An apparatus, system and method. An apparatus may include an RF power assembly, arranged to output an RF signal; a resonator, coupled to receive the RF signal, the resonator comprising a first output end and a second output end, and a drift tube assembly, configured to transmit an ion beam, and coupled to the resonator. As such, the drift tube assembly may include a first AC drift tube electrode, coupled to the first output end, and a second AC drift tube electrode, coupled to the second output end and separated from the first AC drift tube by a first gap. The RF power assembly may be switchable to switch output from a first Eigenmode frequency to a second Eigenmode frequency.