Mitigating Particle Integration Error in Relativistic Laser-Plasma Simulations

In particle-in-cell simulations of laser wakefield accelerators with $a_0$ greater than unity, errors in particle trajectories produce incorrect beam charges and energies [1], predicting performance not realized in experiments such as the Texas Petawatt Laser [2]. In order to avoid these errors, the simulation time step must resolve a time scale smaller than the laser period by a factor of $a_0$. If the Yee scheme advances the fields with this time step, the laser wavelength must be over-resolved by a factor of $a_0$ to avoid dispersion errors. Here is presented and demonstrated with Vorpal [3] simulations, a new electromagnetic algorithm, building on previous work [4, 5, 6], correcting Yee dispersion for arbitrary sub-CFL time steps, reducing simulation times by $a_0$. \\ [1] A. V. Arefiev, et al., Physics of Plasmas (1994-present) 22, 013103 (2015). \\ [2] X. Wang, et al., Nature communications 4, 1988 (2013). \\ [3] C. Nieter and J. R. Cary, J. Comp. Phys. 196, 448 (2004). \\ [4] B. M. Cowan, et al., Phys. Rev. Special Topics- Accelerators and Beams 16, 041303 (2013). \\ [5] B. Finkelstein and R. Kastner, J. of Comp. Phys. 221, 422 (2007). \\ [6] R. Lehe, A. Lifschitz, C. Thaury, V. Malka, and X. Davoine, Physical Review Special Topics-Accelerators and Beams, 021301 (2013).