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

### Assessing the role of bandwidth effects and frequency fluctuation in laser wake field generation with ensemble averaged PIC simu

V. B Pathak, J. L. Martins, R. A. Fonseca, L. O. Silva

GoLP/Instituto de Plasmas e Fus?o Nuclear, Instituto Superior T?cnico, Lisboa, Portugal

The next generation of ultra high intensity laser systems for laser driven fusion and plasma accelerator facilities will use multiple laser beam systems to achieve very high intensities. These beams may have small frequency mismatches, due to the separate optics involved. We study the effect of random variation in the frequencies of the multiple laser drivers on wake-field generation in underdense plasmas with averages over statistical ensembles of PIC simulations. In our 2D PIC simulations, we have explored the conditions close to optimal excitation of the wake field, by using 10 laser pulses propagating in same direction, with FWHM~$\small c/\lambda_{p}$, normalized vector potential $\small a_{0}=0.1$ and frequency of $\small j_{th}$ beam $\small \omega_{j}=\omega_{0}\pm\Delta_{j}$, where $\small \Delta_{j}$ is the random small fluctuation. In each run we introduce random fluctuation in the frequencies. Taking advantage of the absolute reproducibility of the numerical features of the simulations in Osiris [1], we take ensemble average over a large number of runs to explore the effects associated with the enhanced laser bandwidth. For $\small \Delta_{j}$ up to 20% of the frequency we observe no significant change in wake field generation in each run.

[1] R. A. Fonseca, L. O. Silva, F. S. Tsung, et al., OSIRIS: a three-dimensional, fully relativistic particle in cell code for modeling plasma based accelerators, Lect. Notes Comput. Sci., 2331, 342 (2002).

Work partially supported by FCT (Portugal).