title: Exceeding the leading spike intensity and fluence limits in backward Raman amplifiers.
abstract: The leading amplified spike in backward Raman amplifiers can reach nearly relativistic intensities before the saturation by the relativistic electron nonlinearity. The saturation sets an upper limit to the largest achievable leading spike intensity. It is shown here that this limit can be substantially exceeded by the initially subdominant spikes, which surprisingly outgrow the leading spike after its nonlinear saturation. Furthermore, an initially negligible group velocity dispersion of the amplified pulse in strongly undercritical plasma appears to be capable of delaying the longitudinal filamentation instability in the nonlinear saturation regime. This enables further amplification of the pulse to even larger output fluences.
authors.affiliation: Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey 08540, USA.
authors.forename: V M
authors.initials: VM
authors.lastname: Malkin
authors.affiliation: Department of Electrical Engineering, Technion Israel Institute of Technology, Haifa 32000, Israel.
authors.forename: Z
authors.initials: Z
authors.lastname: Toroker
authors.affiliation: Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey 08540, USA.
authors.forename: N J
authors.initials: NJ
authors.lastname: Fisch