Nonlinear Evolution of the Ion-Weibel Instability in Interpenetrating Plasmas of CH, Al, and Cu

The ion-Weibel instability is a leading candidate mechanism for the formation of collisionless shocks observed in may astrophysical systems. Experimental and computational studies have shown that the ion-Weibel instability drives current filamentation in interpenetrating plasma flows 1 , 2 with the capability to mediate collisionless shock formation and subsequent particle acceleration 3 in the lab. The present work focuses on the study of nonlinear ion-Weibel evolution under various plasma conditions through utilization of different ion species and experimental geometries. Temporally varying plasma condition are determined using benchmarked FLASH simulations. Path-integrated B-field distributions are retrieved from experimental proton images in all cases and Fourier analyzed to quantify the dominant filament scale-size and estimate the B-field strength. This new analysis methodology demonstrates that the first ~400ps of plasma interpenetration sets the spectral characteristics of ion-Weibel filamentation, and that underlying plasma conditions later in time do not significantly alter nonlinear filament evolution.