Accurate measurement of magnetic fields produced by laser-driven coil targets via proton radiography

The spatiotemporal evolution of electromagnetic fields generated by a relativistic-intensity laser pulse irradiating a capacitor–coil target was diagnosed using proton radiography. In the experiments, both an electromagnetic pulse (EMP) propagating at approximately the speed of light immediately after the laser–target interaction and a magnetic field generated by the coil current were observed. The results demonstrate a clear spatiotemporal separation between the proton signals induced by the EMP and those induced by the coil magnetic field. This separation enables accurate measurement of the magnetic field generated by the coil current after the EMP has subsided.