In this study, we experimentally evaluated the quantum efficiency (QE) enhancement and storage stability of cesium iodide (CsI) coated microchannel plates (MCPs), which are widely used as high-sensitivity detectors for extreme ultraviolet (EUV) observations. A 42 mm diameter MCP was partially coated with CsI and irradiated with a common EUV light source to directly compare the relative QE and gain between the CsI-coated and uncoated (bare) regions. To simulate pre-launch storage conditions, we also investigated QE variations after storing the MCP in low-vacuum (10-1000 Pa) and dry nitrogen environments for up to 30 days. The results demonstrated that the CsI coating yielded an increase by a factor of 100 in QE at wavelengths above 100 nm, with no significant degradation observed during vacuum-sealed storage. Furthermore, the observed reduction in gain over time could be compensated by fine-tuning the applied high voltage, posing no operational issue. These findings demonstrate that CsI-coated MCPs maintain high QE during extended storage and are, therefore, suitable for future small-scale space missions.
Yoshioka et al. (Fri,) studied this question.