Microchannel Plate Imaging Detectors for High Dynamic Range Applications

Abstract

Microchannel plate (MCP) imaging detectors are widely used in astronomical, biological imaging and remote sensing applications. Photon counting mode imagers with event timing can make use of the high spatial resolution (~10- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$50~\mu \text {m}$ </tex-math></inline-formula> ) and very high time resolution (subnanoseconds) of MCP detectors to enhance the performance of such detectors in dynamic environments (for example airborne surveillance of moving objects, LIDAR, and 3-D topographic imaging). The total information that can be collected is limited by the dynamic range of the detector (cross delay line sensors can support detected photon rates up to ~2 MHz over the entire effective area). The ideal sensor for many applications, such as bright images or fast transient behavior, would combine the desirable attributes of high spatial and time resolution for each detected photon with event rates of 100 MHz or more. A new class of MCPs constructed using atomic layer deposition (ALD) on borosilicate glass microcapillary arrays is providing enhancements towards this goal. The ALD MCP manufacturing process decouples the operational functionalization from the substrate fabrication, opening the door for new resistive layers and high secondary emissive materials. Many improvements over traditional MCPs have been demonstrated, including robust substrates able to withstand high processing temperatures, very low background rates, high stable gains, and low outgassing. Higher global photon counting rates can be supported by ALD MCP detector schemes while greatly improving the instrument lifetime. Additionally, the robustness of these MCPs provide them with surface properties capable of supporting the deposition of a wide range of efficient photocathode materials (III-V), which require high processing temperatures (>500 C), to achieve a high quantum efficiency at near UV to near IR wavelengths. Sealed tube sensors incorporating nano-engineered MCPs can support nonproliferation and remote sensing enabling technologies by advancing the state-of the-art single-photon electro-optical remote sensing detectors. The progress of this effort, including results from the deposition of opaque photocathodes directly onto the front surface of the MCPs and the performance and lifetime characteristics of open faced and seal tube detectors, is reported here.