Scaling laws for linear collective ion acceleration in the neutral gas geometry

In this paper several observations of collective ion acceleration as a function of drift tube geometry are summarized. It is found that variations in the ion pulse resulting from variations in the space charge limiting current of the drift tube cavity may be produced by varying either the cavity length to radius ratio or by varying the ratio of the beam radius to the cavity radius. Furthermore, such variations are well correlated. In addition, several measurements of the accelerated ion energy spectrum are reported. For high diode impedance beams (ν/γ ≤ 0.4) protons with maximum energies of approximately three times the electron beam kinetic energy are obtained. On the other hand, for low diode impedance beams (ν/γ ≥ 1) accelerated deuterons with energies in excess of 11.5 times the electron beam kinetic energy have been observed.