Large Area Avalanche Photodiodes Research Articles

A low-temperature proton detector for a neutron lifetime experiment

PENeLOPE is a new high-precision experiment with stored ultra-cold neutrons (UCN) to measure the neutron lifetime τ n planned at the Technische Universität München. A key element to reach the goal of 0.1 s precision is the in situ detection of the decay protons during storage. For this reason we plan to cover the top of the storage volume by a large-area scintillation counter working at cryogenic temperatures: a 1 μ m thin layer of CsI scintillator, evaporated on a light-guide structure and read from the side by large-area avalanche photo diodes (LAAPDs) will be used. Simulations showed that the layer thickness of 1 μ m is sufficient to stop the n-decay protons after additional post-acceleration by 40-keV from our PENeLOPE setup. A small scale test detector with a 1.5 μ m thick evaporated CsI layer was successfully operated at cryogenic temperatures in the range of 50 K. The produced scintillation light was measured from the side window of the light guide by an LAAPD from RMD. The signal-to-noise ratio of a 40-keV proton beam from the paff accelerator showed a signal-to-noise ratio of 17:1. Electron–proton separation was successfully demonstrated by shooting 40-keV protons and 15-keV electrons simultaneously onto the detector.

Avalanche Photodiode Arrays Enable Large-Area Measurements of Medium-Energy Electrons

We demonstrate the performance of a large-area avalanche photodiode array as a medium-energy electron detector. This avalanche photodiode array is composed of eight pixels with 1.2 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of total active area. The energy resolution (Delta <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</i> / <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</i> ) is as low as 4.5% in full width at half maximum for 25-keV electrons, and the linearity is excellent. Monte Carlo modeling by Geant4 shows that the detection efficiency of this device is appropriate for the detection of electrons ranging from < 5 to > 200 keV. This new device can be coupled with magnetic deflectors, electrostatic analyzers, and other physics instruments requiring position-sensitive or large-area solutions for the detection of electrons in this energy range.

Simultaneous reconstruction of scintillation light and ionization charge produced by 511 keV photons in liquid xenon: Potential application to PET

In order to assess the performance of liquid xenon detectors for use in positron emission tomography we studied the scintillation light and ionization charge produced by 511 keV photons in a small prototype detector. Scintillation light was detected with large area avalanche photodiodes while ionization electrons were collected on an anode instrumented with low noise electronics after drifting up to 3 cm. Operational conditions were studied as a function of the electric field. Energy resolutions of < 10 % (FWHM) were achieved by combining the scintillation light and ionization charge signals. The relationship between scintillation light and ionization signals was investigated. An analysis of the sources of fluctuations was performed in order to optimize future detector designs.

Characterization of large area APDs for the EXO-200 detector

Enriched Xenon Observatory (EXO)-200 uses 468 large area avalanche photodiodes (LAAPDs) for detection of scintillation light in an ultra-low-background liquid xenon (LXe) detector. We describe initial measurements of dark noise, gain and response to xenon scintillation light of LAAPDs at temperatures from room temperature to 169 K—the temperature of liquid xenon. We also describe the individual characterization of more than 800 LAAPDs for selective installation in the EXO-200 detector.

A Comparative Study of Silicon Drift Detectors With Photomultipliers, Avalanche Photodiodes and PIN Photodiodes in Gamma Spectrometry With LaBr$_{3}$ Crystals

The performance of a silicon drift detector (SDD) with an integrated FET, delivered by the company PNSensor, Munich, Germany, was studied in gamma spectrometry at room temperature (23-25degC) with a LaBr3:Ce crystal of 6 mm diameter and 6 mm height. The SDD characteristics were compared with those measured with a Photonis XP5212 photomultiplier, a Large Area Avalanche Photodiode (LAAPD) of Advanced Photonix, Inc., and a Hamamatsu S3590-18 Photodiode (PD). Energy resolution versus gamma ray energies and its components related to the photoelectron/electron-hole pair statistics and dark noise were measured and compared. At low energies, below 100 keV, the light readout by the photomultiplier gives the best results, while for high energies, above 300 keV, the light readout by the SDD delivers superior energy resolution. In particular, the best energy resolution of 2.7% was determined for 662 keV gamma rays from a 137Cs source.

Characterization of Large Frustum CsI(Tl) Crystals for the ${\rm R}^{3}{\rm B}$ Calorimeter

Studies with different bi-frustum CsI(Tl) crystal samples from several providers, coupled to large area avalanche photodiodes (Hamamatsu S8664-1010 2CH), specifically developed for this project, were performed as part of the R&D program for the design of the R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> B calorimeter (CALIFA). Particular attention is given to the energy resolution optimization for CsI(Tl) crystal samples with realistic dimensions. The results obtained with Large Area Avalanche Photo-Diode (LAAPD) are very promising and suggest CsI(Tl) as a suitable candidate for the Barrel part of the calorimeter.

Secondary scintillation yield from gaseous micropattern electron multipliers in direct Dark Matter detection

Efforts are being made in direct Dark Matter search experiments to detect the primary ionisation in the liquid by extracting the electrons to the gas phase and use the secondary ionization produced in the micropattern electron multipliers for signal amplification in noble-liquid dual-phase TPCs. We have studied the secondary scintillation yield of a single Gas Electron Multiplier (GEM) and of a Micro-Hole & Strip Plate (MHSP) for xenon at room temperature. Values for secondary scintillation yield between 5.0×103 and 1.3×103 photons per primary electron were obtained for the GEM and between 7.2×104 and 1.8×103 photons per primary electron for the MHSP, as the pressure increased from 1.0 to 2.5 bar in the GEM-setup and from 1.0 to 3.3 bar in the MHSP-setup, respectively. These values can be more than one order of magnitude higher than what has been obtained in the uniform-field scintillation gaps of the XENON and ZEPLIN-III experiments. Although in the present setups the amount of secondary scintillation obtained is sufficient in view of the use of PMTs, if a different type of readout is considered, such as large area avalanche photodiodes, it will be important to increase the amount of secondary scintillation. The attained results demonstrate the clear advantage of reading the secondary scintillation instead of the charge produced in the electron avalanches of micropattern electron multipliers, in low-background and low-rate experiments, as is the case in direct Dark Matter search.

Avalanche photodiodes and vacuum phototriodes for the electromagnetic calorimeter of the CMS experiment at the Large Hadron Collider

The homogeneous lead tungstate electromagnetic calorimeter for the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider operates in a challenging radiation environment. The central region of the calorimeter uses large-area avalanche photodiodes to detect the fast blue-violet scintillation light from the crystals. The high hadron fluence in the forward region precludes the use of these photodiodes and vacuum phototriodes are used in this region. The constructional complexity of the calorimeter, which comprises 75848 individual crystals, plus the activation of material make repair during the lifetime of the detector virtually impossible. We describe here the key features and performance of the photodetectors and the quality assurance procedures that were used to ensure that the proportion of photodetectors that fail over the lifetime of CMS will be limited to a fraction of a percent.

Secondary scintillation yield in pure argon

The secondary scintillation yield is of great importance for simulating double phase detectors, which are used in several of the ongoing Dark Matter search experiments, as well as in the future large-scale particle detectors proposed in Europe as the next generation underground observatories. The argon secondary scintillation yield is studied, at room temperature, as a function of electric field in the gas scintillation gap. A Large Area Avalanche Photodiode (LAAPD) collects the VUV secondary scintillation produced in the gas, as well as the 5.9 keV x-rays directly absorbed in the photodiode. The direct x-rays were used as a reference for the determination of the number of charge carriers produced by the scintillation pulse and, so, the number of photons impinging the LAAPD. A value of 81 photons/kV was obtained for the scintillation amplification parameter, defined as the number of photons produced per drifting electron and per kilovolt. The scintillation yields obtained in this work are in agreement with those obtained by Monte Carlo calculations and a factor of ∼10 higher than those determined by the WARP experiment.

A Study of CsI(Tl) Scintillator with Optimized Conditions of Large Area Avalanche Photodiode

Avalanche photodiode (APD) is a kind of photodiode that internally amplifies the photocurrent by an avalanche effect. The quantum efficiency of the APD is about 80% which is five times higher than that of typical photomultiplier tube (PMT). A 16 mm diameter of beveled-edge large area avalanche photodiode (LAAPD) made by Advanced Photonics was used for the CsI(Tl) scintillator characterization. A CsI(Tl) crystal was attached to LAAPD and energy spectra were measured with various γ-ray sources. Measurements of energy spectra of the CsI(Tl) crystal to optimize the energy resolutions were performed with different shaping time constants by shaping amplifier and with different gains by high voltage variation. The absolute light yield and energy resolution of CsI(Tl) crystals were measured with the LAAPD for 662 keV γ-rays from a 137Cs source. The LAAPD was calibrated with X-ray of 55Fe source for the calibration of the number of e-h pairs per channel. The absolute light yield of newly developed SrCl2 scintillation crystal is determined by this method. This study shows that it is possible to use the LAAPD for the characterization of newly developed scintillation crystal and for the photo-sensor of scintillation detector.

Study of LaBr$_{3}$ Crystals Coupled to Photomultipliers and Avalanche Photodiodes

The performance of several BrilLanCe LaBr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> crystals that range in size from Oslash 6 times 6 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> up to Oslash 38 times 38 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> coupled to XP5212 and R6231MOD photomultipliers were studied, and in the case of the small crystals, the crystals were also coupled to large area avalanche photodiodes (LAAPD) of Advanced Photonix, Inc. First, the performance of several photomultipliers from Photonis and Hamamatsu with LaBr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> were compared to select the best one, not affecting energy resolution, besides the photoelectron statistics. The light output and energy resolution for 662 keV gamma rays from <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">137</sup> Cs source were measured for all crystals. Moreover, for some crystals, the non-proportionality of the light yield and energy resolution versus gamma ray energy were measured and the intrinsic resolution of the crystals was calculated. For the smallest crystals of Oslash 6 times 6 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> further comparative tests with LAAPD were carried out.

Performance of PWO-II Prototype Arrays for the EMC of PANDA

The response function of a 3 times 3 matrix of 200-mm-long PWO-II crystals has been measured with energy-marked photons up to 675 MeV energy. For the first time the crystals were readout individually with one large area avalanche photo diode of the second generation operating at a temperature of 0degC. The reconstructed electromagnetic shower distributions show excellent energy resolutions down to 40 MeV. Reducing the temperature and increasing the light collection by an additional large-area avalanche photo diode can achieve further improvement.

Signal to Noise Ratio of APD-Based Monolithic Scintillator Detectors for High Resolution PET

Monolithic scintillator detectors, consisting of several cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> of scintillating material coupled to one or more Hamamatsu S8550 avalanche photodiode (APD) arrays, are proposed as detectors for high resolution positron emission tomography (PET). In this work, the factors contributing to the variance on the signals are investigated, and their effects on the energy, time and spatial resolutions are analyzed. Good agreement was found between a model of the energy resolution and experiments with a 20 x 10 x 10 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> LYSO:Ce crystal coupled to a single channel large-area APD (LAAPD). With the same crystal coupled to an APD array, differences between model and experiment were observed at high APD gain. The measured energy resolution of ~11% FWHM was dominated by scintillation photon statistics, with less important roles for the APD excess noise factor and electronic noise. On the other hand, electronic noise was an important factor both for the time and the spatial resolutions. The time resolution was found to depend strongly on the APD bias voltage, and was best at the highest bias. A time resolution of 1.6 ns full width at half maximum (FWHM) was measured against a BaF2 -PMT detector. The best spatial resolution measured was 1.64 mm FWHM, without correction for the ~0.9 mm FWHM measurement beam. It is estimated that an intrinsic spatial resolution of 1.26 mm FWHM can be achieved at the center of the detector with an infinitely narrow test beam.

Large Area APDs for the PANDA EMC

PANDA is a 4pi detector planned for the antiproton storage ring at the proposed International Accelerator Facility for Antiproton and Ion Research (FAIR) at GSI. Experiments utilizing the excellent antiproton beam of up to 15 GeV/c beam momentum require an electromagnetic calorimeter of high granularity and resolution to measure photons of several GeV down to 10 MeV in energy. High fluence and thick internal targets deliver unprecedented luminosities which require a fast scintillator. A candidate for the scintillation material for the calorimeter of PANDA is PbWO4 with significantly improved light yield. For the detection of the scintillation light adequate photo sensors are required, which operate magnetic field independently and cover a large part of the readout surface of each crystal. Avalanche photo diodes (APDs) have become attractive devices for this purpose. First APDs with an active area of 10 times 10 mm2 (LAAPDs) have been developed and were tested concerning their radiation hardness due to proton irradiation at room temperature as well as under detector operation conditions of a designated temperature of T = -25 degC. A quality assurance procedure for the approx. 44000 APDs for the PANDA-EMC has been developed during the last year, which includes the measurements of the device properties at those two temperatures. Based on the experience of the CMS collaboration with this kind of photo sensors a screening procedure of the property changes due to irradiation will be performed at GSI. The mounting of the APDs on the rear side of each crystal will be realized by using a capsule built out of PEEK, a special kind of plastic, manufactured by precision injection molding. The temperature screening during the measurements will be realized by using a special kind of radiation hard thermistor, mounted on the rear side of the APD capsule.

Development of wideband X-ray and gamma-ray spectrometer using transmission-type, large-area APD

The avalanche photodiode (APD) is a high-performance and compact light sensor recently applied in various fields of experimental physics. Among several types of APDs, the reach-through APD offers an advantage in direct X-ray detection, thanks to its thick depletion layer ( ⩾ 100 μ m ) in front of the amplification region. This type of APD is also sensitive to weak scintillation light from gamma-ray scintillators with a high quantum efficiency of ∼ 80 % (at λ ≃ 500 nm ). In this paper, we propose a novel design of a compact X-ray-to-gamma-ray detector widely applicable between 1 keV and several hundreds of keV. The prototype consists of a reach-through APD (transmission type) optically coupled with a cubic CsI(Tl) crystal 4 × 4 × 4 mm 3 in size. By applying the pulse shape discrimination technique to the APD output, we successfully discriminated the X-ray signals directly detected within the APD (1–40 keV), and gamma-ray signals absorbed in a CsI(Tl) scintillator (10–800 keV) located immediately behind the APD. Optimum FWHM energy resolutions of 15.1 ± 0.2 % , 6.6 ± 0.4 % , and 7.6 ± 0.1 % were obtained for 5.9 keV X-rays, 32 keV X-rays, and 662 keV gamma rays, respectively, measured at + 20 ∘ C . This stacked configuration is viable for various future applications in space science and nuclear medicine.

Characterization of large area avalanche photodiodes in X-ray and VUV-light detection

The present manuscript reviews our R&D studies on theapplication of large area avalanche photodiodes (LAAPDs) to thedetection of X-rays and vacuum ultraviolet (VUV) light. Theoperational characteristics of LAAPDs manufactured by AdvancedPhotonix Inc. were investigated for X-ray detection at roomtemperature. The optimum energy resolution obtained in four LAAPDsinvestigated was found to be in the range 10-18% for 5.9 keVX-rays. The observed variations are associated with dark currentdifferences between the several prototypes. LAAPDs have demonstratedhigh counting rate capability (up to about 105/s) and applicabilityin diverse areas, mainly low-energy X-ray detection, whereLAAPDs selected for low dark current may achieve better performancethan proportional counters. LAAPDs were also investigated as VUVphotosensors, presenting advantages compared to photomultipliertubes. X-rays are often used as a reference in light measurements;this may be compromised by the non-linearity between gains measuredfor X-rays and VUV-light. The gain was found to be lower for X-raysthan for VUV light, especially at higher bias voltages. For 5.9 keVX-rays, gain variations of 10% and 6% were measured relative to VUVlight produced in argon ( ∼ 128 nm) and xenon ( ∼ 172 nm) forgains of about 200. The effect of temperature on the LAAPD performancewas investigated for X-ray and VUV-light detection. Gain variations ofmore than -4% per oC were measured for 5.9 keV X-rays for gainsabove 200, while for VUV light variations are larger than -5% peroC. The energy resolution was found to improve with decreasingtemperature, what is mainly attributed to dark current. The excessnoise factor, another contribution to the energy resolution, wasexperimentally determined and found to be independent of temperature,increasing linearly with gain, from 1.8 to 2.3 for a 50-300 gainrange. The LAAPD response under intense magnetic fields up to 5 Teslawas investigated. While for X-ray detection the APD responsepractically does not vary with the magnetic field, for 172 nm VUVlight a significant amplitude reduction of more than 20% wasobserved.

Non-Proportionality and Energy Resolution of NaI(Tl) at Wide Temperature Range ($-40^{\circ}{\hbox {C}}$ to $+23^{\circ}{\hbox {C}}$)

The performance of a Nal(Tl) crystal coupled to a Large Area Avalanche Photodiode (LAAPD) was investigated as a function of temperature in the range from -40degC to +23degC. The number of electron-hole pairs created per 1 MeV of gamma-ray energy detected by the scintillator, non-proportionality and the energy resolution for various peaking times were measured. It showed a significant variation of the light output and the energy resolution of a Nal(Tl) crystal at reduced temperatures down to -40degC, as measured with different peaking times in the spectroscopy amplifiers. A large slowing down of the light pulse, caused by the intense slow component of the light pulse, requires long peaking times (up to 48 mus) in order to optimize the energy resolution at the most reduced temperatures. In these conditions of a full integration of the light, a weak variation of the light output of a Nal(Tl) crystal is observed, corresponding to -0.16%/degC. The non-proportionality characteristics and intrinsic resolution are somewhat distorted by a partial integration of the light by too short shaping in the amplifier. It confirms the earlier observations that, for crystals which exhibited two component decays of the light pulse, the best non-proportionality and the lowest intrinsic resolution are achieved for the full integration of the light.

Status of the muonic hydrogen Lamb-shift experiment

The Lamb-shift experiment in muonic hydrogen (μ– p) aims to measure the energy difference between the [Formula: see text] atomic levels to a precision of 30 ppm. This would allow the r.m.s. proton charge radius rp to be deduced to a precision of 10–3 and open a way to check bound-state quantum electrodynamics (QED) to a level of 10–7. The poor knowledge of the proton charge radius restricts tests of bound-state QED to the precision level of about 6 × 10–6, although the experimental data themselves (Lamb-shift in hydrogen) have reached a precision of × 10–6. Values for rp not depending on bound-state QED results from electron scattering experiments have a surprisingly large uncertainty of 2%. In our Lamb-shift experiment, low-energy negative muons are stopped in low-density hydrogen gas, where, following the μ– atomic capture and cascade, 1% of the muonic hydrogen atoms form the metastable 2S state with a lifetime of about 1 μs. A laser pulse at λ ≈ 6 μm is used to drive the 2S → 2P transition. Following the laser excitation, we observe the 1.9 keV X-ray being emitted during the subsequent de-excitation to the 1S state using large-area avalanche photodiodes. The resonance frequency and, hence, the Lamb shift and the proton charge radius are determined by measuring the intensity of the X-ray fluorescence as a function of the laser wavelength. The results of the run in December 2003 were negative but, nevertheless, promising. One by-product of the 2003 run was the first observation of the short-lived 2S component in muonic hydrogen. Currently, improvements in the laser-system, the experimental apparatus, and the data acquisition are being implemented. PACS Nos.: 36.10.Dr, 14.20.Dh, 42.62.Fi

Particle and photon detection for a neutron radiative decay experiment

We present the particle and photon detection methods employed in a program to observe neutron radiative beta-decay. The experiment is located at the NG-6 beam line at the National Institute of Standards and Technology Center for Neutron Research. Electrons and protons are guided by a 4.6 T magnetic field and detected by a silicon surface barrier detector. Photons with energies between 15 and 750 keV are registered by a detector consisting of a bismuth germanate scintillator coupled to a large area avalanche photodiode. The photon detector operates at a temperature near 80 K in the bore of a superconducting magnet. We discuss CsI as an alternative scintillator, and avalanche photodiodes for direct detection of photons in the 0.1–10 keV range.

Xenon GPSC high-pressure operation with large-area avalanche photodiode readout

The performance of a xenon high-pressure gas proportional scintillation counter (GPSC) instrumented with a large area avalanche photodiode (LAAPD) as the VUV-photosensor has been investigated for filling pressures from 1 up to 10 bar, for 22- and 60-keV photons. The LAAPD photosensor is placed directly within the xenon envelope, as a substitute for the photomultiplier tube, avoiding the constraints of the use of a quartz scintillation window for GPSC-photosensor coupling, which absorbs a significant amount of scintillation and is a drawback for applications where large detection areas and high filling pressures are needed. The lowest energy resolutions are achieved for pressures around 5 bar (4.5% and 3.0% full width at half-maximum (FWHM), for 22- and 60-keV photons, respectively). Increasing the pressure to the 8 bar range, competitive energy resolutions of 5.0% and 3.6% are still achieved for 22- and 60-keV photons, respectively. This detector could be a compelling alternative in applications where compactness, large detection area, insensitivity to strong magnetic fields, room temperature operation, large signal-to-noise ratio and good energy resolution are important requirements .