Compression and heating of a laser-produced plasma using single and double induction coils

摘要

The results of an experiment on magnetohydrodynamic compression and heating of a laser-produced plasma in vacuum are described. The plasma was produced by laser ablation of copper at 2 J cm(-2). A pulsed magnetic field, with an amplitude of 0.3 T and a period of 2.2 mu s, was produced by a three-turn spiral induction coil placed 10 mm above the ablation spot. Time-resolved imaging revealed that the magnetic field had a strong influence on both the plasma between the coil and the target, and on the plasma which flows through the aperture in the coil. The plasma flow through the coil aperture is strongly pinched due to the Lorentz interaction of the induced current and the coil magnetic field. Heating of the plasma is evidenced by strong enhancement of the overall visible light emission and the appearance of Cu+ line emission. Magnetic compression and plasma heating were also observed in a setup using two induction coils separated by 10 mm. This technique could be used to enhance the sensitivity of laser-induced breakdown spectroscopy, increase the ion yield in laser plasma ion sources, or control the ablation plume expansion in pulsed laser deposition.