Axial proton probing of magnetic and electric fields inside laser-driven coils

In a laser-driven coil, a laser is used to eject electrons from a plate, which then draws a current through a loop. Diagnosing the field strength, geometry, and conditions within these loops has been one of the primary difficulties in fielding this type of target. In this paper, the diagnostic technique of axial proton probing with a mesh fiducial of a laser-driven coil is demonstrated. Multiple coil types were driven by a 1ns, 1.25kJ long pulse beam and probed several times. This technique provides significantly more information than transverse probing on electric- and magnetic-field strength in the region of interest and shows in our experiment complex, non-uniform current path structures and charge distribution.