Practical aspects of tuning a ringed RFQ

A radio frequency quadrupole (RFQ) constructed at Los Alamos for high current H(-) operation at 425 MHz and 2.0-MeV output energy was retrofitted with vane coupling rings (VCRS) introduced at Berkeley. The initial set of seven complete VCR pairs produced excessive operating frequency change, and an arrangement of alternating horizontal and vertical coupling rings eventually was adopted. Because of the periodicity and length of the system, and effects were pronounced. A different type of end tuner was used to adjust the field strength at the ends of the structure that should be of general utility for high power RFQs. Tuning data for various ring and tuning configurations are given.