A 7 T Pulsed Magnetic Field Generator for Magnetized Laser Plasma Experiments

A pulsed magnetic field generator was developed to study the effect of a magnetic field on the evolution of a laser-generated plasma.A 40 kV pulsed power system delivered a fast(~230 ns),55 kA current pulse into a single-turn coil surrounding the laser target,using a capacitor bank of 200 nF,a laser-triggered switch and a low-impedance strip transmission line.A one-dimensional uniform 7 T pulsed magnetic field was created using a Helmholtz coil pair with a 6 mm diameter.The pulsed magnetic field was controlled to take effect synchronously with a nanosecond heating laser beam,a femtosecond probing laser beam and an optical Intensified Charge Coupled Device(ICCD) detector.The preliminary experiments demonstrate bifurcation and focusing of plasma expansion in a transverse magnetic field.     

Optical measurements and analytical modeling of magnetic field generated in a dieletric target

Polarization rotation of a probe pulse by the target is observed with the Faraday rotation method in the interaction of an intense laser pulse with a solid target.The rotation of the polarization plane of the probe pulse may result from a combined action of fused silica and diffused electrons.After the irradiation of the main pulse,the rotation angle changed significantly and lasted ～2 ps.These phenomena may imply a persistent magnetic field inside the target.An analytical model is developed to explain the experimental observation.The model indicates that a strong toroidal magnetic field is induced by an energetic electron beam.Meanwhile,an ionization channel is observed in the shadowgraph and extends at the speed of light after the irradiation of the main beam.The formation of this ionization channel is complex,and a simple explanation is given.