Numerical study of long CO2 laser pulse interactions with hydrogen plasma at ATF

Laser-driven plasma Wakefield Accelerators (LWFAs) can sustain accelerating gradients that greatly surpass those of standard accelerators. Long (~ps) and intense (>TW) laser pulses have been employed in LWFAs to generate bright, hard x-rays which are of interest for imaging and diagnosing warm-dense matter. We explore the LWFA regime using a long TW class CO2 (~10.6µm) laser to excite wakefields in a hydrogen plasma in the experiment AE71 at the ATF facility of the Brookhaven National Laboratory. In that experiment, the laser encompasses hundreds of plasma skin depths allowing for three different regimes of laser and plasma interaction: laser self-modulation, laser disruption along with transversely spread out plasma bubbles and laser self-channeling. In this talk, numerical results will be presented to show the main properties of those laser and plasma interactions for different configurations experimentally tested as well as the effects imprinted on the frequency-doubled Nd:YAG and electron beam probes. The simulations were done using the Particle in Cell code OSIRIS [R.A.Fonseca, LNCS (2331) 342, 2002].