Rosenbluth Award: First observations of Rayleigh-Taylor-induced magnetic fields in laser-produced plasmas using x rays and protons

Recent experiments [Manuel, PRL 108 (2012)] demonstrated the existence of self-generated B-fields from the Rayleigh-Taylor (RT) instability in laser-produced plasmas, as originally predicted by Mima et al. [Mima PRL 41 (1978)]. Misaligned density and temperature gradients caused by RT growth in ablatively driven targets generate B-fields in the plasma through the Biermann battery source. X-ray and proton radiography diagnosed areal-density and B-field perturbations in laser-irradiated targets with seeded sinusoidal surface perturbations. Inferred B-field strengths indicated ratios of thermal to magnetic pressures ($\beta )$ near the ablation surface of 10$^{4}$--10$^{5}$, suggesting no magnetic effects on ablative RT during the linear growth phase. However, the magnitude of this self-generated field increases with the perturbation height [Srinivasan, PRL 108 (2012)] and can affect morphology in the nonlinear regime. The detailed structure of highly nonlinear RT spikes is important to understand the inner wall expansion of hohlraums in indirect-drive inertial fusion and in multiple astrophysical systems, including the explosion phase of core-collapse supernovae and formation of planetary nebulae. Numerical calculations investigating the magnetic effects on nonlinear RT-spike evolution under conditions similar to previous measurements will be covered and implications discussed. \\[4pt] Support for this work was provided by NASA through Einstein Postdoctoral Fellowship grant number PF3-140111 awarded by the Chandra X-ray Center, which is operated by the Astrophysical Observatory for NASA under contract NAS8-03060. This work is funded by the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasma under grant number DE-NA0001840. Previous work described here was supported in part by NLUF (DE-NA0000877), FSC/UR (415023-G), DoE (DE-FG52-09NA29553), LLE (414090-G), and LLNL (B580243).