Heat transport in high-energy-density environments is a fundamental process that is strongly influenced by magnetic fields. Indeed, magnetic fields are expected to play a crucial role in Inertial Confinement Fusion (ICF) [1] and in numerous astrophysical systems, inherently modifying the system behavior, hydrodynamics, and energy dissipation. However, accurately modelling the interplay between thermal transport and magnetic fields remains challenging, further hindered by a lack of experimental data.

To address this, an experimental campaign was undertaken at LULI2000 to investigate the impact of magnetic fields on heat transport. High-power lasers heated up gas jets of various compositions and pressures, while a pulsed-power-driven coil generated external magnetic fields up to 20 T [2]. The plasma conditions were characterized using multiple temporally and spatially resolved diagnostics, including Thomson scattering and interferometry.

Our results show that the peak electron temperature increases by approximately 1.4 times relative to the unmagnetized case, as cross-field thermal conduction is maximally suppressed. This state occurs when the electron Hall parameter exceeds a value of ~50 and is sustained over ~0.5 ns. The subsequent temperature decrease is primarily driven by a drop in inverse-bremsstrahlung heating as the electron density cavitates. These experimental results, corroborated by Vlasov-Fokker-Planck simulations, demonstrate that effective magneto-thermal insulation can occur in magnetized ICF schemes without the need for extremely large magnetic fields.

[1] Moody, J. D., et al. "Increased ion temperature and neutron yield observed in magnetized indirectly driven d 2-filled capsule implosions on the national ignition facility." Physical Review Letters 129.19 (2022): 195002.
[2] Albertazzi, Bruno, et al. "Production of large volume, strongly magnetized laser-produced plasmas by use of pulsed external magnetic fields." Review of Scientific Instruments 84.4 (2013).