Research in Superconducting Radiofrequency Systems

Abstract

The aim of the program is to transfer our successes in single cell high gradient R&D to multi-cell cavities of advanced shapes. We have also developed a new technique for electropolishing (EP) which is much less expensive than the standard EP technique used at other labs. Our aim is to apply this technique to multi-cell cavities of advanced shapes. The scientific program of this grant was concluded in 2010. An extension of this grant allowed us to receive ARRA funding, which we used to improve the helium-liquefier system in Cornell's SRF laboratory. Part of this system had been purchased and installed by another grant. The extension to grant DE-FG02-04ER41354 was proposed to extend this system to sufficient power so that helium can be recovered from SRF-cavity test and simultaneously can be liquefied. This significantly increased the number of cavities we can test per week. This upgrade project was finished in the spring of 2010 and has been in regular use ever since. World Record Gradient in Re-entrant Shape Single Cell Cavity Cornell, in collaboration with KEK, has established world record accelerating fields with a new shape in a single cell superconducting niobium cavity: Eacc = 57-59 MV/m [1]. See Figures 1 and 2 for a picture of the cavity and the Q vs E curve. This is a small aperture (60 mm) RE-ENTRANT shape single cell cavity, where the peak surface magnetic field (Hpk) is lower than in the standard re-entrant shape cavity (70 mm aperture). Our first re-entrant cavity had a larger aperture (70 mm)-the same as the TESLA shape cavity aperture-and reached 53 MV/m at KEK. The best gradient in a standard TESLA shape cavity with 70 mm re-entrant shape aperture is 42 MV/m.