title: Helical electron-beam microbunching by harmonic coupling in a helical undulator.
abstract: Microbunching of a relativistic electron beam into a helix is examined analytically and in simulation. Helical microbunching is shown to occur naturally when an e beam interacts resonantly at the harmonics of the combined field of a helical magnetic undulator and an axisymmetric input laser beam. This type of interaction is proposed as a method to generate a strongly prebunched e beam for coherent emission of light with orbital angular momentum at virtually any wavelength. The results from the linear microbunching theory show excellent agreement with three-dimensional numerical simulations.
authors.affiliation: Particle Beam Physics Laboratory, Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA.
authors.forename: E
authors.initials: E
authors.lastname: Hemsing
authors.forename: P
authors.initials: P
authors.lastname: Musumeci
authors.forename: S
authors.initials: S
authors.lastname: Reiche
authors.forename: R
authors.initials: R
authors.lastname: Tikhoplav
authors.forename: A
authors.initials: A
authors.lastname: Marinelli
authors.forename: J B
authors.initials: JB
authors.lastname: Rosenzweig
authors.forename: A
authors.initials: A
authors.lastname: Gover