Charged particle intense beam dynamics in an RF-injector

Results of calculation of electron beam dynamics in the injector of a high-current linear accelerator which is a part of the VEPP-4, are presented. The macroparticle model in combination with the finite element method was used to calculate beam dynamics. The linear accelerator witn π/2 oscillation acceleration rate 5 MeV/m and operating wave length 70 cm. Diode gun, the front wall grid of the first RF resonator serving as its anode, injects in the resonator a beam with the energy of about 200 keV, pulse current 100-200 A and diameter 3 cm. Beam energy at the outlet of the first resonator is about 2 MeV. Results of calculations have shown that beam dynamics depends considerably on such factors as effect of metal walls of the resonator on the beam intrinsic field near the front wall of the resonator, nonlinear character of RF-fields change of the resonator over the radius. The geometry of the injection resonator, which ensures the maximum current transmission through the accelerating sfructure, is found. The possibility of producing maximum pulse current of about 300 A (when the pulse duration is 20 ns) in Ihe linear accelerator