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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 β values of β=0.61 and β=0.81. An aggressive cavity prototyping program is being pursued at Jefferson Lab, which calls for fabricating and testing four β=0.61 cavities and two β=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 β=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 acc = 10.1 MV/m and Q = 5×10 9 at 2.1K for the β=0.61 and E acc = 12.5 MV/m and Q = 5×10 9 at 2.1 K for the β=0.81.

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A parallel coupled RF cavity structure which provides favorable solutions to all of the require-. merits for use in an e e-storage ring is descnbed. Properties of this structure have been determined mathematically and through measurements on S-band models. An L-band prototype is being constructed and will be tested at high power.

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