Field emission processing of superconducting RF cavities with high peak power

The main difficulty standing in the way of using superconducting RF cavities for teraelectronvolt linear colliders is that, due to field emission, accelerating gradients are generally limited to less than 20 MV/m. One technique which is commonly used to decrease field emission is the use of RF processing in the presence of helium gas. In order to push this technique to yield even higher fields, a facility is being developed to process niobium S-band structures up to 200-k peak incident power for pulse widths up to 2 ms. This system is described and preliminary results are reported. The klystron transmitter system is complete and has been operated with pulsed DC current to a peak power level of 400 kW, average power level of 2 kW, and a pulse width of 2 ms