Thermal Stability Analysis of Superconducting RF Cavities

  • T. Junquera
  • J. Lesrel
  • M. Fouaidy
  • S. Bousson
Part of the Advances in Cryogenic Engineering book series (ACRE, volume 43)


Future linear accelerators using superconducting RF cavities (TESLA proposal), requires accelerating gradients Eacc=25 MV/m to be achieved reliably at large scale. This high gradient level is mainly limited by electron emission and thermal instabilities (quench). Impressive improvements have been recently accomplished by pushing further the onset threshold of electron emision using careful surface cleaning techniques. On the other side micron size resistive defects embedded in the niobium walls of the cavity continue to induce thermal breakdowns for Eacc in the range 15 to 25 MV/m. In this paper the thermal stability of SRF cavities is analysed using analytical and numerical simulation models. The effects of the most relevant parameters (i.e. defect size, RF frequency, thermal conductivity, cooling conditions, etc.) having an incidence on the cavity quench are studied. The steady-state and the transient solutions are presented in two cases : the defect free surface, and the micron size defect on the cavity surface. Experimental observations of the thermal events occuring during the quench have been obtained with the help of two diagnostic systems: surface thermometers working in superfluid helium and RF measurements. All the proposed experimental and modelling methods could contribute to get a more complete insight on the thermal effects taking place in the cavity wall.


Defect Size Thermal Instability Cavity Wall Finite Element Code Cavity Field 
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Copyright information

© Springer Science+Business Media New York 1998

Authors and Affiliations

  • T. Junquera
    • 1
  • J. Lesrel
    • 1
  • M. Fouaidy
    • 1
  • S. Bousson
    • 1
  1. 1.Institut de Physique Nucleaire (CNRS-IN2P3)OrsayFrance

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