Constant Fraction Timing Method Research Articles

Time of flight detector for charged particle identification based on circular electron-positron collider

The circular electron-positron collider (CEPC) requires a 3% precision in the measurement of d<i>E</i>/d<i>x</i> to identify long-lived charged particles. However, the measurement of d<i>E</i>/d<i>x</i> has a blind area for each of charged particles of <inline-formula><tex-math id="M8">\begin{document}$\pi / \rm{K}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20222271_M8.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20222271_M8.png"/></alternatives></inline-formula>, <inline-formula><tex-math id="M9">\begin{document}$\pi / \rm{P}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20222271_M9.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20222271_M9.png"/></alternatives></inline-formula>, and <inline-formula><tex-math id="M10">\begin{document}$\rm{K} / \rm{P}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20222271_M10.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20222271_M10.png"/></alternatives></inline-formula>, having transverse momenta of 1 GeV/<i>c</i>, 1.6 GeV/<i>c</i>, and 2 GeV/<i>c</i> respectively. One potential solution is to use a high-precision time-of-flight (TOF) detector with a time resolution of less than 50 ps to fill in the blind area. To address this, we propose a small particle TOF detector that uses small plastic scintillators (<inline-formula><tex-math id="M11">\begin{document}$1 \;\; \mathrm{cm} \times 1 \;\; \mathrm{cm} \times 0.3 \;\; \mathrm{cm}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20222271_M11.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20222271_M11.png"/></alternatives></inline-formula>) silicon photomultipliers for readout. In this work, we introduce the construction of the detector and calibrate its performance by using <inline-formula><tex-math id="M12">\begin{document}${ }^{90} \mathrm{Sr} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20222271_M12.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20222271_M12.png"/></alternatives></inline-formula> electron collimators and high-speed waveform acquisition electronics. Using a constant fraction timing method, we find that the time resolution of the detector is about 48 ps, satisfying the CEPC’s requirements for TOF detection.

The time shift between the neutron and [formula omitted]-ray timestamps in organic stilbene scintillator

It is shown that the use of the standard constant fraction timing method for obtaining timestamps of signals from an organic stilbene scintillator leads to a systematic difference in timestamps when detecting neutrons and γ-rays. A detailed study of this effect was carried out using a digital time-of-flight spectrometer based on a stilbene detector and a pulsed source of quasi-monoenergetic neutrons based on the 2H(d,n)3He reaction. It is shown that this effect is present for the entire range of crystal light output values and is related to the difference in the rise time of signals induced by neutrons and γ-rays. It is demonstrated that this effect can lead to a systematic error in absolute measurements of the prompt fission neutron spectra using the time-of-flight method with conventional analog constant fraction timing. A method for compensating this systematic shift based on the analysis of the timestamps position for the digital signals at the different values of the constant fraction is suggested.

A method to enhance coincidence time resolution with applications for medical imaging systems (TOF/PET)

A coincidence timing spectrometer was assembled using NaI(Tl) inorganic and BC418 type organic (plastic) scintillation detectors. The constant fraction timing method was used. Coincidence time resolution values of the detectors, which have great importance in TOF/PET measurements, were obtained separately. The resolutions were enhanced using a different method in a start-stop coincidence spectrometer: the signals from the start detectors were delayed. The results from the FLUKA Monte Carlo simulation code agreed well with the experimental results.

Time resolution investigations for general purpose plastic scintillation detectors in different thicknesses

Time spectra of 90Sr, 137Cs and 207Bi radioactive sources were obtained by using a BC 400 type plastic scintillation detectors in different thicknesses. Time resolution values through the time spectra were obtained by means of leading edge and constant fraction timing methods. The obtained time resolution values from leading edge method were compared with those of constant fraction timing method.

Alpha energy resolution enhancement of a Si surface barrier detector

In this work, alpha energy resolution of a Si surface barrier detector was improved. For this purpose, we used constant fraction timing method. Energy resolution enhancement of about 1 % was achieved for alpha peak of 210Po. In order to prove the validity of the timing method, it was applied to the alpha spectrum of 226Ra. It was concluded that proposed method was successful on the energy resolution improvement.

Alpha energy resolution improvement of a general purpose plastic scintillation detector

Alpha energy spectra of 210Po and 226Ra radioactive sources were achieved by using a BC400 type plastic scintillation detector. In order to enhance the energy resolution of the detector, constant fraction timing method was used. Obtained results showed that the used timing method was successful on improving the energy resolution of the detector with the amendment of about 1 % even at the low count rates.

Energy resolution improvement of NaI(Tl) scintillation detectors by means of a timing discrimination method

Gamma-ray energy spectrum of a 137Cs radioisotope was obtained by using a NaI(Tl) scintillation detector. Improvement of the energy resolution of the detector was aimed. To achieve this, constant fraction timing method was used. Energy resolution of the photopeak of the isotope was improved from 7.1 to 6.7% through the timing application.

Research of the navigation accuracy for the X-ray pulsar navigation system

In order to improve the navigation accuracy of the X-ray pulsar navigation system, in this paper we propose a constant fraction timing method based on the low-pass filter to measure the arrival time of the X-ray pulse in X-ray pulsar navigation. According to the technical scheme, the timing accuracies and dead times of original peaking timing and the improved constant fraction timing are measured. Experimental results indicate that the timing accuracy and the dead time of the peaking timing system are 18 ns and 4750 ns, the timing accuracy and the dead time of the constant fraction timing system are 0.78 ns and 105 ns. The timing accuracy and the dead time of constant fraction timing system are significantly improved compared with those of the peaking timing system. In the X-ray pulsar navigation system, the cumulative pulse profile of the X-ray pulse is constructed in the two different timing systems through measuring the arrival time of the X-ray photon. Experimental results indicate that compared with using the peaking timing system, the cumulative pulse profile of the X-ray pulse using the improved constant fraction timing system is improved obviously, therefore, the navigation accuracy could be improved by using the constant fraction timing system.

CsI:X(X=Li+,K+,Rb+단결정의 섬광특성

CsI에 활성제로 Li, K, Rb를 첨가하여 CsI(Li), CsI(K) 및 CsI(Rb) 단결정을 Czochralski방법으로 육성하였다. <TEX>$^{137}CS$</TEX>(0.662 MeV)에 대한 CsI(Li:0.2 mole%) 섬광체의 에너지 분해능은 14.5%이었고 CsI(K:0.5 mole%) 섬광체는 15.9%이었으며 CsI(Rb:1.5 mole%) 섬광체는 17.0%이였다. 이들 CsI(Li), CsI(K) 및 CsI(Rb) 섬광체의 <TEX>$\gamma$</TEX>선 에너지에 대한 에너지 교정곡선은 선형적 이였다. 일정비율 시간분석법(CFT :constant-fraction timing method)으로 측정한 CsI(Li:0.2 mole%), CsI(K:0.5 mole%) 및 CsI(Rb:1.5 mole%) 성광체의 시간 분해능은 각각 9.0 ns, 14.7 ns 및 9.7 ns이였다. CsI(Li:0.2 mole%), CsI(K:0.5 mole%) 및 CsI(Rb:1.5 mole%) 섬광체의 형광감쇠시간은 각각 <TEX>${\tau}_1=41.2\;ns$</TEX>, <TEX>${\tau}_2=483\;ns$</TEX>, <TEX>${\tau}_1=47.2\;ns$</TEX>, <TEX>${\tau}_2=417\;ns$</TEX> 및 <TEX>${\tau}_1=41.3\;ns$</TEX> 및 <TEX>${\tau}_2=553\;ns$</TEX>이였다. 그리고 CsI(Li:0.2 mole%), CsI(K:0.5 mole%) 및 CsI(Rb:1.5 mole%) 단결정의 인광감쇠시간은 각각 0.51 s, 0.57 s 및 0.56 s이였다. CsI single crystals doped with lithium, potassium or rubidium were grown by using Czochralski method at Ar gas atmosphere. The energy resolutions of CsI(Li:0.2 mole%), CsI(K:0.5 mole%) and CsI(Rb:1.5 mole%) scintillators were 14.5%, 15.9% and 17.0% for <TEX>$^{137}Cs$</TEX>(0.662 MeV), respectively. The energy calibration curves of CsI(Li), CsI(K) and CsI(Rb) scintillators were linear for <TEX>$\gamma$</TEX>-ray energy. The time resolutions of CsI(Li:0.2 mole%), CsI(K:0.5 mole%) and CsI(Rb:1.5 mole%) scintillators measured by CFT(constant-fraction timing method) were 9.0 ns, 14.7 ns and 9.7 ns, respectively. The fluorescence decay times of CsI(Li:0.2 mole%) scintillator had a fast component and slow one of <TEX>${\tau}_1=41.2\;ns$</TEX> and <TEX>${\tau}_2=483\;ns$</TEX>, respectively. The fluorescence decay times of CsI(K:0.5 mole%) scintillator were <TEX>${\tau}_1=47.2\;ns$</TEX> and <TEX>${\tau}_2=417\;ns$</TEX>. And the fluorescence decay times of CsI(Rb:1.5 mole%) scintillator were <TEX>${\tau}_1=41.3\;ns$</TEX> and <TEX>${\tau}_2=553\;ns$</TEX>. The phosphorescence decay times of CsI(Li:0.2 mole%), CsI(K:0.5 mole%) and CsI(Rb:1.5 mole%) scintillators were 0.51 s, 0.57 s and 0.56 s, respectively.

Investigation of the jitter of the constant fraction timing method based on the comparison of the original signal and the stretched and attenuated one

In the present study the change of the jitter of the timing method based on the comparison of the original signal and the stretched and attenuated one, was investigated as a function of the ratio of the stretched and original signal. In the case of single CR differentiated and double RC integrated signals it was found, both on the base of theoretical and of experimental investigations, that if the time reference point is on the trailing edge of the pulse, the more the ratio mentioned approaches 1, the smaller the jitter is. On the other hand on the leading edge a minimum was experienced in different ratios depending on the power spectrum of the noise at the output of the system consisting of nuclear detector and preamplifier, whereas experimental investigations carried out in the case of semi-Gaussian signals shaped with a Gaussian shaper, make a small minimum likely even on the training edge.

Some Studies of Reflector Construction and Electronics Configurations for Optimizing Pulse-Height and Pulse-Shape Resolution in Alpha Liquid-Scintillation Spectrometry

Various sample sizes, reflector sizes and shapes, and reflector materials were examined to determine their effect on pulse-height and pulse-shape resolution in alpha liquid-scintillation spectrometry. A section of a metal sphere coated with a diffuse-white reflective material was found to have the best characteristics for both pulse-height and pulse-shape resolution. Although sample volumes as large as 10 ml could be tolerated when used with reflectors to accommodate them, the best results were obtained with 1-ml samples and smaller reflectors. Comparison of two types of pulse-shape discrimination circuitry for separating alpha and beta-gamma pulses indicated that a zero-crossover method was superior to a constant fraction timing method. The combination of these improved detectors with solvent extraction methods of incorporating the sample in the scintillator and pulse-shape discrimination allows alpha spectrometry with a background as low as 0.01 count/min and an energy resolution as high as 5.5%.