Preparation and testing of a superconducting cavity for CESR-B

A 500 MHz niobium cavity was delivered to Cornell in January, 1992. The key features of the cavity design are a large, i.e. 24 cm diameter, circular beam tube which allows all but two of the higher-order modes (HOM´s) to propagate away from the cavity, a “fluted” beam tube which allows the remaining HOM´s to propagate, and a waveguide fundamental input coupler. The cavity was tested vertically in the as-received condition and almost achieved the design criteria. After this initial test the cavity was etched, rinsed and dried, and tested again. Modest helium processing enabled the cavity to exceed the design criteria of E_acc=10 MeV/m and Q₀ =10⁹. No indication of multipacting was observed in any of the tests. Several warm-up/cool-down cycles have been made. A cool-down procedure which avoids the “Q-virus” problem has been identified