The spherical pinch experiment: Generation of laser driven converging blast wave

The interaction of laser radiation with matter has been studied extensively due to its wide variety of applications. Laser fluid interaction implies remarkable phenomena such as energy deposition, cavity formation, bubble formation etc. On the other hand optical break-down of the gas under the action of intense laser pulse precede many interesting processes like plasma expansion, formation of shock wave, detachment of shock wave from the plasma and others. In the latter case, shock wave propagation assumes central importance in plasma fusion scheme like Spherical Pinch. In Spherical Pinch the preformed hot plasma produced at the center of a spherical vessel is confined and compressed by imploding shock wave fired from the cell periphery, in such a way, in principle, that the plasma breakeven condition may be satisfied. With out laser facility of energy up to 20 Joules (7 ns FWHM) at 1.06 μm wavelength in each of the two beams, the authors are performing some experiments on converging motion of the shock wave launched from the periphery of the spherical glass cell. These laser beams from axially opposite directions irradiate a glass cell over a wide solid angle in such a way so that quasi-spherically symmetric convergent shock wave is generated from the evaporation of aluminium layer coated over the internal surface of the glass cell. The authors plan to present the experimental results on the temporal evolution of inwardly converging shock wave consistently followed by frame camera Imacon 792/LC and interference holographic technique, and its comparison with the theoretical results. Apart from this, some experimental results on the dynamics of converging shock wave generated in the same way in water would also be presented