System and method for increasing the efficiency of a cyclotron

Abstract

In a negative hydrogen (H.sup.-) ion cyclotron, a system and method for improving the efficiency of the cyclotron by minimizing loss, i.e., neutralization, of H.sup.- ions within the acceleration region of the cyclotron caused by gas stripping. The system includes a cyclotron volume, an ion source within the ion source volume is maintained at a negative potential and located proximate the cyclotron center on the plane of acceleration. The vacuum system includes a main vacuum pump for evacuating the cyclotron volume and an ion source pump for separately evacuating the ion source volume to remove hydrogen (H.sub.2) gas molecules which could cause gas stripping if injected into the cyclotron volume. In the preferred embodiment, the system further has a pumping volume, communicating between the ion source volume and the cyclotron volume, and a separate pumping volume vacuum passageway whereby the ion source volume is evacuted in two stages. An ion beam passageway from the ion source volume to the pumping volume and one from the pumping volume to the cyclotron volume have gas conductances substantially less than gas conductances of connections between the vacuum pumps and the various volumes whereby enhanced differential pumping of undesired species is accomplished to minimize ion loss. Furthermore, the radio-frequency system is operated at a frequency four times that of the ion beam orbital frequency.