Microchannel Plate Photomultiplier Research Articles

Study on after-pulses of FPMTs

The small-sized Micro-Channel Plate Photomultiplier Tube (MCP-PMT), also called Fast-timing PMT (FPMT), has gained significant attention across various fields due to its single-photon detection capability and great time resolution. The after-pulses are spurious pulses occurring after the main pulse and cannot be distinguished from the true signals, which means the occurrence of the after-pulses can contribute to the noise of the FPMT. In this study, the waveforms of the FPMTs were recorded by a high-sampling-rate oscilloscope, and we measured the after-pulse characteristics of different types of FPMTs, including the time distribution and the after-pulse rate. The causes of different after-pulse groups are also analyzed. Additionally, we conducted a comparative analysis of the distinct properties of after-pulses in different types of FPMTs.

Simultaneous co-axial multi-modal inspection using a laser driven x-ray and neutron source.

Laser-plasma interactions have been demonstrated to produce bright sources of energetic radiation including ions, electrons, photons across the electro-magnetic spectrum, and neutrons. Combinations of species can significantly increase information from non-destructive imaging. Here we demonstrate single-shot co-axial radiography with both x-ray and fast-neutron radiation from a laser-driven source using a pair of gated microchannel plate photomultiplier tube channels and a fast scintillator medium. The outlined system demonstrates recovery full-width-half-maximum of (18 ± 3) ns, which is sufficient to isolate x-rays from neutrons up to (72 ± 20) MeV and could be isolated only a short distance (2m) from the target.

Research progress on long lifetime MCP-PMT for the DTOF detector in STCF

The Super Tau Charm Facility (STCF) is a state-of-the-art electron-positron collider operating in the center-of-mass energy range of 2–7[Formula: see text]GeV and achieving a peak luminosity of more than [Formula: see text][Formula: see text]cm−2s−1, which is pivotal for advancing particle physics research. The DIRC-like time-of-flight (DTOF) detector is one of the crucial components of the STCF, designed to identify high-momentum charged particles with high precision. A significant element of the DTOF is the microchannel plate photomultiplier tube (MCP-PMT), known for its exceptional time resolution in the detection of Cherenkov light. With the STCF expected to operate for over a decade, stringent requirements are imposed on the MCP-PMT, requiring an integrated anode charge (IAC) in excess of 10[Formula: see text]C/cm2. In this paper, the lifetime of the single anode MCP-PMT prototypes is investigated and a multi-anode MCP-PMT design is presented. The results show that the lifetime of the single anode MCP-PMT is greater than 11[Formula: see text]C/cm2 when a 6 nm-thick ALD layer is deposited on the inner surface of the MCP and an electron scrubbing dosage of 0.75[Formula: see text][Formula: see text]A[Formula: see text][Formula: see text][Formula: see text]h/cm2 is applied to the MCP. The lifetime is expected to be further improved by increasing the electron scrubbing dosage and optimizing the ALD layer. The studies on the single anode MCP-PMTs will be applied to the development of the long-life multi-anode MCP-PMT.

Operation of the Belle II imaging Time-Of-Propagation (iTOP) detector before and after the first long shutdown

The iTOP detector is a Cherenkov detector specialized on particle identification at Belle II. The SuperKEKB accelerator collides electrons and positrons with a design luminosity of 6⋅10351cm2s. In order to exploit the high collision rate Belle II has a trigger rate of up to 30 kHz. The iTOP detector uses quartz bars as the source of Cherenkov photons. The photons are reflected inside the bars until they hit photomultipliers installed at one end. The spatial distribution and precise arrival times of the detected photons are used to reconstruct the Cherenkov angle and particle flight time. To achieve a good pion–kaon separation the photon arrival times have to be measured with a resolution of 100 ps. Microchannel plate photomultipliers together with dedicated high-speed electronics for 2.7 GSa/s waveform sampling in 8192 channels are used to achieve this requirement. After four years of operation, the experiment entered its first long shutdown phase in 2022. Aging components of iTOP were exchanged and the detector was prepared for data-taking at increasing luminosities and backgrounds after the long shutdown. In this talk the design of the iTOP detector will be shown and experience and results from operation will be discussed together with an outlook on future running conditions.

An enhanced gated MCP-PMT for neutron detection in laser fusion experiments

The microchannel plate photomultiplier tube (MCP-PMT) is a photodetector that utilizes microchannel plates for signal amplification, offering rapid pulse response time of sub-nanosecond with a compact design and low dark current. A series of enhanced gated MCP-PMTs have been developed by incorporating a gating electrode between the photocathode and the MCPs, which have been employed in neutron detection during the double-cone ignition laser fusion experiment at the SGII Upgrade laser facilities.

Performance testing of a novel short axis photomultiplier tube for the HUNT project

Photomultiplier tubes (PMTs) with large-area cathodes are increasingly being used in cosmic-ray experiments to enhance detection efficiency. The optical modules (OMs) of the High-Energy Underwater Neutrino Telescope (HUNT) have employed a brand new N6205 20-inch microchannel plate photomultiplier tube (MCP-PMT) developed by the North Night Vision Science & Technology (Nanjing) Research Institute Co. Ltd. (NNVT). In order to make the 20-inch PMT fit into the 23-inch diameter pressure-resistant glass sphere, NNVT improved the internal structure of PMT and shortened the height of PMT by more than 10 cm. The first batch of these PMTs has been delivered for preliminary research work. This paper describes a specific PMT testing platform built for the first batch of 15 MCP-PMTs, and some performance parameters of PMT, such as peak-to-valley ratio, TTS and nonliniearity, are measured. The measurement results show that the new PMT still has good performance and can meet the requirements of HUNT project.

First ClearMind gamma detector prototype for TOF-PET imaging

The ClearMind project aims to develop a TOF-PET position-sensitive detection module optimized for time and spatial resolutions and detection efficiency. For this, we use a 59 mm× 59 mm × 5 mm monolithic PbWO4 (PWO) crystal, which is encapsulated within a commercial Micro-Channel Plate Photomultiplier tube MAPMT253 with a bialkali photocathode directly deposited on the crystal. We report the proof of concept of the directly deposited of a bialkali photocathode on a PWO crystal and its stability over time. The full calibration of the ClearMind photodetector module in the single-photoelectron regime is described. We measured a time resolution of 70 ps FWHM using a 20 ps pulsed laser. We present the performance of the prototype used in coincidence with a 3 × 3 × 3 mm3 LYSO:Ca,Ce crystal readout by a SiPM. We obtained a coincidence time resolution of 350 ps FWHM, a spatial resolution of 4 to 5 mm, and a detection efficiency of 28 %, consistent with Monte Carlo simulations of the ClearMind detector module.

Characterization of the BOLDPET optical prototype, an innovative Cherenkov detector for 511 keV γ radiation

In the present work we describe the design, construction, and testing of the optical prototype developed for the BOLDPET project, with the objective of creating a PET detection module with high spatial and time resolution. The BOLDPET technology uses an innovative detection liquid, trimethylbismuth, for detecting 511 keV γ-quanta resulting from positron annihilation. The optical signal is exclusively produced through the Cherenkov mechanism, and the produced photons are detected using Planacon microchannel-plate photomultiplier. We achieve an excellent time resolution of 150 ps (FWHM) within a sizable detection volume measuring 55 mm× 55 mm× 25 mm. Through detailed Geant4 simulations, we examine the limiting factors affecting time resolution and explore potential avenues for improvement. Furthermore, we demonstrate the feasibility of coarse 2D localization of interactions using the optical signal alone, achieving a precision of about 5–8 mm (FWHM) within the homogeneous detection volume.

Systematic approach to measure the performance of microchannel-plate photomultipliers

In this paper, we present our approach to systematically measure numerous performance parameters of microchannel plate photomultiplier tubes. The experimental setups, the analyses and selected results are discussed. Although the techniques used may be different in other locations, the document is intended as a guide for comparable measurements with other types of microchannel plate photomultiplier tubes. Measurements are shown for the following performance parameters: spectral and spatial quantum efficiency, collection efficiency, gain as a function of voltage, position and magnetic field, time resolution, rate capability and lifetime. By using a dedicated 3-axis stepper and an FPGA-based data acquisition system, also inner PMT parameters are measured as a function of the active area, such as relative detection efficiency, dark count rate, time resolution, recoil electron and afterpulse distributions, as well as charge sharing and electronic crosstalk. In addition, some of the parameters are investigated inside a strong magnetic field. For many of these measurements, the change of most setup parameters and the subsequent analysis can be controlled semi-automatically by software scripts.

Advances in the Large Area Picosecond Photo-Detector (LAPPDTM): 8" × 8" MCP-PMT with Capacitively Coupled Readout

We present advances made in the Large Area Picosecond Photodetector (LAPPD), an 8" × 8" microchannel plate photomultiplier tube (MCP-PMT), since pilot production was initiated at Incom, Inc. in 2018. The Gen-I LAPPD utilizes a stripline anode for direct charge readout. The novel Gen-II LAPPD employs an internal resistive thin-film which capacitively couples to a customizable external signal readout board, streamlining production and increasing customer flexibility. The Gen-II LAPPD, with an active area of 373 cm2, is capable of high single photoelectron (PE) gain of ∼107, low dark rates (∼1 kHz/cm2), single PE (SPE) timing resolution of ∼65 ps, and 𝒪(mm) position resolution. Coupled with a UV-grade fused silica window, the LAPPD features a high quantum efficiency (QE) bialkali photocathode of >30% at 365 nm with spectral response down to ∼165 nm. The LAPPD is an excellent candidate for electromagnetic calorimeter (ECAL) timing layers, photon-based neutrino detectors, high energy collider experiments, medical imaging systems, and nuclear non-proliferation applications.

Proton and muon beam tests for ultra-fast MCP-PMT detectors

In collaboration with the North Night Vision Science and Technology (Nanjing) Research Institute Co. Ltd, researchers at the Institute of High Energy of Physics in China have successfully developed the 20-inch micro-channel-plate photomultiplier tube (MCP-PMT) that exhibits high detection efficiency (DE) for use in the Jiangmen Underground Neutrino Observatory (JUNO). Due to the long drift path of electrons from photocathode to MCP, the 20-inch MCP-PMT has a time resolution on the order of nanoseconds. Recently, the team has made advancements in ultra-fast MCP-PMTs (FPMTs), achieving picosecond-level time resolution with both 1-inch and 2-inch types. By now, prototypes featuring single-anode, 2 × 2 anodes, 4 × 4 anodes, and 8 × 8 anodes have been successfully manufactured and tested. The 8 × 8 anode FPMT, in particular, demonstrates a transit time spread (TTS) of 36 ps (Sigma) in single photon mode, thanks to its meticulously engineered structure. To assess the FPMT’s time performance under beam conditions, two beam tests were conducted at Fermi Lab and CERN. In these tests, the 8 × 8 pixel arrays of four distinct radiators, including LYSO, BGO, Pb glass and quartz glass, were paired with the 8 × 8 anodes FPMT. This setup involved the use of two radiator-coupled FPMT detectors for particle detection. The best coincidence time resolution recorded was 64 ps (Sigma) with a 120 GeV proton beam and 56 ps (Sigma) with a 108 GeV muon beam.

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.

Restoration of saturated outputs from microchannel plate photomultiplier tubes in sub-microsecond single-pulse-current mode

Microchannel plate (MCP) photomultiplier tubes (PMTs) are frequently used in experimental diagnostics, where they are operated in single-pulse current measurement mode. However, considering the significant amplitude fluctuations in the measured signal, the resulting output signal from the MCP-PMT is inevitably distorted by gain saturation. Therefore, understanding the correlation between the MCP-PMT output signal and gain saturation is critical in assessing the extent of output signal distortion and determining the MCP-PMT saturation level. This knowledge allows for a more precise assessment of the input signal's features. In this paper, we present an experimental method for restoring the initial waveform from the saturated MCP-PMT signal. To correct the amplitude-drop caused by gain saturation, our technique involves calibrating the MCP-PMT's relative gain as a function of the accumulated output charge using a square-wave light source. We then applied this approach to restore a ∼500 ns saturated pulse from a double-layer 10 mm diameter MCP-PMT. The restored signal showed a deviation of less than 6% from the reference waveform, which validates the effectiveness of the technique.

Performance of the most recent Microchannel-Plate PMTs for the PANDA DIRC detectors at FAIR

In the PANDA experiment at the FAIR facility at GSI two DIRC (Detection of Internally Reflected Cherenkov light) detectors will be used for π/K separation up to 4GeV/c. Due to their location in a high magnetic field and other stringent requirements like high detection efficiency, low dark count rate, radiation hardness, long lifetime and good timing, MCP-PMTs (microchannel-plate photomultiplier) were the best choice of photon sensors for the DIRC detectors in the PANDA experiment. This paper will present the performance of some of the latest 2 × 2inch 2 MCP-PMTs from Photek and Photonis, including the first mass production tubes for the PANDA Barrel DIRC from Photonis. Performance parameters like the collection efficiency (CE), quantum efficiency (QE), and gain homogeneity were determined. The effect of magnetic fields on some properties like gain and charge cloud width was investigated as well. Apart from that the spatial distribution of many internal parameters like time resolution, dark count rate, afterpulse ratio, charge sharing crosstalk and recoil electrons were measured simultaneously with a multihit capable DAQ system. The latest generation of Photonis MCP-PMTs shows a unexpected ”escalation” effect where the MCP-PMT itself produces photons.

Optimizing the design of ultrafast photomultiplier tubes.

Ultrafast microchannel plate (MCP) photomultiplier tubes are under active development. To obtain high gain, high spatial resolution, and good time performance, we comprehensively investigate the effects of the gap distances and voltages from cathode to MCPin and MCPout to anode in a systematic study using the finite integral technique and Monte Carlo method. A three-dimensional model is introduced to simplify the calculations. From the simulation results, a short gap distance and high gap voltage were determined to achieve good time performance, high spatial resolution, and high gain.

A 256 channel photon counting module using a square microchannel plate PMT in a tight packing envelop achieving

Photek have developed a square microchannel plate (MCP) photomultiplier tube (PMT) using 6 μm pore MCPs to achieve superior timing, compared to the previous generation which used 15 μm pores. The native anode pattern is 64 × 64, but for this module the pattern is ganged to a 16 × 16 design using an epoxy bonded PCB giving an anode size of 3.3 × 3.3 mm in a 53 × 53 mm active area. The electronic front-end is the TOFPET2d ASIC from Petsys Electronics, a combined amplifier/discriminator/TDC with 30 ps time bins and capable of 480 kHz per channel count rate, with sufficient dynamic range to allow for the gain variation inherent in large area MCP-PMTs. The outer envelope of the combined PMT and electronic front-end package allows for close packing on 4 sides with outer dimensions of 60 × 62 mm giving a 76% fill factor. We present results showing the combined performance of the PMT and TOFPET2d ASIC and the uniformity of single photon timing accuracy.

Status and perspectives of vacuum-based photon detectors

In this overview article vacuum-based photon detectors are reviewed emphasizing their applications in Cherenkov imaging devices. After the discussion of the basic detector stages such as photo cathode, electron multiplication, and (anode) readout, the status and recent progress with single- and multi-anode dynode photomultipliers (PMTs), hybrid (avalanche) photodetectors and microchannel-plate PMTs are presented. For all of these devices selected examples of their current and planned applications in neutrino, astroparticle, and high energy physics experiments are given. Possible future developments and innovations are also debated. The last part of this review is dedicated to a comparison of important performance parameters like particle detection efficiency, gain inside a magnetic field, rate capability, aging and lifetime issues, and radiation tolerance.

The PANDA Barrel DIRC

The PANDA experiment at the international accelerator Facility for Antiproton and Ion Research in Europe (FAIR), Darmstadt, Germany, will address fundamental questions of hadron physics using p̄p annihilations. Excellent Particle Identification (PID) over a large range of solid angles and particle momenta will be essential to meet the objectives of the rich physics program. Charged PID in the target region will be provided by a Barrel DIRC (Detection of Internally Reflected Cherenkov light) counter. The Barrel DIRC, covering the polar angle range of 22–140 degrees, will provide a π/K separation power of at least 3 standard deviations for charged particle momenta up to 3.5 GeV/c. The design of the Barrel DIRC features narrow radiator bars made from synthetic fused silica, an innovative multi-layer spherical lens focusing system, a prism-shaped synthetic fused silica expansion volume, and an array of lifetime-enhanced Microchannel Plate PMTs (MCP-PMTs) to detect the hit location and arrival time of the Cherenkov photons. Detailed Monte-Carlo simulations were performed, and reconstruction methods were developed to study the performance of the system. All critical aspects of the design and the performance were validated with system prototypes in a mixed hadron beam at the CERN PS. In 2020 the PANDA Barrel DIRC project advanced from the design stage to component fabrication. The series production of the fused silica bars was successfully completed in 2021 and delivery of the MCP-PMTs started in May 2022.

TORCH pattern recognition and particle identification performance

The TORCH detector aims to provide K/π (K/p) separation up to a momentum of about 10 (15) ▪ by measuring their time-of-flight at the LHCb detector. Prompt Cherenkov photons are produced in a quartz radiator bar of 10 mm thickness, and propagated via total internal reflection to the periphery of the detector, where they are focused onto an array of microchannel plate photomultipliers that measure the photon arrival time and position. Pattern recognition techniques are used to compare the likelihood that the detector image is due to a given particle hypothesis. Good performance is obtained even for very high detector occupancies.

Detailed simulation for the ClearMind prototype detection module and event reconstruction using artificial intelligence

The ClearMind project aims to develop the TOF-PET position sensitive detection module optimized for the time resolution, spatial resolution, and detection efficiency. For this, the ClearMind project uses a large (59 × 59 mm2) monolithic PbWO4 (PWO) scintillating crystal with a bialkali photo-electric layer deposited directly on the crystal. Scintillation and Cherenkov photons result together from the 511 keV gamma-ray interaction into the PWO crystal. A micro-channel plate photomultiplier tube (MCP-PMT) encapsulating the PWO crystal amplifies photoelectrons generated at the photocathode, and the corresponding anode signals are collected through the transmission lines read out at both ends and digitized by a SAMPIC module. In this work, we present a realistic Geant4 simulation of the ClearMind prototype detector, including the propagation of the visible photons in the crystal, the modeling of a realistic response of the photocathode and of the PMT, and the propagation of the electrical signals over the transmission lines. The reconstruction of the gamma conversion in the detector volume is performed from the signals registered at both ends of the transmission lines. We compare the reconstruction precision of a statistical algorithm against machine learning algorithms developed using the TMVA package. We expect to reach a spatial resolution down to a few mm3 (FWHM). Finally, we will discuss prospects for the ClearMind detector.