Microchannel plate (MCP) is well known as the core component of image intensifiers and particle detectors. Atomic Layer Deposition (ALD), a powerful and precise thin film deposition technique, has been applied to improve the performance of MCPs by surface modification. In this study, ALD processes for both secondary electron emission (SEE) coatings and resistive coatings on MCPs has been investigated. Al2O3 films were deposited by ALD on traditional MCPs as SEE layers, and aluminum-doped zinc oxide (AZO) films were deposited on white MCPs (MCPs without firing hydrogen) as the resistive layer. The SEM results show good uniformity of the ALD layers inside MCP channels. We have made a preliminary exploration on the relationship between gain of MCP, thickness of SEE layer and reaction temperature. The gain of traditional MCPs with aspect ratio of 39:1 increases from 3200 to 14000 (@Bias Voltage = 800V) by coating a SEE layer under a specific condition. Additionally, the aging experiment result indicates that the liftime of MCPs (from 0.15C to 0.29C) has been extended. The resistance of MCPs can be tuned by changing the doping ratio and thickness of resistive layer. We have successfully found several ALD processes for the resistive coatings, which can control the resistance in the suitable range of MCPs (about 100MΩ@800V). The volt-ampere characteristics of MCP with resistive layer is approximately exponential function relation, which differ with traditional MCPs.
Electron scrubbing is an effective method of degassing the microchannel plate(MCP). In the present work, we investigated the effect of electron scrubbing on MCP through characterizing the gain and dynamic range during and after the electron scrubbing. The gain of the MCP decreases to 25-30% of the initial gain with 28μA·h of electron scrubbing. The dynamic range can be broadened by electron scrubbing. The lower limit of the dynamic range of the MCP limited by the dark current of the test system does not change significantly and the upper limit of the dynamic response range is increased. The ratio of the upper limit before and after scrubbing is inversely proportional to that of the gain. The reasons for variation of gain and dynamic range were discussed, to provide reference for improving the performance of microchannel plate.
Micro-channel plate (MCP) is a two dimensional arrays of microscopic channel charge particle multiplier. Silicate composition and hydrogen reduction are keys to determine surface morphology of micro-channel wall in MCP. In this paper, lead silicate glass micro-channel plates in two different cesium contents (0at%, 0.5at%) and two different hydrogen reduction temperatures (400°C,450°C) were present. The nano-scale morphology, elements content and chemical states of microporous wall surface treated under different alkaline compositions and reduction conditions was investigated by Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS), respectively. Meanwhile, the electrical characterizations of MCP, including the bulk resistance, electron gain and the density of dark current, were measured in a Vacuum Photoelectron Imaging Test Facility (VPIT).The results indicated that the granular phase occurred on the surface of microporous wall and diffuses in bulk glass is an aggregate of Pb atom derived from the reduction of Pb2+. In micro-channel plate, the electron gain and bulk resistance were mainly correlated to particle size and distribution, the density of dark current (DDC) went up with the increasing root-mean-square roughness (RMS) on the microporous wall surface. Adding cesiums improved the size of Pb atomic aggregation, lowered the relative concentration of [Pb] reduced from Pb2+ and decreased the total roughness of micro-channel wall surface, leading a higher bulk resistance, a lower electron gain and a less dark current. Increasing hydrogen reduction temperature also improved the size of Pb atomic aggregation, but enhanced the relative concentration of [Pb] and enlarged the total roughness of micro-channel wall surface, leading a higher bulk resistance, a lower electron gain and a larger dark current. The reasons for the difference of electrical characteristics were discussed.
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