A room temperature test bed for evaluating 700-MHz RF windows and power couplers for the superconducting cavities of the APT linac

Superconducting radio frequency (SCRF) cavities are used in the high-energy portion of the Accelerator Production of Tritium (APT) linac to accelerate the beam to approximately 1700 MeV. To accelerate the 100 mA proton beam and to maintain the field levels in the cavity, up to 420 kW of CW (continuous wave) 700-MHz RF power needs to be delivered to the cavity. This is done using two RF window and power coupler assemblies that can each transmit 210 kW. To evaluate developing window-coupler designs, a Room Temperature Test Bed (RTTB) has been built that utilizes a room-temperature copper coupling cavity for mating two power couplers together. Several parameters are being tested such as: (1) power coupler matching, (2) maximum power handling, (3) RF losses in the power coupler, (4) window/power coupler matching, and (5) coupler/cavity coupling adjustability. The RTTB is also meant to be a conditioning stand for window-coupler assemblies that will go on cryomodules. The design features of the coupling cavity, test stand and layout, vacuum system and controls, data acquisition, RF controls and contamination control are discussed.