Modelling elliptically polarised free electron lasers

J R Henderson, L T Campbell, H P Freund, B W J McNeil

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Abstract

A model of a Free Electron Laser operating with an elliptically polarised undulator is presented. The equations describing the FEL interaction, including resonant harmonic radiation fields, are averaged over an undulator period and generate a generalised Bessel function scaling factor, similar to that of planar undulator FEL theory. Comparison between simulations of the averaged model with those of an unaveraged model show very good agreement in the linear regime. Two unexpected results were found. Firstly, an increased coupling to harmonics for elliptical rather than planar polarisarised undulators. Secondly, and thought to be unrelated to the undulator polarisation, a signifcantly different evolution between the averaged and unaveraged simulations of the harmonic radiation evolution approaching FEL saturation.
Original languageEnglish
Article number062003
Number of pages14
JournalNew Journal of Physics
Volume18
DOIs
Publication statusPublished - 20 Jun 2016

Fingerprint

free electron lasers
harmonic radiation
Bessel functions
radiation distribution
simulation
saturation
harmonics
scaling
polarization
interactions

Keywords

  • free electron laser
  • harmonic radiation fields
  • tunable radiation

Cite this

Henderson, J R ; Campbell, L T ; Freund, H P ; McNeil, B W J. / Modelling elliptically polarised free electron lasers. In: New Journal of Physics. 2016 ; Vol. 18.
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Modelling elliptically polarised free electron lasers. / Henderson, J R; Campbell, L T; Freund, H P; McNeil, B W J.

In: New Journal of Physics, Vol. 18, 062003, 20.06.2016.

Research output: Contribution to journalArticle

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N2 - A model of a Free Electron Laser operating with an elliptically polarised undulator is presented. The equations describing the FEL interaction, including resonant harmonic radiation fields, are averaged over an undulator period and generate a generalised Bessel function scaling factor, similar to that of planar undulator FEL theory. Comparison between simulations of the averaged model with those of an unaveraged model show very good agreement in the linear regime. Two unexpected results were found. Firstly, an increased coupling to harmonics for elliptical rather than planar polarisarised undulators. Secondly, and thought to be unrelated to the undulator polarisation, a signifcantly different evolution between the averaged and unaveraged simulations of the harmonic radiation evolution approaching FEL saturation.

AB - A model of a Free Electron Laser operating with an elliptically polarised undulator is presented. The equations describing the FEL interaction, including resonant harmonic radiation fields, are averaged over an undulator period and generate a generalised Bessel function scaling factor, similar to that of planar undulator FEL theory. Comparison between simulations of the averaged model with those of an unaveraged model show very good agreement in the linear regime. Two unexpected results were found. Firstly, an increased coupling to harmonics for elliptical rather than planar polarisarised undulators. Secondly, and thought to be unrelated to the undulator polarisation, a signifcantly different evolution between the averaged and unaveraged simulations of the harmonic radiation evolution approaching FEL saturation.

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