scholarly journals Detecting of melting by changes of rear surface reflectivity in shocked compressed metals using an interferometric diagnostic method

1999 ◽  
Vol 17 (3) ◽  
pp. 547-556 ◽  
Author(s):  
M. WERDIGER ◽  
S. ELIEZER ◽  
S. MAMAN ◽  
Y. HOROVITZ ◽  
E. MOSHE ◽  
...  
Keyword(s):  
Shock Wave ◽  
Free Surface ◽  
Pulse Width ◽  
Diagnostic Method ◽  
Laser System ◽  
Rear Surface ◽  
Power Laser ◽  
Shock Wave Pressure ◽  
Surface Reflectivity ◽  
Pressure Regime

When a high power laser (1012 W/cm2) irradiates a target, it induces a shock wave, which reaches the (free) rear surface. The free surface is accelerated and the shock wave is back-reflected as a rarefaction wave. In the shock wave pressure regime involved here, melting of the target during the shock or during the rarefaction may occur. An optically recording velocity interferometric system (ORVIS) has been developed to measure the time evolution of the change in the reflectivity of the free surface. Shock waves of the order of hundreds of kilobars are produced in 50–125 μm thick Sn and Al foils, by a Nd:YAG laser system with a wavelength of 1.06 μm, pulse width of 7 ns (FWHM), and irradiance in the range (1.4–2.4)·1013 W/cm2. The changes in the reflectivity occur along two time scales: a slow one, more than 17 ns in Al and more than 30 ns in Sn, and a rapid one, less than 2.5 ns, in both materials. A possible explanation for the sharp decreases in the time scale is that melting occurs during the release of the free surface.

scholarly journals Development of holographic methods for investigating a moving free surface, accelerated by laser-induced shock waves

1999 ◽  
Vol 17 (4) ◽  
pp. 653-660 ◽  
Author(s):  
M. WERDIGER ◽  
S. ELIEZER ◽  
S. MAMAN ◽  
Y. HOROVITZ ◽  
B. ARAD ◽  
...  
Keyword(s):  
Shock Wave ◽  
Free Surface ◽  
Shock Waves ◽  
Atmospheric Pressure ◽  
Laser Light ◽  
Laser System ◽  
Rear Surface ◽  
Green Laser ◽  
Forward Scattering ◽  
High Power Lasers

Holographic methods developed to study the behavior of surfaces shocked by high power lasers are reported. Shock waves of the order of hundreds of kilobars are generated in Sn targets 50-μm thick, by a Nd:YAG laser system with a wavelength of 1.06 μm, a pulse duration of 7.5 ns FWHM, and irradiance in the range (1.0–2.6)·1013 W/cm2. Two configurations of off-axis holography were applied: holograms based on forward scattering, and holograms of both backward and forward scattering. The hologram is produced by scattering of a pulse, 6.7 ns (FWHM), of green laser light synchronized with the laser that generates the shock wave. Holograms of the topology of the rear surface of shocked Sn targets moving in vacuum and in air (at atmospheric pressure) are reported.

High-stability, high-beam-quality, and pulse-width-tunable 1319  nm laser system for VISAR applications in high-power laser facilities

2020 ◽  
Vol 59 (20) ◽  
pp. 6070
Author(s):  
Qi Xiao ◽  
Xue Pan ◽  
Jiangtao Guo ◽  
Xiaoqin Wang ◽  
Jiangfeng Wang ◽  
...  
Keyword(s):  
High Power ◽  
Pulse Width ◽  
High Stability ◽  
Beam Quality ◽  
Laser System ◽  
High Power Laser ◽  
Power Laser ◽  
High Beam ◽  
High Beam Quality

scholarly journals Asymptotic measurements of free surface instabilities in laser-induced shock waves

1996 ◽  
Vol 14 (2) ◽  
pp. 133-147 ◽  
Author(s):  
M. Werdiger ◽  
B. Arad ◽  
Z. Henis ◽  
Y. Horowitz ◽  
E. Moshe ◽  
...  
Keyword(s):  
Free Surface ◽  
Shock Waves ◽  
Pulse Width ◽  
Laser System ◽  
Optical Scattering ◽  
Liquid Transition ◽  
Aluminium Copper ◽  
Metallic Sample ◽  
Mass Ejection ◽  
Surface Occurrence

An experimental technique based on optical scattering to detect melting in release of strongly shocked materials is presented. This method is used to study the asymptotic behavior of the free surface of shock-loaded materials. After reflection of a shock wave from a metallic sample free surface, occurrence of a solid to liquid transition will induce a dynamic behavior such as mass ejection and development of instabilities. A study of the mass ejection due to laser-induced shock waves in aluminium, copper, and tin targets is presented. Shock waves of order of hundreds of kilobars to more than one megabar are produced by a Nd:YAG laser system with a wavelength of 1.06 μm, pulse width of 7 ns FWHM focused to spot of 200 μm. The velocities, size, and topological structure of the ejected particles are measured. The radii of the ejecta are in the range 0.5–7 μm.

scholarly journals Observation of the shock wave propagation induced by a high-power laser irradiation into an epoxy material

2013 ◽  
Vol 46 (23) ◽  
pp. 235501 ◽  
Author(s):  
Romain Ecault ◽  
Laurent Berthe ◽  
Michel Boustie ◽  
Fabienne Touchard ◽  
Emilien Lescoute ◽  
...  
Keyword(s):  
Shock Wave ◽  
Wave Propagation ◽  
Laser Irradiation ◽  
High Power ◽  
Shock Wave Propagation ◽  
High Power Laser ◽  
Power Laser ◽  
Epoxy Material

scholarly journals A Lab-Scale Experiment Approach to the Measurement of Wall Pressure from Near-Field under Water Explosions by a Hopkinson Bar

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Xiongwei Cui ◽  
Xiongliang Yao ◽  
Yingyu Chen
Keyword(s):  
Shock Wave ◽  
Near Field ◽  
Underwater Explosion ◽  
Experimental System ◽  
Hopkinson Bar ◽  
Wall Pressure ◽  
Pressure Loading ◽  
Target Plate ◽  
Wave Pressure ◽  
Shock Wave Pressure

Direct measurement of the wall pressure loading subjected to the near-field underwater explosion is of great difficulty. In this article, an improved methodology and a lab-scale experimental system are proposed and manufactured to assess the wall pressure loading. In the methodology, a Hopkinson bar (HPB), used as the sensing element, is inserted through the hole drilled on the target plate and the bar’s end face lies flush with the loaded face of the target plate to detect and record the pressure loading. Furthermore, two improvements have been made on this methodology to measure the wall pressure loading from a near-field underwater explosion. The first one is some waterproof units added to make it suitable for the underwater environment. The second one is a hard rubber cylinder placed at the distal end, and a pair of ropes taped on the HPB is used to pull the HPB against the cylinder hard to ensure the HPB’s end face flushes with loaded face of the target plate during the bubble collapse. To validate the pressure measurement technique based on the HPB, an underwater explosion between two parallelly mounted circular target plates is used as the validating system. Based on the assumption that the shock wave pressure profiles at the two points on the two plates which are symmetrical to each other about the middle plane of symmetry are the same, it was found that the pressure obtained by the HPB was in excellent agreement with pressure transducer measurements, thus validating the proposed technique. To verify the capability of this improved methodology and experimental system, a series of minicharge underwater explosion experiments are conducted. From the recorded pressure-time profiles coupled with the underwater explosion evolution images captured by the HSV camera, the shock wave pressure loading and bubble-jet pressure loadings are captured in detail at 5  mm, 10  mm, …, 30  mm stand-off distances. Part of the pressure loading of the experiment at 35  mm stand-off distance is recorded, which is still of great help and significance for engineers. Especially, the peak pressure of the shock wave is captured.

ALD anti-reflection coatings at 1ω, 2ω, 3ω, and 4ω for high-power ns-laser application

2018 ◽  
Vol 7 (1-2) ◽  
pp. 23-31 ◽  
Author(s):  
Hao Liu ◽  
Lars Jensen ◽  
Ping Ma ◽  
Detlev Ristau
Keyword(s):  
High Power ◽  
High Surface ◽  
Laser System ◽  
Damage Threshold ◽  
Atomic Layer ◽  
Intensity Difference ◽  
High Power Laser ◽  
Power Laser ◽  
Laser Applications ◽  
Laser Induced Damage

AbstractAtomic layer deposition (ALD) facilitates the deposition of coatings with precise thickness, high surface conformity, structural uniformity, and nodular-free structure, which are properties desired in high-power laser coatings. ALD was studied to produce uniform and stable Al2O3and HfO2single layers and was employed to produce anti-reflection coatings for the harmonics (1ω, 2ω, 3ω, and 4ω) of the Nd:YAG laser. In order to qualify the ALD films for high-power laser applications, the band gap energy, absorption, and element content of single layers were characterized. The damage tests of anti-reflection coatings were carried out with a laser system operated at 1ω, 2ω, 3ω, and 4ω, respectively. The damage mechanism was discussed by analyzing the damage morphology and electric field intensity difference. ALD coatings exhibit stable growth rates, low absorption, and rather high laser-induced damage threshold (LIDT). The LIDT is limited by HfO2as the employed high-index material. These properties indicate the high versatility of ALD films for applications in high-power coatings.

The advancement of pump channel of high peak and high average power laser system

2018 ◽  
Author(s):  
V.V. Petrov ◽  
G.V. Kuptsov ◽  
V.A. Petrov ◽  
A.V. Laptev ◽  
A.V. Kirpichnikov ◽  
...  
Keyword(s):  
Laser System ◽  
Average Power ◽  
High Peak ◽  
High Average Power ◽  
Power Laser
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