校正微中子望遠鏡(NuTel)之光度量測

Abstract

NuTel實驗主要目標是在捕捉超高能量的宇宙射線，利用穿山的技術來尋找能量範圍在一千兆到十萬兆電子伏特的微中子，這些超高能量的微中子很可能源自於活躍星系核、加瑪射線爆、銀河系的中心、、、等，必須做實驗來確定他們的來源。 望遠鏡的偵測器系統包含多陽極光電倍增管(Multi-Anode-Photo-Multiplier-Tube,以下簡稱光電管)、電荷分流板(CSB)、前置放大器(Pre-Amplifier)、數據收集模組(DCM)、、、等。 光電管主要的功能是將電荷訊號放大，一般可以放大三百萬倍，一支光電管有64個像素，每個像素相當於一個次光電管，各自擁有自己的增益。通常，像素之間的增益比例是一比二點五，最大可以到一比四。在鋁製的大黑箱裡，利用強度均勻的光，將其照在光電管上面。藉此，獲得各個像素的增益。 電荷分流板(CSB)接在光電管之後，在這個板上，每四個像素為一組，彼此有電阻相連結，當電荷從光電管輸出到電荷分流板上的某一像素，會將電荷分流到其他兩個像素上，分流的比例為，0.9:0.05:0.05。電荷分流板增加整個系統的動態範圍(Dynamical range)大約十倍，因此，單一像素偵測的範圍從單光電子到一千顆光電子，符合NuTel實驗的要求。使用邏輯分析儀檢測電荷分流板上的像素有無正確的連接，以及像素與電荷分流像素之間訊號衰減的比例。 數據收集模組(DCM)，接收從前置放大器傳來的電壓訊號，內建電位表(potentiometer)具有八位元(256 steps)數位微調的放大倍率，從 到2倍，調整各個像素的電位表,來補償光電管各個像素間不同的增益，使日後分析數據時，更為便利。 本論文著重在望遠鏡的校正，使用發光二極體產生光度均勻的平面光來校正望遠鏡的性能。

The goal of NuTel experiment is to catch the ultra-high-energy cosmic rays. By using technique of Mountain-Watching, we try to search tau-neutrino which energy domain span from PeV to 1000PeV.They may come from Active Galaxy Nuclei(AGN)、Gamma Ray Bursts(GRB)、Galactic Center(GC)、、、etc, or so called Top-Down models. We need experiments to confirm them. This thesis focuses on the calibration of light measurement of neutrino telescope (NuTel). The detector parts of telescope include Multi-Anode-Photo-Multiplier-Tube (MAPMT), Charge Sharing Board(CSB), Pre-Amplifier(PreAmp), Data Collection Module(DCM)……etc. Function of MAPMT is amplifying the signal of charge and generally it can be amplified about million times which is larger than original signal. One MAPMT has 64 anodes of output or so-called 64 pixels. Each pixel is equal to a sub-PMT and each has its own gain (amplification). The typical value of gain variation is 1:2.5 among all anodes and the maximum is 1:4. In the aluminum-made big black box, we used uniform light to shine on the surface of MAPMT and got the non-uniformity of MAPMT (gain variation among all anodes). CSB is 64-channels pins and is connected behind MAPMT. On this board every channel is connected to 2 other channels resistively with 0.9: 0.05: 0.05 to form a cross-talk network. The connected pixels are approximately 2.1° away in field of view to reduce the probability of being shined by the same shower. The 10% coupling to 2 other channels does not affect too much on signal, but when a large pulse saturates the charge pixel, the charge-shared pixel can be used to compute the pulse height. With the charge-sharing board, the dynamic range of the system increases the factor about 10 and becomes from 1 photoelectron to 1000 photoelectrons. We use the logical analyzer to analyze the correct connections of four pixel and correct charge sharing factor. DCM receive the voltage signal from Pre-Amplifiers. It has 8-bits (256 steps) potentiometer inside which is gain-adjustable (factors from 1/2 to 2) for each channel and it can compensate the non-uniformity of MAPMT.