Magnetised thermal self-focusing and filamentation of long-pulse lasers in plasmas relevant to magnetised ICF experiments

• Published in: Physics of plasmas 2018-09, Vol.25 (9)
• Main Authors: Watkins, H. C., Kingham, R. J.
• Format: Article
• Language: English
• Subjects: Computer simulation; Electron transport; Experiments; Heat transfer; Inertial fusion (reactor); Laser beam heating; Lasers; Magnetic fields; Plasma; Plasma physics; Plasmas (physics); Propagation; Thermal conductivity
• ISSN: 1070-664X; 1089-7674
• DOI: 10.1063/1.5049229

In this paper, we study the influence of the magnetised thermal conductivity on the propagation of a nanosecond 1014 W cm−2 laser in an underdense plasma by performing simulations of a paraxial model laser in a plasma with the full Braginskii magnetised transport coefficients. Analytical theory and simulations show the shortening of the self-focal length of a laser beam in a plasma as a result of the reduction of the plasma thermal conductivity in a magnetic field. Furthermore, the filamentation of a laser via the thermal mechanism is found to have an increased spatial growth rate in a magnetised plasma. We discuss the effect of these results on recent magnetised inertial fusion experiments where filamentation can be detrimental to laser propagation and uniform laser heating. We conclude that the application of external magnetic fields to laser-plasma experiments requires the inclusion of the extended electron transport terms in simulations of laser propagation.