## Abstract

Free electron lasers (FELs) are considered, typically, as fast wave devices. The normal FEL interaction satisfies the tuning condition ω≅(k_{z} + k_{W})V_{z} , where ω and k_{z} are the em-wave angular frequency and longitudinal wave number, respectively, V_{z} is the electron axial speed, and k_{W} is the wiggler periodicity. This paper presents an anomalous FEL interaction, which may occur in slow-wave FELs (i.e. loaded by dielectric or periodic structures). The anomalous FEL effect presented here satisfies the tuning condition ω≅(k_{z} - k_{W})V_{z} , and it resembles the anomalous effect in slow-wave cyclotron resonance masers. A necessary condition for the anomalous interaction is ω/k_{z}<V_{z} (i.e., the em-wave phase velocity should be slower than the electron beam). The paper presents a preliminary experimental result demonstrating the anomalous FEL effect in a stripline dielectric-loaded FEL experiment. A linear Pierce equation is applied to describe both the anomalous and normal FELs in the same framework. The paper is concluded with a conceptual discussion.

Original language | English |
---|---|

Pages (from-to) | 482-487 |

Number of pages | 6 |

Journal | Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment |

Volume | 483 |

Issue number | 1-2 |

DOIs | |

State | Published - 1 May 2002 |

Externally published | Yes |

## Keywords

- Free electron laser