Microchannel Plate Photomultiplier Research Articles

Coincidence time resolution of 30 ps FWHM using a pair of Cherenkov-radiator-integrated MCP-PMTs

Radiation detectors dedicated to time-of-flight positron emission tomography (PET) have been developed, and coincidence time resolution (CTR) of sub-100 ps full width at half maximum (FWHM) has been achieved by carefully optimizing scintillators and photodetectors. Achieving a CTR of 30 ps FWHM by using a pair of annihilation γ-rays would allow us to directly localize the annihilation point within an accuracy of 4.5 mm. Such direct localization can potentially eliminate the requirement of image reconstruction processes in clinical PET systems, which would have a huge impact on clinical protocols and molecular imaging. To obtain such a high CTR, researchers have investigated the use of prompt emissions such as Cherenkov radiation and hot-intra band luminescence. Although it is still challenging to achieve a CTR of 30 ps FWHM even with a Cherenkov-based detector, the experimentally measured CTR is approaching the goal. In this work, we developed a Cherenkov-radiator-integrated micro-channel plate photomultiplier tube (CRI-MCP-PMT), where there are no optical boundaries between the radiator and photocathode, and its timing performance was investigated. By removing the optical boundaries, reflections are eliminated and transmission to the photocathode is improved, resulting in high timing capability. As a result, a CTR of 30.1 ± 2.4 ps FWHM, which is equivalent to a position resolution of 4.5 ± 0.3 mm along a line of response (LOR), was obtained by using a pair of CRI-MCP-PMTs.

Characteristics of fast timing MCP-PMTs in magnetic fields

The motivation of this paper is to explore the parameters that affect the performance of Microchannel Plate Photomultiplier Tubes (MCP-PMTs) in magnetic fields with the goal to guide their design to achieve a high magnetic field tolerance. MCP-PMTs based on two different designs were tested.The magnetic field tolerance of MCP-PMT based on a design providing independently biased voltages showed a significant improvement (up to 0.7 T) compared to the one utilizing an internal resistor chain design (up to 0.1 T), indicating the importance of individually adjustable voltages. The effects of the rotation angle of the MCP-PMT relative to the magnetic field direction and of the bias voltage between the photocathode and the top MCP were extensively investigated using the MCP-PMT based on the independently biased voltage design. It was found that the signal amplitude of the MCP-PMT exhibits an enhanced performance at a tilt angle of $\pm$8$^{\circ}$, due to the 8$^{\circ}$ bias angle of the MCP pores. The maximum signal amplitude was observed at different bias voltages depending on the magnetic field strength.

First experimental demonstration of time-resolved X-ray measurements with next-generation fast-timing MCP-PMT

We report the first successful time-resolved X-ray measurements at the APS 10-ID-B beamline by coupling ultrafast scintillators with photodetectors. Multiple scintillator and sensor pairs (LYSO, plastic scintillator, dynode PMTs, MCP-PMT), as well as a standalone detector (diamond), were tested to demonstrate the time-resolved measurements using hard X-rays at energies of 20 keV and above. The experimental results show that a number of choices exist for time-resolved high-energy X-ray beam measurement. Notably, by gating the photocathode, the Argonne fabricated fast-timing microchannel plate photomultiplier and LYSO crystal pair achieved fast signal detection with a rise time of ~6 ns and a decay time of ~33 ns. These experiments pave the way towards ultrafast imaging technologies using hard X-rays for many applications.

Timing-performance evaluation of Cherenkov-based radiation detectors

With the upgradation of detector components, such as scintillators and photodetectors, the PET-image signal-to-noise ratio of time-of-flight positron emission tomography (TOF-PET) systems has been improved, compared to those of ordinary nonTOF-PET systems. A TOF-PET with an ultrahigh time resolution, for example a coincidence time resolution (CTR) better than few tens of picoseconds, can not only improve the image quality, but also remove the image reconstruction process, significantly impacting medical imaging. Therefore, it is crucial to develop a high-time resolution PET detector. We focus on the prompt emission of Cherenkov radiation, owing to the instantaneousness of which, a high time resolution can be expected. One of the candidates for the Cherenkov radiator is lead fluoride (PbF2) due it has excellent properties, including transparency toward the ultraviolet region, high refractive index (n = 1.82), and high density (7.77 g/cm3). Moreover, it does not contain radioisotopes, unlike lutetium-based scintillators, which are commonly used in the currently available TOF-PET detectors. In this work, we experimentally investigate the timing performance of PbF2-based Cherenkov detectors, breaking down the timing performance into physical components. 3×3×5 mm3 and 9.6×9.6×5 mm3 PbF2 crystals are used as Cherenkov radiators; both are attached to a microchannel plate photomultiplier tube (MCP-PMT) because the single channel MCP-PMT is one of the best photodetectors in terms of the SPTR, which is 25 ps full width at half maximum (FWHM). All the surfaces, except the end surface where the MCP-PMT is connected, are wrapped in black tape to suppress the reflections of the Cherenkov photons in the crystal. The CTR is measured by placing a detector pair face-to-face, using an 22Na point source, and an oscilloscope at 20 GS/s with a set bandwidth of 4.2 GHz. A CTR of 46.9 ps FWHM, corresponding to a position resolution of 7.0 mm, is obtained, consistent with our simulation results.

The PANDA DIRC detectors

Abstract The PANDA experiment at the future Facility for Antiproton and Ion Research (FAIR) will address fundamental questions of hadron physics with unprecedented precision. To reach this goal excellent Particle Identification (PID) is essential over a large range of particle momenta and solid angles. Most of the phase space will be covered by two innovative DIRC (Detection of Internally Reflected Cherenkov light) detectors. The Endcap Disc DIRC and Barrel DIRC will cover the polar angle range from 5 to 22°and 22 to 140°, respectively. Both detectors rely on high precision optical components, lifetime-enhanced Microchannel Plate PMTs (MCP-PMTs), and fast readout electronics.

Recent progress with microchannel-plate PMTs

Abstract Microchannel-plate (MCP) PMTs were identified as the only suitable photon sensors for the two DIRC detectors of the PANDA experiment at FAIR. As the long-standing aging problem of MCP-PMTs was recently overcome by coating the MCP pores with an atomic layer deposition (ALD) technique, further improved 2 ″ MCP-PMTs were investigated. The best PHOTONIS device has reached a lifetime of > 20 C/cm2 integrated anode charge without any sign of aging. Also the newly developed 2 ″ MCP-PMTs of Hamamatsu are maturing and are usable in high rate environments. The status of our long-term lifetime measurements and the performance parameters of the currently most advanced ALD-coated MCP-PMTs from PHOTONIS and Hamamatsu are presented. In addition, first results obtained with a new quality assurance setup for MCP-PMTs are discussed. This setup consists of a high performance DAQ system to measure the response of ≥ 64 anode pixels simultaneously. The system allows to study and quantify background parameters like position dependent dark count rates and ion afterpulsing as well as temporal and spacial distributions of recoil electrons and the effects of electronic and charge-sharing crosstalk among the anode pixels.

Fast Interaction Trigger for the upgrade of the ALICE experiment at CERN: design and performance

ALICE (A Large Ion Collider Experiment) at the CERN LHC is designed to study the properties of the Quark–Gluon Plasma (QGP) in heavy-ion collisions. In 2019–2020 the upgrade of the LHC will increase the luminosity and the collision rate beyond the design parameters of the current ALICE setup. To be able to benefit from the improved performance of the LHC, ALICE will upgrade several of its key detector systems including the Fast Interaction Trigger (FIT). FIT is designed to provide the functionality of the existing forward detectors while retaining or even improving their performance. It will provide minimum bias (MB) trigger with an efficiency higher than 90% for pp collisions, measure the luminosity for pp and Pb–Pb collisions, and sustain interaction rates up to 1 MHz and 50 kHz, respectively. FIT will determine the collision time with a resolution better than 50 ps and will be used to measure the event multiplicity, the centrality, and the reaction plane. The detector consists of two arrays of Cherenkov radiators with micro-channel plate photo-multiplier (MCP-PMT) sensors, placed on both sides of the interaction point and of a single large-diameter scintillator ring. This article discusses the main design concepts, detector construction, beam test results, Monte Carlo simulations, and the results of detector performance studies.

Status of the TORCH time-of-flight project

Abstract TORCH is a time-of-flight detector, designed to provide charged π ∕ K particle identification up to a momentum of 10 GeV/c for a 10 m flight path . To achieve this level of performance, a time resolution of 15 ps per incident particle is required. TORCH uses a plane of quartz of 1 cm thickness as a source of Cherenkov photons , which are then focussed onto square Micro-Channel Plate Photomultipliers (MCP-PMTs) of active area 53 × 53 mm 2 , segmented into 8 × 128 pixels equivalent. A small-scale TORCH demonstrator with a customised MCP-PMT and associated readout electronics has been successfully operated in a 5 GeV/c mixed pion/proton beam at the CERN PS facility. Preliminary results indicate that a single-photon resolution better than 100 ps can be achieved. The expected performance of a full-scale TORCH detector for the Upgrade II of the LHCb experiment is also discussed.

Nuclear diagnosis of the fuel areal density for direct-drive deuterium fuel implosion at the Shenguang-II Upgrade laser facility

AbstractIn inertial confinement fusion experiments that involve short-laser pulses such as fast ignition (FI), diagnosis of neutrons is usually very challenging because high-intensity γ rays generated by short-laser pulses would mask the much weaker neutron signal. In this paper, fast-response scintillators with low afterglow and gated microchannel plate photomultiplier tubes are combined to build neutron time-of-flight (nTOF) spectrometers for such experiments. Direct-drive implosion experiments of deuterium-gas-filled capsules were performed at the Shenguang-II Upgrade (SG-II-UP) laser facility to study the compressed fuel areal density (〈ρR〉) and evaluate the performance of such nTOF diagnostics. Two newly developed quenched liquid scintillator detectors and a gated ultrafast plastic scintillator detector were used to measure the secondary DT neutrons and primary DD neutrons, respectively. The secondary neutron signals were clearly discriminated from the γ rays from (n, γ) reactions, and the compressed fuel areal density obtained with the yield-ratio method agrees well with the simulations. Additionally, a small scintillator decay tail and a clear DD neutron signal were observed in an integrated FI experiment as a result of the low afterglow of the oxygen-quenched liquid scintillator.

Calibration and commissioning of the Time Of Propagation PID detector at the Belle II Experiment

Abstract The Time Of Propagation (TOP) counter is a novel particle identification detector which relies on the precise detection time of Cherenkov photons produced by charged particles traversing a quartz bar. The TOP counter is constituted by 16 modules that cover the barrel region of the Belle II detector. Each module is instrumented with 32 Micro-Channel-Plate Photo-Multiplier-Tube (MCP-PMT) detectors, which are read out by dedicated fast waveform-sampling front-end electronics. After recalling the performance goals and stringent design requirements of the TOP counter, a comprehensive overview of its calibration strategies will be given. The status of the integration with the other Belle II sub-detectors and the performance during the commissioning phase with cosmic ray data will be presented, along with a preliminary study of the first SuperKEKB collision events.

Operation of microchannel plate PMTs with TOFPET multichannel timing electronics

We describe an experimental programme to evaluate TOFPET multichannel timing electronics using microchannel plate PMTs in single photon counting mode. Time resolution measurements were made using: (i) the on-board electronic stim signal; (ii) a Photek PMT210 high speed single anode MCP photomultiplier detector, and; (iii) imaging with a PMT240MA multi-anode MCP detector using a pixelated multi-layer ceramic readout. Experimental measurements using an electronic stim with the ASIC electronics gave a time resolution of 43 ps rms. Detector timing of the PMT210 detector was evaluated using a 40 ps wide pulsed laser with amplitude walk correction using the time over threshold capability of the TOFPET electronics. Single photon timing resolution of better than 100 ps rms was demonstrated. Furthermore, 256 discrete pixel imaging has been demonstrated by coupling a multi-anode pixelated MCP detector to the TOFPET system. • First result for coupling TOFPET electronics to microchannel plate detectors. • 43 picosecond electronic time resolution measured. • Photon-counting with 96 picosecond time resolution. • 256 pixel ultra-fast microchannel plate imaging demonstrated. • Amplitude walk correction improves timing resolution from 225 to 96 picoseconds.

Simulation of microchannel plate photomultiplier tube in high magnetic fields

The microchannel plate photomultiplier tube (MCP-PMT) used in high energy physics experiments usually needs to be able to operate in strong magnetic fields. In this paper, a 3D MCP-PMT model is developed in CST studio suite to study the magnetic field up to 5 T effect on the photoelectrons traveling from the photocathode to the MCP. Results predict that a growing number of photoelectrons strike back to the photocathode with enhancing magnetic field, which not only decreases electron collection efficiency and gain, but also impairs the photocathode lifetime. • The effect of magnetic fields up to 5 T on the photoelectrons is studied. • Results predict that photoelectrons could strike back to the photocathode. • High magnetic fields decrease collection efficiency and photocathode lifetime.

Ab initio response functions for Cherenkov-based neutron detectors.

Neutron time-of-flight diagnostics at the NIF were recently outfitted with Cherenkov detectors. A fused silica radiator delivers sub-nanosecond response time and is optically coupled to a microchannel plate photomultiplier tube with gain from ∼1 to 104. Capitalizing on fast time response and gamma-ray sensitivity, these systems can provide better than 30 ps precision for measuring first moments of neutron distributions. Generation of ab initio instrument response functions (IRFs) is critical to meet the <1% uncertainty needed. A combination of Monte Carlo modeling, benchtop characterization, and in situ comparison is employed. Close agreement is shown between the modeled IRFs and in situ measurements using the NIF's short-pulse advanced radiographic capability beams. First and second moments of neutron spectra calculated using ab initio IRFs agree well with established scintillator measurements. Next-step designs offer increased sensitivity and time-response.

Characterization of photodetector temporal response for neutron time-of-flight (nToF) diagnostics at the National Ignition Facility.

The temporal response of a microchannel plate photomultiplier tube used in the suite of neutron time of flight (nToF) diagnostics at the National Ignition Facility has been characterized to reduce uncertainty in, and understanding of, shot parameters obtained from nTOF data. A short pulse laser, neutral density glass filters, and electrical attenuators were used to gather statistically significant samples of photodetector impulse response functions (IRF) in rapid succession. Individual components have been absolutely calibrated to minimize systematic uncertainties. The zeroth (collected charge), first (transit time), and second central moments (transit time spread) of the IRF were calculated as either the bias voltage or the amount of light incident on the detector was varied. Timing reference was provided by a monitor photodiode viewing a pickoff of the incident laser pulse. The primary sources of uncertainty are jitter in the monitor photodiode and the statistical variation across our measurement period. The spreads in the first moment, with respect to the timing photodiode, and the square root of the second central moment were found to be less than 50 ps and 150 ps, respectively.

MCP-PMT production for Belle II TOP detector and further R&amp;D

Abstract We have developed 1-inch square-shaped Micro-Channel-Plate PMT (MCP-PMT) for the barrel particle identification detector, named Time-Of-Propagation (TOP) detector, at the Belle II experiment. The TOP detector utilizes the precise timing measurement to reconstruct the charged particle velocity through the Cherenkov ring image and the time-of-flight information. The MCP-PMT realizes the timing measurement with 40 ps precision for single photon detection. We have tested over 600 MCP-PMTs including spares, and installed 512 of those into the Belle II TOP detector. Along with the mass production, we have studied to improve the MCP-PMT photocathode lifetime. By applying Atomic-Layer-Deposition (ALD) technique on MCP and further residual gas reduction process, the lifetime have improved significantly. The improved PMTs are also installed. To understand the mechanism of photocathode deterioration, we have measured feed-backed ion’s signals using developed MCP-PMTs and studied the correlation between the rate and the lifetime.

Area and extraction field analysis of the analogue saturation of 40 mm microchannel plate photomultiplier tubes.

Microchannel plate (MCP) photomultiplier tubes (PMTs) are a well-established instrument for the inertial confinement fusion (ICF) community, with several detectors installed at NIF, Omega (LLE Rochester), and Orion (AWE). The analog signals produced at these major ICF facilities cover many orders of magnitude and often need multiple detectors operating at different levels of electron gain. As such, understanding the upper saturation limit of MCP-PMTs to large, low rate signals takes on a high importance. A previous study looked at the saturation limit of double and single MCP-PMTs over their full working area with pulse widths between 4 ns and 100 ns. This follow-on analysis will look at the effect of how the illuminated area affects the saturation limit and at the impact of the MCP to anode extraction field on the impulse response and the level of saturation.

Testbeam studies of a TORCH prototype detector

TORCH is a novel time-of-flight detector that has been developed to provide charged-particle identification between 2 and 10 GeV/c momentum. TORCH combines arrival times from multiple Cherenkov photons produced within a 10 mm-thick quartz radiator plate, to achieve a 15 ps time-of-flight resolution per incident particle. A customised Micro-Channel Plate photomultiplier tube (MCP-PMT) and associated readout system utilises an innovative charge-sharing technique between adjacent pixels to obtain the necessary 70 ps time resolution of each Cherenkov photon. A five-year R&D programme has been undertaken, culminating in the construction of a small-scale prototype TORCH module. In testbeams at CERN, this prototype operated successfully with customised electronics and readout system. A full analysis chain has been developed to reconstruct the data and to calibrate the detector. Results are compared to those using a commercial Planacon MCP-PMT, and single photon resolutions approaching 80 ps have been achieved. The photon counting efficiency was found to be in reasonable agreement with a GEANT4 Monte Carlo simulation of the detector. The small-scale demonstrator is a precursor to a full-scale TORCH module (with a radiator plate of 660×1250×10mm3), which is currently under construction.

Timing resolution studies of the optical part of the AFP Time-of-flight detector.

We present results of the timing performance studies of the optical part and front-end electronics of the time-of-flight subdetector prototype for the ATLAS Forward Proton (AFP) detector obtained during the test campaigns at the CERN-SPS test-beam facility (120 GeV π+ particles) in July 2016 and October 2016. The time-of-flight (ToF) detector in conjunction with a 3D silicon pixel tracker will tag and measure protons originating in central exclusive interactions p + p → p + X + p, where the two outgoing protons are scattered in the very forward directions. The ToF is required to reduce so-called pileup backgrounds that arise from multiple proton interactions in the same bunch crossing at high luminosity. The background can fake the signal of interest, and the extra rejection from the ToF allows the proton tagger to operate at the high luminosity required for the measurement of the processes. The prototype detector uses fused silica bars emitting Cherenkov radiation as a relativistic particle passes through them. The emitted Cherenkov photons are detected by a multi-anode micro-channel plate photomultiplier tube (MCP-PMT) and processed by fast electronics.

Particle identification for a future EIC detector

In its latest Long Range Plan for Nuclear Science Research in the U.S., the Nuclear Science Advisory Committee to the Department of Energy recommended that in regards to new nuclear-physics facilities, the construction of an Electron Ion Collider (EIC) be of the highest priority after the completion of the Facility for Rare Isotope Beams. In order to carry out key aspects of the scientific program of the EIC, the EIC central detector must be capable of hadron particle identification (PID) over a broad momentum range of up to 50 GeV/c. The goal of the EIC-PID consortium is to develop an integrated program for PID at EIC, which employs several different technologies for imaging Cherenkov detectors. Here we discuss the conceptual designs and the expected PID performance of two of these detectors, as well as the newest results of gain evaluation studies of photon sensors that are good candidates to read out these detectors. Development of a gas-aerogel dual-radiator Ring Imaging Cherenkov (dRICH) detector with outward focusing mirrors is being pursued for the hadron endcap. Simulations demonstrate that the dRICH can provide a continuous ⩾ 3σ π /K/p separation from 2.5 GeV/c to 50 GeV/c. A modular aerogel Ring Imaging Cherenkov (mRICH) detector with a Fresnel lens as a focusing element is being pursued for the electron endcap. The design provides for hadron identification over a momentum range of 3 GeV/c–10 GeV/c. The working principle of the mRICH design has been proven in a beam test with a first prototype. The location of the sensor readout planes of the Cherenkov detectors in the magnetic field of the central-detector solenoid, which is expected to be within 1.5 T–3 T, makes is necessary to evaluate the limit of the acceptable performance of commercially available photosensors, such as microchannel-plate photomultipliers (MCP PMTs). Here we present the results of gain evaluation of multi-anode MCP PMTs with a pore size of 10 μm. Overall, our preliminary results suggest that the 10-μm pore-size sensors can be operated in a magnetic field with magnitude up to Bmax of 2 T. The value of Bmax depends on the relative orientation between the sensor and the field.

Development of trigger and start detectors for experiments with high-energy heavy ions at the Joint Institute for Nuclear Research

Fast Cherenkov and scintillation detectors based on microchannel-plate photomultiplier tubes and silicon photomultipliers are being developed for application in the multi-purpose detector and baryonic matter at the Nuclotron experiments with the heavy ion beams at the Joint Institute for Nuclear Research. The aim of the detectors is the fast triggering of nucleus–nucleus collisions with high efficiency and to generate the start signal with picosecond time resolution for time-of-flight measurements. The detectors provide a time resolution better than 50 ps and can operate in the strong magnetic field of the experimental facilities.