Superconducting prototype cavities for the Spallation Neutron Source (SNS) project

The Spallation Neutron Source project includes a superconducting linac section in the energy range from 186 MeV to 1000 MeV. For this energy range two types of cavities are needed with geometrical /spl beta/ values of /spl beta/=0.61 and /spl beta/=0.81. An aggressive cavity prototyping program is being pursued at Jefferson Lab, which calls for fabricating and testing four /spl beta/=0.61 cavities and two /spl beta/=0.81 cavities. Both types consist of six cells made from high purity niobium and feature one HOM coupler of the TESLA type on each beam pipe and a port for a high power coaxial input coupler. Three of the four /spl beta/=0.61 cavities will be used for a cryomodule test at the end of 2001. Two cavities of each type have been fabricated and the first tests on both cavities exceeded the design values for gradient and Q value: E/sub acc/=10.1 MV/m and Q=5/spl times/10/sup 9/ at 2.1 K for the /spl beta/=0.61 and E/sub acc/=12.5 MV/m and Q=5/spl times/10/sup 9/ at 2.1 K for the /spl beta/=0.81.