surface roughness effect on the performance of nb3sn cavities

• DOI: 10.18429/jacow-linac2016-moprc027
• Publication Date: 2017-01-01
• Authors: James Maniscalco; Daniel Hall; Matthias Liepe; Ryan Porter
• Keywords: 3 Technology; 0103 physical sciences; 01 natural sciences; Accelerator Physics

Proceedings of the 28th Linear Accelerator Conf., LINAC2016, East Lansing, MI, USA<br/>Surface roughness of current Niobium-3 Tin (Nb3Sn) superconducting radio-frequency (SRF) accelerator cavities can cause enhancement of the surface magnetic field. This enhancement can push the surface magnetic field beyond the critical field, which, if it occurs over a large enough area, can cause the cavity to quench. This paper presents simulations of the surface magnetic field enhancements in SRF cavities caused by the surface roughness of current Cornell Nb3Sn cavities, which have achieved record efficiency. Simple, smooth cavity geometry is defined and surface magnetic fields calculated using SLANS2. The cavity geometry is modified with a small rough region for which the geometry is determined from AFM scans of a Nb3Sn coated sample and the surface fields are calculated again. The calculated surface fields of the smooth and rough cavities are compared to determine the extent of the field enhancement, the area over which the enhancement is significant, and which surface features cause large field enhancement. We find that 1% of the surface analyzed has fields enhance by more than 45%. On average the Q-factor is increased by (3.8 ± 1.0) \%.<br/>