Studies of timing properties for a TOF counter at an external target facility

Timing and amplitude properties of a prototype scintillator TOF counter at an external target facility are studied with a cosmic rays test. The dependence of signal pulse height and time resolution on the coordinate along the scintillator TOF counter is investigated with two different discriminators. A time resolution of 165 ps can be achieved at the center of the counter with a constant fraction discriminator. Time resolution better than 150 ps is obtained at the center with a leading edge discriminator after time walk correction is applied for off-line analysis.     

Studies of timing properties for a TOF counter at an external target facility

Timing and amplitude properties of a prototype scintillator TOF counter at an external target facility are studied with a cosmic rays test. The dependence of signal pulse height and time resolution on the coordinate along the scintillator TOF counter is investigated with two different discriminators. A time resolution of 165 ps can be achieved at the center of the counter with a constant fraction discriminator. Time resolution better than 150 ps is obtained at the center with a leading edge discriminator after time wall（ correction is applied for off-line analysis.     

多气隙电阻板室飞行时间谱仪技术

基于多气隙电阻板室(MRPC)技术的飞行时间谱仪广泛应用于现代物理实验,并在粒子鉴别中发挥了重要作用.随着加速器能量和实验亮度的提高,对飞行时间谱仪的粒子计数率和时间分辨要求越来越高.MRPC飞行时间谱仪按技术上可以分成三代.从第一代到第三代,计数率要求越来越高( 30 kHz/cm~2),时间精度也更加严格(20 ps),相应的探测器结构和读出电子学系统呈现出不同的特性.本文总结了三代飞行时间谱仪技术的主要技术特点及主要物理实验,介绍了已经取得的应用成果,提出了该技术的未来发展方向.同时也介绍了MRPC探测器在工业及医学方面的应用.     

Prototype of time digitizing system for BESⅢ endcap TOF upgrade

The prototype of a time digitizing system for the BESⅢ endcap TOF (ETOF) upgrade is introduced in this paper. The ETOF readout electronics has a distributed architecture. Hit signals from the multi-gap resistive plate chamber (MRPC) are signaled as LVDS by front-end electronics (FEE) and are then sent to the back-end time digitizing system via long shield differential twisted pair cables. The ETOF digitizing system consists of two VME crates, each of which contains modules for time digitization, clock, trigger, fast control, etc. The time digitizing module (TDIG) of this prototype can support up to 72 electrical channels for hit information measurement. The fast control (FCTL) module can operate in barrel or endcap mode. The barrel FCTL fans out fast control signals from the trigger system to the endcap FCTLs, merges data from the endcaps and then transfers to the trigger system. Without modifying the barrel TOF (BTOF) structure, this time digitizing architecture benefits from improved ETOF performance without degrading the BTOF performance. Lab experiments show that the time resolution of this digitizing system can be lower than 20 ps, and the data throughput to the DAQ can be about 92 Mbps. Beam experiments show that the total time resolution can be lower than 45 ps.     

BESⅢ TOF前端读出电子学系统原型设计和实验结果

作为北京谱仪(Beijing Spectrometer, 简称BES)的改造, BESⅢ将把TOF(time-of-flight)测量精度提高到一个新的水平, 总时间分辨不大于90ps. 其中要求前端电子学(Front End Electronics, FEE)对时间测量的不确定性贡献小于25ps. 本文介绍了TOF前端读出电子学系统原型电路的设计和初步的测试结果.     

TOT measurement implemented in FPGA TDC

Time measurement plays a crucial role for the purpose of particle identification in high energy physics experiments. With increasingly demanding physics goals and the development of electronics, modern time measurement systems need to meet the requirement of excellent resolution specification as well as high integrity. Based on Field Programmable Gate Arrays(FPGAs), FPGA time-to-digital converters(TDCs) have become one of the most mature and prominent time measurement methods in recent years. For correcting the time-walk effect caused by leading timing, a time-over-threshold(TOT) measurement should be added to the FPGA TDC. TOT can be obtained by measuring the interval between the signal leading and trailing edges. Unfortunately, a traditional TDC can recognize only one kind of signal edge, the leading or the trailing. Generally, to measure the interval, two TDC channels need to be used at the same time, one for leading, the other for trailing. However, this method unavoidably increases the amount of FPGA resources used and reduces the TDC's integrity.This paper presents one method of TOT measurement implemented in a Xilinx Virtex-5 FPGA. In this method,TOT measurement can be achieved using only one TDC input channel. The consumed resources and time resolution can both be guaranteed. Testing shows that this TDC can achieve resolution better than 15 ps for leading edge measurement and 37 ps for TOT measurement. Furthermore, the TDC measurement dead time is about two clock cycles, which makes it good for applications with higher physics event rates.     

Analog front-end prototype electronics for the LHAASO WCDA

In the readout electronics of the Water Cerenkov Detector Array(WCDA) in the Large High Altitude Air Shower Observatory(LHAASO) experiment, both high-resolution charge and time measurement are required over a dynamic range from 1 photoelectron(P.E.) to 4000 P.E. The Analog Front-end(AFE) circuit is one of the crucial parts in the readout electronics. We designed and optimized a prototype of the AFE through parameter calculation and circuit simulation, and conducted initial electronics tests on this prototype to evaluate its performance. Test results indicate that the charge resolution is better than 1%@4000 P.E. and remains better than 10%@1 P.E., and the time resolution is better than 0.5 ns RMS, which is better than the application requirements.     

Digital discrimination of neutrons and γ rays with organic scintillation detectors in an 8-bit sampling system using frequency gradient analysis

The feasibility of using frequency gradient analysis (FGA), a digital method based on Fourier transform, to discriminate neutrons and γ rays in the environment of an 8-bit sampling system has been investigated. The performances of most pulse shape discrimination methods in a scintillation detection system using the time-domain features of the photomultiplier tube anode signal will be lower or non-effective in this low resolution sampling system. However, the FGA method using the frequency-domain features of the anode signal exhibits a strong insensitivity to noise and can be used to discriminate neutrons and γ rays in the above sampling system. A detailed study of the quality of the FGA method in BC501A liquid scintillators is presented using a 5 G samples/s 8-bit oscilloscope and a 14.1 MeV neutron generator. A comparison of the discrimination results of the time-of-flight and conventional charge comparison (CC) methods proves the applicability of this technique. Moreover, FGA has the potential to be implemented in current embedded electronics systems to provide real-time discrimination in standalone instruments.     

Time calibration for the end cap TOF system of BESⅢ

The time calibration for end cap TOF system of BESⅢ is studied in this paper.It has achieved about 110 ps time resolution for muons in dimu events.The pulse height correction using electronic scan curve and the predicted time calculated using Kalman filter method are introduced.This paper also describes the study of using electrons and muous as calibration samples.     

Studies of a scintillator-bar detector for a neutron wall at an external target facility

To achieve a better time resolution of a scintillator-bar detector for a neutron wall at the external target facility of HIRFL-CSR, we have carried out a detailed study of the photomultiplier, the wrapping material and the coupling media. The timing properties of a scintillator-bar detector have been studied in detail with cosmic rays using a high and low level signal coincidence. A time resolution of 80 ps has been achieved in the center of the scintillator-bar detector.     

Time calibration for the end cap TOF system of BESⅢ

The time calibration for end cap TOF system of BESⅢ is studied in this paper. It has achieved about 110 ps time resolution for muons in dimu events. The pulse height correction using electronic scan curve and the predicted time calculated using Kalman filter method are introduced. This paper also describes the study of using electrons and muons as calibration samples.     

Determination of the time resolution for neutron scintillation detectors by multi-coincidence measurement

Based on the multi-coincidence measurement, the time resolution of three liquid scintillation detectors (BC501A) were determined strictly by solving the coincidence equations, where the influence from electronics estimated by self coincidence measurement as well as the background had been considered. The result of this work agreed well with the result that was deduced from the traditional method, and it will be helpful to analyze the energy resolution of neutron time of flight spectra measured by using such detectors at CIAE (China Institute of Atomic Energy).     

Prototype of time digitizing system for BESⅢ endcap TOF upgrade

The prototype of a time digitizing system for the BESⅢ endcap TOF (ETOF) upgrade is introduced in this paper. The ETOF readout electronics has a distributed architecture. Hit signals from the multi-gap resistive plate chamber (MRPC) are signaled as LVDS by front-end electronics (FEE) and are then sent to the back-end time digitizing system via long shield differential twisted pair cables. The ETOF digitizing system consists of two VME crates, each of which contains modules for time digitization, clock, trigger, fast control, etc. The time digitizing module (TDIG) of this prototype can support up to 72 electrical channels for hit information measurement. The fast control (FCTL) module can operate in barrel or endcap mode. The barrel FCTL fans out fast control signals from the trigger system to the endcap FCTLs, merges data from the endcaps and then transfers to the trigger system. Without modifying the barrel TOF (BTOF) structure, this time digitizing architecture benefits from improved ETOF performance without degrading the BTOF performance. Lab experiments show that the time resolution of this digitizing system can be lower than 20 ps, and the data throughput to the DAQ can be about 92 Mbps. Beam experiments show that the total time resolution can be lower than 45 ps.     

An analogue front-end ASIC prototype designed for PMT signal readout

The Water Cherenkov Detector Array(WCDA) is one of the core detectors in the Large High Altitude Air Shower Observatory(LHAASO),and it consists of 3600 photomultiplier tubes(PMTs).Both high resolution time and charge measurement are required over a large dynamic range from 1 photoelectron(P.E.) to 4000 P.E.The prototype of an analogue front-end Application Specific Integrated Circuit(ASIC) fabricated using Global Foundry 0.35 μm CMOS technology is designed to read out the PMT signal in the WCDA.This ASIC employs leading edge discrimination and an(RC)~4 shaping structure.Combined with the following Time-to-Digital Converter(TDC) and Analog-to-Digital Converter(ADC),both the arrival time and charge of the PMT signal can be measured.Initial test results indicate that time resolution is better than 350 ps and charge resolution is better than 10% at 1 P.E.and better than 1% with large input signals(300 P.E.to 4000 P.E.).Besides,this ASIC has a good channel-to-channel isolation of more than 84 dB and the temperature dependency of charge measurement is less than 5% in the range 0-50°C.     

Determination of the time resolution for neutron scintillation detectors by multi-coincidence measurement

Based on the multi-coincidence measurement, the time resolution of three liquid scintillation detectors (BC501A) were determined strictly by solving the coincidence equations, where the influence from electronics estimated by self coincidence measurement as well as the background had been considered. The result of this work agreed well with the result that was deduced from the traditional method, and it will be helpful to analyze the energy resolution of neutron time of flight spectra measured by using such detectors at CIAE (China Institute of Atomic Energy).     

Status of the front-end-electronics for the time-of-flight measurements at the MPD experiment

The preamplifier based on the ASIC NINO for the Time of Flight system (TOF) of MPD/NICA was developed and tested. The signal is read from both sides of the strip of the multi gap Resistive Plate Chamber (MRPC). In total there are around 14000 channels of electronics. To measure time of flight of secondary particles from collision of heavy ions on the collider NICA the Time over Threshold (ToT) method is used. According to the bench tests the preamplifier board showed stable work and good time resolution <10 ps for one channel. It was also tested at the test beam facility of the Nuclotron. The time resolution of the TOF detector which used the described preamplifier was reached ～42 ps.     

Studies of a scintillator-bar detector for a neutron wall at an external target facility

To achieve a better time resolution of a scintillator-bar detector for a neutron wall at the external target facility of HIRFL-CSR, we have carried out a detailed study of the photomultiplier, the wrapping material and the coupling media. The timing properties of a scintillator-bar detector have been studied in detail with cosmic rays using a high and low level signal coincidence. A time resolution of 80~ps has been achieved in the center of the scintillator-bar detector.     

Effects of acoustic source and filtering on time-of-flight measurements

Time-of-flight (TOF) measurements are valuable in the estimation of distances, displacements and velocities of moving objects, phase differences of wave pulses, temperature of the atmosphere, and so on. The effects of sound source on time-of-flight measurements have been investigated in this paper. The sound sources considered are: electric horn, impact noise source, aerodynamic noise from a free jet, and the Hartmann whistle. The focus of the present study is to highlight the advantage of using Hartmann whistle for TOF measurements as this device is simple and attractive, without any moving parts. Time-of-flight of sound waves is calculated by cross-correlating the signals received by two microphones. Further, the effect of signal filtering on TOF measurements is demonstrated. The results indicate that the sound source has considerable effect on TOF measurements, and the accuracy can be significantly enhanced by appropriate signal conditioning. Hartmann whistle proves to be a good candidate as an acoustic source for TOF measurement.     

频域反射法光纤延时精密测量

本文提出了一种应用于光纤延时系统中实现光纤延时精密测量的新方法,用以提高光纤延时测量的精度和准确性.该方法以1064 nm激光调制信号作为光源,通过测量回波信号的幅值和相位信息得到被测通道的频率响应,采用快速傅里叶逆变换得到被测目标的延时信息,实现光纤延时测量.本文通过理论分析和延时测量实验对频域反射法与传统的时域测量方法进行对比,使用频域反射法在调制频率范围10—200 MHz,采样频率间隔0.5 MHz的实验条件下,实现了3.3 ps延时测量分辨率,并证明了该方法具有比时域方法更高的测量精度,测量结果的准确性更好.     

用于裂变碎片质量测量的MCP和Au-Si SBD飞行时间探测系统

为了能很好地鉴别碎片质量,建立一个好的飞行时间测量方法是十分必要的。阐述了建立用于裂变碎片质量测量的微通道板（MCP）和金硅面垒探测器（SBD）飞行时间探测系统。对于80 μg/cm2厚的碳膜,241Am的α粒子的探测效率约为39%,252Cf（sf）裂变碎片的探测效率约为98%。在动能为78 MeV条件下,对252Cf（sf）重裂变碎片（138~148 u）得到的时间分辨为（224:1±6:1）ps;在动能为102 MeV条件下,对252Cf（sf）轻裂变碎片（101~111 u）,得到的时间分辨为（154:5±5:8）ps。In order to separate the mass number of fragments in the fission reactions, it is essential to develop a good time-of-flight (TOF) method. The purpose of this article is to set up a TOF detector system including a microchannel plate (MCP) and a Au-Si surface-barrier detector (SBD). The TOF system shows a detection efficiency of 39% for α-particles released from 241Am and 98% for fragments in the spontaneous fission of 252Cf. The experimental results show that the time resolutions of (224:1±6:1) ps for the heavy fragments (Ek=78 MeV, AH=138~148 u) and (154:5±5:8) ps for the light fragments (Ek=102 MeV, AL=101~111 u) can be obtained.