Abstract
Measurements in our laboratory have recently shown that the
pulse quantum yield (counts/photon) of Csl x-ray photocathodes, measured
near grazing incidence, depends on the linear polarization state of
the incident beam. These results have implications both for the fundamental
understanding ofthe x-ray photoeffect and, since Csl is well known
as a cathode material of high (unpolarized) quantum efficiency in the 0.1
to 1.0 keV band, for the development of high-throughput astronomical
x-ray polarimetry. This paper, concentrating on the latter topic, describes
the practical accommodation of a photoemission polarimeter at (or near)
the focus of a satellite x-ray telescope. Problems of device format, instrumental
polarization, and data compression are discussed with reference
to the Composite X-ray Polarimeter recently proposed for the European
Space Agency High Throughput Spectroscopy mission (XMM). Examples
of the sensitivity of this instrument are given. In the second part of the
paper, some recent laboratory measurements are presented. These concern
the variation in the number of x-ray photoelectrons with the polarimetric
azimuth of a Csl cathode.
