發(fā)布時(shí)間：2018-05-11 18:35

  本文選題：宇宙線 + 時(shí)間測(cè)量��； 參考：《清華大學(xué)》2014年博士論文

【摘要】：開展寬視場(chǎng)、高靈敏度的伽瑪射線巡天觀測(cè)研究是探索宇宙線起源的重要手段。為此，我國(guó)科學(xué)家提出在海拔4400m處建設(shè)大型高海拔空氣簇射觀測(cè)站（LargeHigh Altitude Air Shower Observatory，LHAASO）。其中平方千米地面探測(cè)器陣列（KM2A）需要對(duì)簇射粒子的到達(dá)時(shí)間進(jìn)行精確的測(cè)量，為了獲得好于0.5°的宇宙線入射角分辨，要求在寬溫環(huán)境下保證5635個(gè)探測(cè)器電子學(xué)達(dá)到500ps （RMS）的時(shí)間測(cè)量準(zhǔn)確度。在此背景下，本文對(duì)LHAASO實(shí)驗(yàn)的高精度時(shí)間測(cè)量系統(tǒng)展開研究。 大范圍的時(shí)間測(cè)量系統(tǒng)要求所有節(jié)點(diǎn)獲得高精度和高準(zhǔn)確度的同步時(shí)鐘。White Rabbit（WR）時(shí)鐘同步方法基于標(biāo)準(zhǔn)以太網(wǎng)，能夠在大范圍、多節(jié)點(diǎn)的應(yīng)用環(huán)境中實(shí)現(xiàn)亞納秒的時(shí)鐘同步準(zhǔn)確度。本文介紹了WhiteRabbit的基本原理和同步鏈路模型，對(duì)該模型中的關(guān)鍵參數(shù)進(jìn)行了標(biāo)定和實(shí)驗(yàn)驗(yàn)證；著重對(duì)White Rabbit同步鏈路各環(huán)節(jié)的溫度效應(yīng)展開研究，量化其對(duì)時(shí)鐘同步性能的影響；針對(duì)WhiteRabbit設(shè)備的硬件延時(shí)溫度效應(yīng)，采取了一種在線校正方法；并對(duì)不同應(yīng)用環(huán)境下的White Rabbit同步性能進(jìn)行測(cè)試和分析。 高精度的時(shí)間數(shù)字轉(zhuǎn)換器（Time-to-Digital Converter, TDC）是保證各節(jié)點(diǎn)時(shí)間測(cè)量性能的關(guān)鍵因素。本文介紹了基于FPGA進(jìn)位鏈的時(shí)間數(shù)字轉(zhuǎn)換器的基本原理和設(shè)計(jì)方法，，分析了進(jìn)位鏈結(jié)構(gòu)、溫度和內(nèi)核電壓等因素對(duì)TDC精度的影響，著重對(duì)FPGA進(jìn)位鏈溫度效應(yīng)的自動(dòng)校正方法展開研究，在低成本的Cyclone II系列FPGA上完成了多通道的TDC設(shè)計(jì)，并在寬溫范圍下取得了優(yōu)于23p（sRMS）的單次測(cè)量精度。 基于上述方法研究，本文完成了LHAASO實(shí)驗(yàn)高精度時(shí)間測(cè)量系統(tǒng)的原型設(shè)計(jì)。針對(duì)宇宙線觀測(cè)實(shí)驗(yàn)的應(yīng)用模式，采用數(shù)據(jù)與定時(shí)鏈路融合、冗余連接的方式設(shè)計(jì)了LHAASO時(shí)鐘分布與數(shù)據(jù)傳輸網(wǎng)絡(luò)結(jié)構(gòu)；采用模塊化的方式完成時(shí)間測(cè)量節(jié)點(diǎn)的硬件和功能設(shè)計(jì)；在不同環(huán)境下對(duì)時(shí)間測(cè)量系統(tǒng)的性能進(jìn)行了測(cè)試和分析。根據(jù)測(cè)試結(jié)果可以推算該時(shí)間測(cè)量系統(tǒng)在40oC溫度變化范圍以及五級(jí)交換機(jī)級(jí)聯(lián)結(jié)構(gòu)下的時(shí)間測(cè)量準(zhǔn)確度好于1ns，任一溫度下單節(jié)點(diǎn)的時(shí)間測(cè)量精度好于65ps，滿足LHAASO-KM2A和大部分宇宙線觀測(cè)實(shí)驗(yàn)的需求。
[Abstract]:It is an important means to explore the origin of cosmic rays to carry out wide field of view and high sensitivity gamma ray survey. Therefore, Chinese scientists have proposed to build a large high altitude air shower observation station at an altitude of 4400m. The square kilometer ground detector array (KM2A) needs to accurately measure the arrival time of the shower particles. In order to obtain a better resolution of the incident angle of cosmic rays than 0.5 擄, It is required to ensure the time measurement accuracy of 5635 detectors in wide temperature environment. Under this background, the high precision time measurement system of LHAASO experiment is studied in this paper. Large-scale time measurement system requires all nodes to obtain high-precision and high-accuracy synchronous clock .White RabbitWR-based clock synchronization method based on standard Ethernet, which can achieve sub-nanosecond clock synchronization accuracy in a wide range and multi-node application environment. In this paper, the basic principle and synchronous link model of WhiteRabbit are introduced, the key parameters of the model are calibrated and verified by experiments, and the temperature effect of each link of White Rabbit synchronous link is studied to quantify its influence on the performance of clock synchronization. Aiming at the hardware delay temperature effect of WhiteRabbit equipment, an on-line correction method is adopted, and the synchronization performance of White Rabbit in different application environments is tested and analyzed. High-precision time-to-digital converter (TDC) is the key factor to ensure the performance of each node. This paper introduces the basic principle and design method of time digital converter based on FPGA carry chain, and analyzes the influence of carry chain structure, temperature and core voltage on the accuracy of TDC. The automatic correction method of FPGA carry chain temperature effect is studied emphatically. The multi-channel TDC design is completed on the low cost Cyclone II series FPGA, and the single measurement accuracy is better than that of 23pcs RMS in wide temperature range. Based on the above research, the prototype design of high precision time measurement system for LHAASO experiment is completed. Aiming at the application mode of cosmic ray observation experiment, the LHAASO clock distribution and data transmission network structure are designed by data and timing link fusion and redundant connection, and the hardware and function design of time measurement node is accomplished by modularization. The performance of time measurement system is tested and analyzed in different environments. Based on the test results, it can be deduced that the time measurement accuracy of the time measurement system under the 40oC temperature range and the cascade structure of the five-stage switch is better than 1ns, and the time measurement accuracy of any temperature sending order node is better than 65ps. it meets the requirements of LHAASO-KM2A and the order node. The demand for most cosmic ray observation experiments.
【學(xué)位授予單位】：清華大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：P172.4

【參考文獻(xiàn)】

相關(guān)期刊論文 前1條

1 曹臻;劉加麗;白云翔;;物理學(xué)中的世紀(jì)難題:高能宇宙線的起源之“謎”[J];中國(guó)科學(xué)基金;2009年06期

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