Anomalous observations using the fast ignition for laser driven fusion energy are interpreted and experimental and theoretical results are reported which are in contrast to the very numerous effects usually observed at petawatt-picosecond laser interaction with plasmas. These anomalous mechanisms result in rather thin blocks (pistons) of these nonlinear (ponderomotive) force driven highly directed plasmas of modest temperatures. The blocks consist in space charge neutral plasmas with ion current densities above 1010A∕cm2. For the needs of applications in laser driven fusion energy, much thicker blocks are required. This may be reached by a spherical configuration where a conical propagation may lead to thick blocks for interaction with targets. First results are reported in view of applications for the proton fast igniter and other laser-fusion energy schemes.

No abstract

Neutron diffraction experiments indicate that hydrogen enters α‐zirconium interstitially. The relative energies of hydrogen in tetrahedral and octahedral interstitial sites of the h. c. p. lattice are calculated assuming that the energy terms most strongly dependent on the site symmetry are the electronic and protonic electrostatic contributions. The calculations show that the tetrahedral site is preferrred, in agreement with experiment. The effects of lattice distortions near a proton are shown to be unimportant in determining the site preference.

The two-dimensional 2D layer Green's function scattering method is used to calculate the energy of surface states and resonances at ⌫ for Al͑111͒ for both below and above the vacuum level. The surface-barrier potential is represented by an empirical form. The above vacuum-level surface electron band structure for this surface has not been calculated before and it is important in understanding many surface phenomena. The geometric structure of the Al͑111͒ surface is known from intensity analysis in low-energy electron diffraction at energies 60-450 eV. The details of the surface barrier for Al͑111͒ were obtained from a match with the below vacuumlevel experimental energy position of the first Rydberg surface resonance and the Shockley surface state at k ʈ =0͑⌫ ͒. The calculation was then extended to the above vacuum-level case for 0-27 eV with the inclusion of inelastic electron interactions. Tamm-type resonances at 6.9 eV and possibly also at 8.3 eV, a Shockley-type resonance at 14.0Ϯ 0.5 eV and a series of Rydberg ͑image͒ resonances near 24 eV all above vacuum level are found at k ʈ = 0. The same 2D layer Green's function scattering method using the same input data was then used to calculate the intensity of the 00 beam for k ʈ =0 ͑normal incidence͒ in very low-energy electron diffraction ͑VLEED͒ from this surface in the energy range 0-65 eV. Features in the VLEED intensities are found due to the Shockley and Rydberg resonances. Experimental data from over 26 years ago found surface features near the energies found in this work. Beam intensities from low-energy electron microscope measurements at normal incidence and new data from other surface spectroscopies could provide experimental confirmation of the resonances predicted in this work.

No abstract