title: Surface acceleration of fast electrons with relativistic self-focusing in preformed plasma.
abstract: We report an observation of surface acceleration of fast electrons in intense laser-plasma interactions. When a preformed plasma is presented in front of a solid target with a higher laser intensity, the emission direction of fast electrons is changed to the target surface direction from the laser and specular directions. This feature could be caused by the formation of a strong static magnetic field along the target surface which traps and holds fast electrons on the surface. In our experiment, the increase in the laser intensity due to relativistic self-focusing in plasma plays an important role for the formation. The strength of the magnetic field is calculated from the bent angle of the electrons, resulting in tens of percent of laser magnetic field, which agrees well with a two-dimensional particle-in-cell calculation. The strong surface current explains the high conversion efficiency on the cone-guided fast ignitor experiments.
authors.affiliation: Graduate School of Engineering, Osaka University, 2-1, Yamada-oka, Suita, Osaka 565-0871, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Habara
authors.forename: K
authors.initials: K
authors.lastname: Adumi
authors.forename: T
authors.initials: T
authors.lastname: Yabuuchi
authors.forename: T
authors.initials: T
authors.lastname: Nakamura
authors.forename: Z L
authors.initials: ZL
authors.lastname: Chen
authors.forename: M
authors.initials: M
authors.lastname: Kashihara
authors.forename: R
authors.initials: R
authors.lastname: Kodama
authors.forename: K
authors.initials: K
authors.lastname: Kondo
authors.forename: G R
authors.initials: GR
authors.lastname: Kumar
authors.forename: L A
authors.initials: LA
authors.lastname: Lei
authors.forename: T
authors.initials: T
authors.lastname: Matsuoka
authors.forename: K
authors.initials: K
authors.lastname: Mima
authors.forename: K A
authors.initials: KA
authors.lastname: Tanaka