title: Collimated multi-MeV ion beams from high-intensity laser interactions with underdense plasma.
abstract: A beam of multi-MeV helium ions has been observed from the interaction of a short-pulse high-intensity laser pulse with underdense helium plasma. The ion beam was found to have a maximum energy for He2+ of (40(+3)(-8)) MeV and was directional along the laser propagation path, with the highest energy ions being collimated to a cone of less than 10 degrees. 2D particle-in-cell simulations show that the ions are accelerated by a sheath electric field that is produced at the back of the gas target. This electric field is generated by transfer of laser energy to a hot electron beam, which exits the target generating large space-charge fields normal to its boundary.
authors.affiliation: Blackett Laboratory, Imperial College London, London SW7 2BZ, United Kingdom.
authors.forename: L
authors.initials: L
authors.lastname: Willingale
authors.forename: S P D
authors.initials: SP
authors.lastname: Mangles
authors.forename: P M
authors.initials: PM
authors.lastname: Nilson
authors.forename: R J
authors.initials: RJ
authors.lastname: Clarke
authors.forename: A E
authors.initials: AE
authors.lastname: Dangor
authors.forename: M C
authors.initials: MC
authors.lastname: Kaluza
authors.forename: S
authors.initials: S
authors.lastname: Karsch
authors.forename: K L
authors.initials: KL
authors.lastname: Lancaster
authors.forename: W B
authors.initials: WB
authors.lastname: Mori
authors.forename: Z
authors.initials: Z
authors.lastname: Najmudin
authors.forename: J
authors.initials: J
authors.lastname: Schreiber
authors.forename: A G R
authors.initials: AG
authors.lastname: Thomas
authors.forename: M S
authors.initials: MS
authors.lastname: Wei
authors.forename: K
authors.initials: K
authors.lastname: Krushelnick