The optimal characteristics of picosecond electron beams obtained in a vacuum diode with cathodes made of tungsten, graphite, copper and samarium were determined experimentally and theoretically (using the electromagnetic relativistic PiC CARAT code) for excitation of strongly non-equilibrium states in the metal. Beam divergence has been estimated by his imprint on the dosimetric film CDP. The diameter of the imprint of the beam obtained in the diode with a copper cathode and L_gap = 2 mm at the level of half the amplitude of intensity of blackening of the film after one and six shots was, accordingly, d₁ = 1.9 and d₆ = 4.42 ± 0.01 mm. Among the cathode materials used, the best results correspond to the graphite cathode: it gives the highest value of the pulse amplitude of the beam current, and the smallest value of its half-width and the maximum value of the electron energy corresponding to the center of gravity of their energy distribution. However, the copper cathode, in principle, is not inferior to the graphite cathode, since the values < W > = 213 ± 6.54 keV are obtained at lower values of the length of the interval and the amplitude of the voltage pulse: L_gap = 2 mm and U_peak = –(142 ± 2) kV, respectively.