Electron flow in the conventional X-ray tube

The electron-flow pattern in a conventional X-ray tube is analyzed with a ray-tracing computer program. It is shown that the emission is temperature-limited (TL) in a forward-facing sector, and space-charge-limited (SCL) in sectors on each side. The angle of the TL sector varies directly with the anode voltage and inversely with the filament temperature, generally in the range 90°-160°. The lines of the focal spot are shown to be direct images of points near the 2 and 4 o\´clock positions on the cathode, while the lines are inverted images of points near 1 and 5 o\´clock.