Characterization of the Intra-Unit-Cell magnetic order in Bi2Sr2CaCu2O8+d

As in YBa2Cu3O6+x and HgBa2CuO8+d, the pseudo-gap state in Bi2Sr2CaCu2O8+d is characterized by the existence of an intra-unit-cell magnetic order revealed by polarized neutron scattering technique. We report here a supplementary set of polarized neutron scattering measurements for which the direction of the magnetic moment is determined and the magnetic intensity is calibrated in absolute units. The new data allow a close comparison between bilayer systems YBa2Cu3O6+x and Bi2Sr2CaCu2O8+d and rise important questions concerning the range of the magnetic correlations and the role of disorder around optimal doping.Comment: 12 pages, 8 figures, submitted to physical review

Field testing and exploitation of genetically modified cassava with low-amylose or amylose-free starch in Indonesia

The development and testing in the field of genetically modified -so called- orphan crops like cassava in tropical countries is still in its infancy, despite the fact that cassava is not only used for food and feed but is also an important industrial crop. As traditional breeding of cassava is difficult (allodiploid, vegetatively propagated, outbreeding species) it is an ideal crop for improvement through genetic modification. We here report on the results of production and field testing of genetically modified low-amylose transformants of commercial cassava variety Adira4 in Indonesia. Twenty four transformants were produced and selected in the Netherlands based on phenotypic and molecular analyses. Nodal cuttings of these plants were sent to Indonesia where they were grown under biosafety conditions. After two screenhouse tests 15 transformants remained for a field trial. The tuberous root yield of 10 transformants was not significantly different from the control. Starch from transformants in which amylose was very low or absent showed all physical and rheological properties as expected from amylose-free cassava starch. The improved functionality of the starch was shown for an adipate acetate starch which was made into a tomato sauce. This is the first account of a field trial with transgenic cassava which shows that by using genetic modification it is possible to obtain low-amylose cassava plants with commercial potential with good root yield and starch quality

Intra-unit-cell magnetic correlations near optimal doping in YBa2Cu3O6.85

International audienc

Laser ablation of a turbid medium : Modeling and experimental results.

International audienceQ-switched Nd:YAG laser ablation of a turbid medium paint is studied. The optical properties absorption coefficient, scattering coefficient, and its anisotropy of a paint are determined with a multiple scattering model three-flux model, and from measurements of reflection-transmission of light through thin layers. The energy deposition profiles are calculated at wavelengths of 532 nm and 1.064 m. They are different from those described by a Lambert-Beer law. In particular, the energy deposition of the laser beam is not maximum on the surface but at some depth inside the medium. The ablated rate was measured for the two wavelengths and compared with the energy deposition profile predicted by the model. This allows us to understand the evolution of the ablated depth with the wavelength: the more the scattering coefficient is higher, the more the ablated depth and the threshold fluence of ablation decrease

Heating and ablation of tokamak graphite by pulsed nanosecond Nd-YAG lasers

International audienceThe results on laser heating and ablation of graphite tiles of thermonuclear tokamaks are presented. Two pulsed Nd-YAG lasers (20 Hz repetition rate, 5 ns pulse duration and 10 kHz repetition rate, 100 ns pulse duration) were applied for ablation measurements. The ablation thresholds (1.0$\pm$0.5 J/cm$^2$ for 5 ns and 2.5$\pm$0.5 J/cm$^2$ for 100 ns laser pulses) were determined for the Tore Supra tokamak graphite tiles (backside) nonexposed to plasma. The high repetition rate Nd-YAG laser (10 kHz, 100 ns pulse duration) and the developed pyrometer system were applied for graphite heating measurements. Some unexpected features of laser heating of the graphite surface were observed. They were explained by the presence of a thin surface layer with the properties different from those of the bulk graphite. The theoretical models of laser heating and near-threshold ablation of graphite with imperfectly adhered layer were developed to interpret the experimental results

Theoretical and Experimental Studies on Molybdenum and Stainless Steel Mirrors Cleaning by High Repetition Rate Laser Beam Theoretical and Experimental Studies on Molybdenum and Stainless Steel Mirrors Cleaning by High Repetition Rate Laser Beam

AbstrAct Our studies were aimed to determine the damage threshold of Molybdenum (Mo) and Stainless Steel (SS) mirrors to provide the maximum fluence which the mirror surfaces could withstand without affecting their reflectivity properties. A high repetition rate ytterbium fiber laser (20kHz, 1.06µm, 120ns) was applied. The experimental single-pulse and multiple-pulse damage thresholds were obtained. To calculate damage thresholds, a 1D analytical model which takes into account the temperature dependent absorptance and multiple pulse damage based on plastic deformations accumulation was applied. The experimental damage thresholds and the theoretical ones are in a good agreement. Cleaning tests with the contaminated mirrors exposed in JET have been performed

In-depth analysis of ITER-like samples composition using laser-induced breakdown spectroscopy

International audienceLaser-induced breakdown spectroscopic in-depth measurements were undertaken for two ITER-like calibrated multi-layered samples made of W-Mo or W/C layers on Ti-substrates. The samples were previously characterized by glow discharge optical emission spectroscopy. For laser-induced breakdown spectroscopic measurements, pulses generated by Nd:YAG laser sources with 1064 nm, 532 nm, 355 nm and 266 nm wavelengths were applied. The effects of laser beam shaping, fluence and wavelength as well as the gas nature (air, Ar, He) and pressure were investigated. The results obtained with laser-induced breakdown spectroscopic in-depth measurements were compared to those obtained with glow discharge optical emission spectroscopy and found to be in agreement. However, a mixing of the layers was observed and attributed to diffusion through the melted material and to the non-homogeneity of the laser beam spatial distribution. The depth resolution was found of the order of several thermal diffusion lengths but should be improved by using picosecond laser pulse duration. The results promote applications to tritium concentration measurements with depth resolution in the deposited layers of Tokamak first walls, as in the case of the future fusion reactor ITER. (C) 2011 Elsevier B.V. All rights reserved