Cross-field free electron laser instability for a tenuous electron beam

Journal Article · Sun Jan 01 04:00:00 EST 1984 · Phys. Fluids; (United States)

DOI:https://doi.org/10.1063/1.864518· OSTI ID:5398190

Davidson, R C; McMullin, W A; Tsang, K

The free electron laser instability is investigated for a tenuous circulating electron beam propagating perpendicular to a uniform magnetic field B/sub 0/e/sub z/ and transverse wiggler field modeled by B/sub w/ sin k/sub 0/ye/sub x/ in planar geometry. Unlike the rippled-field magnetron which operates at Brillouin flow, the present analysis assumes a low-density electron beam with ..omega../sup 2//sub p/ <<..cap omega../sup 2//sub c/. Making use of a macroscopic cold-fluid model for the electrons coupled with Maxwell's equations for the fields, it is found that wave perturbations with ordinary-mode polarization (deltaEparallelB/sub 0/ and deltaBperpendicularB/sub 0/) amplify with characteristic maximum growth rate Im(delta..omega..) = ..omega../sub p/ (..cap omega../sub w//2ck/sub 0/) and emission frequency ..omega../sub r/ = (1+..beta../sub E/)..gamma../sup 2//sub E/k/sub 0/V/sub E/. Here, ..cap omega../sub w/ = eB/sub w//..gamma../sub E/mc, ..beta../sub E/ = V/sub E//C, ..gamma../sub E/ = (1-..beta../sup 2//sub E/)/sup -1//sup ///sup 2/, and V/sub E/ = -cE/sub 0//B/sub 0/, where E/sub 0/ is the applied electric field across the anode--cathode gap. Depending on the size of ..cap omega../sub w//ck/sub 0/, the characteristic exponentiation time ..omega../sup -1//sub p/(..cap omega../sub w//2ck/sub 0/)/sup -1/ for the cross-field free electron laser instability can be relatively short in units of ..omega../sup -1//sub p/.

• Research Organization: Plasma Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
• OSTI ID: 5398190
• Journal Information: Phys. Fluids; (United States), Journal Name: Phys. Fluids; (United States) Vol. 27:1; ISSN PFLDA
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420300* -- Engineering-- Lasers-- (-1989)
BEAMS
CROSSED FIELDS
DIFFERENTIAL EQUATIONS
ELECTRICAL EQUIPMENT
ELECTROMAGNETS
ELECTRON BEAMS
ELECTRON DENSITY
EQUATIONS
EQUIPMENT
FREE ELECTRON LASERS
INSTABILITY
LASERS
LEPTON BEAMS
MAGNETIC FIELDS
MAGNETS
MAXWELL EQUATIONS
MOTION
PARTIAL DIFFERENTIAL EQUATIONS
PARTICLE BEAMS
ROTATION
WIGGLER MAGNETS