Study of a four-rod RFQ structure at 470 MHz

It has been demonstrated that the four-rod RFQ (radio-frequency quadrupole) structure is a viable alternative to the four-vane structure. The four-rod structure is easier to construct and maintain. Also, the unwanted dipole mode is not a problem since the opposite rods are connected by the rod support structure. However, this structure has not been studied extensively for frequencies much above 200 MHz. The authors have developed a four-rod cavity design which can resonate at higher frequencies. They present their design for a 470-MHz structure and show results of computer simulation using the MAFIA codes. It was found using MAFIA that a single-gap cavity at the front end will reduce the entrance potential seen by the beam to a negligible level