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The energy transport in cone-guided low- Z targets has been studied for laser intensities on target of 2.5x10(20) W cm(-2). Extreme ultraviolet (XUV) imaging and transverse optical shadowgraphy of the rear surfaces of slab and cone-slab targets show that the cone geometry strongly influences the observed transport patterns. The XUV intensity showed an average spot size of 65+/-10 microm for slab targets. The cone slabs showed a reduced spot size of 44+/-10 microm. The shadowgraphy for the aforementioned shots demonstrate the same behavior. The transverse size of the expansion pattern was 357+/-32 microm for the slabs and reduced to 210+/-30 microm. A transport model was constructed which showed that the change in transport pattern is due to suppression of refluxing electrons in the material surrounding the cone.

We have developed an advanced design for a time-of-flight (TOF) neutron spectrometer applied to the study of ultraintense laser-plasma interactions in the area of fast ignition research. The interaction of an ultraintense laser pulse with plasma creates intense gamma rays, which generate a high level of background noise in the thermal neutron detection process. High energy-density ions, which are generated by strong electric fields associated with the laser interactions, produce beamlike fusion neutrons with an angular distribution that is dependent on the momentum distribution of the ions. These beamlike fusion neutrons also act as a source of significant background noise in the thermal neutron detection process. In order to improve the signal-to-noise ratio (S/N), we have proposed and applied a wave-coincidence method to the neutron detection process. We have demonstrated the advantages of this advanced method in ultraintense laser-plasma interaction experiments, where an improvement in S/N by a factor of 7–8 compared to the conventional TOF method was achieved. We have calculated that the value of S/N increases with the number of detectors used as well as with the initial value of S/N for a single detector. [ABSTRACT FROM AUTHOR]

We report the demonstrated irradiation effect of laser-accelerated protons on human cancer cells. In vitro (living) A549 cells are irradiated with quasimonoenergetic proton bunches of 0.8–2.4 MeV with a single bunch duration of 15 ns. Irradiation with the proton dose of 20 Gy results in a distinct formation of γ-H2AX foci as an indicator of DNA double-strand breaks generated in the cancer cells. This is a pioneering result that points to future investigations of the radiobiological effects of laser-driven ion beams. Unique high-current and short-bunch features make laser-driven proton bunches an excitation source for time-resolved determination of radical yields. [ABSTRACT FROM AUTHOR]