The energy transfer by stimulated Brillouin backscatter from a long pump pulse (15 ps) to a short seed pulse (1 ps) has been investigated in a proof-of-principle demonstration experiment. The two pulses were both amplified in different beamlines of a Nd:glass laser system, had a central wavelength of 1054 nm and a spectral bandwidth of 2 nm, and crossed each other in an underdense plasma in a counter-propagating geometry, off-set by 10 • . It is shown that the energy transfer and the wavelength of the generated Brillouin peak depend on the plasma density, the intensity of the laser pulses, and the competition between two-plasmon decay and stimulated Raman scatter instabilities. The highest obtained energy transfer from pump to probe pulse is 2.5%, at a plasma density of 0.17n cr , and this energy transfer increases significantly with plasma density. Therefore, our results suggest that much higher efficiencies can be obtained when higher densities (above 0.25n cr ) are used.

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Articles you may be interested inFast ignition realization experiment with high-contrast kilo-joule peta-watt LFEX laser and strong external magnetic field Phys. Plasmas 23, 056308 (2016); 10.1063/1.4948278 Measuring the strong electrostatic and magnetic fields with proton radiography for ultra-high intensity laser channeling on fast ignitiona) Rev. Sci. Instrum. 85, 11E612 (2014) Channel formation during the propagation of a high-energy (120 J) and long duration (30 ps) laser pulse through an underdense deuterium plasma has been spatially and temporally resolved via means of a proton imaging technique, with intrinsic resolutions of a few lm and a few ps, respectively. Conclusive proof is provided that strong azimuthally symmetric magnetic fields with a strength of around 0.5 MG are created inside the channel, consistent with the generation of a collimated beam of relativistic electrons. The inferred electron beam characteristics may have implications for the conefree fast-ignition scheme of inertial confinement fusion. Published by AIP Publishing.

To generate well-defined warm dense state for evaluating electrical conductivity by using pulsed-power discharge, we have proposed an isochoric heating of foamed metal. Isochoric heating can be achieved by surrounding the foamed metal with a rigid-walled sapphire capillary. We evaluate the temperature and electrical conductivity of the foam∕plasma based on the line-pair method of the foam∕plasma emission and on the voltage-current waveforms. The electrical conductivity observed agrees with previous experiments and predictions. Thus, the proposed technique yields the electrical conductivity of warm dense matter with a well-defined temperature.

Three-component coupling reactions of silylene, aldehydes and electron-deficient acetylenes proceed via 1,3-dipolar cycloaddition of silacarbonyl ylides with acetylenic dipolarophiles.The three-component coupling reaction 1 is a versatile method in synthetic organic chemistry because complex molecules can be constructed from readily available starting materials in a one-step operation. Among the methods studied, reactions involving 1,3-dipoles are privileged routes leading to various interesting and useful heterocyclic compounds. 2 Although silylenes are powerful species and afford unique compounds embedded in silicon units, 3 there are no examples of three-component coupling through 1,3-dipoles derived from silylenes. Woerpel and co-workers recently developed silylene chemistry using silacyclopropanes and silver catalysts, producing oxasilacyclopentane from the reaction of silacyclopropanes, aldehydes, and olefins. The mechanism of the reaction involved the copper-or zinc-catalyzed insertion of aldehydes into the C-Si bond of siliranes, generated from silacyclopropanes and olefins, catalyzed by silver salts. 4 On the other hand, previous studies described the novel cycloaddition of silacarbonyl ylides, generated from silylene and carbonyl compounds. 5 In these studies, dipolarophiles reacting with silacarbonyl ylides, were the aldehyde components for generation of the ylide (2:1 cycloaddition), 5a or were the moiety (substituent) of the carbonyl compounds (intramolecular cycloaddition). 5b As preliminary findings, the silacarbonyl ylide generated from a silylene with crotonaldehyde was trapped by the C=C bond of the aldehyde. 5a This result prompted the current investigation of the three-component coupling reaction of silylene, aldehydes and electron-deficient carbon-carbon unsaturated compounds (Scheme 1). Scheme 1The screening of a variety of olefinic dipolarophiles for use in the reaction did not lead to the desired cycloadducts. Therefore, a first experiment was performed to examine the ability of an acetylenic compound to act as a dipolarophile. A solution of trisilane 6 1 and but-3-yn-2-one (20 equiv) in diethyl ether was irradiated at -57°C for 20 hours in a cold bath under a low pressure mercury lamp. The resulting mixture was separated on a silica gel column to give 1-oxa-2-silacyclopentene 2 in a yield of 57% as a mixture of regioisomers. The structures of the cycloadducts were characterized by spectral data, including NOE measurement, as 1: 2 cycloadducts of bismesitylsilylene and the acetylenic ketone (Scheme 2). The formation of the cycloadduct prompted a further examination of the three-component coupling reaction of silylene, aldehyde, and acetylenic dipolarophiles. Scheme 2When a solution of trisilane 1, pivaldehyde (2 equiv), and methyl propiolate (5 equiv) in hexane was photolyzed at -57°C for 20 hours, three-component cycloadducts 3a and 3b were successfully obtained in a yield of 41%, as a mixture of regioisomers. Although the reaction did not proceed at all in dichloromethane, ethers were fo...