Pin-Hole Camera Investigation of Electron Beams

Electron beams produced b y low- and moderate-perveance Pierce-type electron guns have been investigated by means of a pin-hole aperture. Data are presented showing the current density distribution and transverse velocity distribution of electrons at various points in the beam. The thermal velocity distribution is Maxwellian, with a width corresponding to the cathode temperature modified by the geometry of the flow. The transverse velocity distribution also reveals aberrations in the electron gun which has led to improved gun designs and a large improvement in the focusing of electron beams. The theoretical background for this work is given in a companion paper.