Theory of free-electron laser instability for a relativistic electron beam propagating in a dielectric-loaded waveguide

Journal Article · Thu Jun 01 00:00:00 EDT 1989 · Phys Fluids B; (United States)

DOI:https://doi.org/10.1063/1.858956· OSTI ID:6287377

Choi, J; Kim, D; Choi, D; Yang, S; Uhm, H S

A free-electron laser (FEL) with a dielectric-loaded waveguide operating in an undulator (multiple mirror) field is analyzed. The stability properties are investigated self-consistently on the basis of the linearized Vlasov--Maxwell equations for an electron distribution function, in which all electrons have a Lorentzian distribution in the axial canonical momentum. Using appropriate boundary conditions, a dispersion relation is derived in the low density approximation; ..nu../sub b//..gamma../sub b/<<1, and the growth rates of several types of mode couplings are computed. Even for a mildly relativistic electron beam (..gamma../sub b/less than or equal to1.5), the typical maximum growth rate of instability is a few percent of c/R/sub w/. As the axial momentum spread increases, the growth rate decreases substantially while the instability bandwidth increases. For the long-wiggler wavelength (LWW) mode, which only occurs in the dielectric-loaded waveguide, Cerenkov interaction plays an important role in the free-electron laser instability. In the case of the short-wiggler wavelength (SWW) mode, the frequency of the free-electron laser is greatly enhanced in mildly relativistic electron beams with appropriate choices of physical parameter values. Therefore, intense submillimeter microwaves might be produced by making use of a mildly relativistic electron beam with ..gamma..approx. =1.1. A wide band free-electron laser amplifier is also possible with a proper choice of external parameters, such as wiggler wavenumber k/sub 0/, dielectric constant, and beam energy ..gamma../sub b/.

• Research Organization: Department of Physics, Korea Advanced Institute of Science and Technology, P. O. Box 150, Chungryang, Seoul, Korea
• OSTI ID: 6287377
• Journal Information: Phys Fluids B; (United States), Vol. 1:6
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
FREE ELECTRON LASERS
INSTABILITY
BOLTZMANN-VLASOV EQUATION
DIELECTRIC MATERIALS
ELECTRON BEAMS
MICROWAVE RADIATION
RELATIVISTIC RANGE
WAVEGUIDES
BEAMS
DIFFERENTIAL EQUATIONS
ELECTROMAGNETIC RADIATION
ENERGY RANGE
EQUATIONS
LASERS
LEPTON BEAMS
MATERIALS
PARTIAL DIFFERENTIAL EQUATIONS
PARTICLE BEAMS
RADIATIONS
420300* - Engineering- Lasers- (-1989)