Large Area Picosecond Photodetectors Research Articles

Performance of an LAPPD in magnetic fields

Magnetic fields affect the response of Micro-Channel Plate (MCP)-based detectors, although the effect is smaller than that for conventional photo-multiplier tubes. The main effect of the field is a reduction in gain and efficiency.In this article, we report our studies of the effects of the magnetic field on the Large Area Picosecond PhotoDetectors (LAPPDs), photosensors of large sensitive area based on MCP technology. The LAPPD under study was the most recent, short stack, 10μm pore model, expected to have the best capabilities to withstand magnetic field distortions. The measurements were performed at CERN on the MNP-17 and M113 vertical dipole magnets in magnetic fields up to ∼ 1.5 T. The results show the exponential drop of the LAPPD gain as a function of the magnetic field strength, with a rather mild dependence on the angular distribution. The relative photon detection efficiency in magnetic field is also affected. However, both the gain and the efficiency can be partially recovered by increasing the LAPPD bias voltages. Geometrical effects on the anode charge spot and time resolution were also studied.

Experimental results using large area picosecond photo-detectors

We present experimental results obtained with the LAPPD Gen-II large-size MCP-PMT. Using a custom-designed PCB capacitively coupled to the anode backplane with different segmentation patterns, the photo-detector is read out using the PETsys TOFPET2 and FastIC ASICs. The results reported in this paper include characterization using focused laser light and temporal response to picosecond illumination at a single photon level.

A commentary on the NIM A paper by B.W. Adams et al., on the timing Characteristics of Large Area Picosecond Photodetectors

A commentary on the NIM A paper by B.W. Adams et al., on the timing Characteristics of Large Area Picosecond Photodetectors

Characterization of LAPPD timing at CERN PS testbeam

Large Area Picosecond PhotoDetectors (LAPPDs) are photosensors based on microchannel plate technology with about 400 cm2 sensitive area. The external readout plane of a capacitively coupled LAPPD can be segmented into pads providing a spatial resolution down to 1 mm scale. The LAPPD signals have about 0.5 ns rise time followed by a slightly longer fall time and their amplitude reaches a few dozens of mV per single photoelectron.In this article, we report on the measurement of the time resolution of an LAPPD prototype in a test beam exercise at CERN PS. Most of the previous measurements of LAPPD time resolution had been performed with laser sources. In this article we report time resolution measurements obtained through the detection of Cherenkov radiation emitted by high energy hadrons. Our approach has been demonstrated capable of measuring time resolutions as fine as 25-30 ps. The available prototype had performance limitations, which prevented us from applying the optimal high voltage setting. The measured time resolution for single photoelectrons is about 80 ps r.m.s.

Performance of photosensors in a high-rate environment for gas Cherenkov detectors

The solenoidal large intensity device (SoLID) at Jefferson Lab will push the boundaries of luminosity for a large-acceptance detector, which necessitates the use of a light-gas threshold Cherenkov counter for online event selection. Due to the high luminosity, the single-photon background rate in this counter can exceed 160 kHz/cm2 at the photosensors. Therefore, it is essential to validate the high-rate limits of the planned photosensors and readout electronics in order to mitigate the risk of failure. We report on the design and an early set of studies carried out using a small Cherenkov counter in a high-rate environment up to 60 kHz/cm2, in Hall C at Jefferson Lab. Commercially available multi-anode photomultipliers (MaPMT) and low-cost large-area picosecond photodetectors (LAPPD) were tested using the JLab FADC250 modules for readout. The test beam results show that the MaPMT array and the internal stripline LAPPD can detect and identify single-electron and pair-production events in high-rate environments. Due to its higher quantum efficiency, the MaPMT array provided a better separation between the single-electron and the pair-production events compared to the internal stripline LAPPD. A GEANT4 simulation confirms the beam test performance of our counter device.

Development of an MCP-Based Timing Layer for the LHCb ECAL Upgrade-2

The increase in instantaneous luminosity during the high-luminosity phase of the LHC represents a significant challenge for future detectors. A strategy to cope with high-pileup conditions is to add a fourth dimension to the measurements of the hits, by exploiting the time separation of the various proton–proton primary collisions. According to LHCb simulation studies, resolutions of about 10–20 picoseconds, at least an order of magnitude shorter than the average time span between primary interactions, would be greatly beneficial for the physics reach of the experiment. Microchannel plate (MCP) photomultipliers are compact devices capable of measuring the arrival time of charged particles with the required resolution. The technology of large-area picosecond photodetectors (LAPPDs) is under investigation to implement a timing layer that can be placed within a sampling calorimeter module with the purpose of measuring the arrival time of electromagnetic showers. LAPPD performances, using a Gen-I tile with a delay-line anode and a Gen-II with a capacitively coupled anode, have been measured thoroughly both with laser (wavelength of 405 nm and pulse width of 27.5 ps FWHM) and high-energy electron (1–5.8 GeV) beams. Time resolutions of the order of 30 ps for single photoelectrons and 15 ps for electromagnetic showers initiated by 5-GeV electrons, as measured at the shower maximum, are obtained.

Design and first performance results of waveform sampling readout electronics for Large Area Picosecond Photodetector

Large Area Picosecond Photodetectors (LAPPD) are a new generation of microchannel plate photomultipliers being manufactured by Incom. These devices feature large sensitive area of 350 cm2, high quantum efficiency (∼ 20%), and tens of picosecond single photon timing resolution. LAPPDs use an anode structure with 28 striplines, allowing for spatial resolution of 1 ÷ 3 mm while minimizing the number of readout channels. In this report, we present our design of integrated readout electronics for the LAPPD . These electronics read out all 2×28 channels of a stripline-anode LAPPD . Waveform sampling at up to 5GSPS is performed by 8 DRS4 switched-capacitor array ASICs. All DRS4 channels are digitized in parallel with two 32-channel ADCs. An on-board FPGA coordinates digitization and readout of waveforms, and could further be expanded to include some waveform processing. Data packages built in the FPGA are sent to a data acquisition system (DAQ) via optical fiber, with a baseline Gigabit Ethernet interface implemented entirely on the FPGA . The electronics is designed to accommodate different triggering options: self-triggering using DRS4 transparent mode and external triggering, making event control very flexible. Further flexibility is enhanced with embedded software for an on-FPGA soft-core processor, as well as DAQ readout and control software. The device is plug and play with any existing IP network. An open-source ecosystem is being developed to provide full control of the device operation and an easy way to integrate it to any environment. In the report we describe the status of the electronics development, its firmware and readout software. Also the results of the first tests of the electronics with the LAPPD devices will be presented.

Air-transfer production method for large-area picosecond photodetectors.

We have designed and prototyped the process steps for the batch production of large-area micro-channel-plate photomultipliers (MCP-PMT) using the "air-transfer" assembly process developed with single LAPPDTM modules. Results are presented addressing the challenges of designing a robust package that can transmit large numbers of electrical signals for pad or strip readout from inside the vacuum tube and of hermetically sealing the large-perimeter window-body interface. We have also synthesized a photocathode in a large-area low-aspect-ratio volume and have shown that the micro-channel plates recover their functionality after cathode synthesis. These steps inform a design for a multi-module batch facility employing dual nested low-vacuum and ultra-high-vacuum systems in a small-footprint. The facility design provides full access to multiple MCP-PMT modules prior to hermetic pinch-off for leak-checking and real-time photocathode optimization.

Water-based Liquid Scintillator detector as a new technology testbed for neutrino studies in Turkey

This study investigates the deployment of a medium-scale neutrino detector near Turkey’s first nuclear power plant, the Akkuyu Nuclear Power Plant. The aim of this detector is to become a modular testbed for new technologies in the fields of new detection media and innovative photosensors. Such technologies include Water-based Liquid Scintillator (WbLS), Large Area Picosecond Photo-Detectors (LAPPDs), dichroic Winston cones, and large area silicon photomultiplier modules. The detector could be used for instantaneous monitoring of the Akkuyu Nuclear Power Plant via its antineutrino flux. In addition to its physics and technological goals, it would be an invaluable opportunity for the nuclear and particle physics community in Turkey to play a role in the development of next generation of particle detectors in the field of neutrino physics.

ANNIE: Neutron multiplicity in neutrino interactions and new technologies

The Accelerator Neutrino Neutron Interaction Experiment (ANNIE) aims at measuring the neutron abundance in the final state of neutrino-nucleus interactions. This measurement will have a direct impact on our understanding of neutrino interactions and will lead to a better reduction of systematic errors and an improvement of signal-background discrimination in future large neutrino detectors, thus impacting long baseline oscillation experiments as well as proton decay searches and supernova detection. With a volume of about 26 tons of pure water doped with gadolinium to enhance neutron tagging efficiency, ANNIE will provide a measurement of the neutron yield of neutrino interactions as a function of the neutrino energy in the well-characterized Booster Neutrino Beam at Fermilab. The modularity of ANNIE will allow it to perform several fundamental tests of new technologies to be used in neutrino detectors, such as a novel kind of photodetectors called Large Area Picosecond Photodetectors and Water-based Liquid Scintillator, a newly-developed detection medium. The technology behind the ANNIE detector will have a noticeable impact on the development of future large water Cherenkov detectors as well as on detection techniques for neutrino physics.

Performance of Large Area Picosecond Photo-Detectors (LAPPDTM)

We report on performance results achieved for recently produced LAPPDs - largest commercially available planar geometry photodetectors based on microchannel plates. These results include electron gains of up to 107, low dark noise rates (∼100 Hz/cm2 at a gain of 6⋅106), single photoelectron (PE) timing resolution of ∼50 picoseconds RMS (electronics limited), and single photoelectron spatial resolution along and across strips of 3.2mm (electronics limited) and 0.8 mm RMS respectively and high (about 25% or higher in some units) QE uniform bi-alkali photocathodes. LAPPDs is a good candidate to be employed in neutrino experiments (e.g. ANNIE (Back et al., 2017) [1], WATCHMAN (Askins et al., 2015) [2], DUNE (Capozzi et al., 2018) [3]), particle collider experiments (e.g. EIC (Accardi et al., 2016) [4]), neutrinoless double-beta decay experiments (e.g. THEIA (Fischer et al., 2018) [5]), medical and nuclear non-proliferation applications.

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.

Multiple-photon disambiguation on stripline-anode Micro-Channel Plates

Large-Area Picosecond Photo-Detectors (LAPPDs) show great potential for expanding the performance envelope of Micro-Channel Plates (MCPs) to areas of up to 20×20cm and larger. Such scaling introduces new challenges, including how to meet the electronics readout burden of ever larger area MCPs. One solution is to replace the traditional grid anode used for readout with a microwave stripline anode, thus allowing the channel count to scale with MCP width rather than area.However, stripline anodes introduce new issues not commonly dealt with in grid-anodes, especially as their length increases. One of these issues is the near simultaneous arrival of multiple photons on the detector, creating possible confusion about how to reconstruct their arrival times and positions. We propose a maximum a posteriori solution to the problem and verify its performance in simulated scintillator and water-Cherenkov detectors.

Timing characteristics of Large Area Picosecond Photodetectors

The LAPPD Collaboration was formed to develop ultrafast large-area imaging photodetectors based on new methods for fabricating microchannel plates (MCPs). In this paper we characterize the time response using a pulsed, sub-picosecond laser. We observe single-photoelectron time resolutions of a 20cm × 20cm MCP consistently below 70ps, spatial resolutions of roughly 500μm, and median gains higher than 107. The RMS measured at one particular point on an LAPPD detector is 58ps, with ± 1σ of 47ps. The differential time resolution between the signal reaching the two ends of the delay line anode is measured to be 5.1ps for large signals, with an asymptotic limit falling below 2ps as noise-over-signal approaches zero.

Considerations about Large Area___Low Cost Fast Imaging Photo-detectors

The Large Area Picosecond Photodetectors described in this contribution incorporate a photocathode and a borosilicate glass capillary Micro-Channel Plate (MCP) pair functionalised by atomic layer deposition (ALD) of separate resistive and secondary emission materials. Initial testing with matched pairs of small glass capillary test disks has demonstrated gains of the order of 10{sup 5}-10{sup 6}. Compared to other fast imaging devices, these photodetectors are expected to provide timing resolutions in the 10-100 ps range, and two-dimension position in the sub-millimeter range. If daisy chained, large detectors read at both ends with fast digitising integrated electronics providing zero-suppressed calibrated data should be produced at relatively low cost in large quantities.