[en] Results of particle-in-cell (PIC) simulations of fast ion generation in the recently proposed laser-induced cavity pressure acceleration (LICPA) scheme in which a picosecond circularly polarized laser pulse of intensity ∼10²¹ W/cm² irradiates a carbon target placed in a cavity are presented. It is shown that due to circulation of the laser pulse in the cavity, the laser-ions energy conversion efficiency in the LICPA scheme is more than twice as high as that for the conventional (without a cavity) radiation pressure acceleration scheme and a quasi-monoenergetic carbon ion beam of the mean ion energy ∼0.5 GeV and the energy fluence ∼0.5 GJ/cm² is produced with the efficiency ∼40%. The results of PIC simulations are found to be in fairly good agreement with the predictions of the generalized light-sail model.

[en] Results are reported of an experiment performed at the Eclipse laser facility in CELIA, Bordeaux, on the generation of strong electromagnetic pulses. Measurements were performed of the target neutralization current, the total target charge and the tangential component of the magnetic field for the laser energies ranging from 45 mJ to 92 mJ with the pulse duration approximately 40 fs, and for the pulse durations ranging from 39 fs to 1000 fs, with the laser energy approximately 90 mJ. It was found that the values obtained for thick (mm scale) Cu targets are visibly higher than values reported in previous experiments, which is argued to be a manifestation of a strong dependence of the target electric polarization process on the laser contrast and hence on the amount of preplasma. It was also found that values obtained for thin (μm scale) Al foils were visibly higher than values for thick Cu targets, especially for pulse durations longer than 100 fs. The correlations between the total target charge versus the maximum value of the target neutralization current, and the maximum value of the tangential component of the magnetic field versus the total target charge were analysed. They were found to be in very good agreement with correlations seen in data from previous experiments, which provides a good consistency check on our experimental procedures. (paper)

[en] Results are reported on a direct measurement of the electric field of a strong electromagnetic pulse generated through laser interaction with a thick solid target inside an experimental chamber of a 10 TW femtosecond laser. Two Prodyn FD5C conductive D-dot probes were used to demonstrate that the signal-to-noise ratio in this arrangement is 10:1 and that probes are sensitive to the component of the electric field parallel to their axis. Maximum value of the electric field on the order of 18 kV/m was obtained for a 50 fs laser pulse with 270 mJ energy on target. To ascertain a correct estimate of the recorded electric fields a comparative study was performed in an anechoic chamber with two other D-dot probes, involving electromagnetic pulses emitted by a tube antenna and the high-power broadband electromagnetic pulse generator. Some frequency dependence in the FD5C equivalent area was found below 1 GHz.

[en] Acceleration of dense matter to high velocities is of high importance for high energy density physics, inertial confinement fusion, or space research. The acceleration schemes employed so far are capable of accelerating dense microprojectiles to velocities approaching 1000 km/s; however, the energetic efficiency of acceleration is low. Here, we propose and demonstrate a highly efficient scheme of acceleration of dense matter in which a projectile placed in a cavity is irradiated by a laser beam introduced into the cavity through a hole and then accelerated in a guiding channel by the pressure of a hot plasma produced in the cavity by the laser beam or by the photon pressure of the ultra-intense laser radiation trapped in the cavity. We show that the acceleration efficiency in this scheme can be much higher than that achieved so far and that sub-relativisitic projectile velocities are feasible in the radiation pressure regime.