Inducing strong density modulation with small energy dispersion in particle beams and the harmonic amplifier free electron laser

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We present a possible method of inducing a periodic density modulation in a particle beam with little increase in the energy dispersion of the particles. The flow of particles in phase space does not obey Liouville's Theorem. The method relies upon the Kuramoto-like model of collective synchronism found in free electron generators of radiation, such as Cyclotron Resonance Masers and the Free Electron Laser. For the case of an FEL interaction, electrons initially begin to bunch and emit radiation energy with a correlated energy dispersion which is periodic with the FEL ponderomotive potential. The relative phase between potential and particles is then changed by approximately 180 degrees. The particles continue to bunch, however, there is now a correlated re-absorption of energy from the field. We show that, by repeating this relative phase change many times, a significant density modulation of the particles may be achieved with only relatively small energy dispersion. A similar method of repeated relative electron/radiation phase changes is used to demonstrate supression of the fundamental growth in a high gain FEL so that the FEL lases at the harmonic only.
Original languageEnglish
Pages1718 - 1720
Number of pages3
Publication statusPublished - 2005
EventParticle Accelerator Conference, 2005. PAC 2005. Proceedings of the - Knoxville, Tennessee, United States
Duration: 16 May 200520 May 2005


ConferenceParticle Accelerator Conference, 2005. PAC 2005. Proceedings of the
CountryUnited States
CityKnoxville, Tennessee


  • strong density modulation
  • small energy dispersion
  • particle beams
  • harmonic amplifier
  • free electron laser

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