Charge State Selective Ion Beam Acceleration with RFQ Linac

DPIS (Direct Plasma Injection Scheme) is one of the effective methods for high-intensity heavy ion beam acceleration. In DPIS, ions are extracted from laser-produced plasma at the entrance of an RFQ linac. The plasma generated by high power density laser irradiation consists of multiple charge state ions, therefore, the ions with different charge states are simultaneously injected into an RFQ. In an RFQ, ions whose charge state is comparable with that of ions desired for acceleration are captured by RF bucket. To prevent the unneeded ions from being accelerated, we investigated the beam dynamics in an RFQ and performed the particle tracking simulation. The simulation result shows that the discontinuous transition of the synchronous phase inhibits the acceleration of the unneeded ions without significant loss of desired ions. To validate the designed cell parameter via oncoming beam test, we fabricated the new 4-rod RFQ vanes for carbon 5+ acceleration.