We show that a spatially well-defined layer of boron dopants in a hydrogen-enriched silicon target allows the production of a high yield of alpha particles of around 10 9 per steradian using a nanosecond, low-contrast laser pulse with a nominal intensity of approximately 3 × 10 16 W cm. This result can be ascribed to the nature of the long laser-pulse interaction with the target and with the expanding plasma, as well as to the optimal target geometry and composition. The possibility of an impact on future applications such as nuclear fusion without production of neutron-induced radioactivity and compact ion accelerators is anticipated.

The use of a low contrast nanosecond laser pulse with relatively low intensity (3 × 10 16 W cm -2 ) allowed enhancing the yield of induced nuclear reactions in advanced solid targets. In particular the "ultraclean" proton-boron fusion reaction, producing energetic alpha-particles without neutron generation, was chosen. A spatially well-defined layer of boron dopants in a hydrogenenriched silicon substrate was used as target. The combination of the specific target geometry and the laser pulse temporal shape allowed the production of an enormous yield of alpha-particles around 10 9 per steradian. This result can be ascribed to the nonlinear interaction of the long laser pulse with the expanding plasma and to the optimal target geometry and composition.

The paper concerns distinct current filaments which appear inside plasma layers and columns produced by high-current pulse discharges of the Z-pinch and Plasma-Focus (PF) type. Results obtained previously, e. g. pictures taken with high-speed cameras, soft X-ray pinhole images, measurements of angular distributions of fast deuterons, images of so-called hot-spots inside the pinch column etc., have been reviewed and explained on the basis of the filamentary model. For the first time results of the measurements of fusion-produced protons, which were performed at different azimuthal angles (around the pinch column), have been presented. These results constitute a new experimental evidence of the appearance and role of the current filaments in pinch-type discharges.

Solid State Nuclear Track Detectors of the CR-39/PM-355 type were irradiated with protons with energies in the range from 0.2 to 8.5 MeV. Their intensities and energies were controlled by a Si surface barrier detector located in an accelerator scattering chamber. The ranges of protons with energies of 6-7 MeV were comparable to the thickness of the PM-355 track detectors. Latent tracks in the polymeric detectors were chemically etched under standard conditions to develop the tracks. Standard optical microscope and scanning electron microscopy techniques were used for surface morphology characterization.

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