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Title: Theoretical estimates of maximum fields in superconducting resonant radio frequency cavities: stability theory, disorder, and laminates

Theoretical limits to the performance of superconductors in high magnetic fields parallel to their surfaces are of key relevance to current and future accelerating cavities, especially those made of new higher-Tc materials such as Nb$$_3$$Sn, NbN, and MgB$$_2$$. Indeed, beyond the so-called superheating field $$H_{\mathcal{sh}}$$, flux will spontaneously penetrate even a perfect superconducting surface and ruin the performance. We present intuitive arguments and simple estimates for $$H_{\mathcal{sh}}$$, and combine them with our previous rigorous calculations, which we summarize. We briefly discuss experimental measurements of the superheating field, comparing to our estimates. We explore the effects of materials anisotropy and the danger of disorder in nucleating vortex entry. Will we need to control surface orientation in the layered compound MgB$$_2$$? Can we estimate theoretically whether dirt and defects make these new materials fundamentally more challenging to optimize than niobium? Finally, we discuss and analyze recent proposals to use thin superconducting layers or laminates to enhance the performance of superconducting cavities. As a result, flux entering a laminate can lead to so-called pancake vortices; we consider the physics of the dislocation motion and potential re-annihilation or stabilization of these vortices after their entry.
Authors:
 [1] ; ORCiD logo [2] ;  [3] ;  [4] ;  [1] ;  [1]
  1. Cornell Univ., Ithaca, NY (United States)
  2. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
  3. Brigham Young Univ., Provo, UT (United States)
  4. Forschungszentrum Julich, Julich (Germany)
Publication Date:
Report Number(s):
arXiv:1608.00175; FERMILAB-PUB-16-699-TD
Journal ID: ISSN 0953-2048; 1479192
Grant/Contract Number:
AC02-07CH11359; SC0008431; DEAC02- 07CH11359
Type:
Accepted Manuscript
Journal Name:
Superconductor Science and Technology
Additional Journal Information:
Journal Volume: 30; Journal Issue: 3; Journal ID: ISSN 0953-2048
Publisher:
IOP Publishing
Research Org:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; superheating field; superconducting radio frequency cavities; flux penetration; disordered nucleation
OSTI Identifier:
1462248
Alternate Identifier(s):
OSTI ID: 1338075