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Title: Simulation of nonlinear superconducting rf losses derived from characteristic topography of etched and electropolished niobium surfaces

A simplified numerical model has been developed to simulate nonlinear superconducting radiofrequency (SRF) losses on Nb surfaces. This study focuses exclusively on excessive surface resistance (Rs) losses due to the microscopic topographical magnetic field enhancements. When the enhanced local surface magnetic field exceeds the superconducting critical transition magnetic field Hc, small volumes of surface material may become normal conducting and increase the effective surface resistance without inducing a quench. We seek to build an improved quantitative characterization of this qualitative model. Using topographic data from typical buffered chemical polish (BCP)- and electropolish (EP)-treated fine grain niobium, we have estimated the resulting field-dependent losses and extrapolated this model to the implications for cavity performance. The model predictions correspond well to the characteristic BCP versus EP high field Q0 performance differences for fine grain niobium. Lastly, we describe the algorithm of the model, its limitations, and the effects of this nonlinear loss contribution on SRF cavity performance.
Authors:
 [1] ;  [2] ;  [1]
  1. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); College of William and Mary, Williamsburg, VA (United States)
  2. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
Publication Date:
Report Number(s):
JLAB-ACC-14-1882; DOE/OR/23177-3069; arXiv:1406.7276
Journal ID: ISSN 2469-9888; PRABFM
Grant/Contract Number:
AC05-06OR23177
Type:
Published Article
Journal Name:
Physical Review Accelerators and Beams (Online)
Additional Journal Information:
Journal Name: Physical Review Accelerators and Beams (Online); Journal Volume: 19; Journal Issue: 3; Journal ID: ISSN 2469-9888
Publisher:
American Physical Society (APS)
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
OSTI Identifier:
1242876
Alternate Identifier(s):
OSTI ID: 1244079