Plume splitting and sharpening in laser-produced aluminium plasma

Plume splitting and sharpening were observed in laser-produced aluminium plasma created using 532 nm, 8 ns pulses from a frequency doubled Nd : YAG laser. Measurements were made using 2 ns gated fast photography as well as space and time resolved optical emission spectroscopy. The motion of the leading edge of the plume was studied with several background air pressures and the expansion of the plume front was compared with various expansion models. Combining imaging together with time resolved emission diagnostics, a triple structure of the plume was observed.