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11 - Beam-Wave Interaction

Published online by Cambridge University Press:  27 April 2018

Richard G. Carter
Affiliation:
Lancaster University
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Summary

Under small-signal conditions the r.f. properties of a linear, magnetically focused, electron beam can be represented by a pair of normal modes (space-charge waves). The fast space-charge waves carries positive power and has a phase velocity slightly greater than the electron velocity. The slow space-charge waves carries negative power and has a phase velocity slightly less than the electron velocity. An important parameter is the reduced plasma frequency of the beam which depends upon the space-charge density and the boundary conditions. Space-charge wave theory can be used to understand the interaction between an electron beam and the r.f. field of a surrounding electromagnetic structure. The theory of small-signal gain in klystrons and TWTs is discussed in detail. In periodic slow-wave structures the beam can interact with a space-harmonic wave having negative group velocity leading to the possibility of backward-wave gain or oscillation. In large-signal models of electron beams the equations of motion of sample electrons in d.c. and r.f. electromagnetic and space-charge fields are integrated numerically. Results from a model of this type are discussed. Simple models for the exchange of energy between the r.f. field of a gap and modulated and unmodulated electron beams are introduced.

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  • Beam-Wave Interaction
  • Richard G. Carter, Lancaster University
  • Book: Microwave and RF Vacuum Electronic Power Sources
  • Online publication: 27 April 2018
  • Chapter DOI: https://doi.org/10.1017/9780511979231.012
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  • Beam-Wave Interaction
  • Richard G. Carter, Lancaster University
  • Book: Microwave and RF Vacuum Electronic Power Sources
  • Online publication: 27 April 2018
  • Chapter DOI: https://doi.org/10.1017/9780511979231.012
Available formats
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Save book to Google Drive

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.

  • Beam-Wave Interaction
  • Richard G. Carter, Lancaster University
  • Book: Microwave and RF Vacuum Electronic Power Sources
  • Online publication: 27 April 2018
  • Chapter DOI: https://doi.org/10.1017/9780511979231.012
Available formats
×