Ion acceleration in the evacuated drift-tube geometry

The effect of varying the space-charge-limited current on the ion acceleration in the evacuated drift-tube geometry with no external magnetic field has been experimentally tested. The time-resolved current injected into the drift tube, the ion energy spectrum, and the region of ion acceleration have been measured. Different anode and cathode materials have been used. The results of these measurements indicate that ions are collectively accelerated inside the drift tube and that ion acceleration occurs in the drift tube only when the injected beam current exceeds the limiting current, set by the drift-tube radius