Study of the electron beam diagnostics and beam waist

Abstract

In this work a study is made of the factors affecting electron gun design and the diagnostics of the beam extracted from the gun. The use of both Pierce and shaping electrodes is necessary in order to produce thin intense beams. A theoretical study is made to find the beam envelope equation and the factors affecting the radius at the beam waist and its distance from the gun exit in a field free space region. The variations of the beam current, the beam perveance, the beam profile and transverse beam emittance with the extracting voltage are studied. The increase of the anode voltage is found to decrease beam perveance, beam waist and beam emittance. The position and radius of the beam waist is found to depend on the beam perveance and beam slope at the gun exit aperture. In order to produce beams with minimum beam emittance and beam waist would necessitate working with higher extracting voltage.