Kinetic Modelling of CBET Mitigation Using Laser Bandwidth

In the context of direct-drive inertial confinement fusion (ICF), it has been acknowledged that the levels of cross-beam energy transfer (CBET) found in current experiments would likely preclude ignition in a full-scale shot[1]. In experiments on the OMEGA laser, CBET reduces laser-target coupling by up to 30\%[2], with even higher losses on the NIF[1]. Increased laser driver bandwidth offers a promising route to mitigate CBET and other laser-plasma instabilities, which would allow for a significant expansion of the ICF design space. Here we present VPIC[3] particle-in-cell simulations investigating the efficacy of bandwidth in reducing CBET. We compare the PIC results with linearized fluid simulations performed with the LPSE code[4] and discuss the significance of nonlinear kinetic and fluid effects and their response to bandwidth. [1] V. N. Goncharov et al. (2017). Plasma Physics and Controlled Fusion, 59(1), 014008. [2] I. V. Igumenshchev et al. (2010). Physics of Plasmas, 17(12), 21–26. [3] K. J. Bowers et al. (2008). Physics of Plasmas, 15(5), 055703. [4] J. F. Myatt et al. (2019). Journal of Computational Physics, 399, 108916.