Design of a two-cell rf-deflector cavity for ultra-short electron bunch measurement

Y. Nishimura, K. Sakaue*, M. Nishiyama, T. Takahashi, M. Washio, T. Takatomi, J. Urakawa

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)


For a longitudinal characterization of an ultra-short electron bunch, an rf-deflector cavity is the best resolution technique that can directly convert longitudinal distribution to transverse. This paper describes the principle of longitudinal diagnostics using an rf-deflector cavity, the design details of an rf-deflector cavity and the results of rf-characteristics for a manufactured cavity. The cavity is based on a rectangular two-cell structure operating on standing wave π-mode, dipole (TM120) mode at 2856 MHz. We have confirmed using HFSS simulation that this cavity can produce a deflecting voltage of 1.63 MV with an input rf-power of 750 kW. The results of low power rf-measurement of the manufactured cavity show an effective deflecting voltage of 1.00 MV which corresponds to a temporal resolution of 58 fs (rms) (250 fs/mm on the profile monitor) with 750 kW input rf-power, drift length L of 1 m and initial size σoff of 230 μm. These results indicate that we have successfully achieved our target: temporal resolution of less than 100 fs with an electron bunch with energy of 4.5 MeV and charge of 100 pC.

Original languageEnglish
Pages (from-to)291-298
Number of pages8
JournalNuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Publication statusPublished - 2014 Nov 11


  • Ultra-short electron bunch measurement
  • rf deflector cavity
  • rf electron gun

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Instrumentation


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