Topic/Type: 1.3 High intensity Laser Plasma Interaction, Oral

### Numerical study of ion acceleration in the interaction of an intense laser beam normally incident on an overdense plasma

M. Shoucri1, B. Afeyan2

1 -Institut de recherche d?Hydro-Qu?bec (IREQ), Varennes, Qu?bec, Canada, J3X1S1
2 Polymath Research Inc., Pleasanton, CA, USA

An Eulerian code is used for the numerical solution of the one-dimensional relativistic Vlasov-Maxwell equations for both electrons and ions to study the ion acceleration in the interaction of an intense laser beam with an overdense plasma. The laser beam is circularly polarized and normally incident on the plasma surface. We consider the case when the laser wavelength $\small \lambda_0$ is greater than the scale length of the jump in the plasma density at the plasma edge $\small L_{\mathrm{edge}}$ ( $\small \lambda_0 \gg L_{\mathrm{edge}}$), and the ratio of the plasma density to the critical density is . The incident high intensity laser radiation is pushing the electrons at the plasma surface through the ponderomotive pressure, producing a sharp density gradient at the wave-front plasma- surface interface. There is a constant radiation pressure maintained at the plasma surface by the incident circularly polarized laser beam, which results in a build-up of the electron density at this sharp edge and creates a space-charge, giving rise to a longitudinal electric field at the plasma edge. Ions are accelerated in this edge electric field and reach a free streaming expansion phase where they are neutralized by the electrons. A dense and compact bunch of quasineutral plasma is formed and expands. The energetic ions produced have a narrow energy spread. The generation and propagation of collisionless shock waves in this system are investigated. The numerical method used to advance in time the Vlasov equations consists of interpolation along the characteristics in the two-dimensional phase-space, using a tensor product of cubic B-spline [1]. The low noise level of the Eulerian Vlasov code allows a detailed representation of the phase-space structures associated with this system, especially in the low density regions of the phase-space where ions are accelerated.

The contribution of B.Afeyan is funded by the DOE NNSA SSAA Grants program.

[1] M. Shoucri Comm. Comp. Phys. 4, 703 (2008)