Shot-to-shot reproducibility in the emission of fast highly charged metal ions from a laser ion source.

The generation of fast highly charged metal ions with the use of the sub-nanosecond Prague Asterix Laser System, operated at a fundamental wavelength of 1315 nm, is reported. Particular attention is paid to shot-to-shot reproducibility in the ion emission. Au and Pd targets were exposed to intensities up to 5 × 10(16) W∕cm(2). Above the laser intensity threshold of ∼3 × 10(14) W∕cm(2) the plasma is generated in a form of irregular bursts. The maximum energy of protons constituting the leading edge of the fastest burst reaches a value up to 1 MeV. The fast ions in the following bursts have energy gradually decreasing with the increasing burst number, namely, from a value of about 0.5 MeV∕charge regardless of the atomic number and mass of the ionized species.

Generation of high currents of carbon ions with the use of subnanosecond near-infrared laser pulses.

Emission of carbon currents reaching values up to 2 A/cm(2) at a distance of 1 m from the laser ion source driven by the subnanosecond Prague Asterix Laser System operated at a fundamental wavelength of 1315 nm is reported. Graphite targets were exposed to intensities up to 5x10(16) W/cm(2) varying both the laser energy and the position of the laser beam focus with respect to the target surface. The maximum energy gain of carbon ions was approximately = 1 MeV/u. At high laser intensities the shape of time-of-flight spectra is also formed by plasma outbursts, whose growth correlates with the oscillatory self-focusing of the laser beam.

Laser generation of Au ions with charge states above 50+.

Results of recent studies on highly charged Au ion generation, using the intense long pulses of the PALS high power iodine laser (lambda=1.315 microm, E(L)=800 J400 ps), operating under variable experimental conditions (1omega, 3omega, varying target thickness and changing focus positions), are presented. Both the ion collectors and the ion electrostatic analyzers were applied for the identification of ions in a large distance from the target. The time-of-flight collector signals were treated by a means of peak deconvolution assuming a shifted Maxwell-Boltzmann form of the constituent ion current peaks. Attention was paid to the influence of pulse precursor, which becomes evident, especially, if using thinner targets and 1omega. The results for 3omega point to the presence of several groups of ions with the highest recorded charge state Au(53+).

Two-dimensional model of thermal smoothing of laser imprint in a double-pulse plasma

The laser prepulse effect on the thermal smoothing of nonuniformities of target illumination is studied by means of a two-dimensional Lagrangian hydrodynamics simulation, based on the parameters of a real experiment. A substantial smoothing effect is demonstrated for the case of an optimum delay between the prepulse and the main heating laser pulse. The enhancement of the thermal smoothing effect by the laser prepulse is caused by the formation of a long hot layer between the region of laser absorption and the ablation surface. A comparison with experimental results is presented.