Large Area Picosecond Photodetector Research Articles

Latest feasibility studies of LAPPD as a timing layer for the LHCb Upgrade 2 ECAL

The target of the LHCb experiment Upgrade 2 is to operate with an instantaneous luminosity a factor seven higher than the current one to reach the ultimate precision in several domains of its physics program. This objective challenges the development of subdetectors able to cope with the high-occupancy regime foreseen. The time-of-arrival of the particles at the various subdetectors is a promising new feature. Simulation studies show that, with a time resolution of about 10–20 ps, it will be possible to exploit the time separation of the primary proton-proton collisions and effectively mitigate the pileup. Concerning the LHCb Upgrade 2 electromagnetic calorimeter, the “Large Area Picosecond Photo Detector” technology (LAPPD) is currently a candidate to constitute a timing layer placed at the shower maximum.The LAPPD is the largest microchannel-plate photomultiplier ever built, entirely made withinexpensive materials. This paper depicts the status of the art of the ongoing R&D campaign. Inparticular, four LAPPD models have been characterized so far: the Gen-I with stripline readout andthe Gen-II with external pixelated readout, both with 10 or 20 μm pore size. A timeresolution close to the target was measured with test beams at DESY (electrons from 1 to 5.8 GeV)and SPS (electrons from 20 to 100 GeV). The radiation hardness of the MCP layers was stressed andverified up to 1016 protons/cm2 at CERN IRRAD facility and 300 C/cm2 using a UV lamp inthe laboratory. The performances at high rates were investigated with two lasers (λ =405 nm): they will be crucial for the upcoming development steps.

Large Area Picosecond Photodetector for the Upgrade II of the LHCb RICH

The Large Area Picosecond Photodetector (LAPPD) is a new generation microchannel plate (MCP) photodetector that is currently capturing the attention of detector physicists thanks to its excellent timing resolution, high gain and low dark count rate. It consists of a photocathode that responds to a single photon by producing a photoelectron that enters a pair of microchannel plates, where it is multiplied to a million electrons in a fast-rising pulse that is easily detected. The speed of this process provides the time resolution essential for high intensity environments such as the high luminosity Large Hadron Collider (LHC) at the CERN laboratory. The LAPPD has a large sensitive area, 200 × 200 mm 2, which reduces the number of sensors that are needed. The increased particle collision rate in the future LHC-HL phase represents a great challenge for the Ring Imaging Cherenkov (RICH) photodetectors in the LHCb experiment. The LHCb collaboration is working for the Upgrade II that will take place during the Long Shutdown 4 of the LHC (>2032). The LAPPD produced and commercialised by INCOM (US) represents one of the possible alternatives for the future RICH photodetectors, thanks to its good time resolution, low dark noise rate and high gain. The LHCb Edinburgh group is involved in the Upgrade II R&D programme, testing and characterising an LAPPD in the laboratory of the University. The LAPPD technology, the current Edinburgh setup and performance from first tests of the photodetector will be presented.

A Large Area Picosecond Photodetector for Neutron Transmission Measurements at DICER at LANSCE

A Large Area Picosecond Photodetector for Neutron Transmission Measurements at DICER at LANSCE

LAPPD operation using ToFPETv2 PETSYS ASIC

Single photon sensitive detectors used in high energy physics are, in some applications, required to cover areas the size of several m2, and more specifically in very strong demand with an ever finer imaging and timing capability for Cherenkov Ring Imaging Detector (RICH) configurations. We are evaluating the Large Area Picosecond Photo-detector (LAPPD) produced by INCOM company, as a possible candidate for future RICH detector upgrades. In this work we perform tests on the second generation device, which is capacitively coupled to a custom designed anode back plane, consisting of various pixels and strips varying in size, that allows for connecting various readout systems such as standard laboratory equipment, as well as the TOFPET2 ASIC from PETsys company. Our aim is to evaluate what can be achieved by merging currently available technology, in order to find directions for future developments adapted for specific uses.

Cherenkov and scintillation separation in water-based liquid scintillator using an LAPPDTM

This manuscript describes measurements of water-based liquid scintillators (WbLS), demonstrating separation of the Cherenkov and scintillation components using a low energy beta source and the fast timing response of a Large Area Picosecond Photodetector (LAPPD). Additionally, the time profiles of three WbLS mixtures, defined by the relative fractions of scintillating compound, are characterized, with improved sensitivity to the scintillator rise-time. The measurements were made using both an LAPPD and a conventional photomultiplier tube (PMT). All samples were measured with an effective resolution Oleft( 100~text {ps}right) , which allows for the separation of Cherenkov and scintillation light (henceforth C/S separation) by selecting on the arrival time of the photons alone. The Cherenkov purity of the selected photons is greater than 60% in all cases, with greater than 80% achieved for a sample containing 1% scintillator. This is the first demonstration of the power of synthesizing low light yield scintillators, of which WbLS is the canonical example, with fast photodetectors, of which LAPPDs are an emerging leader, and has direct implication for future mid- and large-scale detectors, such as Theia, ANNIE, and AIT-NEO.

Single photoelectron identification with Incom LAPPD 38

Incom Inc. Large Area Picosecond Photodetector (LAPPD) 38 has been tested at Jefferson Lab to identify single-photoelectron signals to assess the potential of this type of device for future applications in Cherenkov light detection. Single-photoelectron signals were clearly detected if a tight masking of photons impinging on the photocathode was used compared to the pixelation of the charge collection signal board.

Measurement of the Parametrized Single-Photon Response Function of a Large Area Picosecond Photodetector for Time-of-Flight PET Applications

We have used a subpicosecond laser with an output trigger synched to a 4-GHz oscilloscope sampling at 25 GSa/s to characterize the temporally resolved response of a large area picosecond photodetector (LAPPD) to single photons/photoelectrons. The LAPPD is a large area (20 cm ×20 cm) photosensor with a nanosecond-width time response arising from its underlying multichannel plate photomultiplier tube (MCP-PMT) structure. We used optical filters to attenuate the laser pulse intensity to a single-photon level. LAPPD pulses are nearly identical in shape, particularly for pulses whose peak amplitude is a large multiple of our system's 0.6-mV rms baseline electronic noise. Three waveform timing algorithms were compared in their measurements of the transit time spread (TTS) Gaussian fitted to the distribution of measured single-photoelectron (SPE) pulse times under zero-width laser excitation: 1) a constant fraction algorithm; 2) a pulse centroid timing algorithm; and 3) a pulse model-fitting algorithm. The measured SPE values with the three algorithms are: [79±17, 67±15, and 82±20] ps Gaussian sigma, respectively. The LAPPD provides independent voltage control for its photocathode (PC), and at the entry and entry faces of its chevron pair of MCPs. We found no or minimal change in TTS with PC voltage for pulses >15 mV.

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.

MCP-PMT development at Argonne for particle identification

The proposed high-energy high-luminosity polarized Electron-Ion Collider (EIC) demands excellent particle identification over a wide range of particles momenta to achieve the best separation between signal and background particles. Various Cherenkov imaging detector sub-systems are being considered in EIC detector concepts for hadron identification for particles momenta up to 50 GeV/c. One important challenge in this case is to provide a reliable highly pixelated photosensor working in the high radiation and high magnetic field environment. The recently commercialized Large Area Picosecond Photo-Detector (LAPPD) provides a promising low-cost photosensor solution for the various EIC Cherenkov imaging sub-systems. Optimization of the phtosensor design for high magnetic field tolerance, precision timing resolution, and pixelated readout was performed at Argonne National Laboratory with 6 × 6 cm2 microchannel plate photomultipliers. The techniques and optimized design parameters would be transferrable to industrial partners for low-cost LAPPD production to achieve the demonstrated performance.

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.

Characterisation and testing of a prototype 6×6 cm2 Argonne MCP-PMT

The Argonne micro-channel plate photomultiplier tube (MCP-PMT) is an offshoot of the Large Area Pico-second Photo Detector (LAPPD) project, wherein 6×6cm2 sized detectors are made at Argonne National Laboratory. Measurements of the properties of these detectors, including gain, time and spatial resolution, dark count rates, cross-talk and sensitivity to fringe magnetic fields are reported. In addition, possible applications of these devices in future neutrino and collider physics experiments are discussed.

MCP-based photodetectors for cryogenic applications

The Argonne MCP-based photo detector is an offshoot of the Large Area Pico-second Photo Detector (LAPPD) project, wherein 6 cm × 6 cm sized detectors are made at Argonne National Laboratory. We have successfully built and tested our first detectors for pico-second timing and few mm spatial resolution. We discuss our efforts to customize these detectors to operate in a cryogenic environment. Initial plans aim to operate in liquid argon. We are also exploring ways to mitigate wave length shifting requirements and also developing bare-MCP photodetectors to operate in a gaseous cryogenic environment.

Development and testing of cost-effective, 6 cm×6 cm MCP-based photodetectors for fast timing applications

Micro-channel plate (MCP)-based photodetectors are capable of picosecond level time resolution and sub-mm level position resolution, which makes them a perfect candidate for the next generation large area photodetectors. The large-area picosecond photodetector (LAPPD) collaboration is developing new techniques for making large-area photodetectors based on new MCP fabrication and functionalization methods. A small single tube processing system (SmSTPS) was constructed at Argonne National Laboratory (ANL) for developing scalable, cost-effective, glass-body, 6cm×6cm, picosecond photodetectors based on MCPs functionalized by Atomic Layer Deposition (ALD). Recently, a number of fully processed and hermitically sealed prototypes made of MCPs with 20μm pores have been fabricated. This is a significant milestone for the LAPPD project. These prototypes were characterized with a pulsed laser test facility. Without optimization, the prototypes have shown excellent results: the time resolution is ~57ps for single photoelectron mode and ~15ps for multi-photoelectron mode; the best position resolution is ≤0.8mm for large pulses. In this paper, the tube processing system, the detector assembly, experimental setup, data analysis and the key performance will be presented.

Pilot production & commercialization of LAPPD™

We present a progress update on plans to establish pilot production and commercialization of Large Area (400cm2) Picosecond Photodetector (LAPPD™). Steps being taken to commercialize this MCP and LAPPD™ technology and begin tile pilot production are presented including (1) the manufacture of 203mm×203mm borosilicate glass capillary arrays (GCAs), (2) optimization of MCP performance and creation of an ALD coating facility to manufacture MCPs and (3) design, construction and commissioning of UHV tile integration and sealing facility to produce LAPPDs. Taken together these plans provide a “pathway toward commercialization”.

Measurements of the gain, time resolution, and spatial resolution of a 20×20 cm2 MCP-based picosecond photo-detector

Microchannel plates (MCPs) allow for micron-level spatial imaging and picosecond-level time resolution, making them a good choice for the next generation of photo-detectors aiming for precision time-of-flight measurements. The Large-Area Picosecond Photo-Detector Collaboration (LAPPD) is currently developing a 20×20cm2, thin, planar, glass-body detector with two MCPs in chevron geometry with 8° bias angle. The modular design of the strip-line anode allows covering large areas while keeping the number of electronics channels low. We have built a complete detector system approximating the final detector design. We have measured a gain of up to 2×107, time-of-flight resolution of up to 35ps, differential time resolution of ~6ps, and spatial resolution of better than 1mm.

Invited Article: A test-facility for large-area microchannel plate detector assemblies using a pulsed sub-picosecond laser

The Large Area Picosecond Photodetector Collaboration is developing large-area fast photodetectors with time resolution </~10 ps and space resolution </~1 mm based on atomic layer deposition-coated glass Micro-Channel Plates (MCPs). We have assembled a facility at Argonne National Laboratory for characterizing the performance of a wide variety of microchannel plate configurations and anode structures in configurations approaching complete detector systems. The facility consists of a pulsed Ti:Sapphire laser with a pulse duration ≈100 fs, an optical system allowing the laser to be scanned in two dimensions, and a computer-controlled data-acquisition system capable of reading out 60 channels of anode signals with a sampling rate of over 10 GS/s. The laser can scan on the surface of a sealed large-area photodetector, or can be introduced into a large vacuum chamber for tests on bare 8 in.-square MCP plates or into a smaller chamber for tests on 33-mm circular substrates. We present the experimental setup, detector calibration, data acquisition, analysis tools, and typical results demonstrating the performance of the test facility.

Using Large Area Microchannel Plate Photodetectors in the Next Generation Water Cherenkov Neutrino Detectors

The next generation of neutrino experiments will require massive water Cherenkov detectors to reach the sensitivity needed to measure CP violation in the lepton sector and the neutrino mass hierarchy. The Large Area Picosecond Photodetector Development (LAPPD) Collaboration is developing new methods to fabricate a 20 cm2 thin planar microchannel plate photo-multiplier tube (MCP) at a cost comparable to those of traditional photomultiplier tubes (PMT). The application of these novel devices to large water Cherenkov detectors could significantly enhance background rejection and vertex resolution in these detectors by improving spatial and timing information. We present details of the MCP fabrication method, and preliminary results from testing and characterization facilities at Argonne National Laboratory. The application of these devices to neutrino detectors is also discussed.

A 4-Channel Waveform Sampling ASIC in 0.13μm CMOS for front-end Readout of Large-Area Micro-Channel Plate Detectors

Abstract We describe here the development of PSEC-3, a custom integrated circuit designed in the IBM-8RF 0.13 μm CMOS process and intended for fast, low-power waveform sampling. As part of the Large-Area Picosecond Photo-Detector (LAPPD) collaboration, this chip has been designed as a prototype application-specific integrated circuit (ASIC) for the front-end transmission line readout of large-area micro-channel plate photomultiplier tubes (MCP-PMTs). With 4 channels, PSEC-3 has a buffer depth of 256 samples on each channel, a chip-parallel ramp-compare ADC, and a serial data readout that includes the capability for region-of-interest windowing to reduce dead time. Chip calibrations and performance results, including achieved sampling rates of 2.5-17 GSa/s, are reported. Some design issues are identified, in particular the dependence of analog bandwidth on location in the sampling array. The causes have been found and addressed in a subsequent PSEC-4 submission.

Development of an Alkali Transfer Photocathode for Large Area Microchannel Plate-Based Photodetectors

The goal of the Large Area Picosecond Photodetector collaboration is to produce 8-inch by 8-inch microchannel plate-based photodetectors, with fast timing resolution of the order of 1-100 ps and high spatial resolution of 0.1-10 mm. At Argonne, the transfer photocathode process being developed is based on a recipe for manufacturing photomultiplier cathodes. Starting with a commercial PMT fabrication facility, the photocathode recipe and growth system will be scaled up using a custom-built glass vessel to produce transfer photocathodes. This leads to the production of the 8-inch by 8-inch photocathode that will be incorporated with the photodetector assembly system.

Systems-Level Characterization of Microchannel Plate Detector Assemblies, using a Pulsed sub-Picosecond Laser

Abstract Microchannel plate photomultiplier tubes (MCP-PMTs) are compact imaging detectors, capable of micron-level spatial imaging and timing measurements with resolutions well below 10 picoseconds. The Large Area Picosecond Photodetector Collaboration (LAPPD) is developing techniques for fabricating 8“x8”, thin, planar, glass-body MCP-PMTs at costs comparable to traditional PMTs. Collaboration between the High Energy Physics Division and the Advanced Photon Source (APS) at Argonne National Laboratory (ANL) has produced an advanced channel-plate characterization facility for testing the time response of MCPs using a pulsed laser capable of sub-picosecond pulses. The MCPs are tested in stacks of one or two plates with a simple photocathode and coupled to a microstripline anode board. LAPPD-made MCPs have already demonstrated gains larger than 10 5 and promising time resolving capabilities. These measurements will guide the systems-level optimization of LAPPD detectors and the development of signal processing algorithms. Predictions made by the LAPPD simulations group based on electron emmission properties of the MCP pore surface are compared with these tests to help further our understanding of MCP performance.