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.

'Intense Relativistic Electron Beam Investigation', was reported in the 'Interim Scientific Report to the AFOSR for the period October 1, 1979 to September 30, 1980' and is herewith included by reference as part of this final report. Progress during the second (final) year of this contract is reported herein. In particular the following topics are discussed: (a) collective ion acceleration experiments using relativistic electron beams and localized ion sources produced by thin films, filaments, puffed gases and vaporization of small diameter wires; and (b) electron beam quality studies experiments in collaboration with Drs. Robert K. Parker and V.L. Granatstein at the Naval Research Laboratory with the objective of obtaining 'cool' beams propagating in vacuum in an axial magnetic field obtaining 'cool' beams propagating in vacuum in an axial magnetic field with minimum energy spread for such applications as the free electron laser.

An intense relativistic electron beam cannot propagate in a metal drift tube when the current exceeds the space charge limit. Very high charge density and electric field gradients (100 to 1000 MV/m) develop at the beam front and the electrons are reflected. When a neutral gas or a plasma is present, collective acceleration of positive ions occur, and the resulting charge neutralization enables the beam to propagate. Experimental results, theoretical understanding, and schemes to achieve high ion energies by external control of the beams front velocity will be reviewed. (Author).

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 methods of ion acceleration using intense relativistic electron beams (IREB) have stimulated a great deal of interest in the past few years. The main virtue of an IREB collective ion accelerator is the high internal electric field strength. The primary drawback has been an insufficient ion energy gain or inadequate scaleability. An extensive study for generating a high quality electron beam has been done and is presented in Section II. In Section III an intense ion injector study was conducted by the method of computer simulation. The last addition to the proposal was a design for producing a toroidal magnetic field. This field will be needed in a future study of high energy and high current electron beams.

The original purpose of this research was an investigation into the use of slow space charge waves on weakly relativistic electron beams for ion acceleration. The work had three main objectives namely, the development of a suitable ion injector, the growth and study of the properties of slow space charge waves on an electron beam, and a combination of the two components parts into a suitable proof of principle demonstration of the wave accelerator. This work focusses on the first two of these objectives.