Microchannel Plate Photomultiplier Research Articles

Study on the linearity of 20'' dynode and MCP PMTs

The linearity of charge response is an important feature of photomultiplier tubes (PMTs) for physics measurements, especially the newly developed 20'' microchannel plate (MCP) PMT (MCP-PMT). In this paper, in addition to the traditional method of double light sources, we applied another relative method of 20'' PMT to 3'' PMT comparison to measure the linearity of the 20'' dynode and MCP PMTs in pulse mode using a waveform digitizer. The measurements show a good linear response of the two types of 20'' PMTs to 1000 photoelectrons (p.e.). The correlations of the amplitude, rise-time, fall-time, FWHM, baseline recovery, overshoot, and the amplitude ratio of late-puse of the 20'' PMTs were derived from the waveform analysis, where the MCP-PMT shows very different features compared to the 20'' dynode-PMT.

Cosmic ray test of a STCF DTOF detector prototype

A time-of-flight detector based on detection of internally reflected Cherenkov light (DTOF), is proposed for the endcap particle identification at the Super Tau-Charm Facility (STCF). A prototype with a trapezoidal fused silica radiator that had a size of 533 mm/ 295 mm × 454 mm × 15 mm is constructed, which is approximately one-third of the size of the DTOF sector proposed for STCF. A field-programmable-gate-array-based dual-threshold time-over-threshold measurement circuit is employed to read signals from the microchannel-plate photomultiplier tube, which performs functions such as signal amplification, discrimination, and digitization. The DTOF prototype was tested in a cosmic ray telescope, which realizes 3D tracking of cosmic ray muons with an angular resolution of < 1 mrad, position resolution of <200μm, and reference time resolution of 24 ps. To analyze and understand the performance of the DTOF prototype, a GEANT4 simulation is employed. The time resolution of the DTOF prototype is 25 ps by using 10 or more photoelectrons in the cosmic ray test, which is in good agreement with the simulation result, proving the feasibility of this technology.

Performance of a prototype TORCH time-of-flight detector

TORCH is a novel time-of-flight detector, designed to provide charged particle identification of pions, kaons and protons in the momentum range 2–20 GeV/c over a 9.5 m flight path. A detector module, comprising a 10 mm thick quartz plate, provides a source of Cherenkov photons which propagate via total internal reflection to one end of the plate. Here, the photons are focused onto an array of custom-designed Micro-Channel Plate Photo-Multiplier Tubes (MCP-PMTs) which measure their positions and arrival times. The target time resolution per photon is 70 ps which, for 30 detected photons per charged particle, results in a 10–15 ps time-of-flight resolution. A 1.25 m length TORCH prototype module employing two MCP-PMTs has been developed, and tested at the CERN PS using a charged hadron beam of 8 GeV/c momentum. The construction of the module, the properties of the MCP-PMTs and the readout electronics are described. Measurements of the collected photon yields and single-photon time resolutions have been performed as a function of particle entry points on the plate and compared to expectations. These studies show that the performance of the TORCH prototype approaches the design goals for the full-scale detector.

Lifetime and performance of the very latest microchannel-plate photomultipliers

The PANDA experiment at the FAIR facility at GSI will study hadron physics using a high intensity antiproton beam of up to 15 GeV/c momentum to perform high precision spectroscopy. Two DIRC detectors with their image planes residing in an ∼1T magnetic field will be used in the experiment. The only suitable photon detectors for both DIRCs were identified to be Microchannel-Plate Photomultipliers (MCP-PMTs). Since the aging problems of MCP-PMTs were solved recently by coating the MCPs with the so-called ALD-technique (atomic layer depostion) we are investigating devices which are significantly improved with respect to other parameters, as, e.g., the collection efficiency (CE) and the quantum efficiency (QE). The latest generation of MCP-PMTs can reach a detective quantum efficiency DQE=QE⋅CE of 30%. This paper will present the performance of the most advanced 53 × 53 mm2 ALD-coated MCP-PMTs from Photonis (8 × 8 and 3 × 100 anodes) and Photek (8 × 8 anodes), also inside the magnetic field. With a picosecond laser and a multi-hit capable DAQ system which allows read out up to 300 pixels simultaneously, parameters like darkcount rate, afterpulse probability and time resolution can be investigated as a function of incident photon position.

Upgraded Cherenkov time-of-flight detector for the AFP project.

We present the results of our performance studies of the upgraded Cherenkov time-of-flight (ToF) detector for the AFP (ATLAS Forward Proton) project. The latest version consists of solid L-shaped fused silica bars, new customized ALD-coated micro-channel plate photomultipliers (MCP-PMTs) miniPlanacon XPM85112-S-R2D2 with an extended lifetime which operate at low gains (order of 103), and an updated construction. The improvements were aimed to increase the efficiency, the lifetime as well as the radiation hardness of the detector which has been designed to operate in high radiation areas (above 400 kGy/year). The detector was finally tested at the CERN-SPS test-beam facility (120 GeV π+ particles) in August 2021 prior to its installation at the Large Hadron Collider (LHC) at CERN. Measurements proved the detector kept its inner timing resolution of 20 ps despite the rather low gain of its photodetector and reduced optical throughput caused by inevitable changes in the detector geometry.

Afterpulse measurement of JUNO 20-inch PMTs

In this study, we present the large photomultiplier tube (PMT) afterpulse measurement results obtained from the Jiangmen underground neutrino observatory (JUNO) experiment. A total of 11 dynode-PMTs (R12860) from the Hamamatsu company (Hamamatsu Photonics K.K. (HPK)) and 150 micro-channel plate PMTs (MCP-PMTs, GDB-6201) from the NNVT company (North Night Vision Technology Co., Ltd. (NNVT)) were tested. Subsequently, an afterpulse model was built according to the afterpulse time distribution and the probability of occurrence for these two types of PMTs. The average ratio of the total afterpulse charge with a delay between 0.5 \(\upmu\)s and 20 \(\upmu\)s to the primary pulse charge is \(\sim\) 5.7% (13.2%) for the tested MCP-PMTs (dynode-PMTs). The JUNO experiment will deploy 20,012 20-inch PMTs; this study will benefit detector simulation, event reconstruction, and data analysis regarding the JUNO experiment.

The R&D of the Ultra-Fast MCP-PMTs for High Energy Physics

Micro-channel plate photomultiplier tube (MCP-PMT) is a kind of photosensitive device with single photon detection capability and great time resolution, which is also called Fast-PMT (FPMT). The characteristic of MCP makes the MCP-PMT capable of reaching great spatial resolution with multi-anodes. With the experience of successfully R&D of the 20-inch MCP-PMT, the researchers in IHEP are now developing the multi-anodes FPMT with great time resolution and spatial resolution. By now, the single-anode, 2×2 anodes, 4×4 anodes and 8×8 anodes FPMT prototypes have been successfully produced. With the fast-timing test system, the performance of these prototypes has been tested. The best TTS can reach 76 ps for single photoelectron and 15 ps for multi photoelectrons.

Simulation of FPMT with single chip MCP

Micro-channel plate photomultiplier tube (MCP-PMT) is a kind of photosensitive device with single photon detection capability and great time resolution, which is also called Fast-PMT (FPMT). The MCP is the electron multiplier structure and in order to achieve single photon detection, two layers of MCPs are always used together. Due to the new-generation particle accelerators with high energy and luminosity, the time resolution of the detector is more important than single-photon detection capability. The single-chip-FPMT is expected to have a greater time resolution. Based on the CST STUDIO SUITE, the single-chip-FPMT model is built and the time performances including the rise time and transit time spread are compared with the double-chips-FPMT model under the same parameter setting. The results show that the FPMT model with single chip MCP has better time response and resolution than the traditional double-chips-FPMT.

Picosecond Timing Electronics for a DIRC-Like Detector at the Super Tau-Charm Facility

The DIRC-like time-of-flight detector (DTOF) at the Super Tau-Charm Facility (STCF) in China is a Cherenkov light detector that uses the TOF technique to identify charged particles. To achieve the expected target that provides a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\sigma \pi $ </tex-math></inline-formula> /K separation at 2-Ge/c momentum, a single-photon time resolution of better than 50 ps is required, while the contribution from electronics should be lower than 15 ps. To meet the requirements with high channel count integration, the timing electronics using leading-edge discrimination and field-programmable gate array (FPGA)-based time-to-digital converters (TDCs) are employed in the DTOF detector. This article reports the results of the first phase of project where the timing electronics with 128 channels has been constructed and its performance has been evaluated. Including the uncertainty of system clock distribution and synchronization, the intrinsic timing resolution of the electronics is better than 10-ps rms. Taking fast microchannel plate photomultiplier tubes (MCP-PMTs) as Cherenkov photodetectors and adopting time-over-threshold (TOT) measurement for time walk correction, the measured single-photon time resolutions are better than 40-ps rms. The test results confirm that the proposed timing electronics has advantages of high precision and high integration, which is highly demanded in future picosecond timing detectors.

Charged particle identification performance of the TOP counters in Belle II

The Time-Of-Propagation (TOP) counter is a novel ring-imaging Cherenkov detector that primarily consists of a quartz bar radiator, micro-channel plate photomultipliers and front-end readout electronics. These TOP counters are installed in the central region of the Belle II detector to provide the crucial information on the charged particle identification (PID). Here, we present an overview of PID studies in Belle II, with a focus on the performance of the TOP detector. The results presented are from the recently recorded data which show reasonable agreement with the expectations from the simulation studies.

Test-beam demonstration of a TORCH prototype module

The TORCH time-of-flight detector is designed to provide a 15 ps timing resolution for charged particles, resulting in π/K particle identification up to 10 GeV/c momentum over a 10 m flight path. Cherenkov photons, produced in a quartz plate of 10 mm thickness, are focused onto an array of micro-channel plate photomultipliers (MCP-PMTs) which measure the photon arrival times and spatial positions. A half-scale (660 × 1250 × 10 mm3) TORCH demonstrator module has been tested in an 8 GeV/c mixed proton-pion beam at CERN. Customised square MCP-PMTs of active area 53 × 53 mm2 and granularity 64 × 64 pixels have been employed, which have been developed in collaboration with an industrial partner. The single-photon timing performance and photon yields have been measured as a function of beam position in the radiator, giving measurements which are consistent with expectations. The expected performance of TORCH for high luminosity running of the LHCb Upgrade II has been simulated.

Single photon counting performance of the Auratek-Square MCP-PMT

This paper reports on the time resolution of the Auratek-Square MCP-PMT, a multi-anode microchannel plate photomultiplier produced by Photek.When operating as single photon counter at low photon rate and with a single pixel illuminated it shows a transit time spread (jitter) of ∼100 ps FWHM, saturating at high rate, above ∼100 kHz/mm2.The worsening of the timing performance depends on the bias voltage between the photocathode and the MCP input and between the MCP slabs.The charge sharing between neighbouring pixels can become a major crosstalk source if not accounted for, degrading the time resolution to ∼170 ps FWHM when the entire pixel area is illuminated.

New developments from the TORCH R&D project

TORCH is a large-area and high-precision time-of-flight detector, designed to provide charged particle identification over a 2–20GeV/c momentum range. The TORCH detector comprises a 10 mm thick quartz radiator, instrumented with photon detectors, which precisely time and measure the arrival positions of the Cherenkov photons. The photon detectors are micro-channel plate photo-multiplier tubes (MCP-PMTs) comprising a finely segmented anode of 64 × 64 anode pads, electronically ganged into 64 × 8 pixels, over a 53 × 53mm2 area, an excellent intrinsic time resolution of ∼ 30ps, and a long lifetime of up to ≳ 5C/cm2. The current version of the MCP-PMTs used by TORCH have been developed with an industrial partner, Photek Ltd, to satisfy the stringent requirements of the detector. The TORCH R&D programme has successfully demonstrated the detector concept through extensive laboratory and beam tests. A TORCH prototype has been constructed and has yielded encouraging results when exposed to low momentum charged hadrons. Characteristic patterns of Cherenkov photons have been recorded, illustrating the required spatial accuracy and timing resolution of 70 ps per photon. Both laboratory and beam test results are approaching the design goals of the TORCH detector.

R & D of a novel single anode fast timing MCP-PMT

Small-sized Micro-Channel-Plate Photomultiplier Tube (MCP-PMT) has attracted extensive attention in the fields of high-energy physics, medical imaging and biological detection due to its high timing resolution. We report the R&D of a novel single anode MCP-PMT with ultrafast rise time (RT) and transit time spread (TTS), which is called fast-timing PMT (FPMT). In this paper, we mainly optimize the time performance of FPMT by simulation and experiments in three parts, including the gap distance between the MCP and anode, anode structure and high voltage distribution on the electrodes. The results show that by optimizing the anode structure of FPMT, the RT of single-anode FPMT is significantly improved from 1.4 ns to 215 ps and the TTS from 71 ps to 35.8 ps. By optimizing the high voltage distribution of the FPMT, the RT and the TTS are further improved, and the trend of the change in relative time performance with the change in high voltage distribution is analyzed. Finally, a single-anode FPMT with a RT of 153 ps and a TTS of 27.2 ps is realized.

Characterization of the miniPlanacon XPM85112-S-R2D2 MCP-PMT with custom modified backend electronics

We report the results of the measurements of three pieces of the new Photonis miniPLANACON microchannel-plate photomultipliers (MCP-PMTs) intended for use in the demanding environment of the Large Hadron Collider (LHC) beamline as a part of the AFP Time-of-Flight detector. These photomultipliers were modified in cooperation with the manufacturer by using a custom backend and were subjected to numerous tests, with the focus on the rate capability and crosstalk behaviour. We determined that the two of them with a lower MCP resistance are able to operate without significant saturation at an anode current density of 1μA/cm2. These two are, therefore, suitable for the intended use and are currently installed as part of the AFP detector packages.

Digital single-photon-avalanche-diode arrays for time-of-flight Thomson scattering diagnostics.

The collection optics of Thomson scattering systems for plasma devices are designed with maximum possible étendue to keep the required laser energy low. If the spatial resolution along the laser beam is performed by a time-of-flight method, then the detectors, in addition to a large sensitive area, must offer a high frequency bandwidth. Up until now, only microchannel-plate photomultipliers meet these requirements. Here, we investigate the potential use of digital avalanche photodiode arrays operated in the Geiger mode as alternative detectors. In this mode of operation, each array will serve as a fast, sensitive detector. The use of these detectors will lead to significant improvements of the Thomson scattering diagnostic. Most important of these will be a better spatial resolution, down to about 2cm without deconvolution. Furthermore, the lifetime of the detectors will be increased; the detectors will cover the whole blue wing of the scattered spectrum when using a single wavelength laser, and this will enable measurements of electron temperature and density profiles at kHz repetition rates.

Development of a magnetic shield for 20-inch microchannel plate photomultiplier tubes

A newly developed 20-inch photomultiplier tube with good timing response and improved energy resolution uses a microchannel plate instead of traditional dynodes. Thin flexible sheets of high-permeability iron-based amorphous alloy foils encased in thin polyethylene terephthalate layers are used to shield the photomultiplier tube from the geomagnetic field. The work reported in this paper shows that the detection efficiency is increased by 87% on average with the help of this magnetic shield, and the number of secondary electrons is reduced by a factor of 2 for 20-inch MCP-PMT at LHAASO-WCDA.

Investigating machine learning solutions for a 256 channel TCSPC camera with sub-70 ps single photon timing per channel at data rates >10 Gbps

The development of a Time Correlated Single Photon Counting (TCSPC) camera with 256 channels has enabled several applications where single photon sensitivity is crucial, such as LiDAR, Fluorescent Lifetime IMaging (FLIM) and quantum information systems. The microchannel plate-based Multi-Anode Photo-Multiplier Tube (MAPMT) is a 16 × 16 array of 1.656 mm pitch pixels with an active anode area of 26.5 × 26.5 mm2. Each pixel can time single photons with an accuracy of 60 ps rms at a maximum photon rate of 480 KHz.The timing electronics are capable of measuring 120 Mcps, producing huge volumes of data for processing, in the region of 10 Gbps per detector. Limitations in algorithmic data analysis techniques are critical for this application, hence this paper demonstrates a machine learning (ML) model which can determine the photon event coordinates with the objective of processing each one photon per 10 μs. The model applies calibrations for the detector and electronics such as amplitude walk, and charge measurement and channel to channel threshold variation. Optimisation of the model is detailed within the paper, including training hyperparameters, the clustering of coincident events and compression of the model through pruning techniques.The ML model is trained and tested on a simulation of the microchannel plate (MCP) PMT with timing electronics configured for use as a TCSPC camera, utilising charge sharing techniques to further improve the spatial resolution of the detector. Further objectives of the research are to test the model on detector data, allowing assessment on the variance of accuracy between simulated and real data. Beyond this, assessment of the performance of this approach compared to algorithmic approaches and introduction of statistical reasoning of the robustness of the model will be completed.

Picosecond timing of charged particles using the TORCH detector

TORCH is a large-area, high-precision time-of-flight (ToF) detector designed to provide charged-particle identification in the 2–20 GeV/c momentum range. Prompt Cherenkov photons emitted by charged hadrons as they traverse a 10 mm quartz radiator are propagated to the periphery of the detector, where they are focused onto an array of micro-channel plate photomultiplier tubes (MCP-PMTs). The position and arrival times of the photons are used to infer the particles’ time of entry in the radiator, to identify hadrons based on their ToF. The MCP-PMTs were developed with an industrial partner to satisfy the stringent requirements of the TORCH detector. The requirements include a finely segmented anode, excellent time resolution, and a long lifetime. Over an approximately 10 m flight distance, the difference in ToF between a kaon and a pion with 10 GeV/c momentum is 35 ps, leading to a 10–15 ps per track timing resolution requirement. On average 30 photons per hadron are detected, which translates to a single-photon time resolution of 70 ps. The TORCH R&D program aims to demonstrate the validity of the detector concept through laboratory and beam tests, results from which are presented. A timing resolution of 70–100 ps was reached in beam tests, approaching the TORCH design goal. Laboratory timing tests consist of operating the MCP-PMTs coupled to the TORCH readout electronics. A time resolution of 50 ps was measured, meeting the TORCH target timing resolution.

A precision time of flight readout system for the TORCH prototype detector

The TORCH detector provides low-momentum particle identification, combining Time of Flight (TOF) and Cherenkov techniques to achieve charged particle pi/K/p separation between 2–20 GeV/c over a flight distance of 10 m. The measurement requires a timing resolution of 70 ps for single Cherenkov photons. For precision photon detection, customised Micro-Channel Plate Photomultiplier Tubes (MCP-PMTs) with high precision TOF measurement electronics have been developed. The electronics measures time-over-threshold from the MCP-PMT and features a 10-Gigabit Ethernet readout. This paper reports the design and performance of a 5120-channel system which currently instruments a pair of MCP-PMTs, but has the capacity to read out ten customised MCP-PMT devices in the future.