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The Low Gain Avalanche Diode (LGAD) is a high-precision silicon-based timing sensor, with pixel sizes of 1.3 × 1. 3 mm 2 utilized in the High Granularity Timing Detector (HGTD) project at ATLAS. However, in future lepton colliders and space based experiments, the particle density is much lower than in Hadron colliders. Therefore, increasing the pixel area of the LGAD could lead to a reduction in the channel density of the readout electronics, resulting in cost and power consumption savings for experiments with low particle densities. It is essential to conduct detailed studies on the impact of area expansion on the time resolution and Signal-to-Noise Ratio (SNR) of LGAD need to be studied in detail to provide a reference for the application of large-area LGADs. Different-area sensors are obtained by connecting different numbers of pixels in parallel within the LGAD array. These LGADs are designed by the Institute of High Energy Physics (IHEP, CAS) and manufactured by the Institute of Microelectronics (IME, CAS), feature an epitaxial layer thickness of 50 μ m. This paper studies the breakdown voltage, leakage current, and depletion process of devices with different areas, while also examining the time resolution, SNR, rise time and other parameters of sensors with varying areas using a beta source ( 90 Sr) test system. The test results indicate that as the area of devices increases from 1.69 mm 2 to 42.25 mm 2 , the time resolution deteriorates significantly from 37 ps to 65 ps. The depletion capacitance of the device increases with the area, resulting in a slower R C process for signal formation, longer signal rise time, and decreased SNR ratio, leading to a deterioration of time resolution. [ABSTRACT FROM AUTHOR]

The thickness of the high-resistivity layer (active layer) is a crucial factor affecting the timing resolution of low gain avalanche diodes (LGADs). We studied the potential improvement of the timing resolution of charge particles based on LGADs with different active layer thicknesses. The Institute of High Energy Physics (IHEP) and the Novel Device Laboratory (NDL) jointly designed two types of LGAD sensors with active layer thicknesses of 33 and 50 $\mu \text{m}$. The timing resolution is given by contributions from the time walk, jitter, and nonuniform charge deposition (Landau term). The jitter and the Landau term contributions in the timing resolution are extracted by the combination of the ${^{90}{Sr}}$ beta source test and the picosecond laser test. The Landau contribution is found to be the dominant contribution for both types of LGAD sensors, and the Landau contribution of the 33 $\mu \text{m}$ sensor is lower than that of the 50 $\mu \text{m}$ sensor. Based on the experimental results, we perform the simulation for thinner active layer LGAD with the WeightField2 program. The timing resolution can be further improved by reducing the active layer thickness from 33 to 20 $\mu \text{m}$. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of the updated version of the Front-End Board (FEB) for the NectarCAM camera, developed for the Cherenkov Telescope Array Observatory (CTAO). The FEB is a critical component responsible for reading and converting signals from the camera's photo-multiplier tubes into digital data and generating module-level trigger signals. This study provides an overview of the design and performance of the new FEB version, including the use of an improved NECTAr3 chip with advanced features. The NECTAr3 chip contains a switched capacitor array for sampling signals at 1 GHz and a 12-bit analog-to-digital converter (ADC) for digitization upon receiving a trigger signal. The integration of the new NECTAr3 chip results in a significant reduction of NectarCAM's deadtime by an order of magnitude compared to the previous version. The paper also presents the results of laboratory testing, including measurements of timing performance, linearity, dynamic range, and deadtime, to characterize the new FEB's performance. [ABSTRACT FROM AUTHOR]

The AC-coupled Strip LGAD (Strip AC-LGAD) is a novel LGAD design that diminishes the density of readout electronics through the use of strip electrodes, enabling the simultaneous measurement of time and spatial information. The Institute of High Energy Physics has designed a long Strip AC-LGAD prototype with a strip electrode length of 5.7 mm and pitches of 150 μ m, 200 μ m, and 250 μ m. Spatial and timing resolutions of the long Strip AC-LGAD are studied by pico-second laser test and beta source tests. The laser test demonstrates that spatial resolution improves as the pitch size decreases, with an optimal resolution achieved at 8. 3 μ m. Furthermore, the Beta source test yields a timing resolution of 37.6 ps. [ABSTRACT FROM AUTHOR]

A signal tapping circuit has been designed to derive the fast timing signal from the Chevron type, 2 stage MCP having phosphor screen as a readout device. Using this, the timing property of the MCP-BaF2 system has been studied using the digital storage oscilloscope in which a timing resolution of ~ 500 ps has been obtained. The applicability of MCP with phosphor screen configuration for timing measurements has been demonstrated. [ABSTRACT FROM AUTHOR]

The proposed Electron-Ion Collider (EIC) will operate high-luminosity high-energy electron+proton and electron+nucleus collisions at the collision energies from 20 GeV to 141 GeV to solve several fundamental questions in the high energy and nuclear physics fields. Its instantaneous luminosity can reach 1 0 33 − 34 cm − 2 s − 1 and the bunching crossing rate is around 10 ns. The EIC project has received CD1 approval from the US DOE in 2021 and moves toward the machine design and preparation for construction. To realize various particle measurements with high precision at the future EIC, a low material-budget and high-granularity silicon vertex and tracking detector with fine spatial and momentum resolutions and nearly 4 π solid angle coverage is desired. The Monolithic Active Pixel Sensor (MAPS) and AC Coupled Low Gain Avalanche Diode (AC-LGAD) technologies stand out of several advanced technology options for the EIC silicon vertex and tracking detector subsystems. The MAPS technology has advanced features of low material budget, low power consumption, good radiation resistance and fine spatial resolution. The AC-LGAD technology can achieve fast timing resolution. Latest studies and progress of the EIC silicon vertex and tracking detector conceptual design, performance validations in simulation and ongoing MAPS and AC-LGAD R&D will be shown. Schedule and plan of the EIC project detector development will be discussed as well. • This paper introduces the latest design concept of the EIC project detector, which is expected to start construction in 2025. • Sub-percentage momentum resolution and better than 10 μ m spatial resolution can be achieved by the EIC vertex and tracking detector in a broad kinematic coverage, which meets most of the EIC detector requirements. • Two advanced silicon detector technologies have been selected for the EIC vertex and tracking detector, one is the Monolithic Active Pixel Sensor (MAPS), and the other one is the AC coupled Low Gain Avalanche Diode (AC-LGAD). • Better than 4. 5 μ m hit spatial resolution has been achieved by the new 65 nm MAPS prototype sensor with up to 1 0 15 1 MeV n e q cm−2 radiation dose. • Around 30 ps timing resolution has been achieved by the AC-LGAD prototype sensor. [ABSTRACT FROM AUTHOR]

Abstract The spatial, timing, and energy resolutions of a detector affect the image quality of a positron emission tomography (PET) system. These parameters are in turn dependent on various factors, such as the choice of scintillator, photodetectors, reflector material, and surface treatment (rough or polished) of the scintillators. In this study, we investigated the performances of sub-millimeter scintillator array, LYSO:Ce (polished and rough surfaces with BaSO 4 reflector or enhanced specular reflector (ESR)), a gadolinium aluminum gallium garnet (Ce:GAGG, rough surface with BaSO 4 reflector), and a new gadolinium fine aluminum gallate (Ce:GFAG, rough surface with BaSO 4 reflector) detectors. The outer dimension of each scintillator block was ∼ 12 × 12 mm with a 12 × 12 matrix of 0.9 × 0. 9 × 6 mm3 crystal elements. These blocks were optically coupled to a digital silicon photomultiplier (dSiPM, DPC-3200-22-44) with a 1 mm thick optical guide. Experiments were conducted at a sensor temperature of ∼ 15 °C, and a two-dimensional position histogram for 22Na gamma photons showed that all pixels were clearly resolved for all block detectors (peak-to-valley ratios ranging from 5.3 to 11.1). The average energy resolutions for the LYSO (ESR, rough), LYSO (ESR, polished), LYSO (BaSO 4 , rough), LYSO (BaSO 4 , polished), GAGG (BaSO 4 , rough), and GFAG (BaSO 4 , rough) arrays were measured as 11.3%, 10.2%, 18.7%, 10.3%, 10.0%, and 13.2% full width at half maximum (FWHM), respectively. The coincidence resolving times (with 3 × 3 × 5 mm3 LYSO crystal as reference) for the LYSO (ESR, rough), LYSO (ESR, polished), LYSO (B aSO 4 , rough), LYSO (BaSO 4 , polished), GAGG (BaSO 4 , rough), and GFAG (BaSO 4 , rough) arrays were 209 ps, 222 ps, 197 ps, 230 ps, 321 ps, and 276 ps, respectively. In conclusion, the new GFAG scintillator may be a promising candidate for future high-resolution time-of-flight (ToF) PET systems, considering the tradeoff between its performance and potential to be grown at a lower cost. [ABSTRACT FROM AUTHOR]

A tin-loaded liquid scintillator has been developed for gamma spectroscopy and neutron detection. The scintillator was characterized in regard to energy resolution, pulse shape discrimination, neutron light output function, and timing resolution. The loading of tin into scintillators with low effective atomic number was demonstrated to provide photopeaks with acceptable energy resolution. The scintillator was shown to have reasonable neutron/gamma discrimination capability based on the charge comparison method. The effect on the discrimination quality of the total charge integration time and the initial delay time for tail charge integration was studied. To obtain the neutron light output function, the time-of-flight technique was utilized with a 252 Cf source. The light output function was validated with the MCNPX-PoliMi code by comparing the measured and simulated pule height spectra. The timing resolution of the developed scintillator was also evaluated. The tin-loading was found to have negligible impact on the scintillation decay times. However, a relatively large degradation of timing resolution was observed due to the reduced light yield. [ABSTRACT FROM AUTHOR]

Purpose: Newer high-performance time-of-flight (TOF) positron emission tomography (PET) systems have the capability to preserve diagnostic image quality with low count density, while maintaining a high raw photon detection sensitivity that would allow for a reduction in injected dose or rapid data acquisition. To assess this, we performed quantitative and visual assessments of the PET images acquired using a highly sensitive (23.3 cps/kBq) large field of view (25-cm axial) silicon photomultiplier (SiPM)-based TOF PET (400-ps timing resolution) integrated with 3 T-MRI in comparison to PET images acquired on non-TOF PET/x-ray computed tomography (CT) systems.Procedures: Whole-body 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) PET/CT was acquired for 15 patients followed by whole body PET/magnetic resonance imaging (MRI) with an average injected dose of 325 ± 84 MBq. The PET list mode data from PET/MRI were reconstructed using full datasets (4 min/bed) and reduced datasets (2, 1, 0.5, and 0.25 min/bed). Qualitative assessment between PET/CT and PET/MR images were made. A Likert-type scale between 1 and 5, 1 for non-diagnostic, 3 equivalent to PET/CT, and 5 superior quality, was used. Maximum and mean standardized uptake values (SUVmax and SUVmean) of normal tissues and lesions detected were measured and compared.Results: Mean visual assessment scores were 3.54 ± 0.32, 3.62 ± 0.38, and 3.69 ± 0.35 for the brain and 3.05 ± 0.49, 3.71 ± 0.45, and 4.14 ± 0.44 for the whole-body maximum intensity projections (MIPs) for 1, 2, and 4 min/bed PET/MR images, respectively. The SUVmean values for normal tissues were lower and statistically significant for images acquired at 4, 2, 1, 0.5, and 0.25 min/bed on the PET/MR, with values of - 18 ± 28 % (p < 0.001), - 16 ± 29 % (p = 0.001), - 16 ± 31 % (p = 0.002), - 14 ± 35 % (p < 0.001), and - 13 ± 34 % (p = 0.002), respectively. SUVmax and SUVpeak values of all lesions were higher and statistically significant (p < 0.05) for 4, 2, 1, 0.50, and 0.25 min/bed PET/MR datasets.Conclusion: High-sensitivity TOF PET showed comparable but still better visual image quality even at a much reduced activity in comparison to lower-sensitivity non-TOF PET. Our data translates to a seven times reduction in either injection dose for the same time or total scan time for the same injected dose. This "ultra-sensitivity" PET system provides a path to clinically acceptable extremely low-dose FDG PET studies (e.g., sub 1 mCi injection or sub-mSv effective dose) or PET studies as short as 1 min/bed (e.g., 6 min of total scan time) to cover whole body without compromising diagnostic performance. [ABSTRACT FROM AUTHOR]

NectarCAM is a Cherenkov camera which is going to equip the Medium-Sized Telescopes (MST) of the northern site of the Cherenkov Telescope Array Observatory (CTAO). NectarCAM is equipped with 265 modules, each consisting of 7 photo-multiplier tubes (PMTs), a Front-End Board and a local camera trigger system used for data acquisition. This paper addresses the timing performance of NectarCAM which are crucial to reduce the noise in shower images and improve image cleaning as well as to discriminate between gamma-ray photons and cosmic-ray background and finally to allow coincidence identification with neighboring telescopes for stereoscopic operations. Verification tests of the system have been performed in a dark room using various light sources to illuminate the first NectarCAM unit. The resulting timing precision and accuracy of the trigger arrival relative to a laser source, of individual and multiple pixel signals have been studied and are shown to comply to CTAO requirements. [ABSTRACT FROM AUTHOR]

The Compressed Baryonic Matter (CBM) experiment has decided to use the Multi-gap Resistive Plate Chambers(MRPC) technology to build its Time-Of-Flight (TOF) wall. CBM-TOF requires a rate capability over 20 kHz/cm 2 for inner region. A 10-gap pad-MRPC assembled with low resistive glass is designed to construct this area. The prototypes, which consist of 10×0.22 mm gas gaps and 2×8 20 mm×20 mm readout pads, require fewer electronic channels compared to the strip design. A timing resolution of around 60 ps and an efficiency above 98% were obtained in a cosmic test and a beam test taken in 2014 October GSI beam time. The results show that the real-size prototypes fulfill the requirements of the CBM-TOF. [ABSTRACT FROM AUTHOR]

In this work we present and discuss the use of state-of-the-art Geiger-mode APDs, also known as single-photon avalanche diodes (SPADs), for the detection of minimum ionizing particles (MIPs) with best-in-class timing resolution. The SPADs were implemented in standard CMOS technology and integrated with on-chip quenching and recharge circuitry. Two devices in coincidence allowed to measure the time-of-flight of 180 GeV/c momentum pions with a coincidence time resolution of 22 ps FWHM (9.4 ps Gaussian sigma). This result paves the path for new generation of cheap plug-and-play trackers with extremely high spatial and timing resolution, meant to be used in beam test facilities. [ABSTRACT FROM AUTHOR]

The PICOSEC Micromegas detector is a precise timing gaseous detector based on a Cherenkov radiator coupled to a semi-transparent photocathode and a Micromegas amplifying structure. First single-pad prototypes demonstrated a time resolution below σ = 25 ps, however, to make the concept appropriate to physics applications, several developments are required. The objective of this work was to achieve an equivalent time resolution for a 10 × 10 cm 2 area PICOSEC Micromegas detector. The prototype was designed, produced and tested in the laboratory and successfully operated with a 80 GeV/c muon beam. Preliminary results for this device equipped with a CsI photocathode demonstrated a time resolution below σ = 25 ps for all measured pads. The time resolution was reduced to be below σ = 18 ps by decreasing the drift gap to 180 μ m and using dedicated RF amplifier cards as new electronics. The excellent timing performance of the single-channel proof of concept was not only transferred to the 100-channel prototype, but even improved, making the PICOSEC Micromegas detector more suitable for large-area experiments in need of detectors with high time resolutions. • 10 × 10 cm 2 PICOSEC MM detector successfully operated with a 80 GeV/c muon beam • Timing performance of a single-channel detector transferred to a 100-channel device • Time resolution of σ = 18 ps achieved for the 10 × 10 cm 2 PICOSEC MM detector [ABSTRACT FROM AUTHOR]

We have chosen to establish the Compton Suppression Spectrometer (CSS) for low activity environmental samples with a high purity germanium (HPGe) primary detector and a removable plug-in detector (NaI(Tl)) surrounded with a cylindrical annulus guard detector (NaI(Tl)). Monte Carlo simulation with PENELOPE (PENetration and Energy LOss of Positrons and Electrons) is used to determine the optimal geometry of the CSS. To verify a correlation between experiment and simulation, the energy distribution of 137 Cs and 60 Co point sources is measured and simulated for each condition. The CSS parameters are studied to determine optimal detector geometry and Compton Suppression Factor (CSF). The timing resolution of the CSS was found to be 44 ns (FWHM), which is an outstanding result in the semiconductor-based gamma-ray spectrometry. All measured values of CSF agree within 5% with the values obtained from the simulation. The optimum geometry and CSF values are discussed. [ABSTRACT FROM AUTHOR]

Ce doped Gd 2 SiO 5 (GSO) is a scintillator which has relatively fast decay time, high density, high light output, and is used for commercial PET systems. However as time-of-flight (TOF) PET systems become more popular in clinical diagnostic, GSO seems less attractive, because its performance is thought to be insufficient for use in TOF-PET application. Although the timing resolution of the GSO combined with photomultiplier tube (PMT) is known to be inappropriate for TOF-PET system, the performance of GSO coupled to silicon photomultipliers (Si-PM) has not been reported to date. In addition, GSO possesses a variety of decay times depending on its Ce concentration. We measured basic performance of GSOs with different Ce concentrations and then coupled them to Si-PMs to measure the precise timing resolution using a high bandwidth digital oscilloscope. The decay time of GSO with 0.4 mol% Ce were longer (63±4 ns) compared with those with 1.0 mol% (40±2 ns) and 1.5 mol% (33±1 ns). With a Si-PM, the photo-peak channels were almost the same for GSOs with 0.4 mol% Ce and those with 1.5 mol% Ce, but the GSO with 1.0 mol% Ce was ~25% higher. Energy resolutions of these three GSOs were ~13% full-width at half-maximum (FWHM) for 662 keV gamma photons without correcting for saturation effects. When coupled to Si-PMs, the timing resolution for GSO with 1.5 mol% Ce (decay time 33 ns) was 549 ps FWHM, almost good enough to use for TOF-PET system. The combination of GSO with 1.5 mol% Ce with Si-PM will be an interesting combination to realize low cost TOF-PET systems. [ABSTRACT FROM AUTHOR]

Time-of-flight positron emission tomography requires high timing resolution. In this paper, we determined the influence of scintillation properties on the detector timing resolution for crystals with non-negligible optical transit timespread. In addition to intrinsic scintillation properties, such as the light yield, decay time constant, and scintillation rise time, we also studied the relation between the timing resolution and extrinsic scintillation properties, such as the dimensions of the crystal, the absorption probability of the reflector, the dwell time of photons inside the reflector during the reflection process, and the crystal polish. For this purpose, we developed ray-tracing software. The crystals simulated in this paper are LSO:Ce, LYSO:Ce, LSO:Ce,0.2%Ca, LYSO:0.11%Ce,0.2%Mg, and LYSO:0.2%Ce,0.2%Ca, with dimensions 3 \times 3 \times 5~\mm^3, 3 \times 3 \times 10~\mm^3, 3 \times 3 \times 20~\mm^3, and 4 \times 4 \times 22~\mm^3. We furthermore studied the optical transit timespread of photons inside polished and etched crystals, which explains the differences in timing resolution. [ABSTRACT FROM AUTHOR]

A detailed characterization of doped paraterphenyl (p-Terphenyl) neutron detectors was obtained by means of γ-sources and a 252 Cf fission chamber. The intrinsic timing resolution, the energy resolution up to 2 MeV ee , and the electron-equivalent energy calibration were determined using γ-sources. The neutron time-of-flight spectrum from the spontaneous fission of 252 Cf provided information on the proton energy calibration, the light output function, and the intrinsic neutron detection efficiency between 0 and 8 MeV for a threshold of 250 keV. Measurements of the latter were also performed using monoenergetic neutron beams. The applied experimental methods were cross-checked using two BC501A scintillation detectors, which were previously calibrated at the Physikalisch-Technische Bundesanstalt in Braunschweig, Germany. Results were compared to Monte-Carlo simulations performed using NRESP7 and NEFF7 codes. [ABSTRACT FROM AUTHOR]

Single-crystal chemical vapor-deposited diamond (sCVD) was investigated for its ability to act as fission-fragment detector. In particular we investigated timing and energy resolution for application in a simultaneous time-of-flight and energy measurement to determine the mass of the detected fission fragment. Previous tests have shown that poly-crystalline chemical vapor deposited (pCVD) diamonds provide sufficient timing resolution, but their poor energy resolution did not allow complete separation between very low-energy fission fragments, α-particles and noise. Our present investigations prove artificial sCVD diamonds to show similar timing resolution as pCVD diamonds close to 100 ps. Improved pulse-height resolution allows the unequivocal separation of fission fragments, and the detection efficiency reaches 100%, but remains with about a few percent behind requirements for fragment-mass identification. With high-speed digital electronics a timing resolution well below 100 ps is possible. However, the strongly varying quality of the presently available diamond material does not allow application on a sufficiently large scale within reasonable investments. [ABSTRACT FROM AUTHOR]

Single Photon Avalanche Diodes (SPAD) are known for their excellent timing performance which enables Time of Flight capabilities in positron emission tomography (PET). However, current array architectures juxtapose the SPAD with its ancillary electronics at the expense of a poor fill factor of the SPAD array. The 3D vertical integration of SPADs and readout electronics represents a solution to the aforementioned problem. Compared to systems with external electronics readout, 3D vertical integration reduces the SPAD interconnect parasitic capacitance while greatly increasing the photosensitive area and improving overall performances. This paper presents the implementation of two SPAD structures designed for PET. The SPAD structures are designed using Teledyne DALSA high voltage (HV) CMOS technology targeted for a 3-dimensional single photon counting module (3DSPCM). SPAD with two types of guard ring (diffusion-based and virtual guard ring) are designed, fabricated and characterized. All structures are based on a p + anode in an n-well cathode and are implemented along with active quenching circuits for proper characterization. The results show that the contact distribution and the anode-cathode spacing impact the dark count rate (DCR). The design of SPADs with a diffusion guard ring have a DCR down to 3~\s^- 1\mu \m^-2 at room temperature, afterpulsing probability of < 2\% , timing resolution of 27 ps FWHM and PDE of 49% at 480 nm. [ABSTRACT FROM PUBLISHER]

Scintillation properties of LSO:Ce, LSO:Ce,0.2%Ca, LYSO:Ce, LYSO:0.11%Ce,0.2%Mg, and LYSO:0.2%Ce,0.2%Ca were studied for application in time-of-flight positron emission tomography. To find the scintillation material with the best timing performance among those, we measured intrinsic scintillation pulse shapes–defined as the number of photons emitted per unit time at the ionization track as a function of time - by means of 100 ps x-ray excitation in the temperature range from 193 K to 373 K, from which intrinsic rise and decay time constants were derived. Photoelectron yields were measured by 662 keV gamma excitation. From these scintillation properties we calculated the corresponding lower bound on the timing resolution for each material. [ABSTRACT FROM PUBLISHER]

To increase contrast in positron emission tomography (PET) images, researchers are investigating detectors that reach below the nanosecond timing resolution. This allows a tight coincidence window which reduces random coincidence counts in the acquired data, as well as to include time-of-flight information into the reconstruction algorithms. With this goal in mind, single photon avalanche diode (SPAD) arrays have been under study for their excellent timing performances. However, their spurious dark counts can blur the start of PET signals where timing information is the most precise and create false starts in the acquisition system, introducing dead time. To minimize these problems in digital SPAD systems using a single time to digital converter (TDC) per PET channel, dark count discriminator circuits are required to reduce timing errors and increase the triggering efficiency in presence of dark counts. This paper compares the performance of a probabilistic and a novel delay line based dark count discriminator. Simulations of a SPAD array investigate the impact of dark counts on triggering efficiency and coincidence timing. Results show that the probabilistic discriminator provides excellent event recovery with regard to dark counts at the cost of some coincidence timing resolution. On the other hand, the delay line discriminator maintains the peak coincidence timing resolution but does not provide as much efficiency at high dark count rate levels. [ABSTRACT FROM PUBLISHER]

The scintillator is one of the key building blocks that critically determine the physical performance of PET detectors. The quest for scintillation crystals with improved characteristics has been crucial in designing scanners with superior imaging performance. Recently, it was shown that the decay time constant of high lutetium content Lu1.8Gd0.2SiO_5\!\!:Ce (LGSO) scintillators can be adjusted by varying the cerium concentration from 0.025 mol% to 0.75 mol%, thus providing interesting characteristics for phoswich detectors. The high light output (90%–120% NaI) and the improved spectral match of these scintillators with avalanche photodiode (APD) readout promise superior energy and timing resolutions. Moreover, their improved mechanical properties, as compared to conventional LGSO (Lu0.4Gd1.6SiO_5\!\!:Ce), make block array manufacturing readily feasible. To verify these assumptions, new phoswich block arrays made of LGSO-90%Lu with low and high mol% Ce concentrations were fabricated and assembled into modules dedicated to the LabPET scanner. Typical crystal decay time constants were 31 ns and 47 ns, respectively. Phoswich crystal identification performed using a digital pulse shape discrimination algorithm yielded an average 8% error. At 511 keV, an energy resolution of 17–21% was obtained, while coincidence timing resolution between 4.6 ns and 5.2 ns was achieved. The characteristics of this new LGSO-based phoswich detector module are expected to improve the LabPET scanner performance. The higher stopping power would increase the detection efficiency. The better timing resolution would also allow the use of a narrower coincidence window, thus minimizing the random event rate. Altogether, these two improvements will significantly enhance the noise equivalent count rate performance of an all LGSO-based LabPET scanner. [ABSTRACT FROM PUBLISHER]

We have constructed and characterized a time-of-flight Positron Emission Tomography (TOF PET) camera called the Tachyon. The Tachyon is a single-ring Lutetium Oxyorthosilicate (LSO) based camera designed to obtain significantly better timing resolution than the \sim 550~\ps found in present commercial TOF cameras, in order to quantify the benefit of improved TOF resolution for clinically relevant tasks. The Tachyon’s detector module is optimized for timing by coupling the 6.15 \times 25~\mm^2 side of 6.15 \times 6.15 \times 25~\mm^3 LSO scintillator crystals onto a 1-inch diameter Hamamatsu R-9800 PMT with a super-bialkali photocathode. We characterized the camera according to the NEMA NU 2-2012 standard, measuring the energy resolution, timing resolution, spatial resolution, noise equivalent count rates and sensitivity. The Tachyon achieved a coincidence timing resolution of 314~\ps +/- 20~\ps FWHM over all crystal-crystal combinations. Experiments were performed with the NEMA body phantom to assess the imaging performance improvement over non-TOF PET. The results show that at a matched contrast, incorporating 314 ps TOF reduces the standard deviation of the contrast by a factor of about 2.3. [ABSTRACT FROM PUBLISHER]

The need for ultra-fast timing is a result of the expected pile-up at the High-Luminosity LHC General-Purpose Detectors. Track timing resolution of the order of tens of picoseconds is required to sufficiently resolve individual vertices. In collaboration with Teledyne e2v, 22 six-inch wafers with Low Gain Avalanche Detectors, featuring a 50 μ m thick high-resistivity epitaxial layer and different gain layer implants, have been completed successfully. Using transient current technique, the charge gain of a 1 × 1 mm 2 LGAD device from one of the wafers was found to be higher than 10, with jitter reaching 10 ps when biased at 240 V. Tests with other wafers are under way. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach towards incorporating photonic crystals (PhCs) into optical Monte Carlo (MC) simulations. This approach affords modeling the full diffractive nature of PhCs including their reflection and transmission behavior as well as the manipulation of the photon trajectories through light scattering. The main purpose of this tool is to study the impact of PhCs on the light yield and timing performance of scintillator-based detectors for positron emission tomography (PET). To this end, the PhCs are translated into look-up tables and implemented into the optical MC algorithm. Our simulations are validated in optical experiments using PhC samples fabricated with electron beam lithography. The experimental results indicate that the simulations match the measurements within the accuracy of the experiments. The application of the combined simulation technique to a PET detector module predicts an increase of the total light yield by up to 23% for PhC coatings versus the reference without PhCs. Timing calculations reveal an improvement of the coincident resolving time by up to 6%. The results underline the potential of PhCs to improve light yield and timing of PET detector modules. [ABSTRACT FROM PUBLISHER]

We report the timing and spatial resolution from the Muon Telescope Detector (MTD) installed in the STAR experiment at RHIC. Cosmic ray muons traversing the STAR detector have an average transverse momentum of 6 GeV/c. Due to their very small multiple scattering, these cosmic muons provide an ideal tool to calibrate the detectors and measure their timing and spatial resolution. The values obtained were ~100 ps and ~1-2 cm. These values are comparable to those obtained from cosmic-ray bench tests and test beams. [ABSTRACT FROM AUTHOR]

Abstract: CeBr3 is a new fast scintillator with timing and energy resolution similar to LaBr3:Ce. The excellent timing resolution, measured here to be 93ps at 511keV for 1cm3 crystals, naturally lends itself to direct electronic measurements of excited nuclear state lifetimes in the nanosecond and sub-nanosecond range. To demonstrate this, half-lives of a 1.40ns isomer in 152Sm and 537 ps isomer in 177Hf were directly measured using the delayed coincidence technique. With its fast timing, high light output and high efficiency, the possibility of CeBr3 as a time-of-flight PET detector was also explored through time-of-flight measurements. [Copyright &y& Elsevier]

Current state-of-art whole-body PET scanners achieve a system spatial resolution of 4–5 mm with limited sensitivity. Since the reconstructed spatial resolution and image quality are limited by the count statistics, there has not been a significant push for developing higher resolution whole-body PET scanners. Our goal in this study is to investigate the impact of improved spatial resolution together with time-of-flight (TOF) capability on lesion uptake estimation and lesion detectability, two important tasks in whole-body oncologic studies. The broader goal of this project is the development of a new state-of-art TOF PET scanner operating within an MRI while pushing the technology in PET system design. We performed Monte Carlo simulations to test the effects of crystal size (4 mm and 2.6 mm wide crystals), TOF timing resolution (300 ps and 600 ps), and 2-level depth-of-interaction (DOI) capability. Spatial resolution was calculated by simulating point sources in air at multiple positions. Results show that smaller crystals produced improved resolution, while degradation of resolution due to parallax error could be reduced with a 2-level DOI detector. Lesion phantoms were simulated to measure the contrast recovery coefficient (CRC) and area under the LROC curve (ALROC) for 0.5 cm diameter lesions with 6:1 activity uptake relative to the background. Smaller crystals produce higher CRC, leading to increased ALROC values or a reduction in scan time. Improved timing resolution provides faster CRC convergence and once again leads to an increase in ALROC value or reduced scan time. Based on our choice of timing resolution and crystal size, improved timing resolution (300 ps) with larger crystals (4 mm wide) has similar ALROC as smaller crystals (2.6 mm wide) with 600 ps timing resolution. A 2-level DOI measurement provides some CRC and ALROC improvement for lesions further away from the center, leading to a more uniform performance within the imaging field-of-view (FOV). Given a choice between having either an improved spatial resolution, improved timing resolution, or DOI capability, improved spatial or timing resolution provide an overall higher ALROC relative to a 2-level DOI detector. [ABSTRACT FROM AUTHOR]

ZnO:Ga films are attractive phosphors for a number of high energy physics and security applications because of their extremely fast temporal response (typically less than 1 ns). Significant efforts have been undertaken to study the dependence of luminescence properties of ZnO:Ga on dopant constituency and temperature. However, most of these studies simply report the decay time of the phosphor, and there is a lack of published values for measured timing resolution with ZnO:Ga. This work aims to present achievable timing resolution with ZnO:Ga through predictive models and experimentally measured values. Careful characterization of a ZnO:Ga sample's temporal distribution and photosensor response provided inputs for an analytical timing model to predict the timing performance of ZnO:Ga. Additionally, the statistical limit on timing performance is calculated via the Cramèr-Rao statistic. The timing performance of a thin-film reference detector is quantified for alpha particle irradiation, and the timing resolution of a ZnO:Ga film is measured against the reference detector. A consistent and precise timestamp from the onset of the rising edge of the ZnO:Ga sample yielded a timing resolution of 52.5 \pm 10.0 ps FWHM was measured for the case of 50 detected photons. Good agreement is shown between measured and predicted timing performance, and the relation to the statistical limit is presented. The reported timing performance for a scintillator with an extremely fast decay but poor light yield has meaningful impact in many areas of study where a fast scintillator is required, including its use in the associated particle detector of a neutron generator to enable multimodal, time-of-flight (TOF) based imaging and TOF Positron Emission Tomography Imaging. [ABSTRACT FROM PUBLISHER]

The timing performance of TlBr detectors was evaluated at room temperature (22^\circC). 0.5-mm-thick planar TlBr detectors with Tl circular electrodes with a diameter of 3 mm were fabricated from TlBr crystals grown by the traveling molten zone method using a zone-purified material. The pulse rise time of the TlBr detector was measured using a digital oscilloscope as the cathode surface of the device was irradiated with a ^22Na gamma-ray source. Coincidence timing spectra were obtained between the TlBr detector and a BaF2 scintillation detector when both detectors were irradiated with 511 keV positron annihilation gamma-rays. The timing resolution of the TlBr detector was found to be inversely proportional to the applied bias voltage. The TlBr detector, in coincidence with the BaF2 detector, exhibited timing resolutions characterized by a 6.5 ns full width at half maximum (FWHM) and an 8.5 ns FWHM with and without an energy window of 350 keV–560 keV, respectively. [ABSTRACT FROM PUBLISHER]

Abstract: Cs2LiYCl6:Ce (CLYC) has been demonstrated to be sensitive to thermal neutrons via the 6Li(n, )t reaction, and recently to fast neutrons via the 35Cl(n,p) reaction. The scintillation properties of CLYC have been investigated in more detail to further understand its capabilities. Pulses from thermal neutron, fast neutron, and -ray induced excitations were captured, digitized over a time range, and analyzed to identify the scintillation mechanisms responsible for the observed shapes. Additionally, the timing resolutions of CLYC crystals of different sizes were measured in coincidence with a fast CeBr3 scintillator. The effect of high count rates on fast neutron energy resolution and pulse-shape discrimination was investigated up to 45kHz. [Copyright &y& Elsevier]

In the framework of the construction of the double time-of-flight spectrometer VERDI, where we aim at measuring pre- and post-neutron masses directly and simultaneously, ultra-fast time pick-up detectors based on artificial diamond material were investigated for the first time with fission fragments from 252Cf ( ). Signal stability under a high radiation fluence was determined up to at least fission-fragments/cm2 together with more than 3.5×109 neutrons/cm2 and 3×1010 . This fluence is characteristic for fission experiments. The pre-requisite for the observed signal stability is the application of priming of the diamond material with a strong for about 48h. The intrinsic timing resolution of a thick polycrystalline CVD diamond detector with a size of 1×1cm2 was determined to by comparison with Monte-Carlo simulations. Using broadband pre-amplifiers, 4-fold segmented detectors of same total size and with a thickness of show an intrinsic timing resolution of . This is highly competitive with the best micro-channel plate detectors. Due to the limited and batch-dependent charge collection efficiency of poly-crystalline diamond material, the detection efficiency for fission fragments may be smaller than 100%. [ABSTRACT FROM AUTHOR]

An SPX4 4H-silicon carbide detector consisting of 4\,\times\,4 pixels was developed and studied experimentally. Its pixel size is 400\times 400\ \mu\m^2. A timing resolution of 117 \pm 11 ps full width at half-maximum (FWHM) has been measured for the detection of alphas. With such good timing performance and high granularity, the SiC pixel detector holds great promise as an associated alpha-particle detector for fast neutron imaging. [ABSTRACT FROM PUBLISHER]

As nuclear physicists increasingly design large scale experiments with hundreds or thousands of detector channels, there are growing needs for high density readout electronics with good timing and energy resolution that at the same time offer lower cost per channel compared to existing commercial solutions. Recent improvements in the design of commercial analog to digital converters (ADCs) have resulted in a variety of multi-channel ADCs that are natural choice for designing such high density readout modules. However, multi-channel ADCs typically are designed for medical imaging/ultrasound applications and therefore are not rated for their spectroscopic characteristics. In this work, we evaluated the gamma-ray spectroscopic performance of several multi-channel ADCs, including their energy resolution, nonlinearity, and timing resolution. Some of these ADCs demonstrated excellent energy resolution, 2.66% FWHM at 662 keV with a LaBr3 or 1.78 keV FWHM at 1332.5 keV with a high purity germanium (HPGe) detector, and sub-nanosecond timing resolution with LaBr3. We present results from these measurements to illustrate their suitability for gamma-ray spectroscopy. [ABSTRACT FROM PUBLISHER]

Abstract: In this paper we demonstrate the employment of scintillation detectors for the identification of prompt fission from in contrast to other reactions. We present the properties of cylindrical 1.5in.×1.5in. detectors in terms of intrinsic activity, energy resolution, intrinsic full peak efficiency and intrinsic timing resolution. In addition, we show results from the measurement of emitted in coincidence with the spontaneous fission of 252Cf, which lead us to the conclusion that the properties of the detectors used in this work, in particular the good timing resolution and a reasonably good energy resolution, are more than just sufficient for the assessment of prompt in future nuclear reactors as requested by the OECD. Hence, in our opinion, detectors, compared to those made out of crystals, represent an appropriate and quasi low-cost choice for the above mentioned applications. [Copyright &y& Elsevier]

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 LaBr3:5%Ce. CRTs as low as 138\,ps \pm 2 ps FWHM for LYSO:Ce and 95\,ps \pm 3 ps FWHM for LaBr3:5%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. [ABSTRACT FROM PUBLISHER]

Time-of-flight (TOF) data can improve the imaging quality of positron emission tomography (PET) cameras by estimating the location of the positron annihilation. In this study, we measured the TOF resolution of lutetium yttrium orthosilicate (LYSO) blocks based on the photomultiplier-quadrant-sharing (PQS) design, which has no external light guide and therefore has higher light collection efficiency than the conventional block design with a light guide. We investigated three digital timing methods to achieve better timing resolution: constant fraction discriminationleading edge discrimination, and linear fitting. A time-energy correction, estimated from a least mean square fit, was applied to minimize time walk caused by the variation of signal shapes. The average block-to-block coincidence timing resolution for two 13\,\times\,13 blocks, each made of 4\,\times\,4\,\times\,20 mm^3 LYSO crystals, with fast R9779 PMTs from Hamamatsu (51-mm diameter) was estimated to be 422 ps (full width at half maximum). Another 13\,\times\,13 block of smaller 1.4\,\times\,1.4\,\times\,10 mm^3 LYSO crystals coupled to regular 19-mm-diameter XP1912 PMTs from Photonis was also tested and an average block-to-block timing resolution of 527 ps was achieved. This study shows that with PQS detector blocks, good time resolution suitable for TOF PET systems can be obtained, as well as high spatial resolution and lower PMT costs. [ABSTRACT FROM AUTHOR]

Abstract: In view of highly demanded new and accurate data on prompt emission in nuclear fission a major part of investigations is directed towards the selection of suitable detector systems. Here we have studied a new type of crystal scintillation detectors made from cerium bromide (CeBr3). For the first time a full characterization of such a detector is presented in terms of energy resolution, pulse-height linearity, intrinsic activity and intrinsic timing resolution. In particular the latter one is very important for prompt fission studies, because the presence of fast neutrons, emitted in fission too, requires the time-of-flight method for their discrimination. The energy resolution has been found to be comparable to that of cerium-doped LaCl3:Ce detectors at an efficiency comparable to the one of a LaBr3:Ce detector of the same size. The intrinsic activity of the CeBr3 crystal was observed to be much lower compared to lanthanum halide crystals. The intrinsic timing resolution of a coaxial 1in.×1in. sized detector was measured relative to that of a previously characterized LaCl3:Ce detector and found to be (326±7)ps at 60Co energies, which is in between those of a LaBr3:Ce and a LaCl3:Ce detector of same size. [Copyright &y& Elsevier]

Current PET systems with fully digital trigger rely on early digitization of detector signals and the use of digital processors, usually FPGAs, for recognition of valid gamma events on single detectors. Timestamps are assigned and later used for coincidence analysis. In order to maintain a decent timing resolution for events detected on different acquisition boards, it is necessary that local timestamps on different FPGAs be synchronized. Sub-nanosecond accuracy is mandatory if we want this effect to be negligible on overall timing resolution. This is usually achieved by connecting all boards to a common backplane with a precise clock delivery network; however, this approach forces a rigid structure on the whole PET system and may pose scalability problems. [ABSTRACT FROM PUBLISHER]

Abstract: Micro-channel plate (MCP) amplifiers are commonly used in detectors of fast time signals with picosecond resolution. The main parameters of the MCP amplifier, such as the gain factor and time resolution are strongly dependent on the work regime of the device. The saturation effects occur with a high-level input signal. In our paper these effects are studied numerically for large-area fast photo-detectors. It is shown that the saturation effect for short pulses can be reduced by introducing a thin, resistive layer between the bulk material and the emissive coating. A set of 2D and 3D numerical tools (MCP simulator, Monte Carlo simulator) was developed to simulate photo, secondary emission, fringe fields, and saturation phenomena in MCP amplifiers. The gain and time resolution dependencies on the pore size and voltage were studied numerically. The results are compared with the simulations of other authors and available experimental data. [Copyright &y& Elsevier]

Abstract: A Monte Carlo simulation of the light transit time in scintillation detectors is described, with the wavelength dependencies of different interaction processes being taken into account. The simulation results presented give an estimate of the contribution of light transport to the timing resolution of scintillation detectors. [ABSTRACT FROM AUTHOR]

Abstract: This paper focuses on the evaluation of a microchannel-plate photomultiplier tube (MCP-PMT) as a candidate detector, suitable for positron lifetime studies. Several properties of MCP-PMTs, such as their fast time response, compact size, low susceptibility to magnetic fields, relatively high gain and the low power consumption make them attractive for positron lifetime spectroscopy. The preliminary tests were performed with a 85001-501 Burle PlanaconTM photomultiplier tube assembly. Initial measurements were conducted with a pulsed Picosecond Injection Laser (PiLas) system. The engineering sample of the 85001 exhibits a transit-time-spread (TTS) of 110ps (FWHM). Further timing experiments showing the suitability of the device as Cherenkov detector are presented. For the first time, a conventional positron lifetime spectrum of a Cz-Si probe measured with a spectrometer, where an MCP-PMT detector is included, has been demonstrated. [ABSTRACT FROM AUTHOR]

We report on an investigation of a mulit-anode microchannel plate PMT for time-of-flight PET detector modules. The primary advantages of an MCP lie in its excellent timing properties (fast rise time and low transit time spread), compact size, and reasonably large active area, thus making it a good candidate for TOF applications. In addition, the anode can be segmented into an array of collection electrodes with fine pitch to attain good position sensitivity. In this paper, we investigate using the Photonis Planacon MCP-PMT with a pore size of 10 \mum to construct a PET detector module, specifically for time-of-flight applications. We measure the single electron response by exciting the Planacon with pulsed laser diode. We also measure the performance of the Planacon as a PET detector by coupling a 4\ mm\times 4\ mm\times 10\ mm LSO crystal to individual pixel to study its gain uniformity, energy resolution, and timing resolution. The rise time of the Planacon is 440 ps with pulse duration of about 1 ns. A transit time spread of 120 ps FWHM is achieved. The gain is fairly uniform across the central region of the Planacon, but drops off by as much as a factor of 2.5 around the edges. The energy resolution is fairly uniform across the Planacon with an average value of 18.6 \pm 0.7% FWHM. While the average timing resolution of 252 \pm 7 ps FWHM is achieved in the central region of the Planacon, it degrades to 280 \pm 9 ps FWHM for edge pixels and 316 \pm 15 ps FWHM for corner pixels. We compare the results with measurements performed with a fast timing conventional PMT (Hamamatsu R-9800). We find that the R9800, which has significantly higher PDE, has a better timing resolution than the Planacon. Furthermore, we perform detector simulations to calculate the improvement that can be achieved with a higher PDE Planacon. The calculation shows that the Planacon can achieve significantly better timing resolution if it can attain the same PDE as the R-9800, while only a 30% improvement is needed to yield a similar timing resolution as the R-9800. [ABSTRACT FROM PUBLISHER]

The renewal of interest in Time of Flight Positron Emission Tomography (TOF-PET), as well as the necessity to precisely tag events in high energy physics (HEP) experiments at future colliders are pushing for an optimization of all factors affecting the time resolution of the whole acquisition chain comprising the crystal, the photo detector, and the electronics. The time resolution of a scintillator-based detection system is determined by the rate of photo electrons at the detection threshold, which depends on the time distribution of photons being converted in the photo detector. The possibility to achieve time resolution of about 100 ps Full Width at Half Maximum (FWHM) requires an optimization of the light production in the scintillator, the light transport and its transfer from the scintillator to the photo detector. In order to maximize the light yield, and in particular the density of photons in the first nanosecond, while minimizing the rise time and decay time, particular attention must be paid to the energy transfer mechanisms to the activator as well as to the energy transition type at the activator ion. Alternatively other light emission mechanisms can be considered. We show that particularly Cerenkov emission can be used for this purpose. Special emphasis was put on the light transport within the crystal and at its interface with the photo detector. Since light is produced isotropically in the scintillator the detector geometry must be optimized to decrease the optical path-length to the photo detector. Moreover light bouncing within the scintillator, affecting about 70% of the photons generated in currently used crystals, must be reduced as much as possible. We also investigate photonics crystals that are specifically designed to favor specific light propagation modes at the limit of total reflection inside and outside of the crystal and how they might increase the light transfer efficiency to the photo detector and hence improve time resolution. Examples for the production and deposition of photonics crystals as layers on Lutetium Yttrium Ortho-Silicate (LYSO) and Lutetium Yttrium Aluminum Perovskite (LuYAP) crystals are shown here, as well as first results on an improved light extraction resulting from this method. [ABSTRACT FROM PUBLISHER]

Abstract: When optimizing the timing performance of a time-of-flight positron emission tomography (TOF-PET) detector based on a monolithic scintillation crystal coupled to a photosensor array, time walk as a function of annihilation photon interaction location inside the crystal needs to be considered. In order to determine the 3D spatial coordinates of the annihilation photon interaction location, a maximum likelihood estimation algorithm was developed, based on a detector characterization by a scan of a 511keV photon beam across the front and one of the side surfaces of the crystal. The time walk effect was investigated using a 20mm×20mm×12mm LYSO crystal coupled to a fast 4×4 multi-anode photomultiplier tube (MAPMT). In the plane parallel to the photosensor array, a spatial resolution of 2.4mm FWHM is obtained. In the direction perpendicular to the MAPMT (depth-of-interaction, DOI), the resolution ranges from 2.3mm FWHM near the MAPMT to 4mm FWHM at a distance of 10mm. These resolutions are uncorrected for the beam diameter. A coincidence timing resolution of 358ps FWHM is obtained in coincidence with a BaF2 detector. A time walk depending on the 3D annihilation photon interaction location is observed. Throughout the crystal, the time walk spans a range of 100ps. Calibration of the time walk vs. interaction location allows an event-by-event correction of the time walk. [ABSTRACT FROM AUTHOR]

We describe the development of readout electronics for fast radiation detectors that digitize signals at a rate of 500 MHz, process the digital data stream to measure pulse heights, bin the results in on-board MCA spectra, and optionally capture waveforms for pulse shape analysis. The electronics are targeted for applications requiring good energy resolution and precise timing, for example life time measurements on exotic nuclei, timing measurements with fast scintillators such as LaBr3 or BaF2, or pulse shape analysis with liquid scintillators or phoswich detectors. Upgrading the existing XIA Pixie-4 spectrometer design with a 12-bit, 500 MHz analog to digital converter, we built a prototype of a 4-channel electronics module and evaluated its performance in terms of energy resolution, timing resolution, and improvements in pulse shape analysis. [ABSTRACT FROM AUTHOR]

In this paper the results of charge and timing resolution characterization realized at Fermi National Accelerator Laboratory (Fermilab) on 3.5 \times 3.5~mm^2 Silicon PhotoMultipliers fabricated at STMicroelectronics Catania R&D clean room facilities are presented. The device consists of 4900 microcells and has a geometrical fill factor of 36%. Timing measurements were realized at different wavelengths by varying the overvoltage and the temperature applied to the photodetector. The results shown in this manuscript demonstrate that the device, in spite of its large area, exhibits relevant features in terms of low dark current density, fast timing and very good single photoelectron resolution. All these characteristics can be considered very appealing in view of the utilization of this technology in applications requiring detectors with high timing and energy resolution performances. [ABSTRACT FROM PUBLISHER]

We have explored methods for optimizing the timing resolution of an LSO-based detector module for a single-ring, "demonstration" time-of-flight PET camera. By maximizing the area that couples the scintillator to the PMT and minimizing the average path length that the scintillation photons travel, a single detector timing resolution of 218 ps fwhm is measured, which is considerably better than the ~385 ps fwhm obtained by commercial LSO or LYSO TOF detector modules. We explored different surface treatments (saw-cut, mechanically polished, and chemically etched) and reflector materials (Teflon tape, ESR, Lumirror, Melinex, white epoxy, and white paint), and found that for our geometry, a chemically etched surface had 5% better timing resolution than the saw-cut or mechanically polished surfaces, and while there was little dependence on the timing resolution between the various reflectors, white paint and white epoxy were a few percent better. Adding co-dopants to LSO shortened the decay time from 40 ns to ~30 but maintained the same or higher total light output. This increased the initial photoelectron rate and so improved the timing resolution by 15%. Using photomultiplier tubes with higher quantum efficiency (blue sensitivity index of 13.5 rather than 12) improved the timing resolution by an additional 5%. By choosing the optimum surface treatment (chemically etched), reflector (white paint), LSO composition (co-doped), and PMT (13.5 blue sensitivity index), the coincidence timing resolution of our detector module was reduced from 309 ps to 220 ps fwhm. [ABSTRACT FROM AUTHOR]

Abstract: The angular coverage extension of the KLOE-2 electromagnetic calorimeter, from a polar angle of down to , will increase the multiphoton detection capability of the experiment enhancing the search reach for rare kaon, and prompt decay channels. The basic layout of the calorimeter extension consists of two small barrels of LYSO crystals readout with APD photosensors aiming to achieve a timing resolution between 300 and 500ps for 20MeV photons. The first test of a prototype for such a detector was carried out in April 2009 at the Beam Test Facility of Laboratori Nazionali di Frascati of INFN with an electron beam from 100 to 500MeV. In the selected energy range, we measured a light yield of , an energy resolution which can be parametrized as , a position resolution of 2.8mm and a timing resolution of . [Copyright &y& Elsevier]