié)果顯示,其避光性、電磁屏蔽能力、分光均勻性,以及電子學(xué)和數(shù)據(jù)獲取系統(tǒng)工作正常,各項性能能夠滿足批量測試的需求。 研究結(jié)果為LHAASO立項及WCDA工程設(shè)計提供重要的數(shù)據(jù),為下一步研究奠定了必要的基礎(chǔ)。
[Abstract]:Since the discovery of the cosmic ray has become an important medium for human exploration of the universe. Over the past 100 years, scientists have gradually learned a lot of information about the cosmic ray, including the composition and spectrum of the cosmic rays, but there are still many unsolved mysteries in the cosmic ray.
Looking for the origin of cosmic rays is the core of cosmic ray physics. In order to explore and study this problem, Chinese scientists have proposed to build a large cosmic ray observatory at high altitude in our country, the large high altitude air shower observation station (Large High Altitude Air Shower Observatory, LHAASO). The core science of LHAASO. The goal is to explore the origin of the high-energy cosmic ray, and to study the evolution of the celestial bodies and the dark matter, such as the.LHAASO consists of four detector arrays, including the Kilometer-square Array (KM2A), the water Cherenkov detector array (Water Cherenkov Detector Array, WCDA), and the wide angle Cherenkov array. Column (Wide Field of View Cherenkov Telescope Array, WFCTA), shower core detector (Shower Core Detector Array, *).
WCDA is an important part of LHAASO. Its detection target is very high energy 1 in the northern hemisphere, the total area of the ray source.WCDA is 90000 square meters, and it is composed of four same sized pools. Each pool is divided into 900 5m x 5m unit detectors. Each unit detector needs a eight inch hemispherical photomultiplier. It is used to record the charge and time information of the Cherenkov light produced in the water. The physical simulation results show that the performance indexes of the WCDA signal readout include: the signal gain is about 2.5 x 106, the peak to valley ratio of the single photoelectron spectrum is 2, the dark noise counting rate is 5kHz, the signal rise time is 4ns, the crossing time dispersing 4ns, the linear dynamic range is reached. To 1-4000 photoelectrons.
The key problem of the development of LHAASO WCDA is to solve the large dynamic readout performance of the photomultiplier tube. The difficulty lies in maintaining a large linear dynamic range at a higher gain level, and having a good single photoelectron resolution and time performance. The conventional PMT signal readout design is difficult to meet at the same time. Therefore, it is necessary to study how to improve and optimize the voltage divider and readout circuit of photomultiplier tube.
This paper first discusses the cosmic ray physics, including the composition of the cosmic ray, the energy spectrum, the origin, the propagation and the acceleration mechanism, the detection method, and so on. It investigates some large water Cherenkov detectors at home and abroad, as well as the properties of the photomultiplier tubes used by these detectors. The water Cherenkov detector and WCD are discussed in detail. The working mechanism of A and the requirements of the experiment.
The main topic of this paper is to design and improve the readout circuit of the large area photomultiplier (Hamamatsu R5912) for the specific experimental requirements of WCDA. A design scheme of PMT partial pressure and signal readout to meet the requirements of the WCDA experiment is proposed by a large number of experimental studies. The results of the test show that under the working voltage of 1000V, light is used. The gain of the multiplier tube can reach 2.5 x 106, the peak to valley ratio of the single photoelectron spectrum is 2.4, the pulse signal rise time is about 4ns, the single photon crossing time is 3.67ns, the dark noise counting rate is about L kHz under the working gain, and the maximum linear dynamic range of the anode and tenth hits can reach 3500 photoelectrons and the eighth hits the polar line. The sexual dynamic range can reach 6000 optoelectronics. This is the first time that R5912 can reach such a large linear dynamic range under this gain. It solves the key problem of WCDA development and PMT readout design. The specific testing methods of these performance parameters are discussed in detail, and the PMT performance test system is set up to carry out this research. Unification.
Since WCDA has 3600 unit detectors, a total of 3600 photomultiplier tubes are required to perform performance testing. Therefore, a set of devices is needed to achieve batch testing. On the basis of a single PMT performance test, we complete a batch test device. The test device includes a dark box, a splitter, an optical fiber, a electronics, a data acquisition system. Test results show that the device can avoid light, electromagnetic shielding, optical uniformity, and the electronic and data acquisition system work normally, and the performance can meet the needs of batch testing.
The research results provide important data for LHAASO project and WCDA engineering design, and lay a necessary foundation for further research.
【學(xué)位授予單位】：中國科學(xué)技術(shù)大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：P172.4

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本文編號：1916027