Microchannel Plate Gain Research Articles

Single electron charge spectra of 8-inch high-collection-efficiency MCP-PMTs

The microchannel plates (MCP) can serve as the electron amplifier of the photomultiplier tubes (PMT). The collection efficiency of the newly developed 8-inch MCP-PMT for the Jinping Neutrino Experiment is maximized thanks to the high-secondary-emission coating. The resulting single electron response (SER) charge distribution deviates from the Gaussian distribution in large charge regions. To understand the nature of the jumbo-charged SER, we designed a voltage-division experiment to quantify the dependence of the MCP gain on the energy of incident electrons. Combining the relationship with the Furman probabilistic model, we reproduced the SER charge spectra by introducing an additional amplification stage on the input electrode of the first MCP. Our results favor a Gamma-Tweedie mixture to describe the SER charge spectra of the MCP-PMTs.

Spatial extension of the transient gain drop in a microchannel plate for a single-pulse irradiation

It is widely recognized that a microchannel plate gain drops temporarily after a particle initiates an electron avalanche and that a large amount of charge is extracted from the channel. Electron multiplication is expected to deplete the charges from the microchannel and produce depleted charges (wall charges), and this gain drop is known to persist until charges are replenished. In addition, it was reported that a gain drop occurs not only in the activated channels, where the electrons are multiplied, but also in the surrounding channels. A proposed mechanism for this phenomenon is suggested that the wall charges in the activated channels change the electric field in the surrounding channels, which affects the electron multiplications. In this study, the spatial extent of the gain drop of a chevron microchannel plate detector was evaluated by measuring gains as a function of distance from an activated channel. The experiment used two ultraviolet pulses with different beam sizes, which initially activated one channel and the six neighboring channels with carefully focused laser light, and then applied another light pulse to the surrounding 900 μm × 30 μm area. The gain of each channel was measured using a charge-coupled device camera, and the change in gain as a function of the output charge for the laser pulse was analyzed. A gain drop of 20% was observed at a channel located 110 μm far from the initial activated channel when the output charge was 4 pC. The obtained relationship between the radius of gain drop area and the output charge for the laser pulse was in good agreement with that predicted from the transverse electric field due to the wall charges by computational analysis.

Enhancing stability of microchannel plates (MCPs) through freeze-drying method

The crystallization and gain decrease of microchannel plates (MCPs) have a significant impact on the dark noise and working life of optoelectronic devices. By employing a freeze-drying method instead of high-temperature drying during MCP manufacturing, stability can be improved. Freeze-drying at low temperatures (−100 °C) mitigates chemical reactions between potassium (K) and oxygen (O2) or water (H2O) in the secondary emission layer, reducing crystallization during production and storage. Furthermore, freeze-drying eliminates the need for organic solvents, which can lead to carbon (C) element pollution on the MCP surface. Minimizing C element pollution is beneficial in reducing unstable “gas gain” and attenuating MCP gain during electron scrubing. Long-term storage tests demonstrate that freeze-dried MCPs exhibit over 20% reduction in crystallization and more than 10% decrease in gain loss rates. These findings highlight freeze-drying as an effective approach to enhance MCP stability, resulting in photomultiplier tubes (PMTs) with lower dark counting rates and higher gains.

High performance cross strip imaging readout Planacon sealed tubes

Sealed tube microchannel plate (MCP) detectors have provided a valuable platform for high time resolution photon counting detectors. Specifically, electronic readout MCP based sensors have been used as photon counting, imaging, event time tagging detectors for astronomy, time resolved biological imaging, imaging LIDAR, Cherenkov (RICH), scintillation detection, and neutron imaging. For future initiatives we have been developing novel atomic layer deposited MCPs, UV photocathodes and cross strip (XS) readouts for sealed tube detectors. Novel, atomic layer deposited MCPs can replace standard MCPs, providing enhanced gain stability with reduced intrinsic background and lower gamma ray sensitivity. Additionally, XS readouts provide a compact package to achieve high resolution imaging of single photon positions at low MCP gain. The Photonis Planacon is a commercial sealed tube detector (∼50 mm area) which we have modified to incorporate these novel technologies and demonstrate their performance and robustness.

Design of MIRA, a low-noise pixelated ASIC for the readout of micro-channel plates

We present the design of the first prototype of MIRA (MIcro-channel plate Readout ASIC) that has been designed to read out Micro-Channel Plates (MCP), in particular for UV spectroscopy. MIRA will be able to detect the cloud of electrons generated by each photon interacting with the MCP, sustaining high local and global count rates to fully exploit the MCP intrinsic dynamic range with low dead time. The main rationale that guided the electronics design is the reduction of the input Equivalent Noise Charge (ENC) in order to allow operations with lower MCP gain, thus improving its lifetime, crucial aspect for long missions in space. MIRA features two selectable analog processing times, 133 ns or 280 ns (i.e. fast mode or slow mode), granting a count rate per pixel of 100 kcps. Moreover, it shows an Equivalent Noise Charge ENC . A spatial resolution of 35 μm and an operation with zero dead time, due to the readout, are targeted. The low noise, high count rate and high spatial resolution requirements are expected by keeping a compact pixel size (35 μm × 35 μm) for a total of 32 × 32 pixels in a 2 mm × 2 mm ASIC area. In this work, the ASIC design is described.

Numerical Simulation Study on Gain Nonlinearity of Microchannel Plate in Photomultiplier Tube

Microchannel plate-photomultiplier tubes (MCP-PMTs) with high dynamic ranges and strong outputs are still challenges for the future inertial confinement fusion (ICF) studies, aiming at detecting the large-scale intensities of the radiation pulses. In this article, to investigate the influence factors of the gain nonlinearity causing high-linearity limits of the MCP-PMTs, 3-D microchannel plate (MCP) channel models were built in computer simulation technology (CST) Particle Studio. The Monte Carlo and particle-in-cell methods were carried out to simulate the electron cascade processes in the channels of the MCPs. The dependences of MCP gain nonlinearity on the number of incident electrons, operating voltage, and secondary electron emission (SEE) yield properties were studied. The gains obtained by the simulations for the conventional one-stage and two-stage MCPs are in good agreement with the available experimental data, which verifies the reliabilities of the 3-D MCP models. The simulation results show that the gain of the MCP single channel decreases as the number of incident electrons increases due to the space charge effects. The higher the operating voltage and SEE yield of the MCP, the faster the gain deteriorates. To mitigate the gain saturation effect of MCP single channels, a novel structural design of MCP-PMTs has been proposed by adjusting the design of the MCP chevron pair. A significant improvement in the output pulse peak can be obtained.

Proximity-gated X-ray framing camera with gain uniformity

A novel proximity gated microchannel plate (MCP) framing camera has been designed and tested. The camera system consists of two basic components with a traveling wave microstrip photocathode gated proximity focusing X-ray image tube framing and electrical control system. The voltage of the phosphor screen, the strobe pulse of the MCP and the bias voltage of the MCP are all provided by the electronic control unit. The photocathode of image-converted tube consists of Au.Four line cathodes with a width of 12 mm and an interval of 4 mm are deposited onto the illuminated side of MCP. The camera's temporal record length is ∼1.5 ns. When the cathode is applied by a pulse with full width at half maximum of 190 ps and amplitude of -2.5 kV with -100 V bias, the temporal resolution is measured to be ∼62 ps. The gain uniformity of the cathode was characterized using a short X-ray pulse produced by a laser beam focused on a copper target. The results show that the MCP gain decreases by about 28% along the pulse direction, while the gain change perpendicular to the strip direction is within 5%.

Performance of microchannel plate based detectors for

We present the results of Monte Carlo simulations of the microchannel plate (MCP) response to x rays in the 250eV to 25 keV energy range as a function of both x-ray energy and impact angle and their comparisons with the experimental results from the X8A beamline at the National Synchrotron Light Source at Brookhaven National Laboratory. Incoming x rays interact with the lead glass of the microchannel plate, producing photoelectrons. Transport of the photoelectrons is neglected in this model, and it is assumed that photoelectrons deposit all their energy at the point they are created. This deposition leads to the generation of many secondary electrons, some fraction of which diffuse to the MCP pore surface where they can initiate secondary electron cascades in the pore under an external voltage bias. X-ray penetration through multiple MCP pore walls is increasingly important above 5 keV, and the effect of this penetration on MCP performance is studied. In agreement with past measurements, we find that the dependence of MCP sensitivity with angle relative to the pore bias changes from a cotangent dependence to angular independence and then proceeds to a secant dependence as the x-ray energy increases. We also find that with the increasing x-ray energy, the MCP gain sensitivity as a function of bias voltage decreases. The simulations also demonstrate that for x rays incident normal to the MCP surface, spatial resolution shows little dependence on the x-ray energy but degrades with the increasing x-ray energy as the angle of incidence relative to the surface normal increases. This agrees with experimental measurements. Simulation studies have also been completed for MCPs gated with a subnanosecond voltage pulse. We find that the optical gate profile width increases as the x-ray energy is increased above 5 keV, a consequence of increased x-ray penetration at energies >5 keV. Simulations of the pulsed dynamic range show that the dynamic range varies between ∼100 and 1000 depending on x-ray energy and peak voltage.

Evaluation of microchannel plate gain drops caused by high ion fluxes in time-of-flight mass spectrometry: A novel evaluation method using a multi-turn time-of-flight mass spectrometer.

Use of a two-stage microchannel plate (MCP) detector is common in time-of-flight (TOF) mass spectrometry because it shows excellent time resolution with sufficient gains. However, the gain drops significantly when the detector detects intense ion fluxes, such as matrix ions, by matrix-assisted laser desorption/ionization mass spectrometry. As a result, significant ion signals corresponding to analytes, such as proteins, are hidden, thereby hampering the mass spectral interpretation. However, details of this phenomenon have not previously been investigated using ions because of the lack of suitable measurement methods and apparatus. Thus, we herein report a novel method for controlling the TOF of two selected ions, as a function of time differences between each other using a multi-turn TOF mass spectrometer. This method involves the use of an isotope cluster of ions that fly in a figure-of-eight orbit and the extraction of an ion at a given lap number. A series of time differences (∆t) between two ions in a TOF spectrum can be generated using this method. We evaluated the time constants of gain recovery after high ion-flux detection for two sets of two-stage MCP detectors to obtain values of 1,600 and 180 μs for channel plate resistances of 500 and 71 MΩ, respectively. The obtained time constants from the gains determined at various values of ∆t were 0.48 and 0.38 fold (for 500 and 71 MΩ, respectively) of the values suggested from the channel plate resistance and capacitance.

The Study of Microchannel Plate Gain Using SIMION

Microchannel plates (MCP) are widely used for particle detection. The gain of chevron MCPs is related to geometrical parameters, but no study has been done through SIMION simulation. The purpose of this study is to model a chevron MCP and its secondary emission process using SIMION and determine the relationship between microchannel plate gain, voltage, channel bias angle, and diameter. Two geometry files simulated MCP electric field and shape, and a Lua program simulated secondary emission. Simulation results showed that MCP gain is proportional to voltage, angles between 5 and 15 degrees maximize gain, and gain is inversely proportional to the diameter. This study accurately simulates a chevron MCP and yields the relationship between gain, voltage, channel bias angle, and diameter. Further studies are needed to simulate electron trajectories for improved precision.

Changes of Alkali Metal Ions and Alkaline Earth Metal Ions on The Surface of Lead Silicate Glasses

Lead silicate glasses are currently the most employed glasses for microchannel plates (MCP) and other applications. X-ray photoelectron spectroscopy was used to determine the changes of alkali metal ions and alkaline earth metal ions on glasses surface during hydrogen reduction. The results showed that the chemical states of alkali metal ions and alkaline earth metal ions did not change. However, the content of these metal ions increases, which is beneficial to secondary electron emission yield of lead silicate glasses and the gain of MCPs.

Position-dependent microchannel plate gain correction in Rosetta's ROSINA/DFMS mass spectrometer

Mass spectrometers that rely on microchannel plate (MCP) detectors age when they are used intensively. The ageing process is due to a reduction of the MCP gain as ions repeatedly bombard the MCP, leading to a reduction of the secondary electron yield of an impacting ion and to a reduction of the electron amplification within the MCP pores. MCP gain therefore is both time- and position-dependent. This is particularly true for the Double Focusing Mass Spectrometer DFMS, part of the ROSINA instrument, embarked on the European Space Agency's Rosetta spacecraft that studied comet 67P/Churyumov-Gerasimenko continuously for over more than 2 years. A position-dependent gain correction technique is developed here. A detailed assessment of the technique demonstrates that improper treatment of this position-dependent gain can lead to misleading results and false conclusions, especially regarding less abundant species whose mass peak signature overlaps with peaks of abundant species. The correction technique presented here avoids such problems, especially in the situation where detector ageing is significant and uneven across the detector. It is also able to explain why all recorded mass peaks have a nearly symmetric double Gaussian shape, despite the strong variations in the position-dependent gain.

Thermal characterization of resistance and gain of microchannel plate (MCP) detectors for the JENI experiment

The microchannel plate (MCP) has been used for decades as a photon, electron and atoms detector in most of the space instruments dedicated for X-rays, energetic neutral atoms and charged particle imaging. The deep-space missions, as near-future ESA Jupiter Icy moon Explorer (JUICE) mission, expect very low temperature conditions on the destination orbit. Since instruments are usually calibrated on the ground under the “room” temperature, it is very important to know the variation of the detectors’ properties with temperature. The resistance and the gain of MCP detectors, dedicated for the Jovian Energetic Neutrals and Ions (JENI) sensor as part of the Particle Environment Package (PEP) instrument onboard JUICE, were measured as a function of temperature at INTRASPEC TECHNOLOGIES, Toulouse, France over the temperature range of − 50 to + 50 °C and at the CALIPSO-3 facility of the Institut de Recherche en Astrophysique et Planetologie (IRAP), Toulouse, France over the temperature range of − 25 to + 25 °C using samples from PHOTONIS France and PHOTONIS USA. Depending on how the resistance of an MCP detector behaves with temperature, it is possible to properly size a high voltage source or, conversely, to choose a glass technology according to the resistance range required for the MCP detector or their minimum operational bias strip current in relation to the extracted current due to the particle counts. Moreover, since the environment of Jupiter is very severe, the sensors of the PEP package instrument onboard JUICE will operate in the presence of high-energy particles which represent a noise source for them despite the shielding of the instrument against radiation. In particular, the background radiation in the Jovian environment represents a crucial issue for the JENI MCP detectors whose gain can be degraded prematurely if too much of charge is extracted from them. Our measurements show that the gain variation of JENI MCP detectors depends on their characteristics, which is an important result that can be used to optimize their gain performance and lifetime. We also show that the resistance of the JENI MCP detectors increases when the temperature decreases and is influenced by the MCP-resistive heating.

X-Ray Imager With a 20 mm Width Microstrip Line for the Extreme Ultraviolet Spectrometer

A time-resolved x-ray imager based on the gated microchannel plate (MCP) technology is reported. The single MCP microstrip line with a width of 20 mm is formed to improve the spatial resolving capability. The microstrip line cathode coated on the MCP is driven by four gating pulses simultaneously. Each gating pulse has an amplitude of -1.7 kV and a width of 160 ps. The temporal resolution of the imager is demonstrated by utilizing an ultraviolet (UV) laser pulse and a fiber bunch optics. A measured temporal resolution of 68 ps is achieved, while the photocathode is applied with the four gating pulses plus a -200 V DC bias. Moreover, the gain uniformity of the imager is charactered at the Shenguang-III (SG-III) laser facility. An x-ray with 3 ns width is used to irradiate the microstrip line cathode uniformly. Then, the gating pulses travel along the microstrip line cathode with a gradually reduced amplitude, which lead to a decreasing gain. The measured results show that the MCP gain is dropped to 30% along the gating pulse traveling direction, and a perpendicular gain variation of 4% is obtained.

Effect of Hydrogen Reduction on Properties of Lead Silicate Glass for Microchannel Plates

Hydrogen reduction process is an important process in the produce of microchannel plates (MCPs). The influence of hydrogen reduction temperature and time on the properties of lead silicate glass and MCPs were investigated by analyzing the spectral transmission, XRD, surface resistivity of the lead silicate glass and electron gain and bulk resistance of MCPs. Results show that the metal crystal of lead has been produced on the surface of glass after hydrogen reduction. With the increase of the reduction temperature or the reduction time, the transmittance and surface resistivity decreases. Meanwhile, the bulk resistance has the same changing trend. The best reduction temperature and time are available for the MCPs prepared by the lead silicate glass.

Extending the dynamic range of microchannel plate detectors using charge-integration-based counting

Microchannel plate (MCP) detectors provide a mechanism to produce a measureable current pulse (∼0.1 mA over several nanoseconds) when stimulated by a single incident particle or photon. Reductions of the device's amplification factor (i.e., gain) due to high incident particle flux can lead to significant degradation of detection system performance. Here we develop a parameterized model for the variation of MCP gain with incident flux. This model provides a framework with which to quantify the limits of high-flux MCP operation. We then compare the predictions of this model to laboratory measurements of an MCP's response to a pulsed charged particle beam. Finally, we demonstrate that through integration of the MCP output current in pulsed operation, effective count rates up to ∼1 GHz can be achieved, more than an order of magnitude increase over conventional counting techniques used for spaceflight applications.

Microchannel plate lifetime experiment for the DIS and DES instruments on the Magnetospheric Multiscale Mission

The stability of microchannel plate (MCP) gain with time impacts the success of long-term space plasma missions that use such detectors. Gain stability is of particular importance for the Fast Plasma Investigation (FPI) suite on NASA's Magnetospheric Multiscale (MMS) mission, which operates 64 independent MCP assemblies. Due to this massive number of sensors, there was not sufficient time to fully precondition all flight detectors prior to MMS launch. Therefore, an understanding of the change of MCP gain with time is vital to ensure quality FPI performance. We have conducted lifetime experiments with flight-grade FPI-like MCP assemblies for both ion and electron detectors. These experiments demonstrate that MCP gain stabilizes after≈1.0 C/cm2 has been extracted from the plates. Based on these results, the FPI MCPs could potentially operate for 20+ years on-orbit.

Gain regulation of the microchannel plate system

We demonstrate two two-dimension array of microchannels plates and study the electrical performance of the microchannels plate to further investigate the mechanism of the electron multiplication. • This paper is actually the research on electrical properties of microchannel plate, namely, changes in the relationship between the resistance, gain with work voltage can provide to technical guide for the designers who intend to use microchannel plate as electron multiplier. • The gain of any microchannel plate can determine the application field of MCP electron multipliers. • It is revealed that the system gain rises as the voltage of microchannel plate increases, and can be improved also by varying input current properly. • The output current saturation phenomena of MCP are pointed out in this paper. • We qualitatively explain the physical mechanism of saturation phenomenon. • A possible mechanism of output current saturation phenomenon is the space-charge effect, the channel wall charging and high resistance. The gain of microchannel plate (MCP) is the key index to the signal multiplication property of photomultiplier system. To investigate the signal multiplication mechanism and the electrical property thoroughly, we demonstrated two microchannel plate systems and investigated the cooperative effect from resistance, voltage and gain, which were triggered by ultraviolet signal. Electron amplification is demonstrated and analyzed by current measurement technique. It is revealed that the system gain rises as the voltage of microchannel plate increases, and can be improved also by varying input current properly. And MCP demonstrates gain saturation which depends on the effectiveness of the charge replenishment in the channel walls. These investigations help us understand the gain regulation of the voltage controlled microchannel plate and qualitatively explain the physical mechanism of saturation phenomenon. The results may be important for improving the system resolution of particle detection and image intensifier based on MCP.

Determination of the laser intensity applied to a Ta witness plate from the measured x-ray signal using a pulsed micro-channel plate detector

The laser intensity distribution at the surface of a high-Z material, such as Ta, can be deduced from imaging the self-emission of the produced x-ray spot using suitable calibration data. This paper presents a calibration method which uses the measured x-ray emissions from laser spots of different intensities hitting a Ta witness plate. The x-ray emission is measured with a micro-channel plate (MCP) based x-ray framing camera plus filters. Data from different positions on one MCP strip or from different MCP assemblies are normalized to each other using a standard candle laser beam spot at ∼1 × 1014 W/cm2 intensity. The distribution of the resulting dataset agrees with results from a pseudo spectroscopic model for laser intensities between 4 and 15 × 1013 W/cm2 . The model is then used to determine the absolute scaling factor between the experimental results from assemblies using two different x-ray filters. The data and model method also allows unique calibration factors for each MCP system and each MCP gain to be compared. We also present simulation results investigating alternate witness plate materials (Ag, Eu and Au).

The Gain and Time Characteristics of Microchannel Plates in Various Channel Geometries

Microchannel plates (MCPs) are widely used as electron, ion, and X-ray detectors. The gain factor and time resolution of the MCP are strongly dependent on its operating and geometry parameters (applied voltage, length-to-diameter ratio, bias angle, and electrode penetration depth). Measurements about this dependence are sparse and do not cover the full range of the parameters. In this paper, 3-D single channel models are developed in computer simulation technology studio suit to systematically and comprehensively calculate the MCP gain and time resolution for various operating and geometry parameters. Furman secondaries electron emission model is employed in our simulation. Simulated result of the gain versus bias voltage is validated by the available experimental data. Finally, geometry parameters of $L = 373.6~\mu \text{m}$ , $D =10~\mu \text{m}$ , $h_{{{\text {in}}}}=h_{{{\text {out}}}}= 5~\mu \text{m}$ , and $\theta =12^{\circ }$ are proposed to optimize the MCP performances. Simulation results show that the gain, mean transit time, and transit time spread of the optimized MCP are expected to reach 128 012, 128 ps and 19 ps at the applied voltage of 1000 V.