Collimation of dense plasma jets created by low-energy laser pulses and studied with soft x-ray laser interferometry

The physical mechanisms driving the collimation of dense plasma jets created by low-energy (∼0.6J) laser pulse irradiation of triangular grooves were studied for different target materials using soft-x-ray interferometry and hydrodynamic code simulations. The degree of collimation of jets created by irradiating C, Al, Cu, and Mo targets at intensities of I=1× 1012W cm ^-2 with 120 ps laser pulses was observed to increase significantly with the atomic number. Radiation cooling is found to be the cause of the increased collimation, while the main effect of the increase in mass is to slow the jet evolution.