Interferometric investigations of laser-produced plasma in strong external magnetic field

The paper presents results of investigations and the analysis of the behaviour of a laser-produced plasma in a strong external magnetic field. The studies were carried out for a plasma generated from a planar teflon target irradiated with a neodymium laser beam of the power density of 1014 W/cm2. Magnetic fields of 5 T up to 15 T in induction and a force-lines geometry parallel to the laser heating beam direction were used. A three-frame laser interferometry was used for the study of the plasma column formation and the disintegration process. The interferometric system was illuminated with a Nd laser beam (λ = 1.06 μm). Two kinds of plasma creation were observed in the external magnetic field, i.e., angular and axial expansion, related to the target illumination conditions. In the case of the angular expansion, a characteristic plasma configuration called ''horseshoe'' was observed again. Interaction of such configuration with the external magnetic field results in formation (at t > 25 ns) of a plasma cylinder of about 1 mm in length and with the external radius equivalent to the plasma magnetic confinement radius (RB ∼ B-2/30). In the case of axial expansion, the plasma concentrated on the axis has the longest lifetime as in the case of free expansion (B0 0). (orig.)