Conventional Microchannel Plate Research Articles

Simulating the secondary electron avalanche of MCP by Geant4

Nowadays, Microchannel Plate (MCP), as a kind of electron multipliers based on the secondary electron emission, is widely used in many high-sensitive experiments, such as neutrino detection, which require the noise to be as low as possible, while the conventional straight-channel MCP will inevitably have ion feedback, resulting in the sequential after-pulses being the major source of noise. Normally, the problem can be effectively avoided by coupling two straight-channel MCPs in cascade and combining the channels into a “V” shape known as chevron MCPs, but this method is limited by the manufacturing techniques due to the unavoidable gap between the two pieces that will worsen the resolution and peak-to-valley ratio. However, the ion feedback can be inhibited significantly for MCPs with curved channels. Based on Geant4, we investigate how the geometrical parameters of curved-channel MCP influence the gain and get the optimum pore diameter for an MCP to reach the maximum gain with fixed thickness and applied voltage. Additionally, the track-by-track simulation reveals that the average acceleration distance of a secondary electron inside the curved-channel is approximately 20μm when the applied voltage, length-to-diameter ratio and pore diameter are 950 V, 50:1 and 20μm, respectively.

Performance evaluation of a single microchannel plate with large length-to-diameter ratio

The conventional microchannel plate (MCP) detector has found widespread application in various fields. This article focuses on investigating the performance of a single MCP with a large length-to-diameter ratio (L/D) of 80:1, particularly for single electron counting. To enhance MCP performance, alumina with a high secondary electron yield (SEY) is coated onto the MCP using atomic layer deposition (ALD). The SEYs of alumina thin films with different thicknesses are measured using a pulsing electron beam method. The 80:1 L/D MCPs operate in electron counting mode, and the optimal alumina thickness is determined through a comparative study of MCP performance before and after coating. The relationships between maximum SEY, primary electron energy, gain, peak-to-valley ratio (P/V), and pulse height resolution (PHR) are analyzed. After alumina coating, the single 80:1 MCP exhibits improved gain, P/V and PHR. The optimal P/V and PHR of a single MCP as functions of the primary electron energy align with the relationship between the SEY of the alumina coating and the primary electron energy. Additionally, the variation of DC gain with extracted charge is investigated. This article provides valuable insights for parameter selection in achieving the optimal working state of MCP and explores the potential application of single electron counting using a single MCP.

Low-dose TOF-PET based on surface electron production in dielectric laminar MCPs

We present simulations of whole-body low-dose time-of-flight positron emission tomography (TOF-PET) based on the direct surface production (Domurat-Sousa et al., 2023) by 511 keV gamma rays of energetic electrons via the Photo-electric and Compton Effects, eliminating the scintillator and photodetector sub-systems in PET scanners. In Ref. Domurat-Sousa et al. (2023) we described Microchannel Plates (MCP) constructed from thin dielectric laminae containing heavy nuclei such as lead or tungsten (LMCPTM). The laminae surfaces are micro-patterned to form channels, which can then be functionalized to support secondary electron emission in the manner of conventional MCPs. After assembly of the laminae, the channels form the pores of the conversion LMCP. This conversion stage is then followed by a high-gain MCP-based amplification stage, which also can be constructed using the laminar technique, but with pores typical of currently-available large-area MCPs .We have simulated direct conversion using modifications to the TOPAS Geant4-based tool kit. A 20 × 20 × 2.54 cm3 LMCP, composed of 150-micron thick lead-glass laminae, is predicted to have a ≥30% conversion efficiency to a primary electron that penetrates an interior wall of a pore. The subsequent secondary electron shower is largely confined to one pore and can provide high space and time resolutions.In whole-body PET scanners the technique eliminates the scintillator and photodetector subsystems. The consequent absence of a photocathode allows assembly of large arrays at atmospheric pressure and less stringent vacuum requirements, including use of pumped and cycled systems.TOPAS simulations of the Derenzo and XCAT-brain phantoms are presented with dose reductions of factors of 100 and 1000 from a literature benchmark. New applications of PET at a significantly lower radiation dose include routine screening for early detection of pathologies, the use in diagnostics in previously unserved patient populations such as children, and a larger installed facility base in rural and under-served populations, where simpler gamma detectors and lower radiation doses may enable small low-cost portable PET scanners.

A novel bowl-shaped microchannel plate with high electron collection efficiency and good time performance

Abstract Owing to the severe loss of photoelectrons striking at the input electrode of conventional microchannel plate (MCP), photoelectron collection efficiency (CE) of devices based on traditional MCP fluctuates around the MCP open area ratio and cannot make a breakthrough. Photoelectron backscattering from the MCP surface also causes late pulses smearing timing and spatial performance. In this work, a novel bowl-shaped MCP with an open area ratio higher than 90% whose input electrode is coated by a thin film with high secondary electron emission yield (SEY) is proposed as an effective approach to improve CE and suppress late pulses. A three-dimensional MCP-PMT model is developed in CST Studio Suite to evaluate CE and time performance of the bowl-shaped MCP, and compared with the traditional one. Results show that CE of the PMT based on the bowl-shaped MCP is nearly 100% and the delayed pulse is less than 2%. This indicates that good temporal and spatial resolution can be achieved with the bowl-shaped MCP.

A Method for Measuring the Weak Value of Spin for Metastable Atoms.

A method for measuring the weak value of spin for atoms is proposed using a variant of the original Stern–Gerlach apparatus. A full simulation of an experiment for observing the real part of the weak value using the impulsive approximation has been carried out. Our predictions show a displacement of the beam of helium atoms in the metastable state, , that is within the resolution of conventional microchannel plate detectors indicating that this type of experiment is feasible. Our analysis also determines the experimental parameters that will give an accurate determination of the weak value of spin. Preliminary experimental results are shown for helium, neon and argon in the and metastable states, respectively.

Amorphous silicon-based micro-channel plate detectors with high multiplication gain

With their fast response time and a spatial resolution in the range of a few microns, microchannel plates (MCPs) are a prominent choice for the development of detectors with highest resolution standards. Amorphous silicon-based microchannel plates (AMCPs) aim at overcoming the fabrication drawbacks of conventional MCPs and the long dead time of their individual channels. AMCPs are fabricated via plasma deposition and dry reactive ion etching. Using a state-of-the-art dry reactive ion etching process, the aspect ratio, so far limited to a value of 14, could be considerably enhanced with a potential for very high gain values. We show first fabricated AMCP devices and provide an outlook for gain values to be expected based on the fabrication results.

Atomic layer deposition of alternative glass microchannel plates

The technique of atomic layer deposition (ALD) has enabled the development of alternative glass microchannel plates (MCPs) with independently tunable resistive and emissive layers, resulting in excellent thickness uniformity across the large area (20 × 20 cm), high aspect ratio (60:1 L/d) glass substrates. Furthermore, the use of ALD to deposit functional layers allows the optimal substrate material to be selected, such as borosilicate glass, which has many benefits compared to the lead-oxide glass used in conventional MCPs, including increased stability and lifetime, low background noise, mechanical robustness, and larger area (at present up to 400 cm2). Resistively stable, high gain MCPs are demonstrated due to the deposition of uniform ALD resistive and emissive layers on alternative glass microcapillary substrates. The MCP performance characteristics reported include increased stability and lifetime, low background noise (0.04 events cm−2 s−1), and low gain variation (±5%).

Enhanced Detection of High‐Mass Proteins by Using an Active Pixel Detector

Flying high: Application of an active pixel detector with high charge sensitivity to a linear time-of-flight mass spectrometer results in enhanced detection of high-mass proteins (such as Immunoglobulin G; IgG) using a conventional microchannel plate detection system. This technique thus provides a means to extend the mass range of such detectors as well as allowing direct visualization of mass-dependent ion-focusing phenomena.

Modulated electron-multiplied fluorescence lifetime imaging microscope: all-solid-state camera for fluorescence lifetime imaging

We have built an all-solid-state camera that is directly modulated at the pixel level for frequency-domain fluorescence lifetime imaging microscopy (FLIM) measurements. This novel camera eliminates the need for an image intensifier through the use of an application-specific charge coupled device design in a frequency-domain FLIM system. The first stage of evaluation for the camera has been carried out. Camera characteristics such as noise distribution, dark current influence, camera gain, sampling density, sensitivity, linearity of photometric response, and optical transfer function have been studied through experiments. We are able to do lifetime measurement using our modulated, electron-multiplied fluorescence lifetime imaging microscope (MEM-FLIM) camera for various objects, e.g., fluorescein solution, fixed green fluorescent protein (GFP) cells, and GFP-actin stained live cells. A detailed comparison of a conventional microchannel plate (MCP)-based FLIM system and the MEM-FLIM system is presented. The MEM-FLIM camera shows higher resolution and a better image quality. The MEM-FLIM camera provides a new opportunity for performing frequency-domain FLIM.

Operation of superconducting nano-stripline detector (SSLD) mounted on cryogen-free cryostat

Abstract Recently, various types of superconducting detectors have been applied to time-of-flight mass spectrometers (TOF MS) because they can achieve 100% detection efficiency for a wide mass range from atoms to huge biomolecules. The wide mass range coverage is impossible with conventional microchannel plate (MCP) ion detectors. Superconducting stripline detectors (SSLD) that consist of several hundreds of superconducting nanostrips with a width of

Improvement of the detection system in the soft X‐ray absorption spectroscopy

A unique soft X‐ray absorption spectroscopy detection system has been developed for depth profiling analysis of a sample with combined different detection methods: total electron yield, partial electron yield (PEY), and partial fluorescent X‐ray yield. We found that a PEY spectrum measured with a conventional microchannel plate detector is sometimes deformed by inclusion of unexpected fluorescent X‐rays. In this system, a new PEY detector has been designed and constructed to overcome the aforementioned problem. In addition, the developed PEY detector successfully works with higher surface sensitivity and higher signal‐to‐background ratio than the total electron yield method recorded by a sample drain current. Combining this PEY detector with a sample drain current recorder and a silicon drift detector, we have established a useful soft X‐ray absorption spectroscopy detection system to probe surface, interface, and bulk of a sample simultaneously. Copyright © 2011 John Wiley & Sons, Ltd.

Timing resolution of fast neutron and gamma counting with plastic microchannel plates

The performance of novel plastic Microchannel plates (MCPs) with nano-engineered conduction and emission films have been shown to match the performance of conventional glass MCPs, widely used in image intensifying and event counting devices. In this paper we investigate the timing resolution of event detection with a 5 mm-thick polymethyl methacrylate (PMMA) microchannel plate with 50 μm circular pores hexagonally packed at 70 μm center-to-center spacing, which was developed for fast neutron detection. A detector consisting of the PMMA plastic MCP followed by a chevron stack of conventional glass MCPs for event multiplication was used in the timing experiments. The resolution of event counting was measured with Co-60 (1.17, 1.33 MeV γ) source. The timing accuracy was derived from the time difference of event detection with plastic MCP and a detector with liquid scintillator (BC519) coupled to a photomultiplier tube . The measured ∼4 ns FWHM timing accuracy of gamma photon counting agrees well with the results of our predictions performed with the help of a fully 3-dimensonal model of the MCP amplification process. The same model and measurements of photon detection with conventional glass MCPs indicate that substantially better (sub-ns) accuracy can be achieved with smaller pores. Although we could not directly measure the timing accuracy of fast neutron detection with our plastic MCP due to the time of flight limitation of non-monoenergetic source the fast neutron timing resolution should be on the same scale due to the similarity of amplification process once the secondary electrons are produced within a pore.

Surface studies of semiconducting glass using ion beam methods

We have studied the near surface stoichiometry of a semiconducting vanadium phosphate glass for microchannel plate application using MeV ion beam techniques including Rutherford backscattering spectrometry (RBS), particle induced X-ray emission (PIXE) and elastic recoil detection (ERD) analysis. A conventional microchannel plate made of dielectric lead silicate glass with a surface conducting layer was also measured for comparison. The elemental profiles of the two samples showed that the semiconducting glass have a more uniform surface structure as compared to conventional microchannel plate glasses suggesting that the former is more stable. We suggest that our results indicate microchannel plates (MCPs) made of semiconducting glass should have long-term stability and therefore should have longer service life.

Simultaneous measurement of flight time and energy of large matrix-assisted laser desorption ionization ions with a superconducting tunnel junction detector

We evaluated a cryogenically cooled superconducting Nb-Al2O3-Nb tunnel junction (STJ) for use as a molecular ion detector in a matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometer. The STJ responds to ion energy and theoretically should detect large molecular ions with a velocity-independent efficiency approaching 100%. The STJ detector produces pulses whose heights are approximately proportional to ion energy, thus the height of a pulse generated by the impact of a doubly charged ion is about twice the height of a singly charged ion pulse. Measurements were performed by bombarding the STJ with human serum albumin (HSA) (66,000 Da) and immunoglobulin (150,000 Da) ions. We demonstrate that pulse height analysis of STJ signals provides a way to distinguish with good discrimination HSA+ from 2HSA2+, whose flight times are coincident. The rise time of STJ detector pulses allows ion flight times to be determined with a precision better than 200 ns, which is a value smaller than the flight time variation typically observed for large isobaric MALDI ions detected with conventional microchannel plate (MCP) detectors. Deflection plates in the flight tube of the mass spectrometer provided a way to aim ions alternatively at a MCP ion detector.

A pulsed ion deflection system for background reduction in 252Cf-plasma desorption mass spectrometry

The use of an electrostatic particle guide (EPG) for background reduction in a time-of-flight mass spectrometer is described. Operating with reverse polarity, the EPG deflects ions radially from the beam axis, separating the ionic and neutral components of the beam. Use of the deflection EPG in a synchronized pulsed mode with a barrier disk aligned in the center of the beam axis eliminates up to 80% of the spectral background in the molecular ion region of an insulin spectrum obtained by 252Cf-plasma desorption mass spectrometry. The background eliminated is due to the neutral products of metastable fragmentation and to uncorrelated events. Although peak intensities are reduced when the pulsed deflection EPG system is used, the reduction in background achieved is greater, resulting in an overall improvement in peak-to-background ratios of up to a factor of three. A new large-area stop detector designed for use with the pulsed deflection EPG is described. the new hybrid detector, which utilizes the combination of a large (75-mm active diameter) microchannel plate (MCP) and a scintillation detector, provides greater sensitivity for high-mass ions than a conventional MCP chevron detector.

Analysis for an electron source based on microchannel plate principles

An analysis is carried out for the channel output current density of a microchannel plate constructed from a crystalline semiconducting bulk. It is shown that the current density can be increased to the order of 1 A/cm/sup 2/, which is several orders of magnitude higher than that of conventional microchannel plates, allowing its use for cold cathode applications.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Microchannel plate detector for 0.5 MeV gamma rays

To investigate the use of a thick microchannel plate as a converter to detect and locate 511 keV photons, we have performed model calculations to optimize hole size, spacing and glass material. The results indicate a potential for greater than 10% detection efficiency for microchannel plates of 1 cm thickness and 50% lead content, with 75 μm holes spaced on a lattice of 100 μm. Higher efficiency would be achieved with higher lead content. Such detectors would be operated in a low gain mode with a conventional microchannel plate of gain about 10 5 in proximity. This detector system should be capable of millimeter spatial resolution and nanosecond timing accuracy. These results are sufficiently promising that we suggest a small scale prototype be developed to explore applications in physics and in medical imaging.

Operating characteristics of sandwich microchannel plates

A sandwich plate is a novel type of high-gain electron multiplier formed by bonding, in permanent contact, three standard (channel length-to-diameter ratio L/D=40:1) image-intensifier multichannel plates. This geometry has the advantage of mechanical and electrical simplicity when compared with conventional multiplate stacks. An evaluation of sandwich plates for X-ray photon counting is presented. Sandwich plate gain, gain uniformity, pulse height FWHM, dark noise, high-count-rate operation, and X-ray quantum efficiency are compared with previous measurements made with conventional two-stage MCP (microchannel plate) multipliers.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>