The Experts below are selected from a list of 4032 Experts worldwide ranked by ideXlab platform
Atsushi Sunahara - One of the best experts on this subject based on the ideXlab platform.
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pure tin microdroplets irradiated with double Laser pulses for efficient and minimum mass extreme ultraviolet light source production
Applied Physics Letters, 2008Co-Authors: S Fujioka, Masashi Shimomura, Yoshinori Shimada, Shinsuke Maeda, Hirokazu Sakaguchi, Yuki Nakai, Tatsuya Aota, H Nishimura, Norimasa Ozaki, Atsushi SunaharaAbstract:Laser-driven expansion of pure-tin microdroplets was demonstrated to produce an efficient and low-debris extreme-ultraviolet (EUV) light source. The pre-expansion is indispensable for resolving the considerable mismatch between the optimal Laser Spot Diameter (∼300μm) and the Diameter (∼20μm) of microdroplets containing the minimum-mass Sn fuel for generating the required EUV radiant energy (∼10mJ/pulse). Explosive expansion of microdroplets was attained by using a Laser prepulse, whose intensity was at least 3×1011W∕cm2. The expanded microdroplet was irradiated with a CO2 Laser pulse to generate EUV light. A combination of low density and long-scale length of the expanded microdroplet leads to a higher EUV energy conversion efficiency (4%) than that (2.5%) obtained from planar Sn targets irradiated by a single CO2 Laser pulse. This scheme can be used to produce a practical EUV light source system.
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pure tin microdroplets irradiated with double Laser pulses for efficient and minimum mass extreme ultraviolet light source production
Applied Physics Letters, 2008Co-Authors: S Fujioka, Masashi Shimomura, Yoshinori Shimada, Shinsuke Maeda, Hirokazu Sakaguchi, Yuki Nakai, Tatsuya Aota, H Nishimura, Norimasa Ozaki, Atsushi SunaharaAbstract:Laser-driven expansion of pure-tin microdroplets was demonstrated to produce an efficient and low-debris extreme-ultraviolet (EUV) light source. The pre-expansion is indispensable for resolving the considerable mismatch between the optimal Laser Spot Diameter (∼300μm) and the Diameter (∼20μm) of microdroplets containing the minimum-mass Sn fuel for generating the required EUV radiant energy (∼10mJ/pulse). Explosive expansion of microdroplets was attained by using a Laser prepulse, whose intensity was at least 3×1011W∕cm2. The expanded microdroplet was irradiated with a CO2 Laser pulse to generate EUV light. A combination of low density and long-scale length of the expanded microdroplet leads to a higher EUV energy conversion efficiency (4%) than that (2.5%) obtained from planar Sn targets irradiated by a single CO2 Laser pulse. This scheme can be used to produce a practical EUV light source system.
A K Nath - One of the best experts on this subject based on the ideXlab platform.
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effect of tempering on Laser remelted aisi h13 tool steel
Surface & Coatings Technology, 2019Co-Authors: Debapriya Patra Karmaka, Muvvala Gopinath, A K NathAbstract:Abstract The effect of tempering temperature on surface hardened AISI H13 tool steel by Laser remelting process using an Yb-fiber Laser has been investigated. Single remelting tracks were produced in argon environment at different Laser power and scan speed in the range of 400–600 W and 200–1600 mm/min respectively, maintaining the Laser Spot Diameter fixed at 3 mm. Their effects on geometrical aspects, microstructure and microhardness were analyzed considering the thermal history of molten pool recorded using an IR pyrometer. Microstructure was found to be associated with cooling rate and melt pool lifetime, estimated from the temperature signal. Thereafter, remelted surface with 30% overlapping tracks was generated and subjected to 1 h tempering cycle at different temperatures in 500–900 °C range followed by hardness and wear tests. Hardness was retained fully up to 500 °C and significant softening occurred at 600 °C and 700 °C. At 800 °C and higher temperatures, effects of Laser remelting were impaired completely, but substrate got hardened through martensite formation in a conventional manner. Wear resistance followed the trend of hardness. Changes in microstructure and formation of various phases were found to be the reasons behind the modifications in hardness.
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Laser forming of a bowl shaped surface with a stationary Laser beam
Optics and Lasers in Engineering, 2016Co-Authors: Shitanshu Shekhar Chakraborty, Harshit More, A K NathAbstract:Abstract Despite a lot of research done in the field of Laser forming, generation of a symmetric bowl shaped surface by this process is still a challenge mainly because only a portion of the sheet is momentarily deformed in this process, unlike conventional sheet metal forming like deep drawing where the entire blank undergoes forming simultaneously reducing asymmetry to a minimum. The motion of Laser beam also makes the process asymmetric. To counter these limitations this work proposes a new approach for Laser forming of a bowl shaped surface by irradiating the centre of a flat circular blank with a stationary Laser beam. With high power Lasers, power density sufficient for Laser forming, can be availed at reasonably large Spot sizes. This advantage is exploited in this technique. Effects of duration of Laser irradiation and beam Spot Diameter on the amount of bending and asymmetry in the formed surface were investigated. Laser power was kept constant while varying irradiation time. While varying Laser Spot Diameter Laser power was chosen so as to keep the surface temperature nearly constant at just below melting. Experimental conditions promoted almost uniform heating through sheet thickness. The amount of bending increased with irradiation time and Spot Diameter. It was interesting to observe that blanks bent towards the Laser beam for smaller Laser beam Diameters and the reverse happened for larger Spot Diameters (~10 times of the sheet thickness). Effect of Spot Diameter variation has been explained with the help of coupled thermal-structural finite element simulations.
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parametric study on bending and thickening in Laser forming of a bowl shaped surface
Optics and Lasers in Engineering, 2012Co-Authors: Shitanshu Shekhar Chakraborty, Vikranth Racherla, A K NathAbstract:Abstract Shaping a circular sheet into a bowl requires in-plane thickening as well as out-of-plane bending. Combinations of radial and circular Laser scan paths can make that. In this work, the effects of various process parameters, viz. Laser Spot Diameter, Laser power and scan speed, on the in-plane and out-of-plane forming of stainless steel circular blanks were studied for various circular and radial scan schemes. Taguchi method was used to plan the experimental runs. Both bending angle and thickness increment for circular and radial scan schemes, respectively, were found to increase with reducing Laser beam Diameter and scan speed, and increasing Laser power. The experimental results were corroborated with the predictions by simplified analytical models. Further, the bending angle was found to increase with increasing radius of the circular scan path. Increase in the number or in the length of radial scan lines increased the thickness increment and the bending angle, induced due to the resultant shrinkage in the periphery of the blanks. It was found that the combination of radial and circular scan schemes works better for achieving higher bending angle with smaller coefficient of variation, which gives a measure of wrinkling in the formed blanks.
S Fujioka - One of the best experts on this subject based on the ideXlab platform.
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pure tin microdroplets irradiated with double Laser pulses for efficient and minimum mass extreme ultraviolet light source production
Applied Physics Letters, 2008Co-Authors: S Fujioka, Masashi Shimomura, Yoshinori Shimada, Shinsuke Maeda, Hirokazu Sakaguchi, Yuki Nakai, Tatsuya Aota, H Nishimura, Norimasa Ozaki, Atsushi SunaharaAbstract:Laser-driven expansion of pure-tin microdroplets was demonstrated to produce an efficient and low-debris extreme-ultraviolet (EUV) light source. The pre-expansion is indispensable for resolving the considerable mismatch between the optimal Laser Spot Diameter (∼300μm) and the Diameter (∼20μm) of microdroplets containing the minimum-mass Sn fuel for generating the required EUV radiant energy (∼10mJ/pulse). Explosive expansion of microdroplets was attained by using a Laser prepulse, whose intensity was at least 3×1011W∕cm2. The expanded microdroplet was irradiated with a CO2 Laser pulse to generate EUV light. A combination of low density and long-scale length of the expanded microdroplet leads to a higher EUV energy conversion efficiency (4%) than that (2.5%) obtained from planar Sn targets irradiated by a single CO2 Laser pulse. This scheme can be used to produce a practical EUV light source system.
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pure tin microdroplets irradiated with double Laser pulses for efficient and minimum mass extreme ultraviolet light source production
Applied Physics Letters, 2008Co-Authors: S Fujioka, Masashi Shimomura, Yoshinori Shimada, Shinsuke Maeda, Hirokazu Sakaguchi, Yuki Nakai, Tatsuya Aota, H Nishimura, Norimasa Ozaki, Atsushi SunaharaAbstract:Laser-driven expansion of pure-tin microdroplets was demonstrated to produce an efficient and low-debris extreme-ultraviolet (EUV) light source. The pre-expansion is indispensable for resolving the considerable mismatch between the optimal Laser Spot Diameter (∼300μm) and the Diameter (∼20μm) of microdroplets containing the minimum-mass Sn fuel for generating the required EUV radiant energy (∼10mJ/pulse). Explosive expansion of microdroplets was attained by using a Laser prepulse, whose intensity was at least 3×1011W∕cm2. The expanded microdroplet was irradiated with a CO2 Laser pulse to generate EUV light. A combination of low density and long-scale length of the expanded microdroplet leads to a higher EUV energy conversion efficiency (4%) than that (2.5%) obtained from planar Sn targets irradiated by a single CO2 Laser pulse. This scheme can be used to produce a practical EUV light source system.
Costas P Grigoropoulos - One of the best experts on this subject based on the ideXlab platform.
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micron scale modifications of si surface morphology by pulsed Laser texturing
Physical Review B, 2001Co-Authors: T Schwarzselinger, S.j. Moon, David G Cahill, Shaochen Chen, Costas P GrigoropoulosAbstract:The morphologies of Si surfaces are modified with single, tightly focused nanosecond Laser pulses and characterized by atomic force microscopy ~AFM!. Dimple-shaped features with Diameters 1 –4 mm and depths 1–300 nm are produced by varying the Laser-Spot Diameter and the peak energy densities F0 in the range 0.4,F0,1.3 J cm . Greater control of the depth of shallow dimples and quantitative comparison of theory and experiment is enabled by first removing the native oxide of Si with dilute HF acid. We develop approximate analytical solutions for two-dimensional fluid-flow driven by gradients in the surface tension; these solutions provide fundamental insight on how the morphology depends on Laser parameters and the thermophysical properties of the melt and its surface. Quantitative comparisons between theory and experiment are enabled by using numerical simulations of heat flow in one-dimension as inputs to the analytical fluid-flow equations; we find good agreement with AFM data for the dimple shape and depth.
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micron scale modifications of si surface morphology by pulsed Laser texturing
Physical Review B, 2001Co-Authors: T Schwarzselinger, S.j. Moon, David G Cahill, Shuo Chen, Costas P GrigoropoulosAbstract:The morphologies of Si surfaces are modified with single, tightly focused nanosecond Laser pulses and characterized by atomic force microscopy (AFM). Dimple-shaped features with Diameters $1--4 \ensuremath{\mu}\mathrm{m}$ and depths 1--300 nm are produced by varying the Laser-Spot Diameter and the peak energy densities ${F}_{0}$ in the range $0.4l{F}_{0}l1.3 \mathrm{J} {\mathrm{cm}}^{\ensuremath{-}2}.$ Greater control of the depth of shallow dimples and quantitative comparison of theory and experiment is enabled by first removing the native oxide of Si with dilute HF acid. We develop approximate analytical solutions for two-dimensional fluid-flow driven by gradients in the surface tension; these solutions provide fundamental insight on how the morphology depends on Laser parameters and the thermophysical properties of the melt and its surface. Quantitative comparisons between theory and experiment are enabled by using numerical simulations of heat flow in one-dimension as inputs to the analytical fluid-flow equations; we find good agreement with AFM data for the dimple shape and depth.
H Nishimura - One of the best experts on this subject based on the ideXlab platform.
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pure tin microdroplets irradiated with double Laser pulses for efficient and minimum mass extreme ultraviolet light source production
Applied Physics Letters, 2008Co-Authors: S Fujioka, Masashi Shimomura, Yoshinori Shimada, Shinsuke Maeda, Hirokazu Sakaguchi, Yuki Nakai, Tatsuya Aota, H Nishimura, Norimasa Ozaki, Atsushi SunaharaAbstract:Laser-driven expansion of pure-tin microdroplets was demonstrated to produce an efficient and low-debris extreme-ultraviolet (EUV) light source. The pre-expansion is indispensable for resolving the considerable mismatch between the optimal Laser Spot Diameter (∼300μm) and the Diameter (∼20μm) of microdroplets containing the minimum-mass Sn fuel for generating the required EUV radiant energy (∼10mJ/pulse). Explosive expansion of microdroplets was attained by using a Laser prepulse, whose intensity was at least 3×1011W∕cm2. The expanded microdroplet was irradiated with a CO2 Laser pulse to generate EUV light. A combination of low density and long-scale length of the expanded microdroplet leads to a higher EUV energy conversion efficiency (4%) than that (2.5%) obtained from planar Sn targets irradiated by a single CO2 Laser pulse. This scheme can be used to produce a practical EUV light source system.
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pure tin microdroplets irradiated with double Laser pulses for efficient and minimum mass extreme ultraviolet light source production
Applied Physics Letters, 2008Co-Authors: S Fujioka, Masashi Shimomura, Yoshinori Shimada, Shinsuke Maeda, Hirokazu Sakaguchi, Yuki Nakai, Tatsuya Aota, H Nishimura, Norimasa Ozaki, Atsushi SunaharaAbstract:Laser-driven expansion of pure-tin microdroplets was demonstrated to produce an efficient and low-debris extreme-ultraviolet (EUV) light source. The pre-expansion is indispensable for resolving the considerable mismatch between the optimal Laser Spot Diameter (∼300μm) and the Diameter (∼20μm) of microdroplets containing the minimum-mass Sn fuel for generating the required EUV radiant energy (∼10mJ/pulse). Explosive expansion of microdroplets was attained by using a Laser prepulse, whose intensity was at least 3×1011W∕cm2. The expanded microdroplet was irradiated with a CO2 Laser pulse to generate EUV light. A combination of low density and long-scale length of the expanded microdroplet leads to a higher EUV energy conversion efficiency (4%) than that (2.5%) obtained from planar Sn targets irradiated by a single CO2 Laser pulse. This scheme can be used to produce a practical EUV light source system.
