Structure of Self-Generated Magnetic Fields in Laser-Solid Interaction from Proton Tomography.

Self-generated magnetic fields in laser-solid interactions are experimentally characterized to reveal the 3D location and local field strength, rather than path-integrated quantities, using multiview proton radiography and tomographic inversion. We infer magnetic fields that extend several millimeters off the target into the hot, rarefied corona, sufficient to strongly magnetize the plasma (Ω_{e}τ_{e}≫1). The data are compared to magnetohydrodynamic simulations incorporating recent improvements in modeling magnetic field generation and transport; the volume-averaged coronal field strength and magnetic flux agree to within 25% using a model with magnetic relocalization of transport, although the near-target morphology is not reproduced. This Letter demonstrates tomographic proton radiography as a valuable tool for investigating magnetic fields in laser-produced plasmas.