Proton moire fringes for diagnosing electromagnetic fields in opaque materials and plasmas

High contrast proton moire fringes have been obtained in a laser-produced proton beam. Moire fringes with modulation of 20%–30% were observed in protons with energies in the range of 4–7 MeV. Monte Carlo simulations with simple test fields showed that shifts in the moire fringes can be used to give quantitative information on the strength of transient electromagnetic fields inside plasmas and materials that are opaque to conventional probing methods.