Non-interrupting electron beam diagnostic using coherent off-axis undulator radiation

C. P. Neuman, William Graves, P. G. O'Shea

Research output: Chapter in Book/Report/Conference proceedingConference contribution


We propose a technique for measuring the length of an electron bunch from a linear accelerator without interrupting the electron beam. Bunch lengths are measured by observing off-axis undulator radiation. The wavelength of undulator radiation increases with the angle of emission. At angles as large as 10 degrees, the wavelength may be longer than the electron bunch, and as a result coherence effects emerge. As the angle of observation increases and the radiation becomes coherent, the intensity may change by up to a factor of 109. The angle at which this change occurs is related to the bunch length. Thus the bunch length may be obtained by observing the change in intensity of the radiation with respect to the angle of observation. This electron beam diagnostic does not interrupt the electron beam and would be useful for single-pass FELs. Electron bunches could be characterized while the FEL is operating, and thus the FEL could be optimized in real time. In this paper, we develop the theory of coherent off-axis undulator radiation (COUR), including near-field effects, and we discuss future experimental efforts to observe this radiation and to use it to characterize electron bunches.

Original languageEnglish (US)
Title of host publicationProceedings of the IEEE Particle Accelerator Conference
Number of pages3
StatePublished - 1999
Externally publishedYes
EventThe 18th Biennial Particle Accelerator Conference - New York, NY, USA
Duration: Mar 27 1999Apr 2 1999


OtherThe 18th Biennial Particle Accelerator Conference
CityNew York, NY, USA

ASJC Scopus subject areas

  • Engineering(all)


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