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排序方式: 共有62条查询结果,搜索用时 15 毫秒
1.
The water Cherenkov detector array (WCDA) for the Large High Altitude Air Shower Observatory (LHAASO) will employ more than 3600 hemisphere 8-inch photomultiplier tubes (PMTs). Good time performance of the PMT, especially the transit time spread (TTS), is required for the WCDA. In order to meet the demand of the WCDA experiment, an accurate measurement of PMT TTS based on the photoelectron spectrum is studied. The method is appropriate for multi-photoelectrons and makes it possible to measure the TTS of different photoelectrons simultaneously. The TTS of different photoelectrons for a Hamamatsu R5912 PMT is tested with a specially designed divider circuit. The relationship between TTS and number of photoelectrons is also presented in this paper.  相似文献   
2.
通过系统分析绿色植被在紫外可见波段光谱的产生机理,得出绿峰和红边是由叶绿素产生的.从叶绿素的结构上看,它属于卟啉类化合物,为了进一步探究红边产生的机理,合成了四苯基卟啉、四(4-甲氧基苯基)卟啉、四(4-磺酸钠苯基)卟啉、四吡啶基卟啉、四甲基卟啉、四(4-甲氧基苯基)卟啉合锌和四(4-甲氧基苯基)卟啉合铜,并采用紫外可见光谱、红外及核磁进行表征.通过对其紫外可见光谱的系统分析,提出"红边"不仅限于叶绿素,而是卟啉类化合物特有的光谱特征,红边是由卟啉环a2 u(π)-eg(π*)跃迁产生的Q带所致.其位置不仅与卟啉的浓度相关,与卟啉化合物外侧取代基类型也有关系,金属卟啉对红边的位置影响较大.  相似文献   
3.
A GEANT4-based Monte-Carlo (MC) model is developed to study the performance of endcap time-of-flight (ETOF) at BESⅢ. It's found that the multiple scattering effects, mainly from the materials at the MDC endcap, can cause multi-hit on the ETOF's readout cell and significantly influence the timing property of ETOF. A multi-gap resistive plate chamber (MRPC) with a smaller readout cell structure is more suitable for the ETOF detector due to significantly reduced multi-hit rate (per channel), from 71.5% for currently-used scintillator-based ETOF to 21.8% or 16.7% for MRPC-based ETOF, depending on the readout pad size used. The timing performance of an MRPC ETOF is also improved. These simulation results suggest and guide an ETOF upgrade effort at BESⅢ.  相似文献   
4.
A prototype multi-gap resistive plate chamber (MRPC) with a 2×6 gap structure is developed for the upgrading of the endcap time-of-flight (ETOF) detector in the Beijing Spectrometer (BESⅢ). The prototype MRPC is tested in the E3 beam line of the Beijing Electron Positron Collider (BEPC) with secondary charged particles (π and p, etc) of 600 MeV/c. The test results show that the time resolution of the MRPC can reach 50 ps and that the detection efficiency is greater than 98%.  相似文献   
5.
言杰  李澄  刘荣  蒋励  鹿心鑫  王玫 《物理学报》2011,60(3):32901-032901
本文利用252Cf快裂变室和多参数数据采集系统,逐事例的同时记录了自发裂变中子和瞬发伽马的飞行时间(TOF),脉冲形状甄别(PSD)和反冲能量(RE,裂变中子是通过测量反冲质子;瞬发伽马是通过测量康普顿反冲电子)三维信息.详细介绍了通过离线数据分析完全扣除三维信息中的伽马事例贡献,以获得Φ50.8 mm×50.8 mm的BC501A液闪探测器的相对探测效率和响应函数的方法.在不通过探测器响应函数进行数据转换的条件下,利用中子的能量直接确定了中子的有效测量阈值.得到的中子 关键词: 252Cf快裂变室')" href="#">252Cf快裂变室 BC501A液闪探测器 相对探测效率 响应函数  相似文献   
6.
The endcap of time-of-flight (ETOF) detector in BES (Beijing Spectrometer) III is planned to be upgraded by using multi-gap resistive plate chambers (MRPCs) and the designed time resolution of the MRPCs is around 50 ps. Thus a time-zero (T0) detector needs to be built to offer a high quality reference time for the MRPCs beam test. So a T0 detector is built using plastic scintillator tiles (BC420) to couple with four fast phototubes (PMTs, Hamamatsu H6533). The timing properties of the detector is studied by using a cosmic ray test and factors related to the time resolution, such as plastic scintillator size, readout mode and angle effects, are discussed. T0 detector timing resolutions of ~41-62 ps are achieved, which means that the T0 detector can be used in the MRPC beam test.  相似文献   
7.
A new kind (two end readout) of Multi-gap Resistive Plate Chamber with long readout-strip (LMRPC) is developed to be used at the large-area Muon Telescope Detector (MTD) at mid-rapidity at RHIC/STAR experiment for Time-of-Flight (TOF) measurement. The LMRPC has an active area of 87 cm× 17 cm, 10 gas gaps of 250 μm arranged in 2 stacks, with readout strips of 2.5 cm wide and 90 cm long. The considerations in LMRPC design related to its performance are discussed in this paper. The cosmic ray test results of a prototype LMRPC show a detection efficiency 〉95% and the time resolution -70 ps.  相似文献   
8.
根据粒子的平均寿命测量原理,采用大面积塑料闪烁探测器和可编程逻辑器件设计了宇宙线μ子寿命测量的实验教学装置,使用该装置可实现对宇宙μ子寿命的直接测量.通过该实验,可使学生对高能物理理论、高能粒子探测器、高能粒子探测技术和数据获取、处理有整体的理解和认识.本文从实验教学内容和教学方法上对μ子寿命测量实验进行了探讨.  相似文献   
9.
10.
本文采用p~+/p-Si作为光阴极进行了光电化学电池和光助析氢电池的研究,光转换效率分别达到了7.4%(V~(2+/3+)电对)和7.8%(Co—W修饰),并讨论了导致高效率的原因,强调了高-低结对于改善半导体光电极性能的重要性。  相似文献   
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