Control of unsteady laser-produced plasma-flow with a multiple-coil magnetic nozzle

Taichi Morita, Masafumi Edamoto, Satoshi Miura, Atsushi Sunahara, Naoya Saito, Yutaro Itadani, Tomihiko Kojima, Yoshitaka Mori, Tomoyuki Johzaki, Yoshihiro Kajimura, Shinsuke Fujioka, Akifumi Yogo, Hiroaki Nishimura, Hideki Nakashima, Naoji Yamamoto

We report an experimental demonstration of controlling plasma flow direction with a magnetic nozzle consisting of multiple coils. Four coils are controlled separately to form an asymmetric magnetic field to change the direction of laser-produced plasma flow. The ablation plasma deforms the topology of the external magnetic field, forming a magnetic cavity inside and compressing the field outside. The compressed magnetic field pushes the plasma via the Lorentz force on a diamagnetic current: j × B in a certain direction, depending on the magnetic field configuration. Plasma and magnetic field structure formations depending on the initial magnetic field were simultaneously measured with a self-emission gated optical imager and B-dot probe, respectively, and the probe measurement clearly shows the difference of plasma expansion direction between symmetric and asymmetric initial magnetic fields. The combination of two-dimensional radiation hydrodynamic and three-dimensional hybrid simulations shows the control of the deflection angle with different number of coils, forming a plasma structure similar to that observed in the experiment.