Ultimate-Gradient SRF Test Cavity and Low Loss Tangent Measurements in Ultra Pure Sapphire

Conference · Fri Apr 01 00:00:00 EDT 2011

OSTI ID:1996958

Pogue, Nathaniel; McIntyre, Peter; Reece, Charles

A test cavity has been designed to test wafer samples of superconducting materials at 1.3 GHz. Operating in TE01 mode, this mushroom shaped cavity creates a unique distribution of surface fields. The surface magnetic field on the sample wafer is 3.75 times greater than elsewhere on the Niobium (Nb) cavity surface. This made possible by loading the cavity with an ultra-pure sapphire just above the sample wafer. The maximum field seen by the Nb wall is only 25% of the value deposited on the sample surface. Therefore, it should be possible to push the sample wafer well beyond the BCS limit for Nb while still obtaining a respectable Q. The sapphire’s loss tangent and dielectric constant must be measured to finalize the design for the Wafer Test Cavity. A sapphire loaded CEBAF cavity has been constructed and tested; these results on the dielectric constant and loss tangent will be presented.

• Research Organization: Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP)
• DOE Contract Number: AC05-06OR23177
• OSTI ID: 1996958
• Report Number(s): JLAB-ACC-10-1318; DOE/OR/23177-2310
• Country of Publication: United States
• Language: English