CONSERVATION OF SPACE-CHARGE-DOMINATED BEAM EMITTANCE IN A STRONG NONLINEAR FOCUSING FIELD

Beam dynamics in a nonlinear uniform focusing channel is studied from the viewpoint of keeping emittance of a high current beam. Conservatio n of beam emittance is treated as a problem of proper matching of the beam with the uniform focusing channel. To obtain matching conditions for a beam with an arbitrary distribution function, it is necessary to accept that the potential of the external focusing field contains hig her-order terms than quadratic. The solution for the external potentia l is obtained from the stationary Vlasov's equation for the beam distr ibution function and Poisson's equation for the electrostatic beam pot ential. An analytical approach is illustrated by results of a particle -in-cell simulation.