Home > Research > Publications & Outputs > High-gradient behavior of a dipole-mode rf stru...

Electronic data

  • CLIC_Crab_Cavity_paper_181120

    Accepted author manuscript, 1.69 MB, PDF document

    Available under license: CC BY: Creative Commons Attribution 4.0 International License


Text available via DOI:

View graph of relations

High-gradient behavior of a dipole-mode rf structure

Research output: Contribution to Journal/MagazineJournal articlepeer-review

  • B. Woolley
  • G. Burt
  • A.C. Dexter
  • R. Peacock
  • W.L. Millar
  • N. Catalan Lasheras
  • A. Degiovanni
  • A. Grudiev
  • G. McMonagle
  • I. Syratchev
  • W. Wuensch
  • E. Rodriguez Castro
  • J. Giner Navarro
Article number122002
<mark>Journal publication date</mark>17/12/2020
<mark>Journal</mark>Physical Review Accelerators and Beams
Issue number12
Number of pages11
Publication StatusPublished
<mark>Original language</mark>English


A normal-conducting, X-band traveling wave structure operating in the dipole mode has been systematically high-gradient tested to gain insight into the maximum possible gradients in these types of structure. Measured structure conditioning, breakdown behavior, and achieved surface fields are reported as well as a postmortem analysis of the breakdown position and a scanning electron microscope analysis of the high-field surfaces. The results of these measurements are then compared to high-gradient results from monopole-mode cavities. Scaled to a breakdown rate of 10-6, the cavities were found to operate at a peak electric field of 154 MV/m and a peak modified Poynting vector Sc of 5.48 MW/mm2. The study provides important input for the further development of dipole-mode cavities for use in the Compact Linear Collider as a crab cavity and dipole-mode cavities for use in x-ray free-electron lasers as well as for studies of the fundamental processes in vacuum arcs. Of particular relevance are the unique field patterns in dipole cavities compared to monopole cavities, where the electric and magnetic fields peak in orthogonal planes, which allow the separation of the role of electric and magnetic fields in breakdown via postmortem damage observation. The azimuthal variation of breakdown crater density is measured and is fitted to sinusoidal functions. The best fit is a power law fit of exponent 6. This is significant, as it shows how breakdown probability varies over a surface area with a varying electric field after conditioning to a given peak field.