Test ion acceleration in a dynamic planar electron sheath
Institute for Theoretical and Experimental Physics, B. Cheremushkinskaya 25, 117218 Moscow, Russian Federation
Corresponding author: a email@example.com
Revised: 13 October 2006
Published online: 8 December 2006
New exact results are obtained for relativistic acceleration of test positive ions in the laminar zone of a planar electron sheath evolving from an initially mono-energetic electron distribution. The electron dynamics is calculated against the background of motionless foil ions. The limiting gamma-factor γp∞ of accelerated ions is shown to be determined primarily by the values of the ion-electron charge-over-mass ratio μ=meZp/mp and the initial gamma-factor γ0 of the accelerated electrons. For μ> 1/8 a test ion always overtakes the electron front and attains γp∞> γ0. For μ< 1/8 a test ion can catch up with the electron front only when γ0 is above a certain critical value γcr, which for μ≪1 can most often be evaluated as . In this model the protons and heavier test ions, for which γcr> 10398 is enormous, always lag behind the front edge of the electron sheath and have γp∞< γ0; for their maximum energy an appropriate intermediate asymptotic formula is derived. The domain of applicability of the laminar-zone results is analyzed in detail.
PACS: 52.38.Kd – Laser-plasma acceleration of electrons and ions / 52.40.Kh – Plasma sheaths
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2006