Dynamics of laser produced annular plasmas

We present preliminary experimental observations of the plasma dynamics of laser produced annular plasmas, expanding freely in a 80 mTorr Argon background. A Nd:YAG laser, 340 mJ, 3.5 ns, at 1.06 mu m, operating at 10 Hz, is used in the experiments. To produce the annular plasma the laser pulse is focused on a titanium target using a combination of axicon and convergent lens. The dynamics of the laser plasma is characterized by 50 ns time resolved plasma imaging of the visible plasma emission. The inwards radial expansion of the initial plasma ring result in on-axis stagnation, giving rise to an expanding axial laser plasma plume. A quantitative description of the laser plasma dynamics is presented.