Prototype 350 MHz Niobium Spoke-Loaded Cavities

This paper reports the development of 350 MHz superconducting cavities of a spoke-loaded geometry [1], intended for the velocity range of 0.2<v/c<0.6. Two prototype single-cell cavities have been designed, one optimized for velocity v/c=0.4, and the other for v/c=0.29. Construction of the prototype niobium cavities is nearly complete. Details of the design and construction will be discussed, along with the results of cold tests