A novel type of electron gun is described in which a spherically symmetric field is simulated. The structure is hemispherical: The inner hemisphere is a space‐charge‐limited emitter, and the outer concentric hemisphere is the anode. The hemispheres are terminated by a plane electrode with a radial potential variation designed to match the field between concentric spheres. This field is known from a new numerical solution to Poisson's equation. The energy distribution produced by the gun is measured and compared with the calculated distribution.