Abstract
We present measurements of the quantum detection efficiency (QDE) of potassium chloride, applied directly to the surface of a microchannel plate (MCP), over the 44–1460-Å wavelength range. The contributions of the photocathode material in the channels, and on the interchannel web, to the QDE have been determined. Two broad peaks in the QDE centered at λ ≅ 500 Å and λ ≅ 900 Å are apparent, the former with ~40% peak QDE and the latter with ~30% peak QDE. The photoelectric threshold is observed at λ ~ 1400 Å, and there is a narrow QDE minimum at λ 670 Å, which correlates with 2× the band gap energy for KCl. The angular variation of the QDE from 0 to 35° to the channel axis has also been examined. We describe a simple QDE model and show that its predictions are in accord with our QDE measurements. Assessment of the stability of KCl shows that there was no significant degradation of the QDE at wavelengths of ≤ 1066 Å during a 4-month storage period in dry nitrogen with a limited exposure to air.
© 1988 Optical Society of America
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