A novel high-power (10 MW) sub-millisecond electron beam is developed for injection into the open (linear) plasma devices. The beam is produced by extraction of electrons from a plasma of pulsed arc discharge in hydrogen. The beam is extracted and accelerated with multiaperture diode-type electron optical system with 241 small round apertures, which are arranged in a hexagon-al pattern. The injector prototype was installed into the end plasma tank of GOL-3 multiple mirror trap and tested to produce an electron beam with up to 100 keV electron energy, about 100 A total beam current and 0.7 ms or longer pulse duration. In a series of preliminary experiments the electron beam was injected into the GOL-3 plasma chamber filled with deuterium gas with a density of 1014-1015cm-3 and transported in a corrugated magnetic field (⟨B⟩ up to 1.4 T) along the trap at a distance of 12 m.