Microchannel Plate Photomultiplier Research Articles

Optimizing Parameters of the Fiber-Optic Beam-Loss Monitor for the VEPP-5 Injection Complex

The distributed beam-loss monitor based on the Cherenkov radiation in an optical fiber installed on the e–e+ Injection Complex at the Budker Institute of Nuclear Physics is considered. Monitor parameters are optimized based on a numerical model and experimental data. For a 45-m-long quartz fiber (with a core diameter of 550 μm) and a microchannel plate photomultiplier as a signal detector, a spatial resolution of less than 1 m is achieved. Software for processing photodetector signals, which allows the real-time monitoring of the distribution of beam loss along the entire beam line, is developed.

Precise analysis of the timing performance of Cherenkov-radiator-integrated MCP-PMTs: analytical deconvolution of MCP direct interactions

In order to achieve the ultimate goal of reducing coincidence time resolution (CTR) to 10 ps, thus enabling reconstruction-less positron emission tomography, a Cherenkov-radiator-integrated microchannel plate photomultiplier tube (CRI) reaching CTR of sub-50 ps full width at half maximum (FWHM) has been developed. However, a histogram of time differences between a pair of the CRIs shows undesirable side peaks, which are caused by gamma rays directly interacting with the micro channel plates (MCPs). Such direct interaction events are detrimental to the timing performance of the CRI. In this paper, we demonstrate an analytical method of deconvolving MCP direct interaction events from the timing histogram. Considering the information of the main and the two side peaks, the timing uncertainty caused by the MCP direct interaction events is deconvolved and the CTR of the CRI is analytically investigated. Consequently, the CTR is improved from 41.7 to 40.5 ps FWHM by the deconvolution. It means that a mixture of the Cherenkov radiator events and the MCP direct interaction events contribute to the CTR by a factor of 10 ps. The timing performance of the MCP direct interaction events are also evaluated. The CTR between the two MCPs is found to be 66.2 ps FWHM. This indicates that a photocathode-free radiation detector with high timing performance is possible. Elimination of the photocathode from the detector would make detector construction easier and more robust.

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

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

Status of the TORCH Project

The TORCH time-of-flight detector will provide particle identification between 2–10 GeV/c momentum over a flight distance of 10 m, and is designed for large-area coverage, up to 30 m2. A 15 ps time-of-flight resolution per incident particle is anticipated by measuring the arrival times from Cherenkov photons produced in a synthetic fused silica radiator plate of 10 mm thickness. Customised Micro-Channel Plate Photomultiplier Tube (MCP-PMT) photon detectors of 53 × 53 mm2 active area with a 64 × 64 granularity have been developed with industrial partners. Test-beam studies using both a small-scale TORCH demonstrator and a half-length TORCH module are presented. The desired timing resolution of 70 ps per single photon is close to being achieved.

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.

Status of the PANDA Endcap Disc DIRC project

The PANDA experiment at FAIR near Darmstadt, Germany, is under construction, planned to investigate fundamental questions of hadron physics with a fixed proton target by using an antiproton beam within a momentum range of 1.5 to 15 GeV/c. A novel Cherenkov detector, the Endcap Disc DIRC (EDD), has been developed to separate π± and K± by at least 3 standard deviation up to 4 GeV/c. It will cover the polar angle range of the forward endcap of the PANDA target spectrometer from 5̂ to 22̂. The EDD uses a 2 cm thick fused silica radiator plate with focusing elements at the outer rim and lifetime-enhanced Microchannel-Plate PMTs (MCP-PMTs) as light sensors. The Cherenkov radiator of the EDD consists of four identical independent quadrants, polished with highest precision in order to conserve the internally reflected Cherenkov angle during light propagation. This manuscript confirms basic functionalities of the EDD design and tests of the prototype with particle beams at CERN in 2018.

Simulation of magnetic field effects on the MCP gain

A multi-anode microchannel plate photomultiplier (Ma MCP-PMT) is an appropriate photo sensor for particle identification in high energy physics experiments such as PANDA, Belle II, etc. Since these detectors usually work in a strong magnetic field, the sensors must be immune to the field. In this article, the effects of the magnetic field on the conventional MCP and the atomic layer deposited MCP (ALD-MCP) are studied by simulating the electron multiplication in the microchannel of the MCP . Simulation results show that the gain of conventional MCP-PMTs increases a little before it starts decreasing while the magnetic field is further increasing. We found that the shortening of electronic trajectories and the reduction of secondary electrons mainly contribute to gain variations of a conventional MCP . For the ALD-MCP that usually has higher secondary emission yields, it is found that high re-diffusion secondary electron yields could make it more vulnerable to magnetic fields.

Test-beam studies of a small-scale TORCH time-of-flight demonstrator

TORCH is a time-of-flight detector designed to perform particle identification over the momentum range 2–10 GeV/c for a 10 m flight path. The detector exploits prompt Cherenkov light produced by charged particles traversing a quartz plate of 10mm thickness. Photons are then trapped by total internal reflection and directed onto a detector plane instrumented with customised position-sensitive Micro-Channel Plate Photo-Multiplier Tube (MCP-PMT) detectors. A single-photon timing resolution of 70ps is targeted to achieve the desired separation of pions and kaons, with an expectation of around 30 detected photons per track. Studies of the performance of a small-scale TORCH demonstrator with a radiator of dimensions 120×350×10mm3 have been performed in two test-beam campaigns during November 2017 and June 2018. Single-photon time resolutions ranging from 104.3ps to 114.8ps and 83.8ps to 112.7ps have been achieved for MCP-PMTs with granularity 4 × 64 and 8 × 64 pixels, respectively. Photon yields are measured to be within ∼10% and ∼30% of simulation, respectively. Finally, the outlook for future work with planned improvements is presented.

Timing performance of a Micro-Channel-Plate Photomultiplier Tube

The spatial dependence of the timing performance of the R3809U-50 Micro-Channel-Plate PMT (MCP-PMT) by Hamamatsu was studied in high energy muon beams. Particle position information is provided by a GEM tracker telescope, while timing is measured relative to a second MCP-PMT, identical in construction. In the inner part of the circular active area (radius r<5.5 mm) the time resolution of the two MCP-PMTs combined is better than 10 ps. The signal amplitude decreases in the outer region due to less light reaching the photocathode, resulting in a worse time resolution. The observed radial dependence is in quantitative agreement with a dedicated simulation. With this characterization, the suitability of MCP-PMTs as t0 reference detectors has been validated.

The study of test method of time characteristic for ultra-fast-MCP-PMT

Study of the time characteristics of photomultiplier tube with ultra-fast time characteristics has an important guiding role for the further development of ultra-fast time response microchannel plate photomultiplier tube (FPMT). Based on the VME test system in high-energy physics and picosecond laser with single-photon pulse mode, this manuscript designs a device to test the FPMT with 25 ps system error. The time characteristics of various FPMTs were tested by optimizing the FPMT signal readout anode, the voltage divider structure and voltage division ratio. The intrinsic time lower limit value of the FPMT in the non-single-photon working mode, is proposed to compare and analyze the time resolution of different FPMTs in different working states. After completing various optimized readout anode structural design for the FPMTs, it can be find that the best FPMT prototype in our Lab has the best intrinsic time resolution lower limit of 30 ps.

New large aperture photodetectors for water Cherenkov detectors

New 50cm-diameter photo-detectors based on three different types of amplification systems were developed for future large water Cherenkov detectors. The R12860 PMT, based on a box-and-line dynode, was developed with Hamamatsu Photonics K.K. (Hamamatsu). Its detection efficiency is twice that of a conventional 50 cm PMT, while also improving by a factor two the charge and timing resolutions and being able to resist pressures up to 1.25MPa. A 50 cm hybrid photo-detector (HPD) using an avalanche diode (Hamamatsu, R12850) realized further improvement on the resolutions by the successful development of a preamplifier. It requires higher bias voltage (eight kilovolts), which lead to the development of a built-in power supply or water tight connector. Finally, a 50-cm micro-channel plate PMT (GDB-6203) was developed for water Cherenkov detectors by North Night Vision Technology Co., LTD in China. It is based on the GDB-6201 model, with improved timing performances. The charge resolutions for single photoelectron of the R12860, R12850 and GDB-6203 PMTs were evaluated to be 35%, 15%, and 40% (standard deviation), while the transit time spreads measured for single photoelectrons at a fixed threshold were 4.1, 3.6 and 4.3 nsec (FWHM) respectively. We obtained operational waterproof designs for all those photodetectors.

Investigating microchannel plate PMTs with TOFPET2 multichannel picosecond timing electronics

TOFPET2 is the second-generation design of a high-performance multichannel picosecond timing readout electronics ASIC produced by PETsys Electronics SA, Portugal. Originally developed for time-of-flight positron emission tomography using silicon photomultipliers, in this work we describe an experimental programme to evaluate the performance of TOFPET2 with pixelated microchannel plate (MCP) photomultiplier tube (PMT) detectors.Investigations were performed using various signal input methods; injected electronic stim signals, SiPM photodetectors, a single anode MCP photomultiplier detector and finally imaging with a demountable multi-anode MCP detector using a 16 x 16 pixelated multi-layer ceramic readout. The detector utilised an active anode plus image charge configuration to provide the positive signal pulses required by the electronics.Measurements were undertaken using the PETsys Time-of-Flight ASIC evaluation kit (mark2) operating in single photon counting mode. We present performance results for time resolution, cross channel coincidence time resolution and energy resolution using internal pulse amplitude measurement and time-over-threshold signal paths.Photodetector timing performance was evaluated using a 40 ps wide pulsed laser, operating at single photon level using a temperature stabilised setup within a dark enclosure. Amplitude walk correction was applied using the in-built time-over-threshold output from the TOFPET2 system. Single photon timing resolution of better than 110 FWHM was demonstrated. Preliminary results obtained using signal spread over adjacent pixels of a pixellated anode yield a coincidence timing resolution of ∼87 ps rms.

Deep diffused Avalanche photodiodes for charged particles timing

The upgrades of ATLAS and CMS for the High Luminosity LHC (HL-LHC) highlighted physics objects timing as a tool to resolve primary interactions within a bunch crossing. Since the expected pile-up is around 200, with an r.m.s. time spread of 180ps, a time resolution of about 30ps is needed. The timing detectors will experience a 1-MeV neutron equivalent fluence of about Φeq=1014 and 1015cm−2 for the barrel and end-cap regions, respectively. In this contribution, deep diffused Avalanche Photo Diodes (APDs) produced by Radiation Monitoring Devices are examined as candidate timing detectors for HL-LHC applications. To improve the detector’s timing performance, the APDs are used to directly detect the traversing particles, without a radiator medium where light is produced. Devices with an active area of 8 × 8mm2 were characterized in beam tests. The timing performance and signal properties were measured as a function of position on the detector using a beam telescope and a microchannel plate photomultiplier (MCP-PMT). Devices with an active area of 2 × 2mm2 were used to determine the effects of radiation damage and characterized using a ps pulsed laser. These detectors were irradiated with neutrons up to Φeq=1015cm−2.

Latest improvements of microchannel-plate PMTS

The DIRC detectors of the P̄ANDA experiment at FAIR will use multi-anode MCP-PMTs as photon sensors. After long and extensive R&D work the performance parameters of the recent 2” MCP-PMT models are converging towards the required values. The lifetime of most ALD-coated MCP-PMTs is well surpassing the DIRC requirements with the best tube currently reaching >22 C/cm2 integrated anode charge without aging. The performance of the most advanced MCP-PMTs from PHOTONIS and Hamamatsu fulfill basically all requirements with a highlight being the high detective quantum efficiency (DQE) of almost 30% for the PHOTONIS 9002108. The improvements of the latest MCP-PMT models compared to former tubes are emphasized in this paper. In addition, some performance features of a recently developed 2” MCP-PMT by Photek Ltd are presented and discussed.

Front-end electronic readout system for the Belle II imaging Time-Of-Propagation detector

The Time-Of-Propagation detector is a Cherenkov particle identification detector based on quartz radiator bars for the Belle II experiment at the SuperKEKB electron-positron collider. The purpose of the detector is to identify the type of charged hadrons produced in electron-positron collisions, and requires a single photon timing resolution below 100 picoseconds. A novel front-end electronic system was designed, built, and integrated to acquire data from the 8192 microchannel plate photomultiplier tube channels in the detector. Waveform sampling of these analog signals is done by switched-capacitor array application-specific integrated circuits. The processes of triggering, digitization of windows of interest, readout, and data transfer to the Belle II data acquisition system are managed by Xilinx Zynq-7000 programmable system on a chip devices.

Performance of the Belle II imaging Time-Of-Propagation (iTOP) detector in first collisions

The iTOP detector is a novel Cherenkov detector developed for barrel particle identification at Belle II, an upgrade of the previous Belle experiment at KEK. The SuperKEKB accelerator, an upgrade of KEKB, collides electrons and positrons with a design luminosity of 8⋅1035cm−2s−1. In order to exploit the high collision rate, Belle II has a trigger frequency of up to 30 kHz. The iTOP detector uses quartz bars as source of Cherenkov photons. The photons are reflected inside the bars until they hit photomultipliers at one end. The spatial distribution and precise arrival times of the detected photons are used to reconstruct the Cherenkov angle. The photon arrival times have to be measured with a resolution better than 100 ps to achieve a good pion–kaon separation. Microchannel plate photomultipliers together with dedicated high-speed electronics for 2.7 GSa/s waveform sampling are used to achieve this timing resolution. The iTOP detector consists of 16 modules with 512 channels each, in total the detector has 8192 channels. First collisions were recorded in spring 2018. A phase of physics operation with a ramp up to full luminosity starts in March 2019. The design of the iTOP detector is shown and experience and results from initial operation are discussed together with an outlook on future running conditions.

Gated liquid scintillator detector for neutron time of flight measurements in a gas-puff Z-pinch experiment.

Detection of secondary D(t, n)4He neutrons produced when thin argon or krypton gas shells implode on a deuterium gas target is a very challenging task because the secondary neutron yield is a small fraction of the primary neutron yield and because the implosion is often accompanied by an intense hard X-ray burst. We built a large volume neutron time of flight (nTOF) detector using liquid scintillator (xylene solvent with small quantities of wavelength shifting PPO + bis-MSB fluors) in an attempt to increase the detection probability for secondary neutrons in our staged Z-pinch experiments at the 1 MA Zebra pulsed-power generator. Two fast, gated microchannel plate photomultiplier tubes detect the light created in 21 liters of liquid. The hard X-rays were successfully suppressed in the recorded nTOF traces, but we found no evidence of secondary neutrons. The signal quality from the primary D(d, n)3He neutrons was higher compared to the signal quality from a plastic scintillator nTOF, thus providing a more reliable estimate of the deuterium ion temperature at the pinch stagnation time. Cross-calibration with a silver activation detector enables standalone neutron yield measurement.

Particle identification in the Belle II experiment

The Belle II experiment integrates two dedicated particle identification (PID) subdetectors for pion/kaon separation. The Aerogel Ring Image Cherenkov (ARICH) detector is a forward region PID detector based on two layers of aerogel read out by hybrid avalanche photo detectors. The Time of Propagation (TOP) detector is a novel Cherenkov barrel PID system built for the Belle II detector upgrade based on quartz radiator bars read out by Micro-Channel Plate PMTs. The readout electronics of the TOP system are built around a switched capacitor array waveform sampling ASIC operating at 2.7 GSa/s. Acquired waveforms are processed in real time in the front-end electronics, extracting the individual timing of detected photons to better than 100 ps. This contribution presents the concept of the Belle II particle identification systems with a focus on the current status of commissioning, calibration and operation of the Belle II TOP detector.

The Jiangmen Underground Neutrino Observatory (JUNO)

The Jiangmen Underground Neutrino Observatory (JUNO) is an experiment under construction in China with the primary goal of determining the neutrino mass hierarchy (MH) with reactor anti-neutrinos. The JUNO detector system consists of a central detector, an active veto system and a calibration system. The central detector is a 35 m diameter transparent acrylic sphere containing a 20 kton liquid scintillator neutrino target. A primary photo-detection system consisting of 18,000 large (20” diameter) dynode and micro-channel plate photomultipliers surrounds the central detector. A second interlaced photo-detection system is made of 25,600 small (3” diameter) photomultipliers working in the single photo-electron regime for the reactor anti-neutrino detection. The detector is designed to achieve an unprecedented energy resolution of 3% @1MeV and an absolute energy scale uncertainty better than 1%. A veto system, consisting of a water Cherenkov detector and a top tracker, is used help maximally remove cosmogenic backgrounds. Due to its unprecedented scale and precision, JUNO will be an exceptional multipurpose detector with a rich physics program in neutrino oscillation, geo-neutrinos, astrophysical neutrinos and the search for physics beyond the Standard Model (sterile neutrinos, dark matter, proton decay and others).

Time resolution of the SiPM-NUV3S

Abstract Silicon photomultipliers (SiPMs) have become an interesting alternative to conventional and micro-channel plate photomultipliers, proving to be a very good option for Cherenkov light based time-of-flight detectors. The important characteristic for this application is the intrinsic time resolution for a wide range of wavelengths (from below 250 nm up to about 600 nm). We present a study of the time resolution of two SiPMs: a 3 × 3 mm2 FBK SiPM-NUV3S and a 3.5 × 3.5 mm2 STMicroelectronics prototype SiPM. The measurement was performed for two representative wavelengths (280 nm and 420 nm) under the variation of SiPM overvoltage and light intensity . The measured transition time spread (TTS) of the devices was (285 ± 9) ps (FBK) and (154 ± 20) ps (STM). The time resolution dropped with increasing mean number of photoelectrons ( N pe ) as σ TTS N pe − 1 2 with saturation observed for high N pe . The obtained best time resolutions were (8 ± 1) ps and (4 ± 1) ps for the FBK and STM SiPM respectively at N pe of the order of 1 0 6 for 420 nm photons. The results for the two wavelengths were comparable, with 280 nm photons providing worse results at very high illumination.