| |
Superconducting (SC) TEM-class cavities have been developed at laboratories and institututions worldwide for cw and pulsed proton and ion linac applications. New geometries spanning nearly the full velocity range from 0.1 < v/c < 0.8 include co-axial quarter- and half-wave and single- and multi-spoke cavities. Optimized designs have large beam acceptance, high shunt impedance and good microphonics properties. Rapidly evolving and improving clean surface processing techniques have been applied to TEM cavities where achieved surface fields and rf losses are comparable to the best results presently achieved in elliptical cavity designs. Recent results for a three-spoke cavity following hydrogen degassing after fabrication show very low rf losses even at high accelerating fields and now open the possibility for substantially reduced effective cryogenic load in 2 Kelvin, rather than the historically-used 4 Kelvin, operation. At present performance levels, SC TEM-class cavities constitute the technology of choice for most ion linac applications requiring cavities up to or beyond 60 percent of the speed-of-light.
|
|