A triple gap resonator design for the separated function DTL at TRIUMF

A separated function, variable energy, drift tube linac (DTL) operating in CW mode is being built for the ISAC radioactive beam facility at TRIUMF. Longitudinal focusing is achieved by positioning 105 MHz rebunching cavities immediately upstream of the second, third and fourth IH accelerating tanks. The three devices must operate at a relatively low /spl beta/ (2.3%, 2.7%, 3.3%) and deliver peak effective voltages in CW mode of 0.19, 0.26 and 0.32 MV respectively. In addition the geometry must allow a large voltage dynamic range for the variable energy operation. A three gap cavity has been chosen as a trade-off between velocity acceptance and peak effective voltage. Several cavity geometries have been considered in order to identify the optimal geometry for this application. We present here a summary of the available buncher designs.