[en] To improve the ion beam focusing and to simplify the design of an ion gun consisting of a coaxially positioned conducting cathode and anode, the anode inner surface, that faces the cathode, having hydrogen-containing portions, the ion gun cathode is suggested to be made in the form of a straight solenoid. When connecting a power source to the cathode, the current passing across the solenoid creates an insulating magnetic field. As the maximum magnetic field intensity is attained, a high-voltage positive pulse is supplied to the anode. This results in the generation of the anode plasma which serves as the ion source. The ions accelerated in the anode-cathode gap pass between the cathode coils and move in the direction toward the gun axis. As the ions are conducting the zero magnetic flux, they are focused either to a line, in the case of a cylindrical solenoid, or to a point, in the case of a spherical one