Studies of plasma dynamics in colliding laser plasma plumes

Abstract

The collision dynamics of laser produced plasma plumes exhibits particular features depending on the geometry of pre-collision laser plasma expansion conditions. In this context we have investigated the dynamic processes involved in the collision of two orthogonal laser produced plasma plumes. In the experiments we used a Nd:YAG laser, 3.5 ns, 340 mJ, at 1.06 μm, operating at 10 Hz. By using a 50% beam splitter, the laser beam is divided in two and then focused at ∼3 J/cm2, over two orthogonal targets, in such a way that the resulting plasma plumes intersect at 1 cm from the target surfaces. Main diagnostics used are time and space resolved visible spectroscopy, with up to 15 ns time resolution, and plasma imaging, with 50 ns time resolution. Plasma collision experiments are performed either with two graphite target, or with graphite and titanium target. Argon background gas, up to a pressure of 100 mTorr, is used as an extra parameter to influence the plasma expansion dynamics.