Thermal Shock Wave Research Articles

Laser-Induced Damage on Fused Silica With Photo-Acoustic Spectrum Analysis

Laser-induced damage on fused silica is studied with photo-acoustic spectrum. The damage characteristics are evaluated with the spectral analysis of photo-acoustic signal. The experimental results show that the damage threshold of fused silica samples is about 20.9 J/cm2 at 1-ON-1 condition at the wavelength of 1064 nm and the pulse duration of 10 ns. The damage morphology observed with confocal microscopy is gray haze, and the diameter and depth of the largest crater in gray haze are $6.7~\mu \text{m}$ and 200 nm, respectively. The reproducibility of photo-acoustic spectrum analysis and the characteristic spectral peak is discussed. Compared to the photo-acoustic method judged by signal amplitude, the photo-acoustic spectrum is more sensitive, which may provide an effective support for the study on laser-generated thermal explosion and shock wave propagation. Moreover, the photo-acoustic spectrum may provide a clue for early-damage judgment.

Analysis of Domino Effect Based on Bayesian Probability Explosion and Oil Tank Fire in Mixing Tank Area

Based on the domino effect and Bayesian network, this paper establishes the accident probability model of hybrid storage tank area. Taking a chemical storage tank area as an example to analyze the accident domino effect caused by accident parameters such as thermal radiation and explosion shock wave, we analyzed and calculated the damage probability of shock wave over-pressure and pool fire to adjacent equipment in liquefied gas storage tanks by considered that the occurrence of a pool fire accident in a single tank is a result of the incident. The results show that the control measures are combined with the energy transfer sequence of the accident, so that the safety protection measures proposed under this scenario can more effectively ensure the safety of the chemical tank farm.

Numerical studies on the radiation uniformity of Z-pinch dynamic hohlraum

Radiation uniformity is important for Z-pinch dynamic hohlraum driven fusion. In order to understand the radiation uniformity of Z-pinch dynamic hohlraum, the code MULTI-2D with a new developed magnetic field package is employed to investigate the related physical processes on Julong-I facility with drive current about 7–8 MA. Numerical simulations suggest that Z-pinch dynamic hohlraum with radiation temperature more than 100 eV can be created on Julong-I facility. Although some X-rays can escape out of the hohlraum from Z-pinch plasma and electrodes, the radiation field near the foam center is quite uniform after a transition time. For the load parameters used in this paper, the transition time for the thermal wave transports from r = 1 mm to r = 0 mm is about 2.0 ns. Implosion of a testing pellet driven by cylindrical dynamic hohlraum shows that symmetrical implosion is hard to achieve due to the relatively slow propagation speed of thermal wave and the compression of cylindrical shock in the foam. With the help of quasi-spherical implosion, the hohlraum radiation uniformity and corresponding pellet implosion symmetry can be significantly improved thanks to the shape modulation of thermal wave front and shock wave front.

Wave packet enriched finite element for generalized thermoelasticity theories for thermal shock wave problems

ABSTRACTA unified enriched finite element (FE) formulation for two generalized thermoelsaticity theories is developed for the transient thermal shock problems in one and two dimensional domains. Both the displacement and temperature field interpolations are enriched with harmonic functions defined in the local element coordinates. The coupled field finite element equations are derived using the generalized Hamilton’s principle and solved directly in time domain using the standard Newmark-β time integration technique as opposed to the transform techniques usually adopted for thermal shock problems. The method is assessed in comparison with the Laplace transform based analytical solutions and FE solutions with dynamic meshing available in the literature. It is shown that the present solution with a static uniform mesh captures the sharp discontinuities in the temperature and displacement fields and the wave properties of heat conduction very accurately, practically eliminating the severe drawbacks of the conventional FE solutions such as the spurious undulations and flattening out, while maintaining better computational efficiency.

Sandwich structure panel subjected to thermal loading using fractional order equation of motion and moving heat source

The present work studies the thermoelastic behaviour of a model for a layered thin plate called sandwich structure subjected to a thermal shock wave in light of the generalized thermoelasticity theory using fractional order equation of motion in the presence of a moving heat source. The governing equations are solved using Laplace transform. To obtain the different inverse field functions numerically, we used a complex inversion formula of Laplace transform based on Fourier expansion. The effect of different parameters; namely, the speed, the strength of the heat source, fractional order and time on the thermodynamical temperature, stress, and strain distribution, are discussed and presented graphically. Comparison with previous work in the context of the theory of generalized thermoelasticity shows that the present model is more reliable than the previous. The present model removes the points of discontinuity present in the stress and temperature distributions in the previous model. In the present model we found that the middle layer was affected slightly by some of these parameters. The other new results are discussed.

Laser-driven shock experiments to investigate mitigation ability of polymeric foams

Polymeric foams are widely used in many industrial fields as thermal insulators, structural materials or shock wave mitigators. Polymeric foams would be valuable candidates to protect structures against intense mechanical stress wave loadings generated by laser irradiation or high velocity impact of very small debris. This article presents the results of laser-driven shock experiments performed on polymeric foams to investigate their mitigation ability. The targets consisted of thin aluminum front plate (250 μm-thickness), 1 mm and 2 mm-thick samples made of expanded polyurethane foam (320 kg/m3) or syntactic epoxy foam (624 kg/m3), and 12 μm-thick aluminum foil. The laser beam provided 20 J in 25 ns and was shot through water confinement of the front plate. The dynamic responses of the foams were investigated by measuring time-velocity profiles at the rear surface. Preliminary tests were performed on thin aluminum plate in order to calibrate the stress wave loadings. A dynamic explicit one-dimensional hydrocode was used to simulate the experiments and validate the calibration of pressure generated under laser irradiation. Then, the numerical simulations were used to analyze the velocity profiles recorded at the rear surface of both foams. The dynamic macroscopic response of the foams was described by a phenomenological compaction model. The model has been validated by numerical correlations with the experimental results. The input pressure (front aluminum plate) and the output one (fictitious PMMA plate placed behind foam samples) were compared by help of numerical simulations. The ratio between input and output pressures could achieve 75. Polyurethane foam better mitigated shock waves below 2 GPa, and epoxy foam was better above 2 GPa.

Nonhomogeneous Dual-Phase-Lag Heat Conduction Problem: Analytical Solution and Select Case Studies

Finite integral transform techniques are applied to solve the one-dimensional (1D) dual-phase heat conduction problem, and a comprehensive analysis is provided for general time-dependent heat generation and arbitrary combinations of various boundary conditions (Dirichlet, Neumann, and Robin). Through the dependence on the relative differences in heat flux and temperature relaxation times, this analytical solution effectively models both parabolic and hyperbolic heat conduction. In order to demonstrate several exemplary physical phenomena, four distinct cases that illustrate the wavelike heat conduction behavior are presented. In the first model, following an initial temperature spike in a slab, the thermal evolution portrays immediate dissipation in parabolic systems, whereas the dual-phase solution depicts wavelike temperature propagation—the intensity of which depends on the relaxation times. Next, the analysis of periodic surface heat flux at the slab boundaries provides evidence of interference patterns formed by temperature waves. In following, the study of Joule heating driven periodic generation inside the slab demonstrates that the steady-periodic parabolic temperature response depends on the ratio of pulsatile electrical excitation and the electrical resistivity of the slab. As for the dual-phase model, thermal resonance conditions are observed at distinct excitation frequencies. Building on findings of the other models, the case of moving constant-amplitude heat generation is considered, and the occurrences of thermal shock and thermal expansion waves are demonstrated at particular conditions.

Supersonic thermal excitation-induced shock wave in black phosphorene

Thermal transport in low-dimensional materials possesses various novel features since anomalous energy carriers may heavily contribute. Black phosphorene exhibits excellent thermal properties and thus it attracts attention about the possible existence of anomalous energy carriers. In this paper, we find that shockwave appears as a dominant energy carrier in the zigzag direction of black phosphorene when a supersonic thermal excitation above a critical strength is exerted. Comparing with the diffusive thermal transport, shockwave carries a considerable amount of excitation energy and propagates faster than the local acoustic speed. It leads to a strong anisotropic enhancement in the transport speed of thermal energy in the zigzag direction, up to a factor of twofold compared with no shockwave. The linear increase of velocity with intensity and exponential decay of intensity with time of the shockwave are observed. Unlike solitary waves, the collision of shockwaves exhibits no phase shift in the spatial-temporal trajectory. Moreover, it shows that shockwave velocity decreases with tensile strain, which is favorable for modulation. Our results reveal a possible anomalous energy transport process and may help in designing black phosphorene-based thermal devices.

One-dimensional numerical investigation on the formation of Z-pinch dynamic hohlraum using the code MULTI

Z-pinch dynamic hohlraum can effectively convert Z-pinch plasma kinetic energy into radiation field energy, which has a potential to implode a pellet filled with deuterium-tritium fuel to fusion conditions when the drive current is sufficiently large. To understand the formation process of Z-pinch dynamic hohlraum on JULONG-I facility with a typical drive current of 8-10 MA, a new radiation magneto-hydrodynamics code is developed based on the program MULTI-IFE. MULTI-IFE is a one-dimensional, two-temperature, multi-group, open-source radiation hydrodynamic code, which is initially designed for laser and heavy ion driven fusion. The original program is upgraded to simulate Z-pinch related experiments by introducing Lorentz force, Joule heating and the evolution of magnetic field into the code. Numerical results suggest that a shock wave and a thermal wave will be launched when the high speed plasma impacts onto the foam converter. The thermal wave propagates much faster than shock wave, making the foam become hot prior to the arrival of shock wave. For the load parameters and drive current of shot 0180, the calculated propagation speed of thermal wave and shock wave are about 36.1 cm/s and 17.6 cm/s, respectively. The shock wave will be reflected when it arrives at the foam center and the speed of reflected shock wave is about 12.9 cm/s. Calculations also indicate that the plastic foam will expand obviously due to the high temperature radiation environment (~30 eV) around it before the collision between tungsten plasma and foam converter. The evolution of radial radiation temperature profile shows that a pair of bright strips pointing to the foam center can be observed by an on-axis streak camera and the radiation temperature in the foam center achieves its highest value when the shock arrives at the axis. A bright emission ring moving towards the foam center can also be observed by an on-axis X-ray frame camera. The best time to capture the bright strips and bright emission rings is before the thermal wave reaches the foam center. Even though some amount of X-ray radiation in the foam is expected to escape from the hohlraum via radiation transport process, simulation results suggest that the tungsten plasma can serve as a good hohlraum wall. The radiation temperature is about 80 eV when the dynamic hohlraum is created and can rise more than 100 eV before the shock arrives at the foam center. Most of the X-rays emitted by the wire-array plasma surface have energies below 1000 eV. In this paper, the physical model of the code MULTI-IFE and the simulation results of array implosions on Saturn facility are presented as well.

Characteristics of plasma in culture medium generated by positive pulse voltage and effects of organic compounds on its characteristics

We describe a positive pulse voltage method for generating plasma in culture medium with a composition similar to biological fluids. We also describe the plasma’s characteristics, liquid quality, and the effect of organic compounds in the culture medium on the plasma characteristics through comparisons to a solution containing inorganic salts at the same concentrations as in the culture medium. Light emission with Na and OH spectra was observed within a vapor bubble produced by Joule heating at the tip of the electrode. A downward thermal flow and shock wave were caused by the behavior of the vapor bubble. The culture medium pH gradually increased from 7.9 to 8.3 over the discharge time of 300 s. H2O2 was generated 1.1 mg l−1 in the culture medium after discharge for 300 s, and this value was 0.5 mg l−1 lower than the inorganic salts solution which does not contain organic compounds. This study provides important data that will help facilitate more widespread application of plasma medicine.

Multistrata Subsurface Laser-Modified Microstructure With Backgrind-Assisted Controlled Fracture for Defect-Free Ultrathin Die Fabrication

We report the development of multistrata subsurface IR ( $1.342~\mu \text{m}$ ) nanosecond pulsed laser die singulation [stealth dicing (SD)] on high backside reflectance (up to 82%) Si wafers. We study the microstructural properties and formation mechanisms of the subsurface Si dislocation belt layer with respect to laser scanning speed, pulse laser energies, and interstrata distances. We optimize and exploit the multistrata interactions between generated thermal shock waves and the preceding dislocation belt layers formed to initiate frontal crack fractures that separate out the individual dies from within the interior of the wafer. A new partial-SD before grinding (p-SDBG) integration scheme based upon the tandem use of three-strata SD for controlled crack fracture toward the frontside of the wafer followed by static loading from backgrinding to complete full kerf separation is demonstrated. The optimized three-strata SD process and p-SDBG integration scheme can be used to compensate for the high backside reflectance wafers to produce defect-free eight die stacks of 25- $\mu \text{m}$ -thick mechanically functional and 46- $\mu \text{m}$ -thick electrically functional 2-D NAND memory dies.

Fundamental study of direct microporous process using laser shock wave

In this paper, the mechanism of micropore structures generated inside PP (polypropylene) polymer due to thermal shock propagation caused by a pulsed laser was studied. When a thermal shock wave radiated to the PP film, a stress shock wave was transmitted to the interior. When both the appropriate absorption coefficient of thermoplastic polymer and the rapid pressure drop were provided, micropores were generated due to the crystallization of PP and decrease in viscosity. The micropores generated inside PP film with a low absorption coefficient were observed by employing a copper plate as a heat-transfer medium. The thickness of the PP film and the wavelength of the UV-pulsed laser used in this experiment were 50 µm and 355 nm, respectively.

In this issue ofWeather

This month's issue of Weather will be of particular interest to all those interested in measurement – not only of weather, but of rivers too. In Birmingham, Simon Bell, Dan Cornford and Lucy Bastin have been looking at the accuracy and precision of automatic weather stations. Their article ‘How good are citizen weather stations? Addressing a biased opinion’ on p. 75 compares temperature data from a Meteorological Monitoring System (Met Office) station with those from a range of relatively inexpensive sensors, often used by the public. In some cases, especially where the sensor has been left in direct sunshine, errors can be large, resulting in biases. Now that citizen data are being used by researchers and the Met Office, knowledge of these biases will be important. Many interesting investigations can be carried out by schools and researchers – not least weather differences on the small spatial scale. On p. 85, ‘Simple investigations of local microclimates using an affordable USB temperature logger’ by Geoff Jenkins demonstrates that this has become increasingly easy, using data loggers available for only a few pounds. If well exposed, these loggers can record reasonably accurate data over intervals between a few minutes and several hours. They could prove to be a useful resource to citizen observers, ensuring that data are available even during periods of absence. On p. 92, we turn to the observation of temperature differences in rivers flowing from the Derbyshire Peak. Little data are available to show how these temperatures change, following snowfall, rainfall or drought, but Robert Wilby, Matthew Johnson and Julia Toone help to rectify this in ‘Thermal shockwaves in an upland river’. This high density study covers the reasons for temperature variations in some detail and is a recommended read. Finally, Katy Mulqueen and Dave Schultz turn to the analysis of frontal systems for the North Atlantic and Europe in ‘Non-classical extratropical cyclones on Met Office sea-level pressure charts’ on p. 100. There has been considerable discussion of analysis charts in Weather over the years, reflecting the developments in our understanding. In particular, the authors discuss the reasons for the analysis of more than one front (be it warm or cold) in analysis charts, related to both the relatively simple Norwegian (‘Bergen’) model and the more recent Shapiro-Keyser system. The issue is topped off, on p. 91, by contributors’ photographs of optical phenomena – always a calm and spectacular way to demonstrate the beauty of our science.

A mechanism of combustion mode transition for hydrogen fueled scramjet

The combustion mode transition will occur repeatedly during the real flight of a hydrogen fueled scramjet. Under the assumption of inviscid flow, a series of the equations have been developed to identify combustion mode transition in an analytical way. The processes of heating and accelerating induced mode transition are investigated, respectively. This paper presents an analytical solution to understand the conditions for the transition between ramjet-scramjet operation modes. Besides, this paper also presents a qualitative explanation of the mode transition processes in the physical point of view. The mode transition is closely related to the thermal choking effects and shock wave motion. The process of mode transition is discontinuous and very fast. There is a sudden change with the combustor entry Mach number in this process.

Laser-induced damage of rugate and quarter-wave stacks high reflectors deposited by ion-beam sputtering

Rugate and high/low quarter-wave stacks high reflector coatings for 1064 nm have been prepared with Ta 2 O 5 and SiO 2 by an ion-beam sputtering technique. A laser-induced damage experiment of the samples has been conducted at 1064 nm with pulse duration of 5 ns [full width at half maximum (FWHM)]. These two samples’ damages both initiate at defects and show almost the same damage threshold within the experimental error. Nevertheless, the damage morphology on rugate is less severe at higher fluences. The thermal shock wave induced by a nanosecond pulsed laser is considered to be the main cause of catastrophic damage.

Simulation of Expansion of Thermal Shock and Pressure Waves Inducaed by a Streamer Dynamics in Positive DC Corona Discharges

This paper is devoted to the simulation of the thermal shock and the induced pressure-waves expansion, generated by a dc pin-to-plan corona discharge in the air at ambient temperatures and under atmospheric pressure. The positive dc voltage applied to the tip generates a monofilamentary streamer that crosses the gap from the tip toward the plan. The simulation models are based on the coupling of a 2-D dynamics streamer model with the hydrodynamics conservation equations of a compressible gas. The source term for the gas dynamics equations takes into account the fast-energy relaxation from excited molecules to the random thermal energy. The simulation shows that the streamers generate a thermal shock near the anodic tip, which induces high pressure gradients and finally the gas expansion. The thermal shock is located just in front of the anodic tip, where the injected energy density is the highest. After 0.3 μs, the mean gas temperature increases up to around 800 K in a small volume just in front of the anodic tip while the maximum temperature reaches 1200 K. In addition, two pressure waves, a spherical and a cylindrical one, are induced with a propagation velocity of 370 m s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> i.e., close to the speed of sound in air.

Direct evidence of mismatching effect on H emission in laser-induced atmospheric helium gas plasma

A time-resolved orthogonal double pulse laser-induced breakdown spectroscopy (LIBS) with helium surrounding gas is developed for the explicit demonstration of time mismatch between the passage of fast moving impurity hydrogen atoms and the formation of thermal shock wave plasma generated by the relatively slow moving major host atoms of much greater masses ablated from the same sample. Although this so-called “mismatching effect” has been consistently shown to be responsible for the gas pressure induced intensity diminution of hydrogen emission in a number of LIBS measurements using different ambient gases, its explicit demonstration has yet to be reported. The previously reported helium assisted excitation process has made possible the use of surrounding helium gas in our experimental set-up for showing that the ablated hydrogen atoms indeed move faster than the simultaneously ablated much heavier major host atoms as signaled by the earlier H emission in the helium plasma generated by a separate laser prior to the laser ablation. This conclusion is further substantiated by the observed dominant distribution of H atoms in the forward cone-shaped target plasma.

ChemInform Abstract: Surface Modification of Light Alloys by Low‐energy High‐current Pulsed Electron Beam

AbstractReview: 46 refs.

Influence of laser lift-off on optical and structural properties of InGaN/GaN vertical blue light emitting diodes

The influences of the laser lift-off (LLO) process on the InGaN/GaN blue light emitting diode (LED) structures, grown on sapphire substrates by low-pressure metalorganic chemical vapor deposition, have been comprehensively investigated. The vertical LED structures on Cu carriers are fabricated using electroplating, LLO, and inductively coupled plasma etching processes sequentially. A detailed study is performed on the variation of defect concentration and optical properties, before and after the LLO process, employing high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) observations, cathodoluminescence (CL), photoluminescence (PL), and high-resolution X-ray diffraction (HRXRD) measurements. The SEM observations on the distribution of dislocations after the LLO show well that even the GaN layer near to the multiple quantum wells (MQWs) is damaged. The CL measurements reveal that the peak energy of the InGaN/GaN MQW emission exhibits a blue-shift after the LLO process in addition to a reduced intensity. These behaviors are attributed to a diffusion of indium through the defects created by the LLO and creation of non-radiative recombination centers. The observed phenomena thus suggest that the MQWs, the active region of the InGaN/GaN light emitting diodes, may be damaged by the LLO process when thickness of the GaN layer below the MQW is made to be 5 μm, a conventional thickness. The CL images on the boundary between the KrF irradiated and non-irradiated regions suggest that the propagation of the KrF laser beam and an accompanied recombination enhanced defect reaction, rather than the propagation of a thermal shock wave, are the main origin of the damage effects of the LLO process on the InGaN/GaN MQWs and the n-GaN layer as well.

Surface Modification of Light Alloys by Low-Energy High-Current Pulsed Electron Beam

This paper reviews results obtained by the research groups developing the low-energy high-current pulsed electron beam (LEHCPEB) in Dalian (China) and Metz (France) on the surface treatment of light alloys. The pulsed electron irradiation induces an ultra-fast thermal cycle at the surface combined with the formation of thermal stress and shock waves. As illustrated for Mg alloys and Ti, this results in deep subsurface hardening (over several 100 μm) which improves the wear resistance. The analysis of the top surface melted surface of light alloys also often witnesses evaporation and condensation of chemical species. This phenomenon can significantly modify the melt chemistry and was also suggested to lead to the development of specific solidification textures in the rapidly solidified layer. The potential use of the LEHCPEB technique for producing thermomechanical treatments under the so-called heating mode and, thus, modify the surface crystallographic texture, and enhance solid-state diffusion is also demonstrated in the case of the FeAl intermetallic compound.