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

### Examining electron beam spin conditioning using particle-tracking simulations in QuickPIC

J. Vieira1, R. A. Fonseca1, 2, L. O. Silva1, C. Huang3, W. B. Mori3, 4

1 GoLP/Instituto de Plasmas e Fus?o Nuclear
2 Insituto Superior de Ciencias do Trabalho e da Empresa
3 Department of Electrical Engeneering, University of California, Los Angeles, U.S.A.
4 Department of Physics and Astronomy, University of California, Los Angeles, U.S.A.

Particle-in-cell (PIC) simulations play a major role in the design and planning of laser and plasma wakefield accelerator (LWFA/PWFA) experiments. However, as future experiments plan to reach $\small 1-10$ GeV electron beams in $\small 1-10$ cm scale plasmas, full PIC simulations become very computationally expensive. Therefore, innovative numerical algorithms (for instance, the use of quasi-static approximation [1] or simulations in boosted frames [2,3]) have been or are currently being developed to reduce the computational requirements associated with LWFA/PWFA PIC simulations. One of such codes is QuickPIC, a fully relativistic PIC code which works under the quasi-static approximation, and that can be up to three orders of magnitude faster than standard PIC codes.

In this work, a particle-tracking algorithm was implemented in QuickPIC to examine in detail the dynamics of externally injected beams during the acceleration. In order to track the beam particles, a random fraction of the beam was initialized with extra-tags, and pushed like the regular beam, without, however, depositing any charge or current. The particle tracked data, which includes both fields and particle data, is used to examine the spin-precession of polarized electron beams in LWFA. The simulations indicate that low depolarizations can be reached in the LWFA, which exhibits polarization rates which are comparable or lower than those present in standard linear accelerators.

[1] C. Huang et al, J. of Comp. Phys. 217, 2 (2006).

[2] J.-L. Vay et al, Phys. Rev. Lett. 98, 130405 (2007).

[3] S.F. Martins et al, in preparation.