Recent theoretical and experimental investigations of ion acceleration occurring when an intense relativistic electron beam is injected into low pressure neutral gases have yielded a fairly complete description of the process. In this report the experimental procedure and results of the collective ion acceleration program at the Air Force Weapons Laboratory, including related diode and beam propagation work, are examined in detail. Important conclusions pertaining to the existence of an ion acceleration threshold current, to accelerated ion energy spectra, and to process efficiency are reported. (Author).

Collective acceleration methods that employ an intense relativistic electron beam (IREE) are discussed. A brief history and a classification of collective acceleration methods are given. Methods examined include IREB injection into neutral gas; IREB injection into vacuum; plasma-filled IREB diodes; and vacuum-filled IREB diodes. Accelerating fields of order 106 V/cm have been observed experimentally. The collective acceleration processes for IREB injection into neutral gas and vacuum are discussed. It is noted that the collective acceleration processes for IREB diodes have not been elucidated, yet. A summary of present collective ion acceleration research areas that involve IREB's is given.

Observation of accelerated protons during the injection of rotating relativistic electron beams into neutral hydrogen (50 mTorr to 400 mTorr) indicated that ions from the beam-formed plasma are trapped and accelerated by a potential well at the beamfront. Measurements show that the number of accelerated protons decreases as the beamfront velocity is increased. Moreover, at a given velocity, the number accelerated is relatively insensitive to the neutral gas pressure.

Recently there has been an increased interest in a compact high energy intense light-ion accelerator. Some of the areas of application for such an accelerator include directed energy research, inertial fusion and magnetic fusion. The new approach that has been proposed for investigation is the space charge wave accelerator. With the space charge wave type of collective ion acceleration scheme, one can expect a compact, efficient ion accelerator which is capable of producing high energy and high current ion beams. The ion energy limit occurs when the ion velocity equals that of the electrons. Thus, for an easily producible 1 MeV electron beam about 2 GeV protons are expected. Since a large number of electrons are needed for an intense relativistic electron beam, a proportional but smaller number of ions are expected by momentum balance. With an accelerating electric field having a strength of 1 MV/cm, the 2 GeV proton can be obtained in a short accelerator length of 20 meters.