  To explore possibilities for X-ray flux monitoring on optical elements
electrical responses of silicon and diamond single crystals and that of an
X-ray mirror were studied under exposure to hard X-rays in a single electrode
configuration in ambient air. To introduce flux monitoring as a non-invasive
capability a platinum electrode was deposited on a small unexposed portion of
the entrance surface of the crystals while for the X-ray mirror the entire
mirror surface served as an electrode. It was found that the electrical
responses are affected by photoemission and photoionization of the surrounding
air. The influence of these factors was quantified using estimations of total
electron yield and the ionization current. It is shown that both phenomena can
be used for the non-invasive monitoring of hard X-ray flux on the optical
elements. Relevant limits of applicability such as detection sensitivity and
charge collection efficiency are identified and discussed.
