Single Photoelectron Research Articles

Single-photon image sensor at room temperature with only four anodes

A two-dimensional tetra-lateral position-sensitive cap-resistive-layer silicon photomultiplier (CRL-SiPM) is employed as a single-photon imaging sensor at room temperature. The CRL-SiPM has only four anodes and one back cathode with an active area of 2.77 mm × 2.77 mm and a micro avalanche photodiode cell pitch of ~10 μm. It achieved a 150 μm-linewidth-resolved single-photon image, which is near the device's theoretical intrinsic single-photon position resolution limit of ~115 μm. With increasing light intensity, the position resolution of the device improved. When the mean photoelectron numbers were 1.34 and 41.56, the corresponding intrinsic position resolutions were 101.6 and 14.08 μm, respectively. Finally, owing to the single photoelectron imaging capability of the CRL-SiPM, we achieved the lensless imaging of dark counting sites, i.e., the locations of thermal carriers inducing avalanche breakdown of the device.

The XENON1T data acquisition system

The XENON1T liquid xenon time projection chamber is the most sensitive detector built to date for the measurement of direct interactions of weakly interacting massive particles with normal matter. The data acquisition system (DAQ) is constructed from commercial, open source, and custom components to digitize signals from the detector and store them for later analysis. The system achieves an extremely low signal threshold by triggering each channel independently, achieving a single photoelectron acceptance of (93 ± 3)%, and deferring the global trigger to a later, software stage. The event identification is based on MongoDB database queries and has over 98% efficiency at recognizing interactions at the analysis threshold in the center of the target. A readout bandwidth over 300 MB/s is reached in calibration modes and is further expandable via parallelization. This DAQ system was successfully used during three years of operation of XENON1T.

The Jiangmen Underground Neutrino Observatory (JUNO)

The Jiangmen Underground Neutrino Observatory (JUNO) is an experiment under construction in China with the primary goal of determining the neutrino mass hierarchy (MH) with reactor anti-neutrinos. The JUNO detector system consists of a central detector, an active veto system and a calibration system. The central detector is a 35 m diameter transparent acrylic sphere containing a 20 kton liquid scintillator neutrino target. A primary photo-detection system consisting of 18,000 large (20” diameter) dynode and micro-channel plate photomultipliers surrounds the central detector. A second interlaced photo-detection system is made of 25,600 small (3” diameter) photomultipliers working in the single photo-electron regime for the reactor anti-neutrino detection. The detector is designed to achieve an unprecedented energy resolution of 3% @1MeV and an absolute energy scale uncertainty better than 1%. A veto system, consisting of a water Cherenkov detector and a top tracker, is used help maximally remove cosmogenic backgrounds. Due to its unprecedented scale and precision, JUNO will be an exceptional multipurpose detector with a rich physics program in neutrino oscillation, geo-neutrinos, astrophysical neutrinos and the search for physics beyond the Standard Model (sterile neutrinos, dark matter, proton decay and others).

Performance of the Compact High Energy Camera SiPM Prototype Front-End Electronics proposed for the Cherenkov Telescope Array

The Compact High Energy Camera (CHEC) is a full-waveform capture camera, designed and proposed for the dual mirror, Schwarzschild–Couder, Small Sized Telescope of the Cherenkov Telescope Array. CHEC-S, the second prototype, is based upon silicon photomultiplier (SiPM) photodetectors optimised for single photon counting and nanosecond timing. The camera liquid-cooled focal plane plate comprises a total of 2048 SiPM pixels organised as 32 independent sensor and front-end electronics (FEE) modules providing event detection and signal digitisation of Cherenkov light flashes. Each module comprises an 8 × 8 tile of SiPM pixels, coupled to a 64-channel preamplifier-buffer followed by a FEE module based around the TARGET chipset, which combines triggering (T5TEA) and waveform capture (TARGET C) functionality.We describe a selection of end-to-end performance tests and results conducted at the University of Leicester in the UK. Testing was performed at single module level focusing on characterising the SiPM photodetectors, optimised preamplifier-buffer and updated CHEC-S FEE readout module. Presented results include single photoelectron response, gain-matching, signal range, electronic channel crosstalk, SiPM angular dependency and optical crosstalk.

Fast-timing microchannel plate photodetectors: Design, fabrication, and characterization.

We report a detailed design, fabrication, and characterization of 6 × 6 cm2 fast timing photodetectors based on next-generation microchannel plates (MCPs). The whole assembly is made of low-cost borosilicate glass materials and hermetically sealed with a bialkali photocathode in a vacuum. The flexible photodetector design provides the potential of modifying individual components as well as the entire configuration to fit for different applications. A series of prototype MCP-photodetectors were fabricated following a step-by-step process including functionalization of glass capillary array through atomic layer deposition, MCP baking and scrubbing, photocathode deposition, and hermetic thermo-compression sealing. The prototype MCP-photodetectors exhibit electron gains well beyond 107 level with good relative uniformity. An excellent rise time of 439 ps, timing distribution root-mean-square at a single photoelectron mode of 105 ps, a timing resolution of 20 ps, and magnetic field tolerance up to 1.3 T were achieved for a photodetector with 10 µm pore size MCPs, comparing to that of 536 ps, 205 ps, 63 ps, and 0.7 T for the one with 20 µm pore size MCPs.

The mass production and batch test result of 20″ MCP-PMTs

Abstract Researchers of IHEP have conceived a new concept of MCP-PMT several years ago. Small MCP units replace the bulky Dynode chain in the large PMTs. In addition, transmission and reflection photocathodes are in the same glass bulb to enhance the efficiency of photoelectron conversion. After three years of R&D, a number of 8 inch prototypes were produced in 2013. The 20 inch prototypes followed in 2014 and their performances were improved a lot in 2015. This type of PMT has large sensitive area, high quantum efficiency (QE), and large peak-to-valley (P/V) ratio for good single photoelectron detection. Taking in account the performance and cost of PMT and the radioactivity of PMT glass, JUNO ordered 15000 20-inch MCP-PMT from North Night Vision of Technology CO.(NNVT) in Dec.2015. The MCP-PMT collaboration group finished to build the mass production line in Nanjing, and finished the batch test system in the same place in 2016. From 2017 to 2019, all the 20-inch PMTs are produced and tested individually in NNVT. This paper will focus on the mass production and batch test result of 6000 pieces of MCP-PMT prototypes for JUNO.

Large-area MPPC with enhanced VUV sensitivity for liquid xenon scintillation detector

A large-area Multi-Pixel Photon Counter (MPPC) sensitive to vacuum ultra violet (VUV) light has been developed for the liquid xenon (LXe) scintillation detector of the MEG II experiment. The LXe detector is designed to detect the 52.8MeV photon from the lepton flavour violating decay μ+→e+γ and is based on 900ℓ LXe with a highly granular scintillation readout by 4092 VUV-MPPCs with an active area of 139mm2 each, totalling 0.57m2. The VUV-MPPC shows an excellent performance in LXe, which includes a high photon detection efficiency (PDE) up to 21% for the LXe scintillation light in the VUV range, a high gain, a low probability of the optical cross-talk and the after-pulsing, a low dark count rate and a good single photoelectron resolution. The large active area of the VUV-MPPC is formed by connecting four independent small VUV-MPPC chips in series to avoid the increase of the sensor capacitance and thus, to have a short pulse-decay-time, which is crucial for high rate experiments. Performance tests of 4180 VUV-MPPCs produced for the LXe detector were also carried out at room temperature prior to the installation to the detector and all of them with only a few exceptions were found to work properly. The design and performance of the VUV-MPPC are described in detail as well as the results from the performance tests at room temperature.

A study of the new hemispherical 9-inch PMT

The new 9 inch hemispherical photomultiplier tubes (PMTs) produced by Hainan Zhanchuang Photonics Technology Co.Ltd (HZC) have been studied. The tube shows good transit time spread (FWHM=2.35 ns), nonlinearity (5% to 750 photoelectrons), good charge resolution with single photoelectron (PE) and high stable operation gain (1× 107). Totally 13 tubes are measured for a prototype detector of JUNO at IHEP, China.

Irradiation and performance of RGB-HD Silicon Photomultipliers for calorimetric applications

Silicon Photomultipliers with cell-pitch ranging from 12 μm to 20 μm were tested against neutron irradiation at moderate fluences to study their performance for calorimetric applications. The photosensors were developed by FBK employing the RGB-HD technology. We performed irradiation tests up to 2 × 1011 n/cm2 (1 MeV eq.) at the INFN-LNL Irradiation Test facility. The SiPMs were characterized on-site (dark current and photoelectron response) during and after irradiations at different fluences. The irradiated SiPMs were installed in the ENUBET compact calorimetric modules and characterized with muons and electrons at the CERN East Area facility. The tests demonstrate that both the electromagnetic response and the sensitivity to minimum ionizing particles are retained after irradiation. Gain compensation can be achieved increasing the bias voltage well within the operation range of the SiPMs. The sensitivity to single photoelectrons is lost at ∼ 1010 n/cm2 due to the increase of the dark current.

Large Area Picosecond Photodetector (LAPPDTM) - Pilot production and development status

Abstract We report performance results achieved for fully functional sealed Large Area Picosecond Photodetectors (LAPPD™) in tests performed at Incom Inc., as well as independent test results reported by our early adopters. The LAPPD is a microchannel plate (MCP) based large area picosecond photodetector, capable of imaging with single-photon sensitivity at high spatial and temporal resolutions in a hermetic package. The LAPPD has an active area of 350 square centimeters in an all-glass hermetic package with a fused silica window and bottom plate and sidewalls made of borosilicate float glass. Signals are generated by a bi-alkali Na 2 KSb photocathode and amplified with a stacked chevron pair of MCPs produced by applying resistive and emissive atomic layer deposition coatings to glass capillary array (GCA) substrates. Signals are collected on RF stripline anodes applied to the bottom plates which exit the detector via pin-free hermetic seals under the side walls. LAPPD test and performance results for product produced and delivered to early adopter customers during the first half of 2018 are reviewed. These results include electron gains ≥ 7.5 × 106 @ 850/950 V (entry/exit MCP), low dark noise rates (22 Cts/s/cm2 ), single photoelectron (PE) timing resolution of 64 picoseconds RMS, and single photoelectron spatial resolution along and across strips of 2.8 mm and 1.3 mm RMS respectively. Many of these devices also had very high QE photocathodes that were uniform over the full 195 mm × 195 mm window active area (LAPPD #15 QE% @ 365 nm Max/Avg/Min = 25.8/22.3 ± 3/15.7). An update is also provided of developments that enable capacitive signal coupling from the detector to application specific pads or stripline readout patterns deployed on printed circuit boards positioned beneath the tile, outside of the vacuum package. We conclude with examples of how sensors offering picosecond timing, in diverse applications can bring transformative change to detector technology and applications in future experiments.

Characterization of 3-inch photomultiplier tubes for the JUNO central detector

Jiangmen Underground Neutrino Observation (JUNO) is one of the largest experimental facilities for neutrino detecting. As its main structure, the central detector contains 20 kiloton liquid scintillator filled in an acrylic shell, and there are 18,000 20-inch photomultiplier tubes (PMTs) and 25,000 3-inch PMTs covering the shell. As an independent photon detection system, 3-inch PMTs have been required to have excellent resolution for the single photoelectron detection, high quantum efficiency, small transit time spread and low dark noise rate. Two kinds of 3-inch PMTs from HZC Photonics and Hamamatsu have been investigated as candidates. A dedicated test system for 3-inch PMTs has been designed, and various characterization parameters have been studied. The preliminary results show these PMTs can meet the requirements of JUNO.

An experimental and theoretical study of the photoelectron spectra of cis-dichloroethene: Valence shell vertical ionization and vibronic coupling in the low-lying cationic states.

The valence shell photoelectron spectrum of cis-dichloroethene has been studied both experimentally and theoretically. Photoelectron spectra have been recorded with horizontally and vertically plane polarized synchrotron radiation, thereby allowing the anisotropy parameters, characterizing the angular distributions, to be determined. The third-order algebraic-diagrammatic construction approximation scheme for the one-particle Green's function has been employed to compute the complete valence shell ionization spectrum. In addition, the vertical ionization energies have been calculated using the outer valence Green's function (OVGF) method and the equation-of-motion coupled-cluster, with single and double substitutions for calculating ionization potentials (EOM-IP-CCSD) model. The theoretical results have enabled assignments to be proposed for most of the structure observed in the experimental spectra, including the inner-valence regions dominated by satellite states. The linear vibronic coupling model has been employed to study the vibrational structure of the lowest photoelectron bands, using parameters obtained from ab initio calculations. The ground state optimized geometries and vibrational frequencies have been computed at the level of the second-order Møller-Plesset perturbation theory, and the dependence of the ionization energies on the nuclear configuration has been evaluated using the OVGF method. While the adiabatic approximation holds for the 2B1 state photoelectron band, the 2B2, 2A1, and 2A2 states interact vibronically and form a complex photoelectron band system with four distinct maxima. The 2B1 and 2B2 states also interact vibronically with each other. The potential energy surface of the 2B1 state is predicted to have a double-minimum shape with respect to the out-of-plane a2 deformations of the molecular structure. The single photoelectron band resulting from this interaction is characterized by a highly irregular structure, reflecting the non-adiabatic nuclear dynamics occurring on the two coupled potential energy surfaces forming a conical intersection close to the minimum of the 2B2 state.

First performance evaluation of a Multi-layer Thick Gaseous Electron Multiplier with in-built electrode meshes—MM-THGEM

We describe a new micro-pattern gas detector structure comprising a multi-layer hole-type multiplier (M-THGEM) combined with two in-built electrode meshes: the Multi-Mesh THGEM-type multiplier (MM-THGEM). Suitable potential differences applied between the various electrodes provide an efficient collection of ionization electrons within the MM-THGEM holes and a large charge avalanche multiplication between the meshes. Different from conventional hole-type multipliers (e.g. Gas Electron Multipliers - GEMs, Thick Gas Electron Multipliers—THGEMs, etc.), which are characterized by a variable (dipole-like) field strength inside the avalanche gap, electrons in MM-THGEMs are largely multiplied by a strong uniform field established between the two meshes, like in the parallel-plate avalanche geometry. The presence of the two meshes within the holes allows for the trapping of a large fraction of the positive ions that stream back to the drift region. A gas gain above 105 has been achieved for single photo-electron detection with a single MM-THGEM in Ar/(10%)CH4 and He/(10%)CO2, at standard conditions for temperature and pressure. When the MM-THGEM is coupled to a conventional THGEM and used as first cascade element, the maximum achievable gains reach values above 106 in He/(10%)CO2, while the IBF approaches of 1.5% in the case of optimum detector-bias configuration. This IBF value is several times lower compared to the one obtained by a double GEM/THGEM detector (5–10%), and equivalent to the performance attained by a Micromegas detector.

PICOSEC: Charged particle timing at sub-25 picosecond precision with a Micromegas based detector

The prospect of pileup induced backgrounds at the High Luminosity LHC (HL-LHC) has stimulated intense interest in developing technologies for charged particle detection with accurate timing at high rates. The required accuracy follows directly from the nominal interaction distribution within a bunch crossing (σz∼5cm, σt∼170ps). A time resolution of the order of 20–30 ps would lead to significant reduction of these backgrounds. With this goal, we present a new detection concept called PICOSEC, which is based on a “two-stage” Micromegas detector coupled to a Cherenkov radiator and equipped with a photocathode. First results obtained with this new detector yield a time resolution of 24 ps for 150 GeV muons, and 76 ps for single photoelectrons.

Consistency test of PMT SPE spectrum from dark-noise pulses and LED low-intensity light

Photomultiplier tube (PMT) has been an essential instrument for low background experiments, and the accuracy of single photoelectron (SPE) calibration will directly affect the energy reconstruction of the detector. The SPE spectrum can be acquired from the charge distribution of dark-noise pulses or the low-intensity light signal triggered by LED. However, there are arguments on whether the two methods are consistent. In this paper, the Hamamatsu R5912-20mod PMT and the EMI-D642KNFL PMT have been tested adopting the two methods with signal waveform recording electronics. As comparison, traditional charge-to-digital conversion system is also used to test SPE spectrum. The results show that they are consistent when the PMTs are working at typical recommended high voltage (HV).

A technique for estimating the absolute gain of a photomultiplier tube

Detection of low-intensity light relies on the conversion of photons to photoelectrons, which are then multiplied and detected as an electrical signal. To measure the actual intensity of the light, one must know the factor by which the photoelectrons have been multiplied. To obtain this amplification factor, we have developed a procedure for estimating precisely the signal caused by a single photoelectron. The method utilizes the fact that the photoelectrons conform to a Poisson distribution. The average signal produced by a single photoelectron can then be estimated from the number of noise events, without requiring analysis of the distribution of the signal produced by a single photoelectron. The signal produced by one or more photoelectrons can be estimated experimentally without any assumptions. This technique, and an example of the analysis of a signal from a photomultiplier tube, are described in this study.

Characterization of the Hamamatsu 8” R5912-MOD Photomultiplier tube

Current and future neutrino and direct detection dark matter experiments hope to take advantage of improving technologies in photon detection. Many of these detectors are large, monolithic optical detectors that use relatively low-cost, large-area, and efficient photomultiplier tubes (PMTs). A candidate PMT for future experiments is a newly developed prototype Hamamatsu PMT, the R5912-MOD. In this paper we describe measurements made of the single photoelectron time and charge response of the R5912-MOD, as well as detail some direct comparisons to similar PMTs. Most of these measurements were performed on three R5912-MOD PMTs operating at gains close to 1×107. The transit time spread (σ) and the charge peak-to-valley were measured to be on average 680ps and 4.2 respectively. The results of this paper show the R5912-MOD is an excellent candidate for future experiments in several regards, particularly due to its narrow spread in timing.

Study of PMT performance in the high dynamic range at LHAASO

In the Large High Altitude Air Shower Observatory (LHAASO), the Water Cherenkov Detector Array (WCDA) and Muon Detector (MD) employ a large number of photomultiplier tubes for cosmic ray detection. In order to explore the cosmic ray sources at very high energy level, these photomultiplier tubes require not only good single photoelectron resolution, but also large linear dynamic range: up to 4000 photoelectrons for WCDA and over 10000 muons for MD. In order to meet these requirements, we design a high dynamic range base for three photomultiplier tube candidates (R5912, CR365 and XP1805) for WCDA and R5912 for MD, and test their performance. The results show that the characteristics of all three candidates with a charge dynamic range up to 1–4000 photoelectrons satisfy the demands of WCDA. For R5912 of MD, the equivalent current non-linearity of DY7 within 5% is up to 1.87A, satisfying the dynamic range requirement of MD.

Investigation of the microstructure of Thick-GEMs with single photo-electrons

Novel Cherenkov detector upgrades favour GEM and ThickGEM based MPGD systems. These detectors have reduced ion backflow, fast signal formation, high gain, and could suppress the MIP signals as well. Their common drawbacks are the inefficiencies of photo-electron collection fromthe top of the ThickGEM and the local variation of multiplication due to the special geometry. The developed high resolution scanner using focused UV light gave the possibility to study single photo-electron response of MPGDs in the sub-millimeter scale. Revealing the microstructure of photo-efficiency and local gain provides a new tool to quantitatively compare different ThickGEM geometries and field-configurations, and thus optimize the detector parameters. The presentation will focus on the key elements of the scanning system; and on the microstructure evolution of different ThickGEM configurations.

Single electron-photon pair creation from a single polarization-entangled photon pair

Quantum entanglement between different forms of qubits is an indication of the universality of quantum mechanics. Entanglement transfer between light and matter, especially photon and spin, has long been studied as the central concept, but it remains technically challenging for single photons and spins. In this paper, we show paired generation of a single electron in a GaAs quantum dot and a single photon from a single polarization-entangled photon pair. We measure temporal coincidence between the single photo-electron detection and the single photon detection. Considering a single photon polarization is converted to an electron spin via an optical selection rule, the present result indicates the capability of photon to spin entanglement transfer. This may be useful to explore the physics of entanglement transfer and also for applications to quantum teleportation based quantum communication.