Experimental investigation of late-time nonlinear evolution of ion-Weibel filaments

The Weibel instability is a candidate mechanism for the generation of astrophysical seed fields: PIC simulations suggest that Weibel-generated fields might scale much more favorably for long length scales (𝐵∝𝐿⁰) than the Biermann-generated fields (𝐵∝𝐿^-1). This possibility, however, requires a mechanism to explain how Weibel field structures grow to large length scales. Existing theory and simulations provide models whose predictions differ substantially depending on the included physics: one model [C. Ruyer et al., Physics of Plasmas 22, 032102 (2015)] predicts filament wavelengths grow as 𝜆∝t², while another model [M. Zhou, et al., Phys. Rev. Res. 1, 012004 (2019)] predicts 𝜆∝t^1/2 (with time, t, representing asymptotically late times). Presented in this work are new OMEGA experimental measurements at later times than previously observed. Proton radiography measurements are used to capture filament evolution over a large field of view and Thomson scattering records the plasma conditions and sub-filament structure, with the objective of determining which model best matches the late-time filament dynamics.