INTENSE ELECTRON-BEAM PROPAGATION BY CHARGE NEUTRALIZATION FROM A DIELECTRIC COLLIMATOR

An intense beam is not propagated in vacuum because of its space charge. In this work, an intense electron beam of 250 keV, 6 kA, 80 ns is propagated after initial collimation inside a short length of dielectric tube and further confinement provided by ions attributed to beam irradiation. Such beams have important potential in particle beam and controlled fusion research. It is seen that electrons are slowed down to the ion velocity, while ions are collectively accelerated by the beam space-charge. Collimator geometry is varied for space-charge control. Elongation of the beam pulse width to 100-300 ns is observed depending on propagation distance. Explanations are presented through physical model and scaling laws.