The target backsheath field acceleration mechanism is one of the main mechanisms of laser-driven proton acceleration (LDPA) and strongly depends on the comprehensive performance of the ultrashort ultra-intense lasers used as the driving sources. The successful use of the SG-II Peta-watt (SG-II PW) laser facility for LDPA and its applications in radiographic diagnoses have been manifested by the good performance of the SG-II PW facility. Recently, the SG-II PW laser facility has undergone extensive maintenance and a comprehensive technical upgrade in terms of the seed source, laser contrast and terminal focus. LDPA experiments were performed using the maintained SG-II PW laser beam, and the highest cutoff energy of the proton beam was obviously increased. Accordingly, a double-film target structure was used, and the maximum cutoff energy of the proton beam was up to 70 MeV. These results demonstrate that the comprehensive performance of the SG-II PW laser facility was improved significantly.

The mechanism of continental growth of the Altaids is currently under debate between models invoking continuous subduction-accretion or punctuated accretion by closure of multiple ocean basins. We use the Yueyashan–Xichangjing ophiolite belt of the Beishan collage (southern Altaids) to constrain the earliest oceanic crust in the southern Palaeo-Asian Ocean. Five lithotectonic units were identified from S to N: the Huaniushan block, a sedimentary passive margin, the structurally incoherent Yueyashan–Xichangjing ophiolite complex, a coherent sedimentary package and the Mazongshan island arc with granitic rocks. We present a structural analysis of the accretionary complex, which is composed of the incoherent ophiolitic melange and coherent sedimentary rocks, to work out the tectonic polarity. A new weighted mean 206Pb–238U age of 533 ± 1.7 Ma from a plagiogranite in the Yueyashan–Xichangjing ophiolite indicates that the ocean floor formed in early Cambrian time. Furthermore, we present new geochemical data to constrain the tectonic setting of the Yueyashan–Xichangjing ophiolite. The Yueyashan–Xichangjing ophiolite was emplaced as a result of northward subduction of an oceanic plate beneath the Mazongshan island arc to the north in late Ordovician to early Silurian time. Together with data from the literature, our work demonstrates that multiple overlapping periods of accretion existed in the Palaeozoic in the northern and southern Altaids. Therefore, a model of multiple accretion by closure of several ocean basins is most viable.

The structure and magnetic properties of the nanoparticles of immiscible system Co20Cu80 prepared by means of arc-discharge, have been studied in detail. The diameters of the particles are about 20 ~ 30 nm and a core/shell structure forms. The cores are Co-Cu solutions, which show some small Co precipitates, encapsulated with a shell of cupper oxide or cobalt oxide as observed by means of high-resolution transmission electron microscope (HRTEM) and energy dispersive X-ray (EDS). The loop shift in the hysteresis loop indicates the existence of the exchange bias between ferromagnetic and antiferromagnetic components at low temperatures. A block temperature about 180 K has been observed for as-deposited nanoparticles. For the annealed nanoparticles, the thermal magnetization at low temperatures is satisfied with Bloch's law. 


Simulation and experimental work that compare the performance of straight and tapered monocapillaries when used with laboratory x-ray sources are reported. Detailed simulations for various taper profiles give several important conclusions for optimizing the design of a tapered monocapillary. Several tapered monocapillaries were prepared. With a 16W x-ray source, beam intensities of 4×105 photon/sec/μm2 and 3×105photon/sec/μm2 of Cu Kα x rays were obtained from the tapered monocapillaries for output diameters of 8μm and 3.5μm, respectively. These intensities are 1.4 and 1.5 times that obtained from straight capillaries with the same output beam sizes at the experimental set-up optimized for a straight capillary. In addition to the gain in x-ray flux, the tapered monocapillaries produce output beams with significantly reduced high energy bremsstrahlung radiation and increased flux stability with respect to shifts of the x-ray source spot.

Very recently a new technique named multi-ion-bram reactive cosputtering(MIBRECS) was developed for preparing multi-component metal oxide thin films. Epitaxial or highly oriented (Pb,La) TiO3 thin films sputtered from pure metals of lead, titanium and lathanium were deposited by using this technique. In order to consummate the technique and to study the mechanism of reactive cosputtering, a general model of multi-ion-beam reactive cosputter-ing was proposed for the first time based on the well-known gas kinetics under stable sputtering circumstances, and a computer numerical simulation of the model was carried out with the parameters adopted in our experiments. The relationships among the sputtering ratioes of the targets, and the coverage ratioes of simple substances and oxides of the target metals on substrate surface with the total reactive gas flux and the densities of the sputtering ion beam were obtained respectively, and the hysteresis effect of the characteristic of reactive sputtering and the interactions during multi-ion-beam reactive cosputtering processes were also obtained. The numerical simulation results are at least qualitively in agreement with the experiments.

Epitaxial Si layers have been grown under a variety of growth conditions on CoSi2 (001) by molecular beam epitaxy (MBE). The structural properties of the Si overgrowth were studied by in-situ Reflection High Energy Electron Diffraction (RHEED), as well as ex-situ MeV4He+ ion channeling and High Resolution Transmission Electron Microscopy (HRTEM). Strong influences of the CoSi2 surface reconstruction on the Si overgrowth have been observed. RHEED studies show islanding growth of Si on the CoSi2 (001) (3/√2 × √2)R45 reconstructed surface, but smooth growth of Si on the CoSi2 (001) {√2 × √2)R45 reconstructed surface, under the same growth conditions. The growth of Si on thin layers of CoSi2 (2nm-6nm) with (√2 × √2)R45 reconstructed surface at 460°C results in high crystalline quality for the Si top layer, as indicated by good channeling minimum yield (Xmin < 6%), but cross-sectional TEM shows that the CoSi2 layers are discontinuous. We also report preliminary results on Si grown on a 2 × 2 reconstructed CoSi2 (001) surface.

Here, we report on our efforts to engineer Si substrates for growth of compound semiconductors through the use of suitable epitaxial buffer layers of CaF2, SrF2, and BaF2 using a recently installed dual growth chamber MBE system. We have also developed new graphite-heater K-cells which have demonstrated reliable, high temperature deposition of the fluorides with excellent uniformity across substrates up to 6 inches in diameter. Excellent epitaxial quality (Xmin<5.0%) and smooth surface morphologies have been achieved for epitaxial CaF2 and SrF2 grown directly on Si (111) and BaF2 grown directly on Si (001). The BaF2 is (111) oriented on the Si (001) substrates with one of the {110} planes of the BaF2 aligned with the (110) plane in the Si (001). PbS1−xSex of excellent epitaxial quality has recently been demonstrated on the BaF2 (111)/Si (001) films. Comparable epitaxial quality has been demonstrated for CaF2 grown on Si (001) substrates using a two step growth method. We also report on preliminary results on epitaxial mixed fluoride growth on Si (111) and Si (001) substrates.

A 3-dimensional phase diagram is introduced to describe the dependence of the RHEED pattern from GaAs(111)B surface on growth conditions. The 2×2, transitional(1×1), and √19×,√19 surface reconstructions correspond to different zones in the phase diagram. A equation is given for the planes that separate these zones, which fit experimental data well. Homoepitaxial films on GaAs(111)B grown in the 2×2 region generally have bad crystal quality as determined by the ion channeling, and growth in the √19×√19 region generally yields rough surface morphology. At higher substrate temperatures (∼ 650 °C), featureless films with minimum ion channeling yields of less than 4% are achieved.