RF TEST AND COMMISSIONING OF THE LOW AND HIGH BETA BUNCHERS FOR THE TRIUMF ISAC FACILITY

The high energy beam transport (HEBT) line for the ISAC radioactive beam facility at TRIUMF requires a low beta buncher at 11.78 MHz and a high beta buncher at 35.36 MHz operating in cw mode. The low beta buncher is required to bunch beams from 0.15 to 0.4 MeV/u and the high beta buncher is for beams from 0.4 to 1.5 MeV/u and are placed 12 m downstream from the DTL. The main requirement for the low beta buncher is to operate with an effective voltage of 100 kV. This three gap buncher has been realized by using two identical lumped element resonant circuits. The resonant frequency is obtained by using an inductive coil in parallel with the capacitance of the drift tube and the capacitance of the rf feedthrough. The high beta buncher is designed to operate with an effective voltage of 255 kV. This is a two-gap spiral structure similar to the rebuncher used in the medium energy beam transport (MEBT) line in ISAC. Both bunchers have been tested and commissioned to full rated power at 1.5 kW and 12 kW respectively.