Experimental Studies of the Collective Acceleration of Gas Ions by Intense Pulsed E-BEAMS

摘要

The present investigation of collective ion acceleration by intense pulsed e-beams in neutral gas consisted of experiments which addressed background gas ionization physics in relation to beam front propagation velocity, and gas density gradients as a technique for extending the range of particle energies attainable. Observation of virtually identical beam propagation in hydrogen and deuterium at equal densities indicates that if beam front velocity is governed by self-electrostatic forces, then ion-produced ionization appears to be a minor effect; or if not a minor effect, then it remains to show how a factor-of-two increase of ion mass could leave an ion-dominated ionization rate unaffected. Direct quantitative measurement of the charge neutralization time by a probing beam deflection technique was thwarted due, probably, to the perturbing effect of the self-magnetic field of the main beam. It is unclear whether this problem can be eliminated. Smoothly accelerating beam front motion was successfully accomplished using gas density gradients, but had little if any effect on accelerated proton energies, and actually quashed the acceleration process when the gradient appreciably overlapped onto the initial acceleration region. Evidently the spatial increase of density was detrimental to the trapping and acceleration process. It is uncertain what conclusions are to be drawn from the negative results of the pressure gradient experiments. (ERA citation 08:000925)