Characteristics Of Laser-produced Plasmas Research Articles

Electromagnetic pulses produced by expanding laser-produced Au plasma

Abstract The interaction of an intense laser pulse with a solid target produces large number of fast free electrons. This emission gives rise to two distinct sources of the electromagnetic pulse (EMP): the pulsed return current through the holder of the target and the outflow of electrons into the vacuum. A relation between the characteristics of laser-produced plasma, the target return current and the EMP emission are presented in the case of a massive Au target irradiated with the intensity of up to 3 × 1016 W/cm2. The emission of the EMP was recorded using a 12 cm diameter Moebius loop antennas, and the target return current was measured using a new type of inductive target probe (T-probe). The simultaneous use of the inductive target probe and the Moebius loop antenna represents a new useful way of diagnosing the laser–matter interaction, which was employed to distinguish between laser-generated ion sources driven by low and high contrast laser pulses.

Effect of neutron irradiation on the characteristics of laser-produced plasma

Using the mass-spectrometric method we studied the formation of multi-charged plasma ions during the interaction of laser radiation with solid targets irradiated by neutron beams. We found that structural defects, caused by the neutron irradiation, influence not only the efficiency of the process of material evaporation and emission of plasma, but also the ionization and recombination processes taking place at the initial stage of plasma formation and expansion. We also show the effect of the dose of neutron irradiation on the threshold of plasma formation from the surface of the target.

Characteristics of laser-produced plasmas in a gas filled chamber and in a gas jet by using a long pulse laser

The dynamics of the laser-produced plasma in a gas filled chamber and in a gas jet were investigated using a relatively low intensity laser (I⩽5×1012 W/cm2) with long pulse duration (7 ns). Visualization methods such as the Mach–Zehnder interferometry and the shadow imaging were employed to characterize the shock velocity, electron densities, and temperatures in the laser-produced plasma. The electron density depletion on the laser propagation axis was observed in a gas jet but not in the gas filled chamber. Qualitative analysis for the density depletion is discussed by employing a fluid theory for the ambipolar diffusion of the plasma species. In the gas filled chamber, increase of the laser energy, and applied gas pressure results in faster and further propagation of the shock front with the distance-time relation of Rs∝t2/5, implicating an instantaneous energy release at a point. However, the plasma produced in a gas jet shows a rather linear relation of Rs∝t at early time (t⩽10 ns).