Kilotesla magnetic field generation via ultraintense laser interaction with hollow microcapsule

We investigate the generation of kilotesla-level magnetic fields in laser-irradiated hollow conical targets through particle-in-cell simulations. This configuration proves effective in producing magnetic fields tens of kiloteslas in strength that persist on a picosecond timescale. Moreover, the hollow conical shape provides an azimuthal structure to the magnetic fields within its interior, leading to large magnetized regions in a confined geometry, even under relatively modest laser intensities. The time evolution of the magnetic field is captured by an effective RL circuit model, in which the current loop-consisting of the driven forward hot electrons and the return currents along the walls-discharges inductively after the laser stops driving the current. The high magnetic field regions shrink closer to the wall through this magnetic energy decay as the magnetic pressure shrinks. These findings provide valuable possibilities for future experimental studies-based on the capability of confining and collimating particles-and have potential applications in areas such as laboratory astrophysics, fast ignition, and particle acceleration.