Superconducting Multicell Cavity Development Program at Los Alamos

The Superconducting RF Cavity Development Program at Los Alamos has designed, fabricated, and tested single-cell niobium cavities at 3 GHz and 805 MHz. This work is being done in preparation for procuring and testing a multicell niobium cavity. The multicell cavity is designed to accelerate protons at β=0.9; initial tests will be without beam. Programmatic changes have required us to modify our plans to install a 6800 litre helium cryostat and a 12.8 g/s helium pump. We will use an installed cryostat to test the multicell cavity. Also, the cavity will be modified from a seven-cell to a four-cell structure to match the dimensions of the installed cryostat. Previous reports concentrated on 3 GHz results. In this paper, some of the latest results of the 805 MHz cavity tests are presented. Modifications to allow high pulsed power testing on 805 MHz single- and four-cell cavities are proceeding. Glow discharge cleaning of an 805 MHz niobium cavity resulted in a decrease in cavity performance. The cavity was restored to previous performance levels with buffered chemical polishing. Initial results with high-pressure water cleaning show the process is useful in restoring cavity performance