Proton radiography of megagauss electromagnetic fields generated by the irradiation of a solid target by an ultraintense laser pulse

Laser generated protons have been used to probe the temporal and spatial evolution of megagauss magnetic fields. Grid deflectometry techniques have been applied to proton radiography to obtain precise measurements of proton beam angles caused by magnetic fields in laser produced plasmas. Data are presented in two different regimes of interactions at ultra high intensity (1020 W/cm ²) where hots electrons are supposed to be responsible of the B field, and at lower intensity (1017 W/cm²) and later time where the gradients of temperature and density are responsible of the B field.