The spherical crystal imaging system,noted for its high energy spectral resolution(monochromaticity)and spatial resolution,is extensively applied in high energy density physics and inertial confinement fusion research...The spherical crystal imaging system,noted for its high energy spectral resolution(monochromaticity)and spatial resolution,is extensively applied in high energy density physics and inertial confinement fusion research.This system supports studies on fast electron transport,hydrodynamic instabilities,and implosion dynamics.The x-ray source,produced through laser-plasma interaction,emits a limited number of photons within short time scales,resulting in predominantly photon-starved images.Through ray-tracing simulations,we investigated the impact of varying crystal dimensions on the performance of a spherical crystal self-emission imager.We observed that increasing the crystal dimension leads to higher imaging efficiency but at the expense of monochromaticity,causing broader spectral acceptance and reduced spatial resolution.Furthermore,we presented a theoretical model to estimate the spatial resolution of the imaging system within a specific energy spectrum range,detailing the expressions for the effective size of the crystal.The spatial resolution derived from the model closely matches the numerical simulations.展开更多
Self-emission x-ray shadowgraphy provides a method to measure the ablation-front trajectory and low-mode nonuniformity of a target imploded by directly illuminating a fusion capsule with laser beams. The technique use...Self-emission x-ray shadowgraphy provides a method to measure the ablation-front trajectory and low-mode nonuniformity of a target imploded by directly illuminating a fusion capsule with laser beams. The technique uses time-resolved images of soft x-rays(>1 ke V) emitted from the coronal plasma of the target imaged onto an x-ray framing camera to determine the position of the ablation front. Methods used to accurately measure the ablation-front radius(δ R= ±1.15 μm), image-to-image timing(δ( t)= ±2.5 ps) and absolute timing(δt= ±10 ps) are presented.Angular averaging of the images provides an average radius measurement of δ( Rav)= ±0.15 μm and an error in velocity of δV / V= ±3%. This technique was applied on the Omega Laser Facility [Boehly et al., Opt. Commun. 133, 495(1997)] and the National Ignition Facility [Campbell and Hogan, Plasma Phys. Control. Fusion 41, B39(1999)].展开更多
Implosion asymmetry is a crucial problem quenching ignition in the field of inertial confinement fusion.A forward-calculation method based on 1D and 2D hydrodynamic simulations has been developed to generate and study...Implosion asymmetry is a crucial problem quenching ignition in the field of inertial confinement fusion.A forward-calculation method based on 1D and 2D hydrodynamic simulations has been developed to generate and study the x-ray images of hot-spot self-emission,indicating asymmetry integrated over the entire drive pulse.It is shown that the x-ray imaging photon energy should be higher to avoid the influence of the remaining shell.The contour level(percentage of the maximum emission intensity)and spatial resolution should be as low as possible,optimally less than 20%and 3μm,for characterization of higher-mode signatures such as Ps-P12 by x-ray self-emission images.On the contrary,signatures of lower-mode such as P2 remain clear at all contour levels and spatial resolutions.These key results can help determine the optimal diagnostics,laser,and target parameters for implosion experiments.Recent typical hot-spot asymmetry measurements and applications on the Shenguang 100 kJ class laser facility are also reported.展开更多
Shadowgraphic imaging was employed to investigate the mid-IR laser induced heat transfer through a double layer thin film. The effect of thin metal coat on the polymer film enhanced the transfer of heat and shock wave...Shadowgraphic imaging was employed to investigate the mid-IR laser induced heat transfer through a double layer thin film. The effect of thin metal coat on the polymer film enhanced the transfer of heat and shock waves due to rapid thermal expansion and the explosive evaporation of the thin fluid layer. Sixty two percent of deposited heat expended for water enthalpy and 38% for other factors. A power of 8.8 kW was launched at the surface of aluminium. The thermal coupling of 45% further reduced the input energy to the film and the non-adiabatic heat diffusion (i.e., ) was transmitted instantaneously within the metal with very small loss. The temperature at the surface of the film was determined ≈301 K, well below the aluminium melting point. The Biot number showed that the metal as single layer and the whole film as double layer satisfies the thermally thin film (i.e., ). Considering the Newtons’s law of cooling, the overall film heat transfer coefficient was found 3 k W·m-2·K-1 equivalent of 3.3 × 10-3 W·m2·K-1 thermal resistance. The analysis of images indicated a reducing percentage of heat transfer as a function of delay time based on the comparison of volume ratios. A calculated power of ≈3 kW was transmitted from the rear side of the film sufficient to thermalize the surrounding water layer and form vapor bubble.展开更多
A terminal ballistic analysis of the effects of 7.62 mm × 51 AP P80 rounds on inclined high-strength armor steel plates is the focus of the presented study.The findings of an instrumented ballistic testing combin...A terminal ballistic analysis of the effects of 7.62 mm × 51 AP P80 rounds on inclined high-strength armor steel plates is the focus of the presented study.The findings of an instrumented ballistic testing combined with 3D advanced numerical simulations performed using the IMPETUS Afea? software yielded the conclusions.The experimental verification proved that slight differences in the pitch-andyaw angles of a projectile upon an impact caused different damage types to the projectile’s core.The residual velocities predicted numerically were close to the experimental values and the calculated core deviations were in satisfactory agreement with the experimental results.An extended matrix of the core deviation angles with combinations of pitch-and-yaw upon impact angles was subsequently built on the basis of the numerical study.The presented experimental and numerical investigation examined thoroughly the influence of the initial pitch and yaw angles on the after-perforation projectile’s performance.展开更多
This article deals with an experimental study on the aerodynamic characteristics of a low-drag high-speed nature laminar flow (NLF) airfoil for business airplanes in the TST27 wind tunnel at Delft University of Techno...This article deals with an experimental study on the aerodynamic characteristics of a low-drag high-speed nature laminar flow (NLF) airfoil for business airplanes in the TST27 wind tunnel at Delft University of Technology, the Netherlands. In this experiment, in an attempt to reduce the errors of measurement and improve its accuracy in high-speed flight, some nonintrusive meas- urement techniques, such as the quantitative infrared thermography (IRT), the digital particle imaging velocimetry (PIV), and the s...展开更多
Understanding shielding cross-effects is a prerequisite for maximal power-specific nanosecond laser ablation in liquids(LAL).However,discrimination between cavitation bubble(CB),nanoparticle(NP),and shielding,e.g.,by ...Understanding shielding cross-effects is a prerequisite for maximal power-specific nanosecond laser ablation in liquids(LAL).However,discrimination between cavitation bubble(CB),nanoparticle(NP),and shielding,e.g.,by the plasma or a transient vapor layer,is challenging.Therefore,CB imaging by shadowgraphy is performed to better understand the plasma and laser beam-NP interaction during LAL.By comparing the fluence-dependent CB volume for ablations performed with 1 ns pulses with reports from the literature,we find larger energy-specific CB volumes for 7 ns-ablation.The increased CB for laser ablation with higher ns pulse durations could be a first explanation of the efficiency decrease reported for these laser systems having higher pulse durations.Consequently,1 ns-LAL shows superior ablation efficiency.Moreover,a CB cascade occurs when the focal plane is shifted into the liquid.This effect is enhanced when NPs are present in the fluid.Even minute amounts of NPs trapped in a stationary layer decrease the laser energy significantly,even under liquid flow.However,this local concentration in the sticking film has so far not been considered.It presents an essential obstacle in high-yield LAL,shielding already the second laser pulse that arrives and presenting a source of satellite bubbles.Hence,measures to lower the NP concentration on the target must be investigated in the future.展开更多
基金Project supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant Nos.XDA25051000,XDA25010100,XDA25010300,XDA25030100,and XDA25030200)。
文摘The spherical crystal imaging system,noted for its high energy spectral resolution(monochromaticity)and spatial resolution,is extensively applied in high energy density physics and inertial confinement fusion research.This system supports studies on fast electron transport,hydrodynamic instabilities,and implosion dynamics.The x-ray source,produced through laser-plasma interaction,emits a limited number of photons within short time scales,resulting in predominantly photon-starved images.Through ray-tracing simulations,we investigated the impact of varying crystal dimensions on the performance of a spherical crystal self-emission imager.We observed that increasing the crystal dimension leads to higher imaging efficiency but at the expense of monochromaticity,causing broader spectral acceptance and reduced spatial resolution.Furthermore,we presented a theoretical model to estimate the spatial resolution of the imaging system within a specific energy spectrum range,detailing the expressions for the effective size of the crystal.The spatial resolution derived from the model closely matches the numerical simulations.
基金supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944the University of Rochester and the New York State Energy Research and Development AuthorityThe support of DOE does not constitute an endorsement by DOE of the views expressed in this paper
文摘Self-emission x-ray shadowgraphy provides a method to measure the ablation-front trajectory and low-mode nonuniformity of a target imploded by directly illuminating a fusion capsule with laser beams. The technique uses time-resolved images of soft x-rays(>1 ke V) emitted from the coronal plasma of the target imaged onto an x-ray framing camera to determine the position of the ablation front. Methods used to accurately measure the ablation-front radius(δ R= ±1.15 μm), image-to-image timing(δ( t)= ±2.5 ps) and absolute timing(δt= ±10 ps) are presented.Angular averaging of the images provides an average radius measurement of δ( Rav)= ±0.15 μm and an error in velocity of δV / V= ±3%. This technique was applied on the Omega Laser Facility [Boehly et al., Opt. Commun. 133, 495(1997)] and the National Ignition Facility [Campbell and Hogan, Plasma Phys. Control. Fusion 41, B39(1999)].
基金National Key R&D Program(No.2017YFA0403204)Laser Fusion Research Funds for Young Talents(No.RCFPD1-2017-1)。
文摘Implosion asymmetry is a crucial problem quenching ignition in the field of inertial confinement fusion.A forward-calculation method based on 1D and 2D hydrodynamic simulations has been developed to generate and study the x-ray images of hot-spot self-emission,indicating asymmetry integrated over the entire drive pulse.It is shown that the x-ray imaging photon energy should be higher to avoid the influence of the remaining shell.The contour level(percentage of the maximum emission intensity)and spatial resolution should be as low as possible,optimally less than 20%and 3μm,for characterization of higher-mode signatures such as Ps-P12 by x-ray self-emission images.On the contrary,signatures of lower-mode such as P2 remain clear at all contour levels and spatial resolutions.These key results can help determine the optimal diagnostics,laser,and target parameters for implosion experiments.Recent typical hot-spot asymmetry measurements and applications on the Shenguang 100 kJ class laser facility are also reported.
文摘Shadowgraphic imaging was employed to investigate the mid-IR laser induced heat transfer through a double layer thin film. The effect of thin metal coat on the polymer film enhanced the transfer of heat and shock waves due to rapid thermal expansion and the explosive evaporation of the thin fluid layer. Sixty two percent of deposited heat expended for water enthalpy and 38% for other factors. A power of 8.8 kW was launched at the surface of aluminium. The thermal coupling of 45% further reduced the input energy to the film and the non-adiabatic heat diffusion (i.e., ) was transmitted instantaneously within the metal with very small loss. The temperature at the surface of the film was determined ≈301 K, well below the aluminium melting point. The Biot number showed that the metal as single layer and the whole film as double layer satisfies the thermally thin film (i.e., ). Considering the Newtons’s law of cooling, the overall film heat transfer coefficient was found 3 k W·m-2·K-1 equivalent of 3.3 × 10-3 W·m2·K-1 thermal resistance. The analysis of images indicated a reducing percentage of heat transfer as a function of delay time based on the comparison of volume ratios. A calculated power of ≈3 kW was transmitted from the rear side of the film sufficient to thermalize the surrounding water layer and form vapor bubble.
文摘A terminal ballistic analysis of the effects of 7.62 mm × 51 AP P80 rounds on inclined high-strength armor steel plates is the focus of the presented study.The findings of an instrumented ballistic testing combined with 3D advanced numerical simulations performed using the IMPETUS Afea? software yielded the conclusions.The experimental verification proved that slight differences in the pitch-andyaw angles of a projectile upon an impact caused different damage types to the projectile’s core.The residual velocities predicted numerically were close to the experimental values and the calculated core deviations were in satisfactory agreement with the experimental results.An extended matrix of the core deviation angles with combinations of pitch-and-yaw upon impact angles was subsequently built on the basis of the numerical study.The presented experimental and numerical investigation examined thoroughly the influence of the initial pitch and yaw angles on the after-perforation projectile’s performance.
文摘This article deals with an experimental study on the aerodynamic characteristics of a low-drag high-speed nature laminar flow (NLF) airfoil for business airplanes in the TST27 wind tunnel at Delft University of Technology, the Netherlands. In this experiment, in an attempt to reduce the errors of measurement and improve its accuracy in high-speed flight, some nonintrusive meas- urement techniques, such as the quantitative infrared thermography (IRT), the digital particle imaging velocimetry (PIV), and the s...
基金We thank the Deutsche Forschungsgemeinschaft(DFG)for funding within the grants GO 2566/7-1 and GO 2566/8-1.
文摘Understanding shielding cross-effects is a prerequisite for maximal power-specific nanosecond laser ablation in liquids(LAL).However,discrimination between cavitation bubble(CB),nanoparticle(NP),and shielding,e.g.,by the plasma or a transient vapor layer,is challenging.Therefore,CB imaging by shadowgraphy is performed to better understand the plasma and laser beam-NP interaction during LAL.By comparing the fluence-dependent CB volume for ablations performed with 1 ns pulses with reports from the literature,we find larger energy-specific CB volumes for 7 ns-ablation.The increased CB for laser ablation with higher ns pulse durations could be a first explanation of the efficiency decrease reported for these laser systems having higher pulse durations.Consequently,1 ns-LAL shows superior ablation efficiency.Moreover,a CB cascade occurs when the focal plane is shifted into the liquid.This effect is enhanced when NPs are present in the fluid.Even minute amounts of NPs trapped in a stationary layer decrease the laser energy significantly,even under liquid flow.However,this local concentration in the sticking film has so far not been considered.It presents an essential obstacle in high-yield LAL,shielding already the second laser pulse that arrives and presenting a source of satellite bubbles.Hence,measures to lower the NP concentration on the target must be investigated in the future.
