Magnetic field measurements in laser-produced plasmas via proton deflectometry

Large magnetic fields generated during laser-matter interaction at irradiances of ∼5×1014 W cm−2 have been measured using a deflectometry technique employing MeV laser-accelerated protons. Azimuthal magnetic fields were identified unambiguously via a characteristic proton deflection pattern and found to have an amplitude of ∼45 T in the outer coronal region. Comparison with magnetohydrodynamic simulations confirms that in this regime the ∇Te×∇ne source is the main field generation mechanism, while additional terms are negligible.