Envelope Model Simulation of Realistic Laser Pulses at the Texas Petawatt Laser

Kathleen Weichman, University of Texas

Photo of Kathleen Weichman

In laser wakefield acceleration, an intense laser pulse drives a nonlinear plasma wave, generating accelerating gradients up to three orders of magnitude higher than found in conventional radio-frequency accelerators. Laser wakefield accelerators can produce sub-milliradian divergence, femtosecond-duration electron bunches over acceleration lengths of less than a meter. Quasi-monoenergetic electron spectra in excess of 2 GeV have been reported at the Texas Petawatt Laser facility<sup>1</sup>. Gaussian and near-Gaussian beam simulations predict energies higher than have been experimentally demonstrated<sup>2</sup>. Real laser pulses often exhibit intensity and phase irregularities and may deviate significantly from the ideal Gaussian profile. New methods in particle-in-cell (PIC) codes, such as the implementation of the envelope model in VORPAL<sup>3,4</sup>, have lowered the computational cost of simulating the early evolution of laser wakefields in three dimensions. Future simulations will capture the entire accelerating structure, starting with an early-time envelope model simulation, continued by a boosted frame PIC simulation<sup>5</sup>. As the first stage in a full 3-D laser wakefield simulation, we present early-time VORPAL envelope model simulations of wakefields produced by laser pulses with experimentally measured profiles from the Texas Petawatt Laser.

<sup>1</sup>X. Wang, R. Zgadzaj, N. Fazel, Z. Li, S. Yi, X. Zhang, W. Henderson, Y.-Y. Chang, R. Korzekwa, H.-E. Tsai, et al., <em>Nature Communications</em> 4, 1988 (2013).
<sup>2</sup>S.Y. Kalmykov, S.A. Yi, A. Beck, A.F. Lifschitz, X. Davoine, E. Lefebvre, A. Pukhov, V. Khudik, G. Shvets, S.A. Reed, et al., <em>New Journal of Physics</em> 12, 045019 (2010).
<sup>3</sup>C. Nieter and J.R. Cary, <em>Journal of Computational Physics</em> 196, 448 (2004).
<sup>4</sup>B.M. Cowan, D.L. Bruhwiler, E. Cormier-Michel, E. Esarey, C.G. Geddes, P. Messmer, and K.M. Paul, <em>Journal of Computational Physics</em> 230, 61 (2011).
<sup>5</sup>J. Vay, D. Bruhwiler, C. Geddes, W. Fawley, S. Martins, J. Cary, E. Cormier-Michel, B. Cowan, R. Fonseca, M. Furman, et al., <em>Journal of Physics: Conference Series</em> 180, 012006 (2009).

Abstract Author(s): K. Weichman, A.V. Higuera, D.T. Abell, B. Cowan, N. Fazel, J.R. Cary, M.C. Downer