CHARACTERISTICS OF AN INTENSE ELECTRON BEAM FOCUSED BY A SOLENOID LENS

Characteristics of a 1.5 MV, 2～3 kA electron beam from a LIA focused by a short solenoid lens are studied.Limits to the minimum spot size, imposed by space-charge effect, emittance and spherical and chromatic aberrations of the lens, are investigated by means of a five-order radial trajectory equation, the K-V envelope equation and an analytical method.The experimental configuration and parameters are optimized. Experimentally, a spot diameter of 5～6 mm （enclosing 90% of the electrons）is obtained. The experimental results are in agreement with the computations.