An Optimized Shape Cavity for Tesla: Concept and Fabrication

The accelerating gradient performance of superconducting niobium cavities is rapidly progressing as a result of reduced field emission due to improvement in surface preparation techniques. Beyond the field emission limitation, there exists a fundamental limit imposed by the critical magnetic field of niobium. One way to tackle this limit is to reduce the ratio of the peak magnetic field to the accelerating gradient so that a higher accelerating gradient is possible while the cavity is still superconducting. New cavity shapes of reentrant type have been proposed and optimized [1]. A single cell 1300MHz cavity of this new class of shapes has been fabricated. Because of the reentrant geometry, the fabrication and surface cleaning of the cavity becomes challenging. In this paper, we present some calculation prerequisites and the fabrication and preparation results for this new cavity.