Collective ion acceleration by a shout pulse-width relativistic electron beam

A short pulse-width relativistic electron beam was injected into a low-pressure neutral helium gas. The beam propagation behavior agreed with Olson´s model. A condition that the beam pulse-width should satisfy was given. However, some aspects of ion acceleration behavior did not seem to agree with Olson´s model. The maximum energy of the accelerated helium ions was 3.1 MeV which is U.6 times the maximum kinetic energy of beam electrons. The number of accelerated ions with energy above 0.9 MeV was about 10⁹ particles/pulse for this case.