We present measurements of the quantum efficiency of opaque CsI photocathodes applied directly onto the surface of microchannel plates in open face detectors and sealed tube devices. The quantum efficiency as a function of the radiation input angle (0° to 40°) and wavelength (44Å to 1800Å) has been studied with and without the use of a photoelectron collection field. These measurements provide confirmation of recent published results of high quantum efficiencies (>60%) at 100Å. We also present new results for the region 250Å to 1800Å which show quantum efficiences higher (>30%) than have been achieved to date. The contribution to the quantum efficiency of a photoelectron collection field is shown to be significant, particularly where the photon absorption coefficient is high. The fabrication of CsI photocathodes is described and the quantum efficiency is discussed in relation to the reflection of incident radiation, cathode absorption coefficient and photoelectron escape probability. Assessments of the spatial uniformity of the quantum efficiency are also presented.

Date Published: 10 December 1986
PDF: 9 pages
Proc. SPIE 0687, Ultraviolet Technology, (10 December 1986); doi: 10.1117/12.936550

Published in SPIE Proceedings Vol. 0687:
Ultraviolet Technology
Robert E. Huffman, Editor(s)