Large format atomic layer deposited microchannel plates for photon counting image sensors

Abstract

For future astronomical applications we have been developing cross-strip anodes with electronic readouts integrated with large format (≥ 50 mm) sealed tubes and photocathodes covering the UV and optical regimes. These large format devices will be important for the next generation of moderate and large NASA astrophysics instruments under study (e.g. LUVOIR, HabEx, CETUS), as well as ground based focal plane instruments. Microchannel plates (MCPs) are used as electron multipliers in these devices. They amplify the detected photon signal to a charge cloud on order of a million electrons, which is then sensed through the imaging readout. A recent enhancement comes by way of incorporating resistive and secondary emissive layers to borosilicate capillary arrays utilizing atomic layer deposition (ALD) processing techniques. The borosilicate substrates are more robust than traditional MCPs, allowing for large formats (20 x 20 cm), while also supporting 10-micron pores (capillaries). We have successfully integrated this type of MCP into 50 mm aperture sealed tube devices for the first time. These devices show stable, uniform gain, and can provide very good event timing accuracy. Spatial resolution of better than 20 microns can be achieved with these MCPs, providing more than 2k x 2k resolution elements for a 50mm device. Compared with the current generation of MCPs, the ALDborosilicate MCPs have shown an order of magnitude increase in lifetime stability gain retention within the vacuum sealed device and long-term preservation of the photocathode efficiency.