Strong surface magnetic field generation in relativistic short pulse laser-plasma interaction with an applied seed magnetic field

• Published in: New journal of physics Vol. 22; no. 11; pp. 113009 - 113020
• Main Authors: Weichman, K, Robinson, A P L, Murakami, M, Arefiev, A V
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.11.2020
• Subjects: Cyclotrons; Diamagnetism; Electrons; high energy density physics; Irradiation; Laser beam heating; laser-plasma interaction; Lasers; magnetic field generation; Magnetic fields; Particle in cell technique; particle-in-cell simulations; Physics; Plasma dynamics; Plasma interactions; Target thickness
• ISSN: 1367-2630; 1367-2630
• DOI: 10.1088/1367-2630/abc496

While plasma often behaves diamagnetically, we demonstrate that the laser irradiation of a thin opaque target with an embedded target-transverse seed magnetic field Bseed can trigger the generation of an order-of-magnitude stronger magnetic field with opposite sign at the target surface. Strong surface field generation occurs when the laser pulse is relativistically intense and results from the currents associated with the cyclotron rotation of laser-heated electrons transiting through the target and the compensating current of cold electrons. We derive a predictive scaling for this surface field generation, Bgen ∼ −2πBseedΔx/λ0 (in the large spot size limit), where Δx is the target thickness and λ0 is the laser wavelength, and conduct 1D and 2D particle-in-cell simulations to confirm its applicability over a wide range of conditions. We additionally demonstrate that both the seed and surface-generated magnetic fields can have a strong impact on application-relevant plasma dynamics, for example substantially altering the overall expansion and ion acceleration from a μm-thick laser-irradiated target with a kilotesla-level seed magnetic field.