Safeguarding the photomultiplier tube

Photomultiplier tubes are sturdy and will provide extended and reliable operation providing reasonable care is taken during storage, handling and operation. This article discusses the precautions necessary to ensure maximum life and efficiency is obtained when using RCA photomultiplier tubes.     

Ultrasensitive and high-dynamic-range two-photon absorption in a GaAs photomultiplier tube

We demonstrate improved efficiency and dynamic range for two-photon absorption at 1.5 microm in a photoelectron-counting GaAs photomultiplier tube. cw laser measurements show pure two-photon absorption occurring in the device from average powers of 1.3 microW to nearly 1 mW. We use the detector to implement an autocorrelator with peak-power x average-power sensitivity of 1.7 x 10(-4) (mW)(2) and discuss practical ways to reduce this figure of merit to as low as 1 x 10(-5) (mW)(2).     

Setup of a photomultiplier tube test bench for LHAASO-KM2A

To fulfill the requirements for testing the photomultiplier tubes(PMTs) of the electromagnetic detector at the Large High Altitude Air Shower Observatory(LHAASO),a multi-functional PMT test bench with a two-dimensional scanning system has been developed.With this 2D scanning system,16 PMTs can be scanned simultaneously for characteristics tests,including uniformity,cathode transit time difference,single photo-electron spectrum,gain vs.high voltage,linear behavior and dark noise.The programmable hardware and intelligent software of the test bench make it convenient to use and provide reliable results.The test methods are described in detail and primary results are presented.     

Suppressing ringing caused by large photomultiplier tube signals

We describe here the characteristic features of the ringing we observed following large PMT signals in the Daya Bay reactor antineutrino experiment. We conclude that the ceramic capacitors used in the circuitry of the PMT bases and the HV-signal decouplers are the primary cause for this ringing. We present some possible schemes to reduce the ringing when replacing these ceramic capacitors is not feasible.     

光电倍增管在检测水泥浆液密度中的应用

为了高精度、非接触动态地检测灌浆工程中水泥浆液的密度，采用CR105型光电倍增管作为感光器件，设计了一种检测装置。该装置选用Cs-137作为光源，光电倍增管作为感光器件，196KB单片机作为微处理器，通过自行设计的模块化软件以及信号处理电路、显示打印输出电路实现对γ射线的检测、数据分析与处理。实验结果表明：该装置能够在恶劣环境下准确、快速地检测水泥浆液的密度；测量值不受浆液的流速、压力、温度、粘度和腐蚀等因素的影响；探测部分安装在高温、潮湿、高灰尘的灌浆工程施工现场仍能正常工作。     

硅光电倍增管自动增益校正系统设计

温度会使硅光电倍增管的增益产生较大的漂移,进而影响硅光电倍增管的增益精度。为了使硅光电倍增管增益不随温度发生较大变化,设计了硅光电倍增管的自动增益校正系统,包括基于单片机的高压电源设计与采集系统设计。高电压模块精确工作的温度范围为?10～60 ℃,电源噪声约为30 mV,满足硅光电倍增管性能测试的需求。采集系统经过扫频测试与激光照射测试,可以较好地通过60 MHz的交流信号,并将光信号转变为较明显的电信号。该系统可以向京邦公司的硅光电倍增管阵列JARY-TP3050-8X8C提供工作电压与采集电路。     

Automatic test system for progressive gain of dynode photomultiplier tube北大核心CSCD

逐级增益是评价打拿极光电倍增管（photomultiplier tube, PMT）性能的重要参数之一,目前国内仅有一台逐级增益测试系统,依靠人工操作,测试效率不高。为提高逐级增益测试效率,设计了一套打拿极PMT逐级增益自动测试系统。该系统使用由可控光阑、电动挡板等组成的自动光源实现光源输出强度连续可调,并通过控制高压模块、分压器模块和继电器模块实现逐级电压的通断。利用精度为0.01 nA的电流计模块完成信号的采集、处理和传输,实现对逐级增益的自动测量。实验证明,该系统可有效测量打拿极PMT的逐级增益特性,测试重复性在2%以内,满足测试需求。     

光电倍增管在磷酸液声致发光实验中的应用

对不同厚度液体进行光强测量,深入探索空化气泡的运动,研究发光机理很有意义。用超声激励法在磷酸液体中实现多泡声致发光,研究不同共振频率下发光的特点。利用光电倍增管多次测量发光强度相互比较,结果是在液体厚度10 cm、驱动频率f=21.061kHz和f=20.316kHz时,周期性较好为50μs,液体通过漩涡集中气泡可以使更多气泡发光;在液体厚度3 mm、驱动频率f=17.91kHz和f=19kHz时,周期性很好为25μs;且光信号都较强。结论是磷酸中声致发光强度、周期与液体厚度、驱动频率密切相关。本文以磷酸液多泡声致发光实验研究为基础,从内部和外部原理来出发,详细介绍了光电倍增管在多泡声致发光光强测量中的实用,为今后研究者提供了一些经验。根据实验过程中遇到的一些实际问题提出了建议和改善意见。     

光电倍增管对14 MeV脉冲中子的直照响应

采用ING-103型DPF脉冲中子源产生的14.1 MeV脉冲中子对EMI两个不同型号的光电倍增管EMI-9815B和EMI-9850B进行了直照实验。针对DPF脉冲中子源产生中子脉冲的同时也会产生X射线脉冲的特点,采取了飞行时间法及吸收衰减法来消除X射线对中子脉冲的干扰。利用中子及X射线速度的差异,将光电倍增管放置在离源较远的测点位置,测得了X射线脉冲和中子脉冲时间上错开的双峰波形。通过在辐射通道内添加5 cm厚的铅吸收体有效地抑制了X射线峰,在离源较近的测量位置测到了干净的脉冲中子波形。根据实测波形,得到的光电倍增管EMI-9815B和EMI-9850B中子直照灵敏度分别为10-13与10-15量级,该结果与理论计算结果在量级上一致。     

光电倍增管对14 MeV脉冲中子的直照响应

 采用ING-103型DPF脉冲中子源产生的14.1 MeV脉冲中子对EMI两个不同型号的光电倍增管EMI-9815B和EMI-9850B进行了直照实验。针对DPF脉冲中子源产生中子脉冲的同时也会产生X射线脉冲的特点,采取了飞行时间法及吸收衰减法来消除X射线对中子脉冲的干扰。利用中子及X射线速度的差异,将光电倍增管放置在离源较远的测点位置,测得了X射线脉冲和中子脉冲时间上错开的双峰波形。通过在辐射通道内添加5 cm厚的铅吸收体有效地抑制了X射线峰,在离源较近的测量位置测到了干净的脉冲中子波形。根据实测波形,得到的光电倍增管EMI-9815B和EMI-9850B中子直照灵敏度分别为10^-13与10^-15量级,该结果与理论计算结果在量级上一致。     

Statistics of count numbers from a photomultiplier tube and its implications for error estimation

We present investigations of counting statistics for five different luminescence-measuring systems. The dark current background and the counts obtained for a PM tube under constant illumination at various light intensities were measured. Where no divider is present in the counting system, the standard deviation of the number of counts exceeds the value predicted by a Poisson distribution but by different amounts in the different systems. This has implications for analysis of the uncertainties in the estimated equivalent doses and other quantitative analyses of luminescence measurements. We suggest how to account for the observed overdispersion of count numbers in uncertainty estimation.     

Ultrafast, jitter-free x-ray streak camera that uses single-photon counting

A novel method developed to increase the temporal resolution of x-ray streak cameras is described. The method is analogous to the time-correlated single-photon-counting technique, which is commonly used in atomic physics. By use of short-pulse x-ray radiation from a laser-produced plasma, generated by an ultrafast laser, it is shown that a standard x-ray streak camera with a nominal temporal resolution of >5ps can yield a temporal response of 1.6 ps. The readout technique also removes temporal jitter with respect to the triggering laser. Capabilities and limitations of the technology are discussed.     

Design of the photomultiplier tube bases for high dynamic range readout in WCDA

The photomultiplier tube (PMT) used in the water Cherenkov detector array (WCDA) of the Large High Altitude Air Shower Observatory (LHAASO) requires a good single photoelectron (SPE) spectrum and a charge dynamic range from 1 to 4000 photoelectrons. In this paper, the bases design and improvement of the photomultiplier tube R5912 are presented. The results show that at the gain of 2.6 × 10~6 , the anode output has a good single photoelectron spectrum, and its charge non-linearity is within 5% when the number of photoelectrons (nPE) is 3500. The charge non-linearity of the 8th dynode output is within 2% when the number of nPE is 4000, which satisfies the dynamic range requirement.     

多阳极PMT的串扰对四象限倾斜跟踪传感器跟踪精度的影响

介绍了四象限倾斜跟踪传感器的原理后,分析了存在光子噪声和串扰条件下的四象限探测器的质心探测误差和光斑位移灵敏度,并推导了存在光子噪声和串扰条件下四象限倾斜跟踪传感器跟踪误差的理论公式,最后通过实验证明了理论分析的正确性．理论分析和实验的结果都表明：当单帧光-电子数一定时,串扰越大,四象限倾斜跟踪传感器的跟踪误差越大;而当串扰一定时,单帧光-电子数越多,四象限倾斜跟踪传感器的跟踪误差越小．     

Two-and three-photon absorption in a novel fluorene-based compound

A novel symmetrical charge transfer fluorene-based compound 2,7-bis (4-methoxystyryl)-9, 9-bis (2-ethylhexyl)-9H-fluorene (abbreviated as BMOSF) was synthesized and its nonlinear absorption was investigated using two different laser systems: a 140-fs, 800-nm Ti:sapphire laser operating at 1-kHz repetition rate and a 38-ps, 1064-nm Nd:YAG pulsed laser operating at 10-Hz repetition rate, respectively. Unique nonlinear absorption properties in this new compound were observed that rise from multiphoton absorption. The nonlinear absorption coefficients were measured to be 6.02 × 10-3 cm/GW (due to two-photon absorption, exciting wavelength is 800 nm) and 3.6×10-20 cm3/W2 (due to three-photon absorption, exciting wavelength is 1064 nm). This new compound possesses strong fluorescence induced by two-photon absorption and obvious three-photon absorption optical limiting effects.     

Comparison of pulsed-excitation and phase-modulation methods for estimating fluorescence lifetime values using a convolved-autoregressive model and a high-gain photomultiplier tube

A comparative study between pulsed excitation (PE) and phase modulation (PM) methods has been carried out numerically and experimentally to estimate fluorescence lifetime values in the combined use of the following two measurement techniques: (i) To enhance the sensitivity in light detection, we have connected a load resistor with a large value at the output of a photomultiplier tube (PMT), which also brings about improvement in the signal-to-noise ratio (SNR) in measurements. (ii) The application of a convolved-autoregressive (C-AR) model to time-series data obtained from such a high-gain PMT enabled us to precisely estimate the fluorescence lifetime values in a nanosecond region. Although dependent on various measurement parameters, we have found that the PM method has potential in the field of biology or biochemistry for screening fluorescent samples.     

Coherent effects in a three-photon CPT process of Ca+

Linewidth narrowing and other quantum coherent effects based on three-photon coherent population trapping (CPT) in Ca⁺ ions are investigated. If the propagation directions of the three lasers obey the phase matching condition, the dark linewidth resulting from the CPT can be very narrow, and it can be controlled by adjusting the parameters of the lasers.