ABSTRACT
Commissariat à l'Énergie Atomique et aux Énergies Alternatives has developed the ARGOS X-ray framing camera to perform two-dimensional, high-timing resolution imaging of an imploding target on the French high-power laser facility Laser MegaJoule. The main features of this camera are: a microchannel plate gated X-ray detector, a spring-loaded CCD camera that maintains proximity focus in any orientation, and electronics packages that provide remotely-selectable high-voltages to modify the exposure-time of the camera. These components are integrated into an "air-box" that protects them from the harsh environmental conditions. A miniaturized X-ray generator is also part of the device for in situ self-testing purposes.
ABSTRACT
Interaction of high-intensity laser pulses with solid targets results in generation of large quantities of energetic electrons that are the origin of various effects such as intense x-ray emission, ion acceleration, and so on. Some of these electrons are escaping the target, leaving behind a significant positive electric charge and creating a strong electromagnetic pulse long after the end of the laser pulse. We propose here a detailed model of the target electric polarization induced by a short and intense laser pulse and an escaping electron bunch. A specially designed experiment provides direct measurements of the target polarization and the discharge current in the function of the laser energy, pulse duration, and target size. Large-scale numerical simulations describe the energetic electron generation and their emission from the target. The model, experiment, and numerical simulations demonstrate that the hot-electron ejection may continue long after the laser pulse ends, enhancing significantly the polarization charge.
Subject(s)
Electrons , Lasers , Models, Chemical , Plasma Gases/chemistry , Plasma Gases/radiation effects , Computer Simulation , Electron TransportABSTRACT
The diagnostic designs for the Laser Megajoule (LMJ) will require components to operate in environments far more severe than those encountered in present facilities. This harsh environment will be induced by fluxes of neutrons, gamma rays, energetic ions, electromagnetic radiations, and, in some cases, debris and shrapnel, at levels several orders of magnitude higher than those experienced today on existing facilities. The lessons learned about the vulnerabilities of present diagnostic parts fielded mainly on OMEGA for many years, have been very useful guide for the design of future LMJ diagnostics. The present and future LMJ diagnostic designs including this vulnerability approach and their main mitigation techniques will be presented together with the main characteristics of the LMJ facility that provide for diagnostic protection.
ABSTRACT
The chemical reduction of dehydroascorbic acid is studied in the presence of organic and vitaminic compounds. Redox properties of the compounds: ascorbic acid, dehydroascorbic acid, thiols such as glutathion, cistein, British anti-Lewisite (BAL), thiamin, riboflavin, para amino benzoic acid, biotin, 1-4 dihydronaphtoquinone and flavonoids (flavone and derived salts, quercetin rutin, 1-epicatechin and dimer) are established by direct and pulse polarography. The redox reactions are analysed by amperometry. From the results, it appears that the catalytic effect of biocatalyst of the dehydroascorbic reduction by thiols has no direct relation with the redox properties. This catalytic effect is specifically obtained with flavan-3 ol complex with antiscorbutic activities of C2 factor type.
Subject(s)
Ascorbic Acid , Dehydroascorbic Acid , Flavonoids , Sulfhydryl Compounds , Vitamin B Complex , Ascorbic Acid/analogs & derivatives , Catalysis , Catechin , Kinetics , Oxidation-Reduction , PolarographyABSTRACT
Besides the l-ascorbic acid (C1 factor), we put in evidence the l-epi-3',4',5',5,7-pentahydroxyflavan-3-ol (C2 factor) in the blood capillary wall. It was mainly located and found in the endothelial cell membranes. To reach that results, we used an original method using a specific polyphenoloxydase extracted from Psaliota campestris.
Subject(s)
Ascorbic Acid , Flavonoids , Animals , Capillaries/analysis , Cell Membrane/analysis , Endothelium/analysis , Guinea Pigs , Laccase , Lung/blood supply , Oxidoreductases/pharmacologyABSTRACT
Histamine chlorhydrate was intravenously injected to Guinea pigs (7 microgram/kg). Alterations of the alveolar walls capillaries were by electronic microscopy studied 1.5, 12 and 15 minutes after injection. It was observed a rapid dilator effect associated with an opening of the endothelial cells tight junctions, an increasing in the size and turnover of pinocytic vesicles, an enlargement and a loss of homogeneity of the basal membrane and an edema of type I pneumocytes. In the last group of animals, lesions reversibility is characterized by a beginning of closing of endothelial cells junctions and of edema resorption. These morphological findings point out the local effect of histamine on the pulmonary capillary microcirculation and show the decrease of resistance and the increase of permeability of the capillaries.
Subject(s)
Histamine/pharmacology , Pulmonary Alveoli/drug effects , Animals , Capillaries/drug effects , Capillaries/ultrastructure , Edema/chemically induced , Endothelium/drug effects , Guinea Pigs , Histamine/adverse effects , Microscopy, Electron , Pulmonary Alveoli/blood supply , Pulmonary Alveoli/ultrastructureABSTRACT
The part of ascorbic acid in the blood capillary wall is shown by deficiency experiment. The pictures obtained by electron microscopy show that, non only is the ascorbic acid needed for the structure integrity of the basement membrane, but also for the permeability of the capillary wall, which when this compound is lacking becomes too important.
Subject(s)
Ascorbic Acid/pharmacology , Capillaries/drug effects , Scurvy/pathology , Animals , Basement Membrane/ultrastructure , Capillaries/ultrastructure , Capillary Permeability/drug effects , Cartilage/ultrastructure , Guinea Pigs , Microscopy, Electron , RibsABSTRACT
The ascorbic acid and the 1-epi-3', 4', 5', 5, 7-pentahydroxy-flavan-3-ol have been located in the blood capillary wall by an histochemical method for electron microscopy. The method consists in an intra-arterial administration of vegetal oxydases specific of the compound to put in evidence. Those oxydases fix themselves on their effectors, and the addition of osmium and lead salts gives co-precipitates opaque to electrons.
