The Experts below are selected from a list of 270 Experts worldwide ranked by ideXlab platform
Elena Kokoliou - One of the best experts on this subject based on the ideXlab platform.
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Knowledge base
internal, 2017Co-Authors: Elena KokoliouAbstract:in a localised area. A co-axial gas jet is used to eject the molten material and create a kerf. A continuous cut is produced by moving the laser beam or workpiece
Jiarong Hong - One of the best experts on this subject based on the ideXlab platform.
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Experimental investigation of ventilated supercavitation with Gas Jet cavitator
Physics of Fluids, 2018Co-Authors: Yunhua Jiang, Siyao Shao, Jiarong HongAbstract:We conduct an experimental study of the ventilated supercavitation generated from Gas Jet cavitator [Gas Jet ventilated supercavitation (GJVS)] over a broad range of ventilation and flow conditions for two Gas Jet nozzle sizes. The experiments show that supercavity evolves across different cavity regimes with distinct patterns, i.e., bubbly flow, Stable Cavity (SC), Unstable Cavity (UC), and Jet Cavity (JC) with increasing ventilation rate. The supercavity transition is shown to be a result of the stagnation location of Gas Jet shifting from the potential core zone to the established turbulent flow zone of the Jet as ventilation increases. The variation of supercavity regimes under a broad range of Froude numbers is compiled, and the map of supercavity regime transition shows similar trends for different Froude numbers and nozzle sizes. Compared to a disc cavitator, in the SC regime, the GJVS exhibits similar ventilation hysteresis with a significantly higher ventilation demand for the formation of a supe...
Yunhua Jiang - One of the best experts on this subject based on the ideXlab platform.
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Experimental investigation of ventilated supercavitation with Gas Jet cavitator
Physics of Fluids, 2018Co-Authors: Yunhua Jiang, Siyao Shao, Jiarong HongAbstract:We conduct an experimental study of the ventilated supercavitation generated from Gas Jet cavitator [Gas Jet ventilated supercavitation (GJVS)] over a broad range of ventilation and flow conditions for two Gas Jet nozzle sizes. The experiments show that supercavity evolves across different cavity regimes with distinct patterns, i.e., bubbly flow, Stable Cavity (SC), Unstable Cavity (UC), and Jet Cavity (JC) with increasing ventilation rate. The supercavity transition is shown to be a result of the stagnation location of Gas Jet shifting from the potential core zone to the established turbulent flow zone of the Jet as ventilation increases. The variation of supercavity regimes under a broad range of Froude numbers is compiled, and the map of supercavity regime transition shows similar trends for different Froude numbers and nozzle sizes. Compared to a disc cavitator, in the SC regime, the GJVS exhibits similar ventilation hysteresis with a significantly higher ventilation demand for the formation of a supe...
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Formation and steady flow characteristics of ventilated supercavity with Gas Jet cavitator
Ocean Engineering, 2017Co-Authors: Yunhua Jiang, Tao Bai, Ye GaoAbstract:Abstract Substantial discrepancies in the formation and attainment conditions for different ventilated cavities are the characteristics of the cavitator and ventilation condition. In this study, a systematic experimental investigation on the concept of using a Gas nozzle at the tip of the object as both the cavitator and the ventilation hole to form a supercavity was performed in a gravity water tunnel. The formation, elimination process and steady shape of the Gas Jet ventilated supercavity, were observed and measured. The dependence relationship of the dimensionless parameters of Gas Jet length, maximum cavity diameter, cavitation number, Froude number and ventilation coefficient were provided based on the experimental data. With the velocity increases in the test section, the irregular cloud cavitation, evolving with a Gas Jet wake, appears, and the Gas Jet wake flows to the back upper location. After that, an ellipsoidal bubble located in front of the Gas Jet cavitator within a certain distance is observed. Eventually, the ellipsoidal bubble gradually grows to a large bubble and cavity, then develops to a supercavity with increasing of the incoming flow velocity in the test section.
X. Ribeyre - One of the best experts on this subject based on the ideXlab platform.
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Proton acceleration by collisionless shocks using a supersonic H 2 Gas-Jet target and high-power infrared laser pulses
Physics of Plasmas, 2019Co-Authors: P. Puyuelo-valdes, J.l. Henares, F. Hannachi, T. Ceccotti, M. Ehret, L. Lancia, J. Domange, E. D'humieres, Jean-raphaël Marquès, X. RibeyreAbstract:For most laser-driven ion acceleration applications, a well-characterized intense ion beam with a low divergence and a controllable energy spectrum produced at a high repetition rate is needed. Gas-Jet targets have given promising results in simulations, and they have several technical advantages for high-repetition-rate lasers. In this work, we report on proton acceleration to energies up to 6 MeV using a supersonic H2 Gas-Jet target at the LULI PICO2000 laser facility. The experimental results are compared with the plasma hydrodynamics and the particle-in-cell simulations to identify the acceleration mechanisms at play.
F. Hannachi - One of the best experts on this subject based on the ideXlab platform.
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Proton acceleration by collisionless shocks using a supersonic H 2 Gas-Jet target and high-power infrared laser pulses
Physics of Plasmas, 2019Co-Authors: P. Puyuelo-valdes, J.l. Henares, F. Hannachi, T. Ceccotti, M. Ehret, L. Lancia, J. Domange, E. D'humieres, Jean-raphaël Marquès, X. RibeyreAbstract:For most laser-driven ion acceleration applications, a well-characterized intense ion beam with a low divergence and a controllable energy spectrum produced at a high repetition rate is needed. Gas-Jet targets have given promising results in simulations, and they have several technical advantages for high-repetition-rate lasers. In this work, we report on proton acceleration to energies up to 6 MeV using a supersonic H2 Gas-Jet target at the LULI PICO2000 laser facility. The experimental results are compared with the plasma hydrodynamics and the particle-in-cell simulations to identify the acceleration mechanisms at play.
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Development of Gas Jet targets for laser-plasma experiments at near-critical density
Rev.Sci.Instrum., 2019Co-Authors: J.l. Henares, P. Puyuelo-valdes, F. Hannachi, T. Ceccotti, M. Ehret, F. Gobet, L. Lancia, J.-r. Marquès, J.j. Santos, M. VersteegenAbstract:Computational fluid dynamics simulations are performed to design Gas nozzles, associated with a 1000 bars backing pressure system, capable of generating supersonic Gas Jet targets with densities close to the critical density for 1053 nm laser radiation (1021 cm−3). Such targets should be suitable for laser-driven ion acceleration at a high repetition rate. The simulation results are compared to the density profiles measured by interferometry, and characterization of the Gas Jet dynamics is performed using strioscopy. Proton beams with maximum energies up to 2 MeV have been produced from diatomic hydrogen Gas Jet targets in a first experiment.
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Optimization of critical-density Gas Jet targets for laser ion acceleration in the collisionless shockwave acceleration regime
2017Co-Authors: J.l. Henares, F. Gobet, J.-r. Marquès, M. Versteegen, M. Tarisien, P. Puyuelo, T. Nguyen-bui, X. Raymond, F. HannachiAbstract:Laser ion acceleration induced by high-power laser systems is nowadays an important research subject due to the large potential range of applications it could satisfy. Most of the available high-power laser facilities deliver only a few laser pulses per hour. The new facilities under development will operate at higher repetition rates (up to 10 Hz). Conventional target technologies (solid targets) and acceleration mechanisms (Target Normal Sheath Acceleration – TNSA) used so far in laser-based ion acceleration are difficult to implement at high repetition rate. New ion acceleration mechanisms such as Collisionless Shockwave Acceleration (CSA) using high density Gas Jets represent therefore a promising alternative. Dense Gas Jet targets show several advantages such as constant refresh and negligible debris production. However, full comprehension of the fluid dynamics involved in the Gas Jet target production is fundamental for its optimization, and at present precise data is scarce. An ongoing study of design and optimization of supersonic Gas Jet nozzles for laser-based ion acceleration is presented.
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Energetic electrons generation in high intensity and ultra-short laser pulse interactions with thin foil or low density Gas Jet targets
2005Co-Authors: G. Malka, F. Hannachi, F. Gobet, M. Tarisien, M.m. Aleonard, G. Claverie, M. Gerbaux, J.n. Scheurer, S. Fritzler, Jérôme FaureAbstract:Energy and angular distributions of the fast outgoing electron beam induced by the interaction of 1-2 J, 30 fs, 3-20x1018 W/cm2 laser with a thin foil or a Gas Jet target are characterized by using both an electron spectrometer and Bremsstrahlung induced photo-nuclear reactions. The supra-thermic electron beams production was investigated for a solid target versus its thickness and its Z number, and for a Gas Jet target versus its pressure. Using a polyethylene target and a supersonic Helium Gas Jet target, we measured, respectively, up to 4x108 and 3x109 electrons produced per laser pulse, with energies up to, respectively, 60 MeV and 160 MeV. The associated Boltzmann temperature of these electrons is colder for thin foils (9 MeV) than for Gas Jet (18 MeV). About, respectively 0.06% and 1% of the laser energy has been converted to outgoing electrons with energies above 5 MeV. Such electrons leave the plasma in the laser direction within a cone with an opening angle of, respectively, 2.5° and 8.5°. We discuss the physical processes of electron acceleration. Numerical calculations show a good agreement with the experiments.
