Avalanche Photodiode Readout Research Articles

A low noise APD readout ASIC for electromagnetic calorimeter in HIEPA

This paper presents a 4-channel avalanche photodiode readout ASIC for the electromagnetic calorimeter in the 2–7 GeV high intensity electron positron accelerator. A large detector capacitance of the avalanche photodiode will increase equivalent noise charge and extend rise time of the front-end preamplifier, resulting in attenuated energy and time resolution of the ASIC. A low-noise preamplifier and a 5th-order high-linearity shaper were proposed to decrease the noise induced by a 270 pF detector capacitance. The ASIC is fabricated using a standard 0.18-μm CMOS technology, and the die size of the prototype chip is 1.1 mm × 2.4 mm. The input charge range of the ASIC is from 4.8 fC to 400 fC. The event rate of the ASIC can achieve 400k count/s. Nonlinear error of the shaper is less than 2%. The measured signal to noise ratio is better than 7.8 at a shaping time of 800 ns. The timing resolution of the ASIC is better than 300 ps at an input charge of 100 fC.

The BELLE Electromagnetic Calorimeter and its Upgrade to BelleII

The new SuperKEKB collider will be an upgrade of the existing KEKB electron-positron asymmetric machine, with a target luminosity of 8×1035 cm−2s−1, about 40 times greater than the previous one. The accelerator upgrade is based on the novel low-emittance "nanobeams" scheme. The detector will also be upgraded to cope with the higher luminosity, pile-up and occupancy. We report on the development of the new pure CsI calorimeter for the forward region. An intensive R&D has been carried out to study the performance of pure CsI crystals with Large Area Avalanche Photodiodes readout (LAAPD). Results on the signal to noise ratio for different sensors and front end electronics configurations will be presented as well as the use of filters and wavelength shifters. Measurements with a source, simulating the background machine, have been performed and will also be presented.

Scintillation and Spectroscopic Characteristics of 90%Lu LGSO With Variable Decay Times

High lutetium content LGSO [Lu1.8Gd0.2SiO5:Ce] scintillators with decay time constants in the range 30-45 ns were introduced some ten years ago. At first an experimental development, mass production was gradually established and mature 90%Lu LGSO scintillators with stable characteristics have become available. The aim of this work was to assess the scintillation characteristics of recent 90%Lu LGSO production with different decay times using avalanche photodiode (APD) readout. Samples of Fast (~ 30 ns), Standard (~ 40 ns) and Slow (~ 47 ns) 90%Lu LGSO, extracted from top, middle and bottom positions into ingots, have been investigated. The decay time and central emission wavelength were found to be stable for samples from the same ingot, irrespective of the position where the sample was obtained. The photoelectron yields of Slow, Standard and Fast LGSO scintillators generally showed good uniformity. Their average photoelectron yields at 511 keV were respectively 34 000 ± 1 000 phe/MeV, 31 200 ± 500 phe/MeV and 28 000 ± 2 000 phe/MeV without any definite trend or bias with respect to position in ingots. The combination of photon yield and decay time results in high initial emission rate and a subnanosecond time resolution performance of 914 ± 18 ps for the three categories of decay times. The average energy resolution at 511 keV of Slow LGSO was 10 ± 2% whereas Standard and Fast LGSO samples had identical energy resolution of 11 ± 3%. The light yield non-proportionality as a function of irradiation energy was also investigated. At 60 keV, the departure from linearity reached 19 ± 2%.

The upgrade of the Belle II forward calorimeter

The new facility SuperKEKB will be an upgrade of the existing KEKB electron–positron asymmetric collider, with a target luminosity of 8×1035cm−2s−1, about 40 times greater than that of KEKB. The detector will also be upgraded to cope with the higher luminosity, pile-up and occupancy. We report here on the design and development of the new pure CsI calorimeter for the forward region. An intensive R&D is being carried on to study the performance of pure CsI crystals with Avalanche Photodiodes readout. Results about the relative energy resolution of this detector, along with radiation hardness studies of all the components, are presented. A matrix of 16 crystals has been put on an electron beam at the BTF facility in Frascati and results in terms of energy resolution of this prototype are also discussed.

A pure CsI calorimeter for the Belle II experiment at SuperKEKB

The new SuperKEKB collider will be an upgrade of the existing KEKB electron-positron asymmetric collider, with a target luminosity of 8×1035cm−2s−1, about 40 times greater than the previous one. The accelerator upgrade is based on the novel low-emittance “nanobeams” scheme. The detector will also be upgraded to cope with the higher luminosity, pile-up and occupancy. We report on the development of the new pure CsI calorimeter for the forward region. An intensive R&D has been carried out to study the performance of pure CsI crystals with Avalanche Photodiodes readout. Results on the signal to noise ratio for different sensors and front end electronics configurations will be presented. A matrix of 16 crystals has been tested with the electron beam at the BTF facility in Frascati. Results in terms of energy resolution of this prototype will also be discussed.

Development and characterization of a multi-APD xenon electroluminescence TPC

The performance of an electroluminescence (EL) Time Projection Chamber (TPC) with a multi avalanche photodiode (APD) readout was studied in pure xenon at 3.8 bar. Intercalibration and reconstruction methods were developed and applied to the data yielding energy resolutions as good as 5.3± 0.1% FWHM for 59.5 keV gammas from 241Am. This result was reproduced with a Monte Carlo (MC) based on Geant4 and Penelope which predicted 5.2% FWHM for the used setup. Point resolutions of ≈ 0.5 mm were obtained with a pitch of 15 mm between the APDs. These results show that multi-APD readout is a competitive technology for EL detectors filled with pure xenon.

The New APD Based Readout for the Crystal Barrel Calorimeter

The CBELSA/TAPS experiment at ELSA measures double polarization observables in meson photoproduction off protons and neutrons. To be able to measure purely neutral reactions off polarized neutrons with high efficiency, the main calorimeter has to be integrated into the first level trigger. This requires to exchange the existing PIN photo diode by a new avalanche photo diode (APD) readout. The newly developed readout electronics will provide an energy resolution compatible to the previous set-up and a fast trigger signal down to 10 MeV energy deposit per crystal. After the successful final tests with a 3x3 CsI crystal matrix in Bonn at ELSA and in Mainz at MAMI all front-end electronics were produced in fall 2013. Automated test routines for the front-end electronics were developed and the characterization measurements of all APDs were successfully accomplished in Bonn.The project is supported by the Deutsche Forschungsgemeinschaft (SFB/TR16) and Schweizerischer Nationalfonds.

Improved LabPET Detectors Using <formula formulatype="inline"><tex Notation="TeX">${\rm Lu}_{1.8}{\rm Gd}_{0.2}{\rm SiO}_{5}\!\!:{\rm Ce}$</tex></formula> (LGSO) Scintillator Blocks

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 Lu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.8</sub> Gd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.2</sub> SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> : 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 ( Lu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.4</sub> Gd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.6</sub> SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> : 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.

Temperature gain correction for CsI(Tl) detection systems based on digital pulse shape analysis

In this paper we propose a pulse shape based method for monitoring the interior temperature of a CsI(Tl) crystal in order to correct the temperature dependence in the energy calibration of the corresponding detector system. The gain dependence on temperature of the CsI(Tl) detector was measured using both, a photomultiplier tube (PMT) and an avalanche photodiode (APD) readout photosensor. The analysis shows that the gain shifts due to temperature variations can be corrected to a precision of better than 1% with both the PMT and the APD, well below the CsI(Tl) intrinsic energy resolution for ~1MeV γ-rays.

Test and Simulation of a LYSO+APD matrix with a tagged Photon Beam from 40 to 300 MeV

Understanding the energy resolution terms for LYSO based calorimeters with APD readout at low energy (< 500 MeV) is relevant both for the completion of the KLOE-2 experiment, at DAΦNE, and for the design of the Mu2e calorimeter. In this work, we present a dedicated comparison between experimental data, taken in 2011 at the MAMI tagged photon beam facility with a crystal matrix prototype, and a full Geant-4 simulation of this detector. The crystal prototype matrix consisted of 9 2×2 × 15 cm3 LYSO crystals read-out by 10×10 mm2 Hamamatsu avalanche photodiodes (APD) surrounded by 8 PbWO4 crystals read-out by Bialkali photomultipliers for outer leakage recovery granting a total transverse coverage of 3 Rm. An energy resolution of ∼5.4% at 100 MeV has been achieved. A fit to the energy dependence of the resolution provides the following parametrization: σE/E = 2.1%/E1/4 ⊕ 3.6%, where the sum is in quadrature. The noise term is completely negligible as expected by the reduced level of the electronic noise achieved. The constant term is still leakage dominated.

An active electron polarized scintillating GSO target for neutrino physics

The feasibility of an electron-polarized, active target to be used as detector in neutrino scattering experiments, suggested by several theoretical papers, has been investigated. We report on the properties of the paramagnetic crystal Gd2SiO5 (GSO), in which 7.7% of the total number of electrons present can be polarized by lowering the temperature and applying an intense external magnetic field.The material magnetic susceptibility has been measured down to cryogenic temperatures showing that for H=5T and T=4K about 80% of the maximum allowed magnetization can be attained. Also the spectral and time response of the crystal have been characterized and the scintillation process has been studied using a photomultiplier to measure the response to gamma rays irradiation and cosmic rays operating the GSO crystal at 13.5K. An avalanche photodiode (APD) readout of the scintillation signal from the GSO crystal has also been performed, since the magnetic field-independent response of this device allows it to be placed close to the crystal in the cryogenic environment.

Low noise preamplifier ASIC for the PANDA experiment

For the electromagnetic calorimeter of the PANDA detector a preamplifier ASIC named APFEL (ASIC for Panda Front-end ELectronics) has been developed at GSI. It is optimized for the readout of large area avalanche photodiodes (LAAPDs) with a capacitance of 300 pF and an event rate of 350 kHz. The ASIC has two equivalent analog channels each consisting of a charge sensitive amplifier, a shaper stage and differential output drivers. For operating the ASIC in a wide temperature range programmable voltage references are implemented on chip.

Extensive studies of MRS APDs for plastic scintillator muon veto detectors of cryogenic experiments

Low background experiments need active muon veto detectors to shield them from cosmic muons. Plastic scintillator panels with WLS fiber and multi-pixel Geiger-mode avalanche photodiodes readout are widely used in such experiments due to their compactness and robustness. In this paper, results from the study of the basic MRS APD parameters, such as breakdown voltages, quenching resistors, internal gain and dark count rates are presented, as well as temperature dependencies of some of these parameters. In a small fraction of the MRS APDs, some strange dips in the I–V curves just preceding the breakdown voltage point have been observed.

Assessment of ${\rm Lu}_{1.8}{\rm Gd}_{0.2}{\rm SiO}_{5}$ (LGSO) Scintillators With APD Readout for PET/SPECT/CT Detectors

Fusion of functional PET or SPECT images and anatomical X-ray CT images would ideally be performed using data recorded concurrently with the same detection system under all three modalities to avoid inaccurate co-registration due to patient movements and normal physiological processes like respiratory motion. One possible approach to achieve this goal is to use an avalanche photodiode (APD) based scintillation detection system. Requirements on scintillators for such an application are high density and high timing resolution for PET, good energy resolution for SPECT, large light output and fast scintillation decay time for counting mode X-ray CT. The purpose of this work is to investigate new Lu1.8Gd0.2SiO5:Ce (LGSO) scintillators with improved performance developed purposely for PET applications, but having suitable characteristics for SPECT and CT detection. LGSO with 90% Lu content has high density (7.3 g/cc), large light output (90-120% of Nal), good energy resolution (~10 - 12% @ 511 keV), and fast decay time that can be adjusted from 34 to 45 ns by varying Ce concentration. In this work, LGSO with 0.025, 0.15 and 0.75 mol% Ce was assessed with APD readout for PET/SPECT/CT applications by measuring energy spectra at 511 keV (PET), 140 keV (SPECT) and 60 keV (CT), and timing resolution in reference to a fast plastic scintillator. LGSO-APD detectors can be considered as promising candidates for combined multimodality imaging scanners.

Background and muon counting rates in underground muon measurements with a plastic scintillator counter based on a wavelength shifting fibre and a multi-pixel avalanche photodiode readout

Abstract In this short note we present results of background measurements carried out with polystyrene based cast plastic 12.0×12.0×3.0 cm3 size scintillator counter with a wavelength shifting fibre and a multi-pixel Geiger mode avalanche photodiode readout in the Baksan underground laboratory at a depth of 200 metres of water equivalent. The total counting rate of the scintillator counter measured at this depth and at a threshold corresponding to ∼0.37 of a minimum ionizing particle is approximately 1.3 Hz.

Characteristics of Lu$_{1.8}$Gd$_{0.2}$SiO$_{5}$:Ce (LGSO) for APD-Based PET Detector

Since its discovery in 1993, LGSO has been seen as a promising scintillator for positron emission tomography (PET) imaging. Recently, new high lutetium content Lu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.8</sub> Gd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.2</sub> SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> :Ce (LGSO-90%Lu) has been produced with Ce concentration varying from 0.025 to 0.75 mol% Ce, yielding decay times in the range of 34.2 to 44.8 ns. These scintillators could potentially be used as phoswich detectors in PET for improving spatial resolution. To validate this assumption, light output, energy resolution, temperature dependence, timing resolution, and pulse-shape discrimination performance were assessed. The light output of these LGSO scintillators is 3.5 to 4.8 times higher than BGO with avalanche photodiode readout [7.5 to 8 times with photomultiplier tube (PMT)] and increases with Ce concentration. The variation of light output for temperature ranging from 10 to 50 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C is less than 18% with PMT readout. Energy resolution at 662 keV is about 11% (10%) with avalanche photodiode (APD) (PMT) readout. Timing resolution with APD is ~ 1.65 ns for all samples relative to a fast PMT-plastic detector. Pulse-shape discrimination of LGSO-90% Lu with 0.025 mol% Ce (¿ = 34.2 ns) and 0.75 mol% Ce (¿ = 44.8 ns) was successfully achieved in a <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">phoswich</i> assembly, making this new high lutetium content LGSO with adjustable decay time constants a strong candidate for a high-resolution depth-of-interaction detector intended for PET imaging.

Multi-pixel Geiger-mode avalanche photodiode and wavelength-shifting fibre-optics readout of plastic scintillator counters for the EMMA underground experiment

The results of a development of a scintillator counter with wavelength shifting (WLS) fibre and a multi-pixel Geiger-mode avalanche photodiode readout are presented. The photodiode has a metal-resistor-semiconductor layered structure and operates in the limited Geiger mode. The scintillator counter has been developed for the EMMA underground cosmic ay experiment.

Application of multi-pixel avalanche photodiodes operating in Geiger mode for scintillator pad detector read-out

Details of application of Si avalanche photodiode read-out for scintillator pad detector are discussed. The detection of charged particles using scintillator pads read-out with embedded WLS fiber is explored in many HEP experiments. The 12 cm×12 cm and 4 cm×4 cm scintillator counter design developed for LHC-b experiment [LHC-b Calorimeters Technical Design Report, CERN/LHCC/, 2000-0036] is being explored for the “OKA” experiment (Protvino) [V.F. Obraztsov, OKA: the experimental program with RF-separated K+-beam, KAON-05, Evanston, 2005, 〈 http://www.oka.ihep.su〉] aimed to K-meson rare decays study. Recently developed multi-pixel avalanche photodiodes operating in Geiger mode have definitive advantages with respect to conventional multi-anode PMT, i.e. larger quantum efficiency, compact detector design and small light losses, lower supply voltage. All this allows one to achieve a high light response of more than 100 photo-electrons per MIP with a simple and economical detector design. In this paper we describe characteristics of 3 batches of MRS APD, produced by the CPTA, Moscow [Center of Perspective Technologies and Apparatus (CPTA), Moscow; Photonique SA, Geneva 〈 http://www.photonique.ch〉]. We tested 3 types of photodiodes with a sensitive area of 1 mm 2 with 556 pixels, defining the noise counting rate and detection efficiency as a function of electronics threshold.

Design of Amplifier Circuit for the HT-7 Tokamak Thomson Scattering System

Thomson scattering diagnostic is important for measuring electron temperature and density profiles. To improve the signal-to-noise ratio, a silicon avalanche photodiode (APD) with high quantum efficiency, high sensitivity, and high gain up to 100 was adopted to measure the Thomson scattering spectrum. A preamplifier, which has low noise, high bandwidth, and high sensitivity, was designed with suitable transimpedance. Using AD8367 as the post-amplifier, good performance of the APD readout electronics have been obtained. A discussion is presented on the performance of the amplifier using a laser diode to simulate the Thomson scattering light. The test results indicate that the designed circuit has a high amplifying factor and fast rising edge. So reduction of the integral gate of the CAMAC ADC converter can improve the signal-to-noise ratio.

System Architecture of the LabPET Small Animal PET Scanner

To address modern molecular imaging requirements, a digital positron emission tomography (PET) scanner for small animals has been developed at Universite de Sherbrooke. Based on individual readout of avalanche photodiodes (APD) coupled to LYSO/LGSO phoswich detectors, the scanner supports up to 4608 channels in a 16.2 cm diameter, 11.25 cm axial field of view with an isotropic ~ 1.2 mm FWHM intrinsic spatial resolution at the center of the field of view. Custom data acquisition boards preprocess and sample APD signals at 45 MHz and compute in real time crystal identification, energy and timing information of detected events at an average sustained rate of up to 1250 raw counts per second per mm2 (10 000 cps/channel). Real time digital signal analysis also filters out events outside the pre-selected energy window with crystal granularity to eliminate Compton events and electronic noise. Retained events are then merged into a single stream through a real-time sorting tree, at which end prompt and delayed coincidences are extracted. A single Firewire link handles both control and data transfers with a host computer. The LabPET features four data recording modes, giving the user the choice to retain data for research or to minimize file size for high coincidence count rate and imaging purposes. The electronic system also supports time synchronized data insertion for flags such as vital signs used in gated image reconstruction. Aside from data acquisition, hardware can generate live energy and discrimination spectra suitable for fast, automatic channel calibration.