Generation, measurement, and modeling of strong magnetic fields generated by laser-driven micro coils

Strong magnetic fields play an important role in high-energy-density plasma. Several approaches have been investigated within a decade to access the strong magnetic field over 100 T using high-power or high-intensity lasers. A laser-driven coil, one of the approaches, can generate a strong magnetic field over 100 T and has been applied to a lot of high-energy-density-plasma experiments. However, the mechanism of the laser-driven coil is still not fully understood and not controllable because of the lack of experimental data. In this review, we briefly introduce several approaches to generate a strong magnetic field by using high-power or high-intensity laser pulses such as spontaneous magnetic field, flux compression, laser-driven micro coils, and their applications to high-energy-density-plasma experiments. Measurement methods of strong magnetic fields are also introduced: pick-up coil, optical polarization probe, Zeeman spectroscopy, and proton radiography. In particular, we review recent progress and analysis methods of proton radiography which is often used to measure the magnetic field generated by laser-driven micro coils. Further, we discuss the validity and predictability of previously proposed models of laser-driven micro coils, and provide small corrections to the models. In the near future, these advances in the measurement techniques and the modeling of the laser-driven coil may promote the understanding of the strong field generation, not only by the laser-driven coil but also by proposed or new approaches.