Experimental evidence of early-time saturation of the ion-Weibel instability in counterstreaming plasmas of CH, Al, and Cu
The collisionless ion-Weibel instability is a leading candidate mechanism for the formation of collisionless shocks in many astrophysical systems, where the typical distance between particle collisions is much larger than the system size. Multiple laboratory experiments aimed at studying this process utilize laser-driven (I≳1015 W/cm2), counterstreaming plasma flows (V≲ 2000 km/s) to create conditions unstable to Weibel-filamentation and growth. This technique intrinsically produces temporally varying plasma conditions at the midplane of the interaction where Weibel-driven B fields are generated and studied. Experiments discussed herein demonstrate robust formation of Weibel-driven B fields under multiple plasma conditions using CH, Al, and Cu plasmas. Linear theory based on benchmarked radiation-hydrodynamic FLASH calculations is compared with Fourier analyses of proton images taken ~5–6 linear growth times into the evolution. Our new analyses presented here indicate that the low-density, high-velocity plasma-conditions present during the first linear-growth time (~300–500 ps) sets the spectral characteristics of Weibel filaments during the entire evolution. It is shown that the dominant wavelength (~300 μm) at saturation persists well into the nonlinear phase, consistent with theory under these experimental conditions. However, estimates of B-field strength, while difficult to determine accurately due to the path-integrated nature of proton imaging, are shown to be in the ~10–30 T range, an order of magnitude above the expected saturation limit in homogenous plamas but consistent with enhanced B fields in the midplane due to temporally varying plasma conditions in experiments.
- Research Organization:
- Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA); General Atomics; National Aeronautics and Space Administration (NASA)
- Grant/Contract Number:
- AC52-07NA27344; NA0003842; NA0001808; PF3-14011
- OSTI ID:
- 2281470
- Report Number(s):
- LLNL-JRNL-859049; 1089702
- Journal Information:
- Physical Review. E, Vol. 106, Issue 5; ISSN 2470-0045
- Publisher:
- American Physical Society (APS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Similar Records
Steady-State Electrostatic Layers From Weibel Instability in Relativistic Collisionless Shocks
Disruption of Current Filaments and Isotropization of the Magnetic Field in Counterstreaming Plasmas