Microchannel Plate Photomultiplier Research Articles

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.

An ultrafast X-ray scintillating detector made of ZnO(Ga)

Owing to its ultrafast scintillation, quite high light yield, strong radiation resistance, and non-deliquescence, ZnO(Ga) is a highly promising choice for an ultrafast X-ray detector. Because of its high deposition rate, good production repeatability and strong adhesive force, reactive magnetron sputtering was used to produce a ZnO(Ga) crystal on a quartz glass substrate, after the production conditions were optimized. The fluorescence lifetime of the sample was 173 ps. An ultrafast X-ray scintillating detector, equipped with a fast microchannel plate (MCP) photomultiplier tube (PMT), was developed and the X-ray tests show a signal full width at half maximum (FWHM) of only 385.5 ps. Moreover, derivation from the previous measurement shows the ZnO(Ga) has an ultrafast time response (FWHM = 355.1 ps) and a high light yield (14740 photons/MeV).

Model-based design evaluation of a compact, high-efficiency neutron scatter camera

This paper presents the model-based design and evaluation of an instrument that estimates incident neutron direction using the kinematics of neutron scattering by hydrogen-1 nuclei in an organic scintillator. The instrument design uses a single, nearly contiguous volume of organic scintillator that is internally subdivided only as necessary to create optically isolated pillars, i.e., long, narrow parallelepipeds of organic scintillator. Scintillation light emitted in a given pillar is confined to that pillar by a combination of total internal reflection and a specular reflector applied to the four sides of the pillar transverse to its long axis. The scintillation light is collected at each end of the pillar using a photodetector, e.g., a microchannel plate photomultiplier (MCP-PM) or a silicon photomultiplier (SiPM). In this optically segmented design, the (x,y) position of scintillation light emission (where the x and y coordinates are transverse to the long axis of the pillars) is estimated as the pillar’s (x,y) position in the scintillator “block”, and the z-position (the position along the pillar’s long axis) is estimated from the amplitude and relative timing of the signals produced by the photodetectors at each end of the pillar. The neutron’s incident direction and energy is estimated from the (x,y,z)-positions of two sequential neutron–proton scattering interactions in the scintillator block using elastic scatter kinematics. For proton recoils greater than 1 MeV, we show that the (x,y,z)-position of neutron–proton scattering can be estimated with < 1 cm root-mean-squared [RMS] error and the proton recoil energy can be estimated with < 50 keV RMS error by fitting the photodetectors’ response time history to models of optical photon transport within the scintillator pillars. Finally, we evaluate several alternative designs of this proposed single-volume scatter camera made of pillars of plastic scintillator (SVSC-PiPS), studying the effect of pillar dimensions, scintillator material (EJ-204, EJ-232Q and stilbene), and photodetector (MCP-PM vs. SiPM) response vs. time. We demonstrate that the most precise estimates of incident neutron direction and energy can be obtained using a combination of scintillator material with high luminosity and a photodetector with a narrow impulse response. Specifically, we conclude that an SVSC-PiPS constructed using EJ-204 (a high luminosity plastic scintillator) and an MCP-PM will produce the most precise estimates of incident neutron direction and energy.

Recent results with lifetime enhanced microchannel-plate photomultipliers

The favored photon sensors for the DIRC (detection of internally reflected Cherenkov light) detectors at the P̄ANDA (Anti-proton Annihilation at Darmstadt) experiment at FAIR (Facility for anti-proton and ion research) are micro-channel-plate photomultipliers (MCP-PMTs). The main problem until a few years ago was the limited lifetime of the MCP-PMTs caused by a rapid decrease in quantum efficiency (QE) of the photo cathode (PC) with increasing integrated anode charge (IAC). These limitations are overcome by applying an atomic layer deposition (ALD) coating on the MCPs, as recently done by PHOTONIS and Hamamatsu. During the last years’ tests of lifetime enhanced MCP-PMTs were performed and their results were compared. For this, the QE was measured in dependence of the IAC as function of the wavelength and position dependent across the PC. The best performing tubes show a lifetime increase compared to not enhanced devices by a factor >50 with an IAC >13C∕cm2. Additionally, performance results of new 2 inch Hamamatsu tubes and a new high QE PHOTONIS tube are presented.

Photoelectron backscattering in the microchannel plate photomultiplier tube

The late pulse occurring in photomultiplier tubes (PMTs) is attributed to photoelectron backscattering. The small effective open area of microchannel plates (MCPs) increases the probability of photoelectrons bouncing on the front surface of MCPs and aggravates late pulses. In this work, a three-dimensional MCP-PMT model is developed in CST particle studio, a powerful electromagnetic field simulation program, to evaluate the effects of secondary emission yield (SEY) property of the MCP input facet and electric field on the photoelectron backscattering. Timing properties and the number of collected electrons are extracted without smearing due to electronic noise and finite pulse width. Results predict that the collection efficiency (CE) and the time performance can be improved by coating the MCP Nickel–Chromium input electrode with a high SEY material and operating in a proper photocathode-MCP bias voltage.

Status of the TORCH time-of-flight detector

The TORCH time-of-flight detector is designed for large-area coverage, up to 30 m2, to provide particle identification between 2–10 GeV/c momentum over a flight distance of 10 m. The arrival times from Cherenkov photons produced within a quartz radiator plate of 10 mm thickness are combined to achieve a 15 ps time-of-flight resolution per incident particle. Micro-Channel Plate Photomultiplier Tube (MCP-PMT) detectors of 53 × 53 mm2 active area have been developed with industrial partners for the TORCH application. The MCP-PMT is read out using charge division to give a 128 × 8 effective granularity. Laboratory results of development MCP-PMTs will be described, and testbeam studies using a small-scale TORCH prototype module will be presented.

Microchannel plates phototubes in high magnetic field

Microchannel plate photomultiplier tubes (MCP PMT) can work in a high magnetic field and have an excellent time resolution. The influence of the magnetic fields up to 4 T on the parameters of several MCP PMTs of different designs was investigated. PMTs with two, three and four MCPs were tested in magnetic fields. The tested samples have different diameters of MCP pores: 3.5, 6, 8 and 10 microns. Dependencies of the time resolution, the gain and the photoelectron collection efficiency on the magnetic field are presented below.

Monte Carlo study of the coincidence resolving time of a liquid xenon PET scanner, using Cherenkov radiation

In this paper we use detailed Monte Carlo simulations to demonstrate that liquid xenon (LXe) can be used to build a Cherenkov-based TOF-PET, with an intrinsic coincidence resolving time (CRT) in the vicinity of 10 ps. This extraordinary performance is due to three facts: a) the abundant emission of Cherenkov photons by liquid xenon; b) the fact that LXe is transparent to Cherenkov light; and c) the fact that the fastest photons in LXe have wavelengths higher than 300 nm, therefore making it possible to separate the detection of scintillation and Cherenkov light. The CRT in a Cherenkov LXe TOF-PET detector is, therefore, dominated by the resolution (time jitter) introduced by the photosensors and the electronics. However, we show that for sufficiently fast photosensors (e.g, an overall 40 ps jitter, which can be achieved by current micro-channel plate photomultipliers) the overall CRT varies between 30 and 55 ps, depending on the detection efficiency. This is still one order of magnitude better than commercial CRT devices and improves by a factor 3 the best CRT obtained with small laboratory prototypes.

The PANDA DIRC detectors at FAIR

The PANDA detector at the international accelerator Facility for Antiproton and Ion Research in Europe (FAIR) addresses fundamental questions of hadron physics. An excellent hadronic particle identification (PID) will be accomplished by two DIRC (Detection of Internally Reflected Cherenkov light) counters in the target spectrometer. The design for the barrel region covering polar angles between 22̂ to 140̂ is based on the successful BABAR DIRC with several key improvements, such as fast photon timing and a compact imaging region. The novel Endcap Disc DIRC will cover the smaller forward angles between 5̂ (10̂) to 22̂ in the vertical (horizontal) direction. Both DIRC counters will use lifetime-enhanced microchannel plate PMTs for photon detection in combination with fast readout electronics. Geant4 simulations and tests with several prototypes at various beam facilities have been used to evaluate the designs and validate the expected PID performance of both PANDA DIRC counters.

Measurement of the photoelectron collection efficiency in MCP PMT

A method of direct measurement of the photoelectron collection efficiency in microchannel plate photomultiplier tubes (MCP PMT) has been developed. The method was verified by testing a PMT with conventional dynode system. The measurement accuracy of 5% was achieved. Large number of MCP PMTs produced in Novosibirsk (Russia) was tested.

The Belle II imaging Time-of-Propagation (iTOP) detector

High precision flavor physics measurements are an essential complement to the direct searches for new physics at the LHC ATLAS and CMS experiments. Such measurements will be performed using the upgraded Belle II detector that will take data at the SuperKEKB accelerator. With 40x the luminosity of KEKB, the detector systems must operate efficiently at much higher rates than the original Belle detector. A central element of the upgrade is the barrel particle identification system. Belle II has built and installed an imaging-Time-of-Propagation (iTOP) detector. The iTOP uses quartz optics as Cherenkov radiators. The photons are transported down the quartz bars via total internal reflection with a spherical mirror at the forward end to reflect photons to the backward end where they are imaged onto an array of segmented Micro-Channel Plate Photo-Multiplier Tubes (MCP-PMTs). The system is read out using giga-samples per second waveform sampling Application-Specific Integrated Circuits (ASICs). The combined timing and spatial distribution of the photons for each event are used to determine particle species. This paper provides an overview of the iTOP system.

Extension of the MCP-PMT lifetime

A micro-channel-plate photomultiplier tube (MCP-PMT) is an excellent photon sensor which has a time resolution better than 50ps. However the lifetime of the photocathode is a major problem of using it under a high background. We developed a square shape multi-anode MCP-PMT for the Belle II TOP counter, and succeeded in extending its lifetime significantly by more than one order of magnitude. It was achieved by adopting an atomic layer deposition coating on the MCP and by applying some processes in the production to reduce the residual gas on the MCP. Due to a dead time after the micro-channel fires, degradation of the MCP-PMT performance under a high background is another concern. It was examined for four MCP-PMTs of different MCP resistances. It was found that the gain and efficiency drops at a background hit rate above 1MHz/anode, and the transit time spread degrades above ∼200kHz/anode independently of the MCP resistance.

The TORCH time-of-flight detector for particle identification and photon vertex association

TORCH (Time Of internally Reflected CHerenkov light) is a novel time-of-flight detector, designed to provide π /K/p particle identification up to 0∼ 1 GeV/c momentum and beyond. To achieve this, a time resolution of ∼ 15 ps combining information from 0∼ 3 detected photons is required over a 10 m flight path. Large areas can be covered with TORCH, nominally up to 30 m2. One such application is for the LHCb experiment, to complement the particle identification capabilities of its RICH detectors. TORCH has a DIRC-like construction with 10 mm-thick synthetic amorphous fused-silica plates as a radiator. Cherenkov photons propagate by total internal reflection to the plate edges and there are focussed onto an array of position-sensitive photodetectors. Custom-built micro-channel plate photo-multipliers (MCP-PMTs) are being developed in collaboration with industry to provide the lifetime, granularity and time resolution to meet the TORCH specifications. In the present paper, laboratory tests of the MCP-PMTs developed for TORCH and its readout electronics are presented. Test beam measurements of a prototype TORCH detector in a low-momentum mixed beam of pions and protons are highlighted. Time resolutions for individual photons approaching 100 ps is achieved, after correction for dispersion effects in the quartz medium. In addition to the particle identification capabilities, the high-precision timing information that TORCH provides could be used at the high-luminosity LHC to associate high-energy photons with the correct primary interaction vertex amongst the many expected.

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

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

A novel ZVS high voltage power supply for micro-channel plate photomultiplier tubes

A novel resonant high voltage power supply (HVPS) with zero voltage switching (ZVS), to reduce the voltage stress on switching devices and improve conversion efficiency, is proposed. The proposed HVPS includes a drive circuit, a transformer, several voltage multiplying circuits, and a regulator circuit. The HVPS contains several secondary windings that can be precisely regulated. The proposed HVPS performed better than the traditional resistor voltage divider, which requires replacing matching resistors resulting in resistor dispersibility in the Micro-Channel Plate (MCP). The equivalent circuit of the proposed HVPS was established and the operational principle analyzed. The entire switching element can achieve ZVS, which was validated by a simulation and experiments. The properties of this HVPS were tested including minimum power loss (240mW), maximum power loss (1W) and conversion efficiency (85%). The results of this research are that the proposed HVPS was suitable for driving the micro-channel plate photomultiplier tube (MCP-PMT). It was therefore adopted to test the MCP-PMT, which will be used in Daya Bay reactor neutrino experiment II in China.

Performance study of the fast timing Cherenkov detector based on a microchannel plate PMT

Prototype of the fast timing Cherenkov detector, applicable in high-energy collider experiments, has been developed basing on the modified Planacon XP85012 MCP-PMT and fused silica radiators. We present the reasons and description of the MCP-PMT modification, timing and amplitude characteristics of the prototype including the summary of the detector’s response on particle hits at oblique angles and MCP-PMT performance at high illumination rates.

Recent developments with microchannel-plate PMTs

Microchannel-plate (MCP) PMTs are the favored photon sensors for the DIRC detectors of the PANDA experiment at FAIR. Until recently the main drawback of MCP-PMTs were serious aging effects which led to a limited lifetime due to a rapidly decreasing quantum efficiency (QE) of the photo cathode (PC) as the integrated anode charge (IAC) increased. In the latest models of PHOTONIS and Hamamatsu an innovative atomic layer deposition (ALD) technique is applied to overcome these limitations. During the last five years comprehensive aging tests with ALD coated MCP-PMTs were performed and the results were compared to tubes treated with other techniques. The QE in dependence of the IAC was measured as a function of the wavelength and the position across the PC. For the best performing tubes the lifetime improvement in comparison to the older MCP-PMTs is a factor of >50 based on an IAC of meanwhile >10C/cm2. In addition, the performance results of a new 2-in. ALD coated MCP-PMT prototype from Hamamatsu with a very high position resolution (128×6anode pixels) is presented and the first conclusions from investigations concerning the PC aging mechanism will be discussed.

Impulse responses of visible phototubes used in National Ignition Facility neutron time of flight diagnostics.

Neutron-induced visible scintillation in neutron time of flight (NToF) diagnostics at the National Ignition Facility (NIF) is measured with 40 mm single stage micro-channel plate photomultipliers and a 40 mm vacuum photodiode, outside the neutron line of sight. In NIF experiments with 14 MeV neutron yields above Y > 10 × 1015 these tubes are configured to deliver of order 1 nC of charge in the nominally 5 ns NToF into a 50 Ω load. We have examined a number of 40 mm tubes manufactured by Photek Ltd. of St. Leonards on Sea, UK, to determine possible changes in the instrument impulse response as a function of signal charge delivered in 1 ns. Precision NToF measurements at approximately 20 m require that we characterize changes in the impulse response moments to <40 ps for the first central moment and ∼2% rms for the square root of the second central moment with ∼500 ps value. Detailed results are presented for three different diode configurations.

Analogue saturation limit of single and double 10 mm microchannel plate photomultiplier tubes

Photek are a well-established supplier of microchannel plate (MCP) photomultiplier tubes (PMTs) to the inertial confinement fusion community. The analogue signals produced at the major inertial confinement fusion facilities cover many orders of magnitude, therefore understanding the upper saturation limit of MCP-PMTs to large low rate signals takes on a high importance. Here we present a study of a single and a double MCP-PMT with 10 mm diameter active area. The saturation was studied for a range of optical pulse widths from 4 ns to 100 ns and at a range of electron gain values: 103 to 104 for the single and 104 to 106 for the double. We have shown that the saturation level of ∼1.2 nC depends only on the integrated charge of the pulse and is independent of pulse width and gain over this range, but that the level of charge available in deep saturation is proportional to the operating gain.

MCP PMT with high time response and linear output current for neutron time-of-flight detectors

A microchannel plate (MCP) photomultiplier tube (PMT) with a subnanosecond time response and a high linear output current has been developed. PMT is designed for detection of weak pulses of radiation in UV-, visible and nearer-IR ranges and can be used in neutron time-of-flight (nTOF) detectors in experiments on laser compression of thermonuclear fuel. The results of measurements of MCP PMT main parameters are presented: photocathode spectral sensitivity, gain, maximum linear output current, and time response.