A new SiPM-based positron annihilation lifetime spectrometer using LYSO and LFS-3 scintillators

Self Cite

Fast timing and energy resolving capabilities are crucial for a silicon-photomultiplier-based positron annihilation lifetime (SiPM-PAL) spectrometer. Time-over-threshold (ToT) offers an attractive method for combining timing and energy encoding with the advantage of simplicity in electronics implementation and SiPM readout. However, single ToT is not appropriate for a SiPM-PAL spectrometer because of its poor energy linearity and limited energy range. In this work, a multi-ToT readout circuit for a SiPM-PAL spectrometer is developed. Each readout channel uses only a pre-amplifier and a comparator for timing, three comparators for energy resolving, resistors, and capacitors. A simple pulse area estimation method using multi-ToT pulse widths and fixed threshold voltages for energy resolving is presented and evaluated. The energy performance and pulse area integral nonlinearity (INL) are investigated using 22Na, 60Co, and 137Cs γ sources with a SiPM-based scintillation detector. For pulse area spectra using the proposed method, multi-ToT (triple and dual threshold cases) resolves γ energies much better than does single ToT. Using triple-ToT, the pulse area linearity in INL in the energy range of 511–1333 keV is superior than 4.21%, which is at least 25% better than that with dual-ToT. Excellent coincidence resolving times of 161.5 ± 1.4 ps and 162.7 ± 1.3 ps in full width at half maximum are achieved using triple-ToT and dual-ToT, respectively, for 3 mm\;×\;3 mm\;×\;5 mm lutetium-fine-silicate scintillators. The quantitative energy and timing results show that the multi-ToT circuit is suitable for the readout electronics of a SiPM-PAL spectrometer.

Section: Coincidence Resolving Timesupporting

confidence: 90%

“…We have previously presented the application of the SiPM technique in developing a new PAL spectrometer using a digital oscilloscope [18]. Good results on the timing and energy performance of the SiPM detector were achieved using lutetium-fine-silicate (LFS) scintillators.…”

Section: Introductionmentioning

confidence: 99%

Multiple time-over-threshold readout electronics for fast timing and energy resolving in a SiPM-based positron annihilation lifetime spectrometer

Wang¹,

Liu²,

Zhang³

et al. 2020

Self Cite

“…Time resolution is considered as one of the key parameters to evaluate the characteristics of a PAL spectrometer. Numerous efforts have been made to improve the time resolution of PAL spectrometers over the past twenty years [15][16][17][18][19][20][21][22][23][24][25][26]. The tendency is to develop digital PAL spectrometers in which analog electric modules are substituted by fast digitizers.…”

Section: Introductionmentioning

confidence: 99%

“…Digital spectrometers have advantages in data processing capability and time performance compared to the conventional ones. Several digital PAL spectrometers with time resolution around 140-200 ps in FWHM (full width at half maximum) have been developed [16,19,22,23,26]. Generally speaking, the performance of a digital PAL spectrometer depends not only on state-of-the-art digitizers and appropriate data processing algorithms but also on fast scintillators and photomultiplier tubes (PMTs).…”

Section: Introductionmentioning

confidence: 99%

Coincidence time resolution investigation of BaF₂-based H6610 detectors for a digital positron annihilation lifetime spectrometer

Wang

et al. 2020

BaF 2 -based detectors have been used in many fields requiring fast timing, especially in positron annihilation lifetime (PAL) spectroscopy. The performance of a PAL spectrometer is closely correlated with the time response of BaF 2 -based detectors. Therefore, it is important to select scintillation detectors with excellent time resolution. In this work, the coincidence time resolution of BaF 2 -based H6610 detectors was investigated using a digital oscilloscope. The time response of detectors has been optimized by tuning the supply voltages, the sampling rate of the oscilloscope, and digital fraction constants, achieving a conicidence time resolution of about 162 ps for the 0.511 MeV annihilation γ-ray pairs and 108 ps for the 60 Co cascade γ-rays, respectively. Furthermore, a digital PAL spectrometer composed of two BaF 2 -based H6610 detectors and an oscilloscope was developed with a time resolution of around 130 ps, much better than most digital PAL spectrometers.

“…With the development of technology, several digital PAL spectrometers using fast oscilloscope or digitizer have been developed to replace nuclear instrumentation modules (NIM modules) such as the constant fraction discriminator (CFD) and the time-to-amplitude converter (TAC) [4][5][6][7]. In addition, recent studies developed a silicon photomultiplier (SiPM) based PAL spectrometer that has many advantages over the conventional PAL spectrometer, which is configured with PMT [8,9].…”

Section: Introductionmentioning

confidence: 99%

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

Choi¹,

Ko²,

Kim³

et al. 2022

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.