Intense free electron laser harmonic generation in a longitudinal magnetic wiggler

Journal Article · Tue Mar 01 04:00:00 EST 1983 · Phys. Fluids; (United States)

DOI:https://doi.org/10.1063/1.864211· OSTI ID:6530316

Davidson, R C; McMullin, W A

The free electron laser instability is investigated theoretically for a tenuous relativistic electron beam propagating parallel to a longitudinal wiggler field (B/sub 0/+deltaB sin k/sub 0/z)e/sub z/ . The stability analysis is based on the linearized Vlasov--Maxwell equations for perturbations about the beam equilibrium f/sup 0//sub b/ = (n/sub b//2..pi..p/sub perpendicular/)delta(p/sub perpendicular/-..gamma../sub b/mV/sub perpendicular/) delta(p/sub z/-..gamma../sub b/mV/sub b/). For (..omega../sub c/b/k/sub 0/V/sub b/)(deltaB/B/sub 0/) of order unity or larger, it is found that the transverse electron orbits experience a strong temporal modulation at harmonics of k/sub 0/v/sub z/approx. =k/sub 0/V/sub b/. In the stability analysis, this orbit modulation is manifest by radiation amplification occurring near the simultaneous zeroes of ..omega.. = kc and ..omega..-kV/sub b/-..omega../sub c/b = nk/sub 0/V/sub b/ for the general harmonic number n, which corresponds to an upshifted (for n> or =1) wavenumber k/sub n/ = (1-V/sub b//c)/sup -1/(..omega../sub c/b/c+nk/sub 0/V/sub b//c). For (..omega../sub c/b/k/sub 0/V/sub b/)(deltaB/B/sub 0/) >1, the instability is typically broadband with several harmonics excited. Moreover, depending on beam and field parameters, the characteristic maximum growth rate can be substantial with Im ..omega../ck/sub 0/ = (3/2)/sup 1/2/ x ((V/sup 2//sub perpendicular//4c/sup 2/)(..omega../sup 2//sub p/b/c/sup 2/k/sup 2//sub 0/) nJ/sup 2//sub n/(..omega../sub c/bdeltaB/k/sub 0/V/sub b/B/sub 0/))/sup 1/3/.

• Research Organization: Plasma Research Institute, Science Applications, Inc., Boulder, Colorado 80302
• OSTI ID: 6530316
• Journal Information: Phys. Fluids; (United States), Journal Name: Phys. Fluids; (United States) Vol. 26:3; ISSN PFLDA
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420300* -- Engineering-- Lasers-- (-1989)
AMPLIFICATION
BEAMS
BOLTZMANN-VLASOV EQUATION
DIFFERENTIAL EQUATIONS
DISTURBANCES
ELECTRICAL EQUIPMENT
ELECTROMAGNETS
ELECTRON BEAMS
ENERGY RANGE
EQUATIONS
EQUILIBRIUM
EQUIPMENT
FREE ELECTRON LASERS
GAIN
HARMONICS
INSTABILITY
INSTABILITY GROWTH RATES
LASERS
LEPTON BEAMS
MAGNETIC FIELDS
MAGNETS
MODULATION
OSCILLATIONS
PARTIAL DIFFERENTIAL EQUATIONS
PARTICLE BEAMS
RADIATIONS
RELATIVISTIC RANGE
TRAJECTORIES
WIGGLER MAGNETS