A multi-parameter discrimination digital positron annihilation lifetime spectrometer using a fast digital oscilloscope

Qi, Zhao; Ye, R.; Wang, H.B.; Cong, L. H.; Liu, J.D.; Zhang, Hongjun; Ye, B.J.

doi:10.1016/j.nima.2021.165974

Cited by 9 publications

(9 citation statements)

References 22 publications

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“…The best pulse smoothing method varies with the type of spectrometer. For the SiPM-based digital spectrometer, 5th polynomial fitting was the best method which reduced the noise influence on the leading edge part of the pulse [14]. The timing resolution of the scintillator detectors (σ t ) is described by equation (3.3).…”

Section: Timing Resolution Measurement Resultsmentioning

confidence: 99%

“…Curve fitting is the method of constructing the mathematical function which has the best fit to data points. Various studies have used interpolation or curve fitting to restore the leading edge part of pulses from radiation detectors, and the timing resolution varies depending on the type of pulse smoothing methods [6,14]. To find the best pulse smoothing method, we used four methods: linear interpolation, spline interpolation, 5th degree polynomial fitting, and Gaussian fitting.…”

Section: Digital Pulse Processing 231 Pulse Smoothing Methods and Bas...mentioning

confidence: 99%

“…Digital constant fraction discrimination (dCFD) is the most common time pick-off method for measuring the arrival time of the γ-ray in scintillator detectors such as the PAL spectrometer and positron emission tomography (PET) detectors [5,7,14,19]. The principle of dCFD is to determine the arrival time of radiation when the pulse amplitude reaches a specific threshold fraction of the maximum amplitude as shown in figure 2.…”

Section: Digital Fraction Discrimination (Dcfd)mentioning

confidence: 99%

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Study of timing performance parameters for a SiPM-based digital positron annihilation lifetime spectrometer

Choi¹,

Ko²,

Kim³

et al. 2022

J. Inst.

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Positron annihilation lifetime spectroscopy (PALS) is a popular method for studying defects in materials. With the development of fast digital oscilloscopes and digitizers, the conventional analog positron annihilation lifetime (PAL) spectrometer is being replaced by a digital PAL spectrometer. Recently, newly conducted research has developed a PAL spectrometer using a silicon photomultiplier (SiPM) instead of a photomultiplier tube (PMT). Timing resolution of PAL spectrometer needs to be improved to identify the lifetimes of positrons. Many parameters affect the timing performance of a SiPM-based digital PAL spectrometer: bias voltage, pulse smoothing, and the constant fraction value of digital constant fraction discrimination (dCFD). Timing resolution depends on the radiation energy, but only a few studies have considered the energy difference of 1274 keV and 511 keV. In this study, we optimized the timing performance parameters of the SiPM-based digital PAL spectrometer by conducting the timing resolution measurements using two γ-ray sources (22Na and 60Co). With a 32 V bias voltage, 5th degree polynomial fitting method, and optimal constant fraction value, we optimized the timing resolution of our SiPM-based digital PAL spectrometer. Furthermore, the optimal constant fraction value depended on the γ-ray energy and we verified it by timing resolution measurement using 207Bi. We studied the reason why performance parameters have optimal conditions and the optimal constant fraction value varies depending on the γ-ray energy. With optimized performance parameters, we measured the lifetime spectrum of pure silicon to confirm the SiPM-based digital PAL spectrometer. The timing resolution function of the SiPM-based digital PAL spectrometer was 185.6 ps.

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Section: Timing Resolution Measurement Resultsmentioning

confidence: 99%

Section: Digital Pulse Processing 231 Pulse Smoothing Methods and Bas...mentioning

confidence: 99%

Section: Digital Fraction Discrimination (Dcfd)mentioning

confidence: 99%

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Study of timing performance parameters for a SiPM-based digital positron annihilation lifetime spectrometer

Choi¹,

Ko²,

Kim³

et al. 2022

J. Inst.

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“…Time resolution is improved with respect to the standard configuration, without decreasing the counting rate [ 62 ]. The introduction of ultra-fast digitizers has represented a real milestone in the PALS technique [ 63 , 64 , 65 ].…”

Section: Methodsmentioning

confidence: 99%

Probing the Free Volume in Polymers by Means of Positron Annihilation Lifetime Spectroscopy

Consolati

Nichetti²,

Quasso

2023

Polymers

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Positron annihilation lifetime spectroscopy (PALS) is a valuable technique to investigate defects in solids, such as vacancy clusters and grain boundaries in metals and alloys, as well as lattice imperfections in semiconductors. Positron spectroscopy is able to reveal the size, structure and concentration of vacancies with a sensitivity of 10−7. In the field of porous and amorphous systems, PALS can probe cavities in the range from a few tenths up to several tens of nm. In the case of polymers, PALS is one of the few techniques able to give information on the holes forming the free volume. This quantity, which cannot be measured with macroscopic techniques, is correlated to important mechanical, thermal, and transport properties of polymers. It can be deduced theoretically by applying suitable equations of state derived by cell models, and PALS supplies a quantitative measure of the free volume by probing the corresponding sub-nanometric holes. The system used is positronium (Ps), an unstable atom formed by a positron and an electron, whose lifetime can be related to the typical size of the holes. When analyzed in terms of continuous lifetimes, the positron annihilation spectrum allows one to gain insight into the distribution of the free volume holes, an almost unique feature of this technique. The present paper is an overview of PALS, addressed in particular to readers not familiar with this technique, with emphasis on the experimental aspects. After a general introduction on free volume, positronium, and the experimental apparatus needed to acquire the corresponding lifetime, some of the recent results obtained by various groups will be shown, highlighting the connections between the free volume as probed by PALS and structural properties of the investigated materials.

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“…Unfortunately, the estimation of PPC t using the current experimental setup is challenging. In the future, it is anticipated that a system with narrower time windows (<1 s) will be developed, incorporating more intense positron sources, including slow positron beams, [16][17][18] and enabling a more precise estimation of defect concentrations and decay parameters.…”

mentioning

confidence: 99%

Transient positron annihilation spectroscopy under light irradiation at liquid nitrogen temperature: evaluation of defect states in single-crystal ZnO

Nakajima,

Kinomura,

et al. 2024

Jpn. J. Appl. Phys.

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A time-dependent measurement system has been developed for positron annihilation spectroscopy to study the effects of light irradiation at liquid nitrogen temperature. The system enables the measurement of positron annihilation lifetimes after pulse light irradiation, utilizing various time windows to investigate the transient changes of photo-excited vacancy-type defects. Additionally, this system facilitates coincidence Doppler broadening measurements during light irradiation at liquid nitrogen temperature. The system was successfully employed to analyze changes in positron lifetime and positron annihilation sites in electron-irradiated single-crystalline ZnO under light irradiation.

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A multi-parameter discrimination digital positron annihilation lifetime spectrometer using a fast digital oscilloscope

Cited by 9 publications

References 22 publications

Study of timing performance parameters for a SiPM-based digital positron annihilation lifetime spectrometer

Study of timing performance parameters for a SiPM-based digital positron annihilation lifetime spectrometer

Probing the Free Volume in Polymers by Means of Positron Annihilation Lifetime Spectroscopy

Transient positron annihilation spectroscopy under light irradiation at liquid nitrogen temperature: evaluation of defect states in single-crystal ZnO

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