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The thermal expansion of NiO-8 mol % Y203-stabilized Zr02 (YSZ) composites and Ni-YSZ cermets in air and hydrogen have been investigated in the temperature range from 50 to 1000°C. The average linear thermal expansion coefficient (TEC) of NiO-YSZ composites in air increased with NiO content over the entire composition range. While NiO in the composites was changed to Ni in the H2 stream, their expansions were governed by the reduction of NiO. For reduced, Ni-YSZ cermets, the TEC increases significantly with Ni content in the composition range >60 vol % Ni. The TEC increased gradually during repeated thermal cycles between room temperature and 1000°C. When cermets were measured in air, the Ni particles were fully oxidized to NiO above 900°C, and many cracks appeared in the samples.

Forced convective subcooled boiling flow experiments were conducted in a BWR-scaled vertical upward annular channel. Water was used as the testing fluid, and the tests were performed at atmospheric pressure. A high-speed digital video camera was applied to capture the dynamics of the bubble nucleation process. Bubble lift-off diameters were obtained from the images for a total of 91 test conditions. A force balance analysis of a growing bubble was performed to predict the bubble lift-off size. The dimensionless form of the bubble lift-off diameter was formulated to be a function of Jacob number and Prandtl number. The proposed model agreed well with the experimental data within the averaged relative deviation of ±35.2 %.

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An approach for accelerating ions, with the use of a cluster-gas target and an ultrashort pulse laser of 150-mJ energy and 40-fs duration, is presented. Ions with energy 10-20 MeV per nucleon having a small divergence (full angle) of 3.4 degrees are generated in the forward direction, corresponding to approximately tenfold increase in the ion energies compared to previous experiments using solid targets. It is inferred from a particle-in-cell simulation that the high energy ions are generated at the rear side of the target due to the formation of a strong dipole vortex structure in subcritical density plasmas.

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.

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