The considered source of triode type produces intense radial converging electron beam for irradiation of cylindrical targets. As an electron emitter an explosive plasma cathode is used. The role of initial transverse velocities of electrons, defocusing effect of the controlling grid, the beam self-magnetic field, electron and ion emission from the controlling grid, backscattering of electrons and ion flow from the target is analyzed. Conditions for achieving required electron beam parameters (the electron kinetic energy - 120 keV, the beam energy density on the target 40 J/cm² on a maximum possible length of the target surface) were determined.