Abstract: A electron emission cathode includes an emitter having an apex from which electrons are emitted. The emitter is attached to a heating filament at a junction and extends from the junction both forward toward the apex and rearward. A reservoir of material that lowers the work function of the emitter is positioned on the rearward extending portion of the emitter. By positioning the reservoir on the rearward extending portion, the reservoir can be positioned sufficiently far from the junction to reduce its temperature and thereby greatly increase the useful life, of the emitter without adversely affected the emission characteristics of the source.

Abstract: In order to achieve suitable positional resolution for an angular scan in Grazing Exit X-ray Fluorescence (GEXRF), the sample (2) should be irradiated with a small spot (14). Consequently, the fluorescent radiation yield is low so that the duration of a measurement is comparatively long. In order to mitigate this drawback, the invention proposes the use of an analyzing X-ray mirror (16) having a line focus (22) extending perpendicularly to the sample surface (4). The line focus (22) coincides with a line-shaped PSD (24), so that every position on the PSD corresponds to a given height on the mirror, which height itself corresponds to a given take-off angle of the fluorescent radiation relative to the sample surface. Excellent positional resolution and an attractive fluorescent radiation yield are obtained by irradiating the sample by way of a focused electron beam.