RF measurement summary of ISAC DLT tanks and DTL bunchers

In the ISAC radioactive ion beam facility at TRIUMF, a variable energy drift tube linac: (DTL) is used to accelerate ions with a charge to mass ratio ⩾1/6 from 0.153 MeV/u to 1.53 MeV/u. The accelerating tanks are five independent interdigital H type rf structures with high shunt impedances. The three bunchers are triple gap split-ring resonators placed between the first four accelerating tanks. Each structure is equipped with fine tuners to compensate for frequency drift during operation. Coarse tuners are installed in the DTL cavities to bring their resonant frequencies within the tuning range of the fine tuners. Except for the loop size, the same rf power couplers have been used in all the structures. All these structures operate at 106.08 MHz and have been tested at power. Signal level measurements have been done to characterize their rf properties. Drift tube gap voltages were measured with x-ray field emissions and compared with voltages estimated from input power and shunt impedance. RF power losses in the DTL tank walls were higher than calculated and hence additional cooling was provided. The results of the signal and power measurements are summarized in this paper