Suppression of Electromagnetic Pulses from Laser-Target Interactions by Strong Magnetic Fields

TL;DR

Applying magnetic fields during laser-target interactions can suppress electromagnetic pulses at moderate intensities but may increase EMP at very high intensities, indicating limited effectiveness for EMP mitigation.

Contribution

This study provides experimental evidence on how magnetic fields influence EMP generation across different laser intensities and geometries, highlighting limitations for high-intensity applications.

Findings

Magnetic fields reduce EMP at moderate laser intensities (~10^{13} to 10^{15} W/cm^2).

EMP suppression factors of 0.65 and 0.32 observed in experiments.

At very high intensities (~10^{19} W/cm^2), magnetic fields increase EMP by 1.75 times.

Abstract

Laser-target interactions generate intense electromagnetic pulses (EMP) that can interfere with measurements and damage equipment. In this paper we show that applying a magnetic field to nanosecond pulse laser-target interactions decreases the magnitude of EMP. We demonstrate this effect in two experiments with different geometries (spherical vs. planar), laser intensities (${\sim}10^{13}$ vs. ${\sim} 10^{15}$~W/cm$^2$) and applied field strength (12~T vs. 0.1~T) that both observed suppression of EMP in the ${\sim} 1$~GHz band (by factors of $0.65\times$ and $0.32\times$ respectively). We then observe the opposite effect at high intensities with a picosecond pulse: for planar experiments with laser intensities ${\sim}10^{19}$~W/cm$^2$ and magnetic fields of 6--10~T, the magnitude of EMP is increased by a factor of $1.75\times$. These results provide a benchmark for models of EMP generation, but suggest that magnetic fields are not a viable solution for mitigating EMP on the high intensity laser facilities where it is most damaging.