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Resonant operation of the cross-field free-electron laser: Kinetic and fluid equilibria

Journal Article · · Phys. Rev. A; (United States)
Multiple-scale perturbation theory is used to obtain periodic orbits of relativistic electrons in the external electric and magnetic fields of a planar cross-field free-electron laser (FEL) operating near the fundamental resonance. The condition for this resonance is 2..gamma../sub 0/k/sub w/v/sub 0/approx. =(eB/sub 0//..gamma../sub 0/m/sub 0/) (1+a/sub w//sup 2/)/sup -1/2/, where k/sub w/ is the wave number of the magnetic wiggler field, v/sub 0/ = E/sub 0//B/sub 0/ is the electron drift speed in the crossed uniform electric and magnetic fields, ..gamma../sub 0/ = (1-v/sub 0//sup 2//c/sup 2/)/sup -1/2/ is the relativistic factor associated with the Lorentz transformation between the laboratory frame and the drift frame, m/sub 0/ is the rest mass of the electron, a/sub w/ = 2/sup -1/2/(eB/sub w//m/sub 0/ck/sub w/) is the normalized rms vector potential of the wiggler field, and B/sub w/ is the magnitude of the wiggler field. The orbits are expressed in an approximate form suitable for use in linearized Vlasov stability analysis and are used to obtain Vlasov distribution functions which correspond to kinetic equilibria that are uniform and nonuniform (across the anode-cathode gap). Appropriate moments of these distribution functions yield corresponding fluid equilibria. These equilibria are developed as a basis for a linear-stability analysis of the cross-field FEL operating near the fundamental resonance.
Research Organization:
Plasma Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
OSTI ID:
7001987
Journal Information:
Phys. Rev. A; (United States), Journal Name: Phys. Rev. A; (United States) Vol. 38:3; ISSN PLRAA
Country of Publication:
United States
Language:
English