title: Spectral enhancement in the double pulse regime of laser proton acceleration.
abstract: The use of two separate ultraintense laser pulses in laser-proton acceleration was compared to the single pulse case employing the same total laser energy. A double pulse profile, with the temporal separation of the pulses varied between 0.75-2.5 ps, was shown to result in an increased maximum proton energy and an increase in conversion efficiency to fast protons by up to a factor of 3.3. Particle-in-cell simulations indicate the existence of a two stage acceleration process. The second phase, induced by the main pulse preferentially accelerates slower protons located deeper in the plasma, in contrast to conventional target normal sheath acceleration.
authors.affiliation: Central Laser Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, United Kingdom. keith.markey@stfc.ac.uk
authors.forename: K
authors.initials: K
authors.lastname: Markey
authors.forename: P
authors.initials: P
authors.lastname: McKenna
authors.forename: C M
authors.initials: CM
authors.lastname: Brenner
authors.forename: D C
authors.initials: DC
authors.lastname: Carroll
authors.forename: M M
authors.initials: MM
authors.lastname: Günther
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authors.initials: K
authors.lastname: Harres
authors.forename: S
authors.initials: S
authors.lastname: Kar
authors.forename: K
authors.initials: K
authors.lastname: Lancaster
authors.forename: F
authors.initials: F
authors.lastname: Nürnberg
authors.forename: M N
authors.initials: MN
authors.lastname: Quinn
authors.forename: A P L
authors.initials: AP
authors.lastname: Robinson
authors.forename: M
authors.initials: M
authors.lastname: Roth
authors.forename: M
authors.initials: M
authors.lastname: Zepf
authors.forename: D
authors.initials: D
authors.lastname: Neely