Performance of 6-m 1300-MHz superconducting niobium accelerator structures

The design, manufacture, and performance of several 6-m-long 1300-MHz superconducting niobium accelerator structures, which are part of the Stanford superconducting accelerator, are briefly described. In these standing-wave accelerator structures, we have achieved cw energy gradients as high as 3.8 MeV/m and unloaded Q's as high as 6.9×109 measured at 3.0 MeV/m and 1.9 K. In addition, electron-beam currents up to 5000 μA have been accelerated through the structure without exciting beam-breakup modes.