Electromagnetic ($E/B$) fields generated by the interaction with plasmas of long-pulse, low-intensity laser beams relevant to inertial confinement fusion have been measured for the first time using novel monoenergetic proton radiography methods. High-resolution, time-gated radiography images of a plastic foil driven by a ${10}^{14}\mathrm{W}/{\mathrm{cm}}^2$ laser implied $B$ fields of $\sim 0.5\mathrm{MG}$ and $E$ fields of $\sim 1.5\times {10}^8\mathrm{V}/\mathrm{m}$. Simulations of these experiments with $\mathrm{LASNEX}+\mathrm{LSP}$ have been performed and are in overall (though not exact) agreement with the data both for field strengths and for spatial distributions; this is the first direct experimental test of the laser-generated $B$-field package in LASNEX. The experiments also demonstrated that laser phase plates substantially reduce medium-scale chaotic field structure.

• Received 2 June 2006

DOI:https://doi.org/10.1103/PhysRevLett.97.135003