title: Measurement of magnetic-field structures in a laser-wakefield accelerator.
abstract: Experimental measurements of magnetic fields generated in the cavity of a self-injecting laser-wakefield accelerator are presented. Faraday rotation is used to determine the existence of multimegagauss fields, constrained to a transverse dimension comparable to the plasma wavelength ∼λp and several λp longitudinally. The fields are generated rapidly and move with the driving laser. In our experiment, the appearance of the magnetic fields is correlated with the production of relativistic electrons, indicating that they are inherently tied to the growth and wave breaking of the nonlinear plasma wave. This evolution is confirmed by numerical simulations, showing that these measurements provide insight into the wakefield evolution with high spatial and temporal resolution.
authors.affiliation: Institut für Optik und Quantenelektronik, Friedrich-Schiller-Universität, 07743 Jena, Germany.
authors.forename: M C
authors.initials: MC
authors.lastname: Kaluza
authors.forename: H-P
authors.initials: HP
authors.lastname: Schlenvoigt
authors.forename: S P D
authors.initials: SP
authors.lastname: Mangles
authors.forename: A G R
authors.initials: AG
authors.lastname: Thomas
authors.forename: A E
authors.initials: AE
authors.lastname: Dangor
authors.forename: H
authors.initials: H
authors.lastname: Schwoerer
authors.forename: W B
authors.initials: WB
authors.lastname: Mori
authors.forename: Z
authors.initials: Z
authors.lastname: Najmudin
authors.forename: K M
authors.initials: KM
authors.lastname: Krushelnick