Mitigating cross-beam energy transfer in directly-driven inertial-confinement-fusion targets using broadband laser light

Cross-beam energy transfer (CBET) is a significant energy-loss mechanism in directly-driven inertial-confinement-fusion (ICF) targets. Simulations performed with the wave-based code LPSE suggest that Gaussian laser bandwidths of 2 – 5 THz (corresponding to normalized bandwidths of 0.2% – 0.6%, respectively, at a laser wavelength of 351 nm) are effective at suppressing CBET under realistic plasma conditions [J. Bates et al., Phys. Rev. E 97, 061202(R) (2018)]. Although such values exceed those currently available with high-energy Nd:glass lasers used in ICF research today, effective CBET mitigation could likely be achieved by employing excimer laser drivers, which have native bandwidths in the multiterahertz regime. An alternate approach for suppressing CBET might be to pass narrow-band, Nd:glass laser light through diatomic gas cells and to rely on the phenomenon of stimulated rotational Raman scattering to augment the laser spectrum with additional discrete-wavelength components [D. Eimerl, D. Milam and J. Yu, Phys. Rev. Lett. 70, 2738 (1993)]. In this presentation, we review our modeling of these approaches with LPSE to date and assess their respective efficacies for suppressing CBET in ICF plasmas.