Isolated proton bunch acceleration by a petawatt laser pulse.

Often, the interpretation of experiments concerning the manipulation of the energy distribution of laser-accelerated ion bunches is complicated by the multitude of competing dynamic processes simultaneously contributing to recorded ion signals. Here we demonstrate experimentally the acceleration of a clean proton bunch. This was achieved with a microscopic and three-dimensionally confined near critical density plasma, which evolves from a 1 µm diameter plastic sphere, which is levitated and positioned with micrometer precision in the focus of a Petawatt laser pulse. The emitted proton bunch is reproducibly observed with central energies between 20 and 40 MeV and narrow energy spread (down to 25%) showing almost no low-energetic background. Together with three-dimensional particle-in-cell simulations we track the complete acceleration process, evidencing the transition from organized acceleration to Coulomb repulsion. This reveals limitations of current high power lasers and viable paths to optimize laser-driven ion sources.

Improvement of density resolution in short-pulse hard x-ray radiographic imaging using detector stacks.

We demonstrate that stacking several imaging plates (IPs) constitutes an easy method to increase hard x-ray detection efficiency. Used to record x-ray radiographic images produced by an intense-laser driven hard x-ray backlighter source, the IP stacks resulted in a significant improvement of the radiograph density resolution. We attribute this to the higher quantum efficiency of the combined detectors, leading to a reduced photon noise. Electron-photon transport simulations of the interaction processes in the detector reproduce the observed contrast improvement. Increasing the detection efficiency to enhance radiographic imaging capabilities is equally effective as increasing the x-ray source yield, e.g., by a larger drive laser energy.

Quality of Life of Children with Congenital Heart Diseases: A Multicenter Controlled Cross-Sectional Study.

To assess the health-related quality of life (QoL) in children with congenital heart diseases (CHD) with a validated questionnaire in comparison with control children. We prospectively recruited 282 children with CHD aged from 8 to 18 years in two tertiary care centers (France and Belgium) and 180 same-age controls in randomly selected French schools. Children's QoL was self-reported with the KIDSCREEN-52 questionnaire and reported by parents with the KIDSCREEN-27. QoL scores of each dimension were compared between CHD and controls and between the classes of disease severity. Both centers were comparable for most demographic and clinical data. Age- and gender-adjusted self-reported QoL scores were lower in CHD children than in controls for physical well-being (mean ± SEM 45.97 ± 0.57 vs 50.16 ± 0.71, p < 0.0001), financial resources (45.72 ± 0.70 vs 48.85 ± 0.87, p = 0.01), peers/social support (48.01 ± 0.72 vs 51.02 ± 0.88, p = 0.01), and autonomy in the multivariate analysis (47.63 ± 0.69 vs 49.28 ± 0.85, p = 0.04). Parents-reported scores were lower in CHD children for physical (p < 0.0001), psychological well-being (p = 0.04), peers/social support (p < 0.0001), and school environment (p < 0.0001) dimensions. Similarly, the disease severity had an impact on physical well-being (p < 0.001), financial resources (p = 0.05), and peers/social support (p = 0.01) for self-reported dimensions, and on physical well-being (p < 0.001), psychological well-being (p < 0.01), peers/social support (p < 0.001), and school environment (p < 0.001) for parents-reported dimensions. However, in multivariate analysis on self-reported QoL, disease severity was significantly associated with the self-perception dimension only. Self-reported QoL of CHD children was similar to that of same-age healthy children in seven of 10 dimensions, but parents-reported QoL was impaired in four of five dimensions.

Electron-ion equilibration in ultrafast heated graphite.

We have employed fast electrons produced by intense laser illumination to isochorically heat thermal electrons in solid density carbon to temperatures of ∼10,000 K. Using time-resolved x-ray diffraction, the temperature evolution of the lattice ions is obtained through the Debye-Waller effect, and this directly relates to the electron-ion equilibration rate. This is shown to be considerably lower than predicted from ideal plasma models. We attribute this to strong ion coupling screening the electron-ion interaction.