On the Role of Secondary Electrons in the Beam Plasma Formation

We show experimentally for the first time that if a negatively-biased metal target is irradiated by a continuous electron beam, the efficiency of beam plasma generation increases significantly due to additional ionization of the gas by secondary electrons emitted from the target. This effect was discovered by a spatial separation of a true-beam plasma, and secondary plasma created solely by secondary electrons from the target. This separation was organized by irradiating the target with a beam incident on target at a certain angle. Using a target with a negative potential allows increasing by 50-100% the beam plasma density at a constant electron beam current. This indicates an increase in the beam energy utilization efficiency.