Showing papers in "Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment in 2019"

Understanding and simulating SiPMs

Abstract: The silicon-photomultiplier (SiPM) is becoming the device of choice for different applications, for example in fast timing like in time of flight positron emission tomography (TOF-PET) and in high energy physics (HEP). It is also becoming a choice in many single-photon or few-photon based applications, like for spectroscopy, quantum experiments and distance measurements (LIDAR). In order to fully benefit from the good performance of the SiPM, in particular its sensitivity, the dynamic range and its intrinsically fast timing properties it is necessary to understand, quantitatively describe and simulate the various parameters concerned. These analyses consider the structure and the electrical model of a single photon avalanche diode (SPAD), i.e. the SiPM microcell, and the integration in an array, i.e. the SiPM. Additionally, for several applications a more phenomenological and complete view on SiPMs has to be done, e.g. photon detection efficiency, single photon time resolution, SiPM signal response, gain fluctuation, dark count rate, afterpulse, prompt and delayed optical crosstalk. These quantities of SiPMs can strongly influence the time and energy resolution, for example in PET and HEP. Having a complete overview on all of these parameters allows to draw conclusions on how best performances can be achieved for the various needs of different applications.

The DESY II Test Beam Facility

Abstract: DESY Hamburg operates a test beam facility with three independent beam lines at the DESY II synchrotron. It is world-wide one of very few facilities providing test beams in the GeV range. To this end, it offers electron/positron beams with user-selectable momenta from 1-6 GeV/c. The available infrastructure for the users is unique, including a high field solenoidal magnet and permanently installed high-precision pixel beam telescopes. This publication gives a detailed description of the facility, the available infrastructure, and the simulated and measured performance.

Radiation resistant LGAD design

Abstract: In this paper, we report on the radiation resistance of 50-micron thick Low Gain Avalanche Diodes (LGAD) manufactured at the Fondazione Bruno Kessler (FBK) employing different dopings in the gain layer LGADs with a gain layer made of Boron, Boron low-diffusion, Gallium, Carbonated Boron and Carbonated Gallium have been designed and successfully produced at FBK These sensors have been exposed to neutron fluences up to ϕ n ∼ 3 ⋅ 1 0 16 n ∕ c m 2 and to proton fluences up to ϕ p ∼ 9 ⋅ 1 0 15 p ∕ c m 2 to test their radiation resistance The experimental results show that Gallium-doped LGAD are more heavily affected by the initial acceptor removal mechanism than those doped with Boron, while the addition of Carbon reduces this effect both for Gallium and Boron doping The Boron low-diffusion gain layer shows a higher radiation resistance than that of standard Boron implant, indicating a dependence of the initial acceptor removal mechanism upon the implant density

Radiation damage of SiPMs

Abstract: The current understanding of radiation tolerance of Silicon Photomultipliers (SiPMs) is reviewed. Radiation damage in silicon sensors is briefly introduced, surface and bulk effects are separately addressed. Results on the operation of irradiated SiPMs with X-ray, gamma, electron, proton and neutron sources are presented. The most critical effect of radiation on SiPMs is the increase of dark count rate, which makes it impossible to resolve signals generated by a single photon from the noise. Methods to characterize irradiated SiPMs after their single photo-electron resolution is lost are discussed. Due to the important similarity in the operation below the breakdown voltage, studies on radiation damage of avalanche photo-diodes (APD) are also reviewed. Finally, ideas are presented on how to approach the development of radiation hard SiPMs in the future.

Overview on the main parameters and technology of modern Silicon Photomultipliers

Abstract: In this paper, we give an overview of the main properties and technological implementation of densely packed Single-photon Avalanche Diode arrays, which are commonly known as Silicon Photomultipliers, or SiPMs. These detectors feature high internal gain, single-photon sensitivity, a high Photon Detection Efficiency, proportional response to weak and fast light flashes, excellent timing resolution, low bias voltage, ruggedness and insensitivity to magnetic field. They compare favorably to the traditional Photomultiplier Tube in several applications. In this overview paper, we go through the SPAD/SiPM theory of operation, the modern SiPM implementations and the typical technological options to build the sensor. This is done in conjunction with the description of the main SiPM parameters, such as the Photon Detection Efficiency, the electrical properties, the primary and correlated noise sources and the Single Photon Time Resolution.

Perovskite CsPbBr3 single crystal detector for alpha-particle spectroscopy

Abstract: Here we report the first spectroscopic alpha particle detection based on CsPbBr 3 detectors with asymmetric contacts. The CsPbBr3 single crystal was grown from the melt using Bridgman method and then fabricated into detectors with different contacts. The In/CsPbBr 3/Au detector presented a low dark current density ( ∼ 100 nA/cm2 ) and temporal stable performance under high electric field (1000 V/cm). Such detector demonstrated excellent gamma ray resolving capability with a full-width at half maximum (FWHM) of ∼ 5.9 keV for the 57Co 122 keV γ ray. The CsPbBr3 detector was capable of simultaneously resolving both the alpha particle (5.5 MeV) and γ ray (59.5 keV) peaks from 241Am radioactive isotope. The transport properties of CsPbBr3 were then determined based on the alpha particle spectra and corresponding rise time distributions. The equivalent values of electron and hole mobilities were indicated as 63 and 49 cm2/(V ⋅ s) respectively. The calculated electron and hole mobility-lifetime products were 4.5 × 10−4 and 9.5 × 10−4 cm2/V, respectively, demonstrating superior transport properties of holes over electrons in CsPbBr3 . This work widens the scope of perovskite detectors to encompass charged radiation as well as high energy X/ γ rays, and will significantly promote and guide further studies on perovskite materials for radiation detection applications.

Characterisation of SiPMs

Abstract: Silicon photomultipliers, thanks to their excellent performance, robustness and relatively simple use, are the photon-detectors of choice for many present and future applications. This paper gives an overview of methods to characterise SiPMs. The different SiPM parameters are introduced and generic setups for their determination presented. Finally, ways to extract the parameters from the measurements are discussed and the results shown. If a parameter can be obtained from different measurements, the results are compared and recommendations given, which is considered to be the most reliable. The characterisation of SiPMs, in particular for high light intensities and in high radiation fields, is presently a field of intensive research with many open questions and problems which will be discussed.

First Measurements of Beam Backgrounds at SuperKEKB

Abstract: The high design luminosity of the SuperKEKB electron–positron collider is expected to result in challenging levels of beam-induced backgrounds in the interaction region. Properly simulating and mitigating these backgrounds is critical to the success of the Belle II experiment. We report on measurements performed with a suite of dedicated beam background detectors, collectively known as BEAST II, during the so-called Phase 1 commissioning run of SuperKEKB in 2016, which involved operation of both the high energy ring (HER) of 7 GeV electrons as well as the low energy ring (LER) of 4 GeV positrons. We describe the BEAST II detector systems, the simulation of beam backgrounds, and the measurements performed. The measurements include standard ones of dose rates versus accelerator conditions, and more novel investigations, such as bunch-by-bunch measurements of injection backgrounds and measurements sensitive to the energy spectrum and angular distribution of fast neutrons . We observe beam–gas, Touschek, beam–dust, and injection backgrounds. As there is no final focus of the beams in Phase 1, we do not observe significant synchrotron radiation , as expected. Measured LER beam–gas backgrounds and Touschek backgrounds in both rings are slightly elevated, on average three times larger than the levels predicted by simulation. HER beam–gas backgrounds are on average two orders of magnitude larger than predicted. Systematic uncertainties and channel-to-channel variations are large, so that these excesses constitute only 1–2 sigma level effects. Neutron background rates are higher than predicted and should be studied further. We will measure the remaining beam background processes, due to colliding beams, in the imminent commissioning Phase 2. These backgrounds are expected to be the most critical for Belle II, to the point of necessitating replacement of detector components during the Phase 3 (full-luminosity) operation of SuperKEB.

Energy response of GECAM gamma-ray detector based on LaBr3:Ce and SiPM array

Abstract: The Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) , composed of two small satellites, is a new mission to monitor the Gamma-Ray Bursts (GRBs) coincident with Gravitational Wave (GW) events with a FOV of 100% all-sky. Each GECAM satellite detects and localizes GRBs using 25 compact and novel Gamma-Ray Detectors (GRDs) in 6 keV–5 MeV. Each GRD module is comprised of LaBr 3 :Ce scintillator , SiPM array and preamplifier . A large dynamic range of GRD is achieved by the high gain and low gain channels of the preamplifier. The energy response of GRD prototype was evaluated using radioactive sources in the range of 5.9–1332.5 keV. A energy resolution of 5.3% at 662 keV was determined from the 137Cs pulse height spectra, which meets the GECAM requirement ( 8% at 662 keV). Energy to channel conversion was evaluated and a nonlinearity correction was performed to reduce the residuals ( 1.5%). Also, a Geant4-based simulated in-flight background and a measured GRD LaBr3:Ce intrinsic activity were used to evaluate the capability of in-flight calibration. These results demonstrate the design of GRD.

Imaging and time stamping of photons with nanosecond resolution in Timepix based optical cameras

Abstract: This contribution describes fast time-stamping cameras sensitive to optical photons and their applications.

The PROSPECT reactor antineutrino experiment

Abstract: The Precision Reactor Oscillation and Spectrum Experiment, PROSPECT, is designed to make both a precise measurement of the antineutrino spectrum from a highly-enriched uranium reactor and to probe eV-scale sterile neutrinos by searching for neutrino oscillations over meter-long baselines. PROSPECT utilizes a segmented 6 Li-doped liquid scintillator detector for both efficient detection of reactor antineutrinos through the inverse beta decay reaction and excellent background discrimination. PROSPECT is a movable 4-ton antineutrino detector covering distances of 7 m to 13 m from the High Flux Isotope Reactor core. It will probe the best-fit point of the ν e disappearance experiments at 4 σ in 1 year and the favored regions of the sterile neutrino parameter space at more than 3 σ in 3 years. PROSPECT will test the origin of spectral deviations observed in recent θ 13 experiments, search for sterile neutrinos, and address the hypothesis of sterile neutrinos as an explanation of the reactor anomaly. This paper describes the design, construction, and commissioning of PROSPECT and reports first data characterizing the performance of the PROSPECT antineutrino detector.

AMS-100: The next generation magnetic spectrometer in space – An international science platform for physics and astrophysics at Lagrange point 2

Abstract: The next generation magnetic spectrometer in space, AMS-100, is designed to have a geometrical acceptance of 100 m 2 sr and to be operated for at least ten years at the Sun–Earth Lagrange Point 2. Compared to existing experiments, it will improve the sensitivity for the observation of new phenomena in cosmic rays, and in particular in cosmic antimatter, by at least a factor of 1000. The magnet design is based on high temperature superconductor tapes, which allow the construction of a thin solenoid with a homogeneous magnetic field of 1 Tesla inside. The inner volume is instrumented with a silicon tracker reaching a maximum detectable rigidity of 100 TV and a calorimeter system that is 70 radiation lengths deep, equivalent to four nuclear interaction lengths, which extends the energy reach for cosmic-ray nuclei up to the PeV scale, i.e. beyond the cosmic-ray knee. Covering most of the sky continuously, AMS-100 will detect high-energy gamma-rays in the calorimeter system and by pair conversion in the thin solenoid, reconstructed with excellent angular resolution in the silicon tracker.

The ISIS Spallation Neutron and Muon Source—The first thirty-three years

Abstract: Thirty-three years of operational history of the accelerator and target aspects of the ISIS Spallation Neutron and Muon Source are summarised. Data on overall percentages of lost time and distributions of lost time amongst different equipment categories are presented. Areas of difficulty are also described, along with measures taken to overcome the difficulties. Further, on the basis of hard-won experience, recommendations for managing operations are made. Altogether, much valuable operational information spanning several decades is presented, and this should be of interest to designers and operators of large accelerator-based facilities.

HERMES: An ultra-wide band X and gamma-ray transient monitor on board a nano-satellite constellation

Abstract: The High Energy Modular Ensemble of Satellites (HERMES) project is aimed to realize a modular X/gamma-ray monitor for transient events, to be placed on-board of a nano-satellite bus (e.g. CubeSat). This expandable platform will achieve a significant impact on Gamma Ray Burst (GRB) science and on the detection of Gravitational Wave (GW) electromagnetic counterparts: the recent LIGO/VIRGO discoveries demonstrated that the high-energy transient sky is still a field of extreme interest. The very complex temporal variability of GRBs (experimentally verified up to the millisecond scale) combined with the spatial and temporal coincidence between GWs and their electromagnetic counterparts suggest that upcoming instruments require sub-microsecond time resolution combined with a transient localization accuracy lower than a degree. The current phase of the ongoing HERMES project is focused on the realization of a technological pathfinder with a small network (3 units) of nano-satellites to be launched in mid 2020. We will show the potential and prospects for short and medium-term development of the project, demonstrating the disrupting possibilities for scientific investigations provided by the innovative concept of a new “modular astronomy” with nano-satellites (e.g. low developing costs, very short realization time). Finally, we will illustrate the characteristics of the HERMES Technological Pathfinder project, demonstrating how the scientific goals discussed are actually already reachable with the first nano-satellites of this constellation . The detector architecture will be described in detail, showing that the new generation of scintillators (e.g. GAGG:Ce) coupled with very performing Silicon Drift Detectors (SDD) and low noise Front-End-Electronics (FEE) are able to extend down to few keV the sensitivity band of the detector. The technical solutions for FEE, Back-End-Electronics (BEE) and Data Handling will be also described.

Properties of HPK UFSD after neutron irradiation up to 6e15 n/cm2

Abstract: In this paper we report results from a neutron irradiation campaign of Ultra-Fast Silicon Detectors (UFSD) with fluences of 1e14, 3e14, 6e14, 1e15, 3e15 and 6e15 neq/cm 2. The UFSD used in this study are circular 50 μ m thick Low-Gain Avalanche Detectors (LGAD), with a 1.0 mm diameter active area. Hamamatsu Photonics (HPK), Japan, produced the UFSD with pre-irradiation internal gain in the range 5–70 depending on the bias voltage. The sensors were tested pre-irradiation and post-irradiation with minimum ionizing particles (MIPs) from a 90Sr β -source. The leakage current, internal gain and the timing resolution were measured as a function of bias voltage at −20 °C and −30 °C. The timing resolution of each device under test was extracted from the time difference with a second calibrated UFSD in coincidence, using the constant fraction discriminator (CFD) method for both. The dependence of the gain upon the irradiation fluence is consistent with the acceptor removal mechanism; at −20 °C the highest gain decreases from 70 before radiation to 2 after a fluence of 6e15 n/cm2. Consequently, the timing resolution was found to deteriorate from 20 ps to 50 ps. The results indicate that the most accurate time resolution is obtained varying with fluence the CFD value used to determine the time of arrival, from 0.1 for pre-irradiated sensors to 0.6 at the highest fluence. Key changes to the pulse shape induced by irradiation, i.e. (i) the contribution of charge multiplication not limited to the gain layer zone, (ii) the shortening of the rise time and (iii) the reduced pulse height, were compared with the WF2 simulation program and were found to be in agreement.

Design and performance of an interferometric trigger array for radio detection of high-energy neutrinos

Abstract: Ultra-high energy neutrinos are detectable through impulsive radio signals generated through interactions in dense media, such as ice. Subsurface in-ice radio arrays are a promising way to advance the observation and measurement of astrophysical high-energy neutrinos with energies above those discovered by the IceCube detector ( ≥ 1 PeV) as well as cosmogenic neutrinos created in the GZK process ( ≥ 100 PeV). Here we describe the NuPhase detector, which is a compact receiving array of low-gain antennas deployed 185 m deep in glacial ice near the South Pole. Signals from the antennas are digitized and coherently summed into multiple beams to form a low-threshold interferometric phased array trigger for radio impulses. The NuPhase detector was installed at an Askaryan Radio Array (ARA) station during the 2017/18 Austral summer season. In situ measurements with an impulsive, point-source calibration instrument show a 50% trigger efficiency on impulses with voltage signal-to-noise ratios (SNR) of ≤ 2.0, a factor of ∼ 1.8 improvement in SNR over the standard ARA combinatoric trigger. Hardware-level simulations, validated with in situ measurements, predict a trigger threshold of an SNR as low as 1.6 for neutrino interactions that are in the far field of the array. With the already-achieved NuPhase trigger performance included in ARASim, a detector simulation for the ARA experiment, we find the trigger-level effective detector volume is increased by a factor of 1.8 at neutrino energies between 10 and 100 PeV compared to the currently used ARA combinatoric trigger. We also discuss an achievable near term path toward lowering the trigger threshold further to an SNR of 1.0, which would increase the effective single-station volume by more than a factor of 3 in the same range of neutrino energies.

New Microscope and Ion Accelerators for Materials Investigations (MIAMI-2) system at the University of Huddersfield

Abstract: Radiation damage is a complex dynamic process with multiple atomic mechanisms interacting and competing to determine the end state of the material. Transmission electron microscopy (TEM) with in-situ ion irradiation allows direct observation of the microstructural evolution of a sample from the virgin to end state. A new TEM with in-situ ion irradiation has been established at the University of Huddersfield: the Microscope and Ion Accelerators for Materials Investigations (MIAMI-2) system. MIAMI-2 combines a 300 kV TEM with medium-energy 350 kV and low-energy 20 kV ion beamlines. Whilst the medium-energy beamline can be used for most species up to Au, the low-energy beamline is primarily designed for implanting light-ion species such as H and He. These can be used individually or mixed prior to entering the TEM allowing dual-ion-beam irradiation experiments to, for example, simulate the combined effects of displacement damage and the introduction of He from (n, α ) nuclear reactions. The TEM can operate from 60–300 kV and is equipped with a 16 megapixel digital camera, an energy-filtered imaging system and an energy-dispersive X-ray spectrometer for elemental and chemical analysis. Sample temperature can be varied from –170 °C to 1300 °C and a gas injection system enables gaseous environments at pressures of up to 10 − 2 mbar at the sample position. The new MIAMI-2 system is a powerful tool for the investigation of radiation damage in a wide range of materials which are exposed to irradiating environments either during processing and/or whilst in-service in areas including nuclear applications, nanotechnology, semiconductor processing and extraterrestrial environments.

The SeaQuest spectrometer at Fermilab

Abstract: Author(s): Aidala, CA; Arrington, JR; Ayuso, C; Bowen, BM; Bowen, ML; Bowling, KL; Brown, AW; Brown, CN; Byrd, R; Carlisle, RE; Chang, T; Chang, WC; Chen, A; Chen, JY; Christian, DC; Chu, X; Dannowitz, BP; Daugherity, M; Diefenthaler, M; Dove, J; Durandet, C; El Fassi, L; Erdos, E; Fox, DM; Geesaman, DF; Gilman, R; Goto, Y; Guo, L; Guo, R; Hague, T; Hicks, CR; Holt, RJ; Isenhower, D; Jiang, X; Katich, JM; Kerns, BM; Kinney, ER; Kitts, ND; Klein, A; Kleinjan, D; Kras, J; Kudo, Y; Lin, PJ; Liu, D; Liu, K; Liu, MX; Lorenzon, W; Makins, NCR; Martinez, JD; McClellan, RE; McDonald, B; McGaughey, PL; McNease, SE; Medeiros, MM; Miller, B; Miller, AJ; Miyasaka, S; Miyachi, Y; Mooney, IA; Morton, DH; Nadim, B; Nagai, K; Nakahara, K; Nakano, K; Nara, S; Obata, S; Peng, JC; Prasad, S; Puckett, AJR; Ramson, BJ; Raymond, RS; Reimer, PE; Rubin, JG; Salinas, R; Sanftl, F; Sawada, S; Sawada, T; Scott, MBC; Selensky, LE; Shibata, TA; Shiu, S; Su, D; Tadepalli, AS; Teo, M; Tice, BG | Abstract: The SeaQuest spectrometer at Fermilab was designed to detect oppositely-charged pairs of muons (dimuons) produced by interactions between a 120 GeV proton beam and liquid hydrogen, liquid deuterium and solid nuclear targets. The primary physics program uses the Drell–Yan process to probe antiquark distributions in the target nucleon. The spectrometer consists of a target system, two dipole magnets and four detector stations. The upstream magnet is a closed-aperture solid iron magnet which also serves as the beam dump, while the second magnet is an open aperture magnet. Each of the detector stations consists of scintillator hodoscopes and a high-resolution tracking device. The FPGA-based trigger compares the hodoscope signals to a set of pre-programmed roads to determine if the event contains oppositely-signed, high-mass muon pairs.

Silicon photomultipliers in particle and nuclear physics

Abstract: Following first large-scale applications in highly granular calorimeters and in neutrino detectors, Silicon Photomultipliers have seen a wide adoption in accelerator-based particle and nuclear physics experiments. Today, they are used for a wide range of different particle detector types, ranging from calorimeters and trackers to particle identification and veto detectors, large volume detectors for neutrino physics and timing systems. This article reviews the current state and expected evolution of these applications, highlighting strengths and limitation of SiPMs and the corresponding design choices in the respective contexts. General trends and adopted technical solutions in the applications are discussed.

Development of a technology for the fabrication of Low-Gain Avalanche Diodes at BNL

Abstract: Low-Gain Avalanche Detectors are gathering interest in the High-Energy Physics community thanks to their fast-timing and radiation-hardness properties. One example of this includes plans to exploit timing detectors for the upgrades of the ATLAS and CMS detectors at the High Luminosity LHC . This new technology has also raised interest for its possible application for photon detection in medical physics, imaging and photon science. The main characteristic of this type of device is a thin and highly-doped layer that provides internal and moderate gain, in the order of 10–20, that enhances the signal amplitude. Furthermore the thin substrate, of only few tens of microns, allows for fast carrier collection. This paper offers details on the fabrication technology, specifically developed at Brookhaven National Laboratory for the detection of minimum ionizing particles. The static electrical characterization and the gain measurements on prototypes will be also reported.

Medical applications of silicon photomultipliers

Abstract: Silicon photomultipliers (SiPMs) are becoming the reference photodetectors in many fields. In medicine they are slowly replacing photomultiplier tubes and avalanche photodiodes in medical imaging and in PET in particular. In this paper a broad overview of the current applications of SiPM in medicine is presented. The major fields where the SiPMs are used, namely PET/MR and hadrontherapy are discussed at length.

The integrated low-level trigger and readout system of the CERN NA62 experiment

Abstract: The integrated low-level trigger and data acquisition (TDAQ) system of the NA62 experiment at CERN is described. The requirements of a large and fast data reduction in a high-rate environment for a medium-scale, distributed ensemble of many different sub-detectors led to the concept of a fully digital integrated system with good scaling capabilities. The NA62 TDAQ system is rather unique in allowing full flexibility on this scale, allowing in principle any information available from the detector to be used for triggering. The design concept, implementation and performances from the first years of running are illustrated.

Characterization of the Hamamatsu VUV4 MPPCs for nEXO

Abstract: In this paper we report on the characterization of the Hamamatsu VUV4 (S/N: S13370-6152) Vacuum Ultra-Violet (VUV) sensitive Multi-Pixel Photon Counters (MPPC)s as part of the development of a solution for the detection of liquid xenon scintillation light for the nEXO experiment. Various MPPC features, such as: dark noise, gain, correlated avalanches, direct crosstalk and Photon Detection Efficiency (PDE) were measured in a dedicated setup at TRIUMF. MPPCs were characterized in the range 163 K ≤ T ≤ 233 K . At an over voltage of 3 . 1 ± 0 . 2 V and at T = 163 K we report a number of Correlated Avalanches (CAs) per pulse in the 1 μ s interval following the trigger pulse of 0 . 161 ± 0 . 005 . At the same settings the Dark-Noise (DN) rate is 0 . 137 ± 0 . 002 Hz/mm 2 . Both the number of CAs and the DN rate are within nEXO specifications. The PDE of the Hamamatsu VUV4 was measured for two different devices at T = 233 K for a mean wavelength of 189 ± 7 nm . At 3 . 6 ± 0 . 2 V and 3 . 5 ± 0 . 2 V of over voltage we report a PDE of 13 . 4 ± 2 . 6 % and 11 ± 2 % , corresponding to a saturation PDE of 14 . 8 ± 2 . 8 % and 12 . 2 ± 2 . 3 % , respectively. Both values are well below the 24 % saturation PDE advertised by Hamamatsu. More generally, the second device tested at 3 . 5 ± 0 . 2 V of over voltage is below the nEXO PDE requirement. The first one instead yields a PDE that is marginally close to meeting the nEXO specifications. This suggests that with modest improvements the Hamamatsu VUV4 MPPCs could be considered as an alternative to the FBK-LF Silicon Photo-Multipliers for the final design of the nEXO detector.

First FBK production of 50 μm ultra-fast silicon detectors

Abstract: Fondazione Bruno Kessler (FBK, Trento, Italy) has recently delivered its first 50 μ m thick production of Ultra-Fast Silicon Detectors (UFSD), based on the Low-Gain Avalanche Diode design These sensors use high resistivity Si-on-Si substrates, and have a variety of gain layer doping profiles and designs based on Boron, Gallium , Carbonated Boron and Carbonated Gallium to obtain a controlled multiplication mechanism Such variety of gain layers will allow identifying the most radiation hard technology to be employed in the production of UFSD, to extend their radiation resistance beyond the current limit of ϕ ∼ 1015 n e q /cm 2 In this paper, we present the characterisation, the timing performance, and the results on radiation damage tolerance of this new FBK production

Dual-ended readout small animal PET detector by using 0.5 mm pixelated LYSO crystal arrays and SiPMs

Abstract: Small animal PET scanners need to have a high spatial resolution since the size of the organs of small animals is much smaller than that of humans, and also need to have a high sensitivity since the allowed injection dose is limited by the radiation dosimetry of the small organs. To simultaneously achieve high spatial resolution and high sensitivity for a small animal PET scanner, detectors with high position resolution, high efficiency and high depth of interaction (DOI) resolution are required. In this work, three 17 × 17 pixelated LYSO arrays with crystal size of ∼ 0 . 5 mm and an outer dimension of 10 × 10 × 20 mm 3 are fabricated. The first LYSO array uses 80 μ m thick BaSO4 reflector . The second and the third LYSO arrays use 65 μ m thick Toray reflectors. The outermost side of the third LYSO array is also wrapped with k9 glass of the same size as the crystals in the array in order to improve the light collection and flood histogram quality for the edge crystals. The LYSO arrays are read out with two Hamamatsu SiPM arrays from both ends. The SiPM array is 4 × 4 , with 3 × 3 mm 2 pixel size and 0.2 mm gap in between the SiPM pixels. The SiPM array is read out with a resistor network circuit to reduce the number of signals from 16 to 4. The performance of the detector in terms of flood histograms, energy resolution, DOI resolution and timing resolution was measured. All three detectors provide good flood histograms and all crystals in an array can be clearly resolved. The average DOI resolutions of individual crystals are 1.84, 1.98 and 1.93 mm for the three detectors for events with energy E > 350 keV. The BaSO4 array has higher light output and provides a better average crystal energy resolution of 21.0 %. The photopeak amplitude of the Toray arrays changes with depth, which results in worse energy resolutions of 24.4 % and 23.8 % for the two detectors respectively. The average timing resolutions of individual crystals are 1.23, 1.27 and 1.24 ns for the three detectors for events with E > 350 keV. All three detector modules achieved high position resolution (0.5 mm crystal size), high efficiency (20 mm crystal length) and high DOI resolution (

Timing performance of small cell 3D silicon detectors

Abstract: A silicon 3D detector with a single cell of 50 × 50 μ m2 was produced and evaluated for timing applications. The measurements of time resolution were performed for 90Sr electrons with dedicated electronics used also for determining time resolution of Low Gain Avalanche Detectors (LGADs). The measurements were compared to those with LGADs and also simulations. The studies showed that the dominant contribution to the timing resolution comes from the time walk originating from different induced current shapes for hits over the cell area. This contribution decreases with higher bias voltages, lower temperatures and smaller cell sizes. It is around 30 ps for a 3D detector of 50 × 50 μ m2 cell at 150 V and − 20 °C, which is comparable to the time walk due to Landau fluctuations in LGADs. It even improves for inclined tracks and larger pads composed of multiple cells. A good agreement between measurements and simulations was obtained, thus validating the simulation results.

Methylammonium lead tribromide semiconductors: Ionizing radiation detection and electronic properties

Abstract: The response of single crystal methylammonium lead tribromide (MAPbBr 3 or MAPB) semiconductors to alpha particles at low voltage is presented. Through analysis of the preamplifier traces induced by 210Po alpha particles and collecting holes, we were able to determine the mobility–lifetime product, apparent mobility, trapping time constant, and the detrapping time constant. In addition, a quantitative study of the rate of positive polarization and device breakdown time at different applied voltages is presented. Finally, using a 239 Pu/Be fast neutron source, we were able to demonstrate the response of MAPB to fast neutrons for the first time via benchmarking experiment with Monte Carlo simulations.

SiPM readout electronics

Abstract: Due to the peculiar characteristics of SiPM sensors in terms of equivalent capacitance, gain and fast rise-time response, in several applications classic readout solutions for radiation detectors are not able to provide optimal performance. Thus, several ad hoc readout approaches have been developed to fully exploit the favourable features of this kind of detectors. In this note the main requirements for the SiPM readout electronics are discussed, for both energy and time measurements, in the light of the detector model, and an overview of the main architectures commonly employed is provided, along with a set of relevant design examples.

Measured neutron light-output response for trans-stilbene and small-molecule organic glass scintillators

Abstract: The neutron light-output response from quasi-monoenergetic neutrons was measured for a O5.08 × 5.08 cm trans-stilbene and a O5.08 × 5.08 cm small-molecule organic glass scintillator . Quasi-monoenergetic neutrons were isolated from a time-of-flight measurement of a Cf-252 spontaneous fission source with a flight distance of 200 cm. Two different methods of waveform analysis were implemented, where the neutron light output response proportional to the detected pulse height distribution (PHD) and pulse integral distribution (PID) were extracted for both types of scintillators. The light output response proportional to the pulse integral was determined by integrating the digitized waveform with an integration window length of 150 ns, which contained > 90% and > 95% of the scintillation light for an averaged neutron and photon waveform above 0.5 MeVee. The extracted light-output data were fitted with a semi-empirical function based on the Birks’ formula. The results show that the small-molecule organic glass scintillator produced more light than the trans-stilbene scintillator for a range of neutron energies of 0.79 ± 0.04 MeV to 3.65 ± 0.38 MeV. The fitted semi-empirical function was used in MCNPX-PoliMi with MPPost to simulate the detector response from an independent measurement of a Cf-252 spontaneous fission source to test the fidelity of the extracted light output response functions. The simulated and measured total neutron count rate agreed to within ± 3 % and ± 1% for the trans-stilbene and small-molecule organic glass scintillators. Due to the different light-output response of the two scintillators, the intrinsic neutron detection efficiency was calculated for equal observable ranges in light output and neutron-equivalent energy units. The intrinsic neutron detection efficiency in the observable light-output range of 0.06 MeVee to 2.4 MeVee was calculated to be 28.66 ± 1.43 % and 34.66 ± 1.73 % for pulse height and pulse integral analysis, respectively. For the same observable light-output range, the intrinsic efficiency of small-molecule organic glass was calculated to be 32.54 ± 1.63 % and 37.39 ± 1.87 % for pulse height and pulse integral analysis, respectively. When observing equal light-output ranges, the small-molecule organic glass was 11.92 ± 6.23% and 7.88 ± 7.35% more efficient than the trans-stilbene using pulse height and pulse integral analysis, respectively. When observing equal neutron-equivalent energy ranges, the trans”–stilbene scintillator was 8.4 ± 6.46% and 11.95 ± 6.23% more efficient than the small-molecule organic glass for pulse height and pulse integral analysis, respectively.

The role of sub-interpolation for Delay-Line Time-to-Digital Converters in FPGA devices

Abstract: Most of the Time-to-Digital Converters (TDCs) implemented in Field Programmable Gate Array (FPGA) devices are based on Tapped Delay Lines (TDLs). This solution makes mandatory the implementation of sub-interpolation procedures in the processing flow in order to mitigate effects of the different characteristics of the FPGA resources used. Specifically, we focus issues of the sub-interpolation topic also still outstanding and realize the experimental comparison of the state-of-art techniques, providing design rules for their optimal implementation. According to the host electronic device, the paper reveals the design rules to get the best performance, by using known sub-interpolation techniques but introducing criteria of choice and design procedures never presented in literature. These are fundamental for the most proper and useful application of sub-interpolation techniques in designing high-performance TDCs.