Influence of the microchannel plate and anode gap parameters on the spatial resolution of an image intensifier

Citation

Hoenderken, T. H., Hagen, C. W., Barth, J. E., Kruit, P., & Nützel, G. O. (2001). Influence of the microchannel plate and anode gap parameters on the spatial resolution of an image intensifier. Journal of Vacuum Science & Technology B, 19, 108. 

Keywords

• Image intensifiers
• Spatial resolution
• Microchannel plate (MCP)
• Anode gap
• End spoiling
• Electron trajectories
• Energy distribution
• Lens effect
• Modulation Transfer Function (MTF)
• Simulation
• Experiment

Brief

The spatial resolution of microchannel plate image intensifiers is heavily influenced by the nonuniform electric field at the end spoiling, especially for low-energy electrons. 

Summary

This article, published in 2001 by T. H. Hoenderken et al. in the Journal of Vacuum Science & Technology B, investigates how the spatial resolution of an image intensifier is affected by the parameters of the microchannel plate (MCP) and anode gap.

The authors use a Monte-Carlo simulation to model the trajectories of 20,000 electrons through a channel, end-spoiling, and anode gap. The study finds that the nonuniform electric field at the end-spoiling region creates a lensing effect, significantly impacting the spatial resolution. This lensing effect is particularly detrimental to low-energy electrons generated at the end-spoiling.

The simulations show that the best spatial resolution is achieved with a small anode gap (300 μm) and low anode voltage (3 kV). Increasing the end-spoiling penetration depth from 10 μm to 20 μm improves the resolution, particularly at high spatial frequencies, while further increases show no additional benefit. Additionally, reducing the channel diameter considerably enhances resolution.

Experimental measurements validate the simulation results, confirming the significant influence of the MCP and anode gap on spatial resolution. The study concludes that the lensing effect at the end-spoiling plays a dominant role in determining the electron spot size on the anode, especially for smaller anode gaps. This lensing effect, overlooked in previous studies, challenges the assumption that a monochromatic beam of low-energy electrons results in a higher modulation transfer function (MTF), a measure of spatial resolution. The authors suggest that improving image intensifier resolution requires mitigating the nonuniform electric field near the end-spoiling and/or minimizing the contribution of electrons emitted from this region.

Origin: https://psec.uchicago.edu/library/microchannel_plates/Hoenderken,%20JVST%20B19%20(2001).pdf