Influence of SiPM Single Photon Timing Resolution on Coincidence Timing Resolution with Fast Scintillator (original) (raw)
Related papers
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2013
In this work we report on the coincidence resolving time performance of SiPMs with different sizes, produced at FBK, coupled to the same LYSO scintillators. The measurements are performed both with and without the differential leading edge discriminator at three different temperatures, 20 1C, 0 1C and À 20 1C. The photo-detectors feature an active area of 2 Â 2 mm 2 and 4 Â 4 mm 2. The scintillators have a crosssection of 1.8 Â 1.8 mm 2 and height of 10 mm. The measurements show that, once we eliminate the effect of noise on the timing measurements, we obtain similar coincidence resolving times for the two SiPM sizes considered. This means that the SiPM capacitance, at least up to 4 Â 4 mm 2 , is not a limiting factor.
IEEE Transactions on Nuclear Science, 2000
Silicon photomultipliers (SiPMs) are expected to replace photomultiplier tubes (PMTs) in several applications that require scintillation detectors with excellent timing resolution, such as time-of-flight positron emission tomography (TOF-PET). However, the theory about the timing resolution of SiPM-based detectors is not yet fully understood. Here we propose a comprehensive statistical model to predict the timing resolution of SiPM-based scintillation detectors. It incorporates the relevant SiPM-related parameters (viz. the single cell electronic response, the single cell gain, the charge carrier transit time spread, and crosstalk) as well as the scintillation pulse rise and decay times, light yield, and energy resolution. It is shown that the proposed model reduces to the well-established Hyman model for timing with PMTs if the number of primary triggers (photoelectrons in case of a PMT) is Poisson distributed and crosstalk and electronic noise are negligible. The model predictions are validated by measurements of the coincidence resolving times (CRT) for 511 keV photons of two identical detectors as a function of SiPM bias voltage, for two different kinds of scintillators, namely LYSO:Ce and LaBr :5%Ce. CRTs as low as ps FWHM for LYSO:Ce and ps FWHM for LaBr :5%Ce were obtained, demonstrating the outstanding timing potential of SiPM-based scintillation detectors. These values were found to be in good agreement with the predicted CRTs of 140 ps FWHM and 95 ps FWHM, respectively. Utilizing the proposed model, it can be shown that the CRTs obtained in our experiments are mainly limited by photon statistics while crosstalk, electronic noise and signal bandwidth have relatively little influence. Index Terms-Gamma ray detection, model, multi pixel photon counter (MPPC), nuclear medicine, positron emission tomography (PET), scintillation counters, silicon photomultiplier (SiPM), time of flight (TOF), timing resolution.
Timing scintillation detector with SiPM incorporated throughout a scintillator’s body
Journal of Physics: Conference Series, 2017
A timing scintillation detector based on a plastic scintillator strip sized 35×5×1 cm 3 and SiPM optical readout has been developed and characterized. For the best uniformity of the detector's response to particle hits across its area, a set of SiPM optical sensors has been incorporated into the scintillator throughout its volume. Time resolution better than 260 ps (sigma) has been achieved for each point of the device. Uniformity of the detector's response is confirmed by amplitude measurements along the strip as well as measurements of the efficiency of scintillation detection, which, on average, is ~99%.
Ultra Precise Timing with SiPM-Based TOF PET Scintillation Detectors
2009 Ieee Nuclear Science Symposium Conference Record, Vols 1-5, 2009
The combination of SiPMs with fast and bright scintillators, such as LaBr 3 :Ce, seems very promising for application in time-of-flight (TOF) PET. We therefore conducted a series of experiments with the goal of obtaining the best possible timing resolution with SiPM-based scintillation detectors in order to establish a bench mark for future experiments with different detector designs. The detectors employed in our measurements consisted of two SiPMs (Hamamatsu MPPC-S10362-33-050C), which were directly coupled to small scintillation crystals, viz. LaBr 3 :Ce and LYSO. An excellent coincidence resolving time (CRT) for 22 Na 511 annihilation photons of 99.5 ps ± 0.6 ps FWHM could be achieved at the optimized electronics and digitizer settings with two LaBr 3 :5%Ce crystals. A CRT of 171.5 ps ± 0.8 ps FWHM was obtained with L(Y)SO crystals. These results compare well to the predictions of a statistical model which was developed to describe the timing performance of SiPM based scintillation detectors.
: Time of flight (TOF) in positron emission tomography (PET) has experienced a revival of interest after its first introduction in the eighties. This is due to a significant progress in solid state photodetectors (SiPMs) and newly developed scintillators (LSO and its derivatives). Latest developments at Fondazione Bruno Kessler (FBK) lead to the NUV-HD SiPM with a very high photon detection efficiency of around 55%. Despite the large area of 4 × 4 mm 2 it achieves a good single photon time resolution (SPTR) of 180±5ps FWHM. Coincidence time resolution (CTR) measurements using LSO:Ce codoped with Ca scintillators yield best values of 73±2ps FWHM for 2 × 2 × 3 mm 3 and 117±3ps for 2 × 2 × 20 mm 3 crystal sizes. Increasing the crystal crosssection from 2 × 2 mm 2 to 3 × 3 mm 2 a non negligible CTR deterioration of approximately 7ps FWHM is observed. Measurements with LSO:Ce codoped Ca and LYSO:Ce scintillators with various cross-sections (1 × 1 mm 2 -4 × 4 mm 2 ) and lengths (3mm -30mm) will be a basis for discussing on how the crystal geometry affects timing in TOF-PET. Special attention is given to SiPM parameters, e.g. SPTR and optical crosstalk, and their measured dependency on the crystal cross-section. Additionally, CTR measurements with LuAG:Ce, LuAG:Pr and GGAG:Ce samples are presented and the results are interpreted in terms of their scintillation properties, e.g. rise time, decay time, light yield and emission spectra.
Characteristics of scintillation detectors based on inorganic scintillators and SiPM light readout
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2013
Recently, a silicon photomultiplier (SiPM) became one of the strongest candidates for application in PET-MR or SPECT-MR dual-modality scanners. However, optimization of the scintillation detectors with SiPM light readout requires different approach than in the case of classic photomultipliers. The finite number of micro-cells in a SiPM creates nonlinear response for high number of incident photons. Moreover, the size and total number of micro-cells defines fill factor, which in turn affects the photon detection efficiency (PDE). Response of SiPMs is also highly sensitive to bias voltage causing changes in PDE and excess noise factor (ENF). Finally, each cell posses an effective dead time needed to fully recharge that cell after the photon detection. In this work the listed above unique features of SiPMs are overviewed. The reported data also contain measurements of energy resolution and 22 Na time resolution.
On timing resolution with thin scintillators
Nuclear Instruments and Methods, 1973
The timing properties of plastic scintillators and photomultipliers are investigated, in view of the more recent technology and electronics available at present. The intrinsic limits of the techniques are discussed.
2010
In this work we present a measurement setup for the determination of scintillation pulse shapes of fast scintillators. It is based on a time-correlated single photon counting approach that utilizes the correlation between 511 keV annihilation photons to produce start and stop signals in two separate crystals. The measurement is potentially cost-effective and simple to set up while maintaining an excellent system timing resolution of 125 ps. As a proof-of-concept the scintillation photon arrival time histograms were recorded for two well-known, fast scintillators: LYSO:Ce and LaBr 3 :5%Ce. The scintillation pulse shapes were modeled as a linear combination of exponentially distributed charge transfer and photon emission processes. Correcting for the system timing resolution, the exponential time constants were extracted from the recorded histograms. A decay time of 43 ns and a rise time of 72 ps were determined for LYSO:Ce thus demonstrating the capability of the system to accurately measure very fast rise times. In the case of LaBr 3 :5%Ce two processes were observed to contribute to the rising edge of the scintillation pulse. The faster component (270 ps) contributes with 72% to the rising edge of the scintillation pulse while the second, slower component (2.0 ns) contributes with 27%. The decay of the LaBr 3 :5%Ce scintillation pulse was measured to be 15.4 ns with a small contribution (2%) of a component with a larger time constant (130 ns).
Fundamental limits of scintillation detector timing precision
Physics in Medicine and Biology, 2014
In this paper we review the primary factors that affect the timing precision of a scintillation detector. Monte Carlo calculations were performed to explore the dependence of the timing precision on the number of photoelectrons, the scintillator decay and rise times, the depth of interaction uncertainty, the time dispersion of the optical photons (modeled as an exponential decay), the photodetector rise time and transit time jitter, the leading-edge trigger level, and electronic noise. The Monte Carlo code was used to estimate the practical limits on the timing precision for an energy deposition of 511 keV in 3 mm × 3 mm × 30 mm Lu 2 SiO 5 :Ce and LaBr 3 :Ce crystals. The calculated timing precisions are consistent with the best experimental literature values. We then calculated the timing precision for 820 cases that sampled scintillator rise times from 0 to 1.0 ns, photon dispersion times from 0 to 0.2 ns, photodetector time jitters from 0 to 0.5 ns fwhm, and A from 10 to 10,000 photoelectrons per ns decay time. Since the timing precision R was found to depend on A −1/2 more than any other factor, we tabulated the parameter B, where R = BA −1/2. An empirical analytical formula was found that fit the tabulated values of B with an rms deviation of 2.2% of the value of B. The theoretical lower bound of the timing precision was calculated for the example of 0.5 ns rise time, 0.1 ns photon dispersion, and 0.2 ns fwhm photodetector time jitter. The lower bound was at most 15% lower than leading-edge timing discrimination for A from 10 to 10,000 photoelectrons/ns. A timing precision of 8 ps fwhm should be possible for an energy deposition of 511 keV using currently available photodetectors if a theoretically possible scintillator were developed that could produce 10,000 photoelectrons/ns.