Aluminum Target Research Articles

Effects of projectile parameters on the momentum transfer and projectile melting during hypervelocity impact

The effects of projectile/target impedance matching and projectile shape on energy, momentum transfer and projectile melting during collisions are investigated by numerical simulation. By comparing the computation results with the experimental results, the correctness of the calculation and the statistical method of momentum transfer coefficient is verified. Different shapes of aluminum, copper and heavy tungsten alloy projectiles striking aluminum, basalt, and pumice target for impacts up to 10 km/s are simulated. The influence mechanism of the shape of the projectile and projectile/target density on the momentum transfer was obtained. With an increase in projectile density and length-diameter ratio, the energy transfer time between the projectile and targets is prolonged. The projectile decelerates slowly, resulting in a larger cratering depth. The energy consumed by the projectile in the excavation stage increased, resulting in lower mass-velocity of ejecta and momentum transfer coefficient. The numerical simulation results demonstrated that for different projectile/target combinations, the higher the wave impedance of the projectile, the higher the initial phase transition velocity and the smaller the mass of phase transition. The results can provide theoretical guidance for kinetic impactor design and material selection.

Double-differential primary target neutron yields from dual-thick-target proton and heavy ion accelerator experiments

Experiments at the NASA Space Radiation Laboratory were performed to develop a benchmark dataset relevant to space radiation shielding scenarios by bombarding aluminum and polyethylene targets with galactic cosmic ray-like ion beams. Unique to this experiment, a dual-target configuration was used to emulate an enclosed environment in space in which the radiation environment must be characterized. Neutrons produced by interactions in both thick targets were detected and characterized; this paper discusses the neutrons produced in the most upstream of the two thick targets, detailing the role of source ion and target configuration on neutron yield.

Dynamic Response Analysis of Projectile Target Penetration Based on an FE-SPH Adaptive Coupling Method

The penetration of projectiles into targets has a broad background in engineering. In this work, numerical simulations of the projectile-target penetration problem are conducted using the Finite Element Method (FEM), the Smoothed Particle Hydrodynamics (SPH) and the Finite Element–Smoothed Particle Hydrodynamics Adaptive Coupling Method (FE-SPH ACM) based on the LS-DYNA software package. First, the penetration experiments using aluminum targets and ceramic targets are simulated. The experimental and simulation results show that the FE-SPH ACM has the better accuracy in calculating the debris cloud head velocity and interface velocity, with an error of no more than 4%. Furthermore, we use the FE-SPH ACM to investigate the anti-penetration performance of aluminum/ceramic composite targets in different combinations. We find that the reasonable layout can improve the protective performance of multi-layered target, especially composite target plates with ceramic as the front layer. In addition, the ballistic limit velocities for ceramic-aluminum ratios of 3/7, 5/5 and 7/3 are approximately 1300 m/s, 1400 m/s and 1500 m/s, respectively. Obviously, increasing the proportion of ceramic materials can enhance the anti-penetration performance.

X-band RADAR Reflected Signal Measurement of Gallium-based Liquid Metal

RADAR(Radio Detection and Ranging) is an important system for surveillance and reconnaissance by detecting a reflected signal which obtains the range from the radar to the target, and the velocity of the target. The magnitude of the reflected signal varies due to the radar cross section of the target, characteristic of the transmission and reception antenna, distance between the radar and the target, and power and wavelength of the transmitted signal. Thus, the RCS is the important characteristic of the target to determine if the target can be observed by the RADAR system. It is based on the material and shape of the target. We have measured the reflection signal of a simple square-shaped (20 × 20 cm) target made of a new material, a gallium-based liquid metal alloy and compared that of well-known metals including copper, aluminum. The magnitude of reflected signal of the aluminum target was the largest and it was 2.4 times larger than that of the liquid metal target. We also investigated the effect of the shape by measuring reflectance of the F-22 3D model(~1/95 ratio) target covered with/without copper, aluminium, and liquid metal. The largest magnitude of the reflected signal measured from side-view with the copper-covered F-22 model was 2.6 times greater than that of liquid metal. The reflectance study of the liquid metal would be helpful for liquid metal-based frequency selective surface or metamaterials.

Ionization of sputtered material in high power impulse magnetron sputtering plasmas—comparison of titanium, chromium and aluminum

The ionization of sputtered species in high power impulse magnetron sputtering of titanium, chromium, and aluminum targets is analyzed using Abel-inverted spectroscopic imaging to locate the position of ionization. From the spatial emission of neutrals, it is deduced that most of the sputtered titanium particles become ionized within 0.5 mm distance from the target, whereas sputtered aluminum or chromium can travel much further through the discharge before ionization occurs. Probe measurements reveal the reason for this difference to be the unusually high electron temperature of around 4.5 eV for titanium compared to 2.6 eV and 1.5 eV for aluminum and chromium as the target material, respectively. These probe measurements are then compared to a global model derived from the ionization region model. Excellent agreement between model and measurements can be reached, but only if the transport physics for the confinement of the species is adjusted. Using the model, the difference between the three discharges can be traced back to be mostly caused by the sputter yield. Thus, we propose that ionization in discharges with low-yield materials should generally be expected to occur closer to the target surface, leading the ions to be affected more strongly by the electric field across the magnetic trap region, resulting in a more severe deposition rate loss compared to high-yield materials.

Study the Influence of Fragment Shape on Penetration Failure Process of Thin Target Plate

In order to study the influence of fragment shape on the process of penetrating the target plate, the spherical and cubic structural steel fragments of the same mass which penetrating aluminum target plate has been studied by theoretical and numerical simulation calculations. The theoretical calculation shows that the ballistic limit velocity of the fragments of the cube structure is higher than that of the spherical structure when the fragments of the same mass penetrate the target plate of the same thickness. Numerical simulations have obtained the penetration process and failure rule of the fragment to the target plate. The results show that the target plate failure during the penetration process of the spherical fragment is a tensile failure mode, however, the penetration process of the cube structure fragment are shear and tensile mixed failure modes.

Diagnosis of fast electron transport by coherent transition radiation

Transport of fast electrons in overdense plasmas is of key importance in high energy density physics. However, it is challenging to diagnose the fast electron transport in experiments. In this article, we study coherent transition radiation (CTR) generated by fast electrons on the back surface of the target by using 2D and 3D first-principle particle-in-cell (PIC) simulations. In our simulations, aluminum targets of 2.7 g cc−1 are simulated in two different situations by using a newly developed high order implicit PIC code. Comparing realistic simulations containing collision and ionization effects, artificial simulations without taking collision and ionization effects into account significantly underestimate the energy loss of electron beams when transporting in the target, which fail to describe the complete characteristics of CTR produced by electron beams on the back surface of the target. Realistic simulations indicate the diameter of CTR increases when the thickness of the target is increased. This is attributed to synergetic energy losses of high flux fast electrons due to Ohm heating and colliding drags, which appear quite significant even when the thickness of the solid target only differs by micrometers. Especially, when the diagnosing position is fixed, we find that the intensity distribution of the CTR is also a function of time, with the diameter increased with time. As the diameter of CTR is related to the speed of electrons passing through the back surface of the target, our finding may be used as a new tool to diagnose the electron energy spectra near the surface of solid density plasmas.

On the use of laser-induced fluorescence to probe the thermodynamic equilibrium in laser-generated plasmas

In this work, we investigate thermodynamic equilibria in a laser-generated plasma from ro-vibrational population distributions in the AlO molecule. We address the congruence between the rotational temperatures of diatomic molecules in their excited state and in their ground state, the latter being assumed to correspond to the kinetic temperature of the species in the plasma. The model system consists of AlO molecules produced by ablation of an alumina target in ambient air using a nanosecond laser pulse. Using laser induced fluorescence spectroscopy, we can directly probe the population of the rotational levels in the ground electronic state X2Σ+ of AlO and deduce the corresponding rotational temperature. This temperature is then compared to the population of the rotational levels in the excited state B2Σ+ deduced from the thermal B − X rovibronic emission. In such plasma, AlO molecules in the excited state are believed to be formed by chemical reaction and might be strongly out of equilibrium, but we find that emission from the B2Σ+ excited state provides a useful indication of kinetic temperature of the species in the plasma for delays longer than a few microseconds.

Ro-vibrational Spectrum of Linear Dialuminum Monoxide (Al2O) at 10 μm.

Dialuminum monoxide, Al2O, has been investigated in the laboratory at mid-IR wavelengths around 10 μm at high spectral resolution. The molecule was produced by laser ablation of an aluminum target with the addition of gaseous nitrous oxide, N2O. Subsequent adiabatic cooling of the gas in a supersonic beam expansion led to rotationally cold spectra. In total, 848 ro-vibrational transitions have been assigned to the fundamental asymmetric stretching mode ν3 and to five of its hot bands, originating from excited levels of the ν1 symmetric stretching mode and the ν2 bending mode. The measurements encompass 11 vibrational energy states (v1 v2l v3). The ro-vibrational transitions show spin statistical line intensity alternation of 7:5, which is caused by two identical aluminum nuclei of spin I = 5/2 at both ends of the centrosymmetric molecule of structure Al-O-Al. The less effective cooling of vibrational states in the supersonic beam expansion allowed measurement of transitions in excited vibrational states at energies of 1000 cm-1 and higher, while rotational levels within vibrational modes exhibited thermal population, with rotational temperatures around Trot = 115 K. Molecular parameters for 11 vibrational states were derived, including rotation and centrifugal distortion constants and l-type doubling constants for the states (v1 v2l v3) = (0 11 0) and (0 11 1) and an l-type resonance between the states (0 20 0) - (0 22 0) and (0 20 1) - (0 22 1). From the experimental results, rotational correction terms and the equilibrium bond length re were derived. The measurements were supported and guided by high-level quantum-chemical calculations that agree well with the derived experimental results.

Modeling Dynamic Rate Dependent Pore Closure with A Range of Pore Sizes

Previously we presented a model (which we call PORT) with rate dependent pore closing/opening, for which we assumed that all pores close/open with the same dynamics [1]. Here we upgrade PORT to take into account different dynamics as function of pore size. We represent different pore sizes by their volume (v), and we have k discrete pore sizes. We therefore call this model VK. For the ith pore size we have ni, i=1,k pores per unit mass. We’re not aware of information on pore size distributions of porous materials, and we assume arbitrarily that pore sizes are initially distributed with a log-normal distribution. Similar to PORT, we define quasistatic pore closure curves that depend on pore volume v, and we compute the rate of pore closure with a linear overstress equation relative to these curves. From the values of v and vdot (rate of change of v) we then compute (for each cell and for each time) the overall porosity j and its rate of change jdot. Finally, we compute Pdot and Tdot (P=pressure and T=temperature) in the same way as in PORT, using the equation of state of the porous material. To show how our VK model works, we apply it to a simple 1D problem: a 20GPa sustained pressure pulse enters a porous aluminum target. We show histories of pressure, temperature and porosity at several locations into the target. We compare these curves to the ones obtained for k=1 (which are as in PORT).

High-Performance Pure Aluminum Coatings on Stainless Steels by Cold Spray

Aluminum target material is an important target material and is widely used in preparations of semiconductor films, integrated circuits, display circuits, protective films, decorative films, etc. In this study, pure aluminum coatings were deposited on stainless steel substrates by cold-spray technology as part of an overall project to produce large-size pure aluminum sputtering target materials. The results show that pure aluminum coatings exhibit high adhesive strength (~98 MPa), high deposition efficiency (~95%), and low porosity (~0.3%) on stainless steel substrates. The bonding mechanisms of pure aluminum coatings on stainless steel are a combination of metallurgical and mechanical interlocking. The evolutions of microstructure and mechanical properties of pure aluminum coatings under different heat treatments were also studied. With the increase of heat treatment temperature, it is found that cold-sprayed aluminum coatings become more homogenous in microstructure, the microhardness is reduced, and the adhesive strength seems to be slightly reduced. Overall, this study demonstrates significant advantages of cold-spray technology in depositing high-performance pure aluminum coatings on stainless steels.

Damage effect of structural reactive projectiles on double-spaced aluminum plates

Ballistic impact experiments and numerical simulations are performed to investigate the damage effects of double-spaced aluminum targets by structural reactive projectile (SRP) impact. The damage behaviors of SRP impacting the double-spaced aluminum targets and damage effects of targets are discussed and analyzed. The experiments and analysis show that, with the impact velocity increasing, the failure mode of front plates evolve from plugging-bulge mode to typical plugging mode and the failure mode of rear plates evolve from kinetic energy perforation mode to overpressure bulge mode, respectively. With a low-velocity, it is difficult for the SRP to present the damage characteristics of the combined of kinetic energy and chemical energy.

Synthesis and Biomedical Activity of Aluminium Oxide Nanoparticles by Laser Ablation Technique

Aluminium oxide (Al2O3) nanoparticles (NPs) were formed via laser ablation of an aluminium target in deionised water (DIW) (Nd: YAG laser; wavelength: 1,064nm; different laser energies: 500, 800 and 1000 mJ; 30min). The optical, structural and morphological features of these Al2O3 NPs were investigated via ultraviolet/visible (UV/Vis) spectroscopy, scanning electron microscopy; X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy. Show that the average size of nanoparticles was between (21-48nm). The antibacterial activities of Al2O3 NPs were produced by utilising the well diffusion method against two pathogens (Pseudomonas aeruginosa and Bacillus cereus). Al2O3 NPs demonstrated significant antibacterial activity against P. aeruginosa and B. cereus compared with the control (P≤0.05). Al2O3 NPs had the best energy at 1000 mJ, indicating that they were more effective towards Gram +ve than Gram -ve bacteria. The synergistic/antibacterial activity of Al2O3 NPs exhibited potential antibacterial activity against the investigated species after being combined with imipenem and gentamicin, which had higher antibacterial action than Al2O3 NPs alone. Furthermore, as determined by DPPH, results suggested that Al2O3 NPs have antioxidant properties. Finally, Al2O3 NPs were tested for cytotoxicity against the breast cancer cell line (MCF-7), where 500mJ was 62.33±2.33, 800 mJ was 73.00±2.082 and 1000mJ was 85.00 ±1.732. The last was more effective than 500 mJ and 800 mJ and more efficient in penetrating cell membrane.

Development of an equation of state to characterize an electron beam interacting with an aluminum target

The Equations Of State (EOS) of materials under extreme conditions of temperature and pressure can be experimentally studied, thanks to intense electron beam-target experiments. The latter are powerful tools to probe materials in the warm dense matter regime. At CEA/CESTA, we use the CESAR pulsed generator (1 MV, 300 kA). During an experimental shot, a high-power 800 keV, 100 kA, 20 mm-diameter, 100 ns electron pulse produces shock waves in an aluminum target. The behavior of the latter is explored by analyzing the time-history of its rear face velocity, as measured by photon Doppler velocimetry. Using simulations, we can test the accuracy of an EOS over a wide range of densities and temperatures. In addition, an accurate EOS allows for reduction of the uncertainties of the beam parameters that have an impact on beam energy deposition. We have observed that the measurements are not correctly restituted by the simulation codes when they use the available EOS (BLF, SESAME). Thanks to both published data and ab initio calculations, which are valid in the considered thermodynamic regime, we have developed a new EOS describing precisely the thermodynamic (isochoric) regime from one-half to one-third the normal density. The corresponding hydrodynamic simulations appear to be in much better agreement with the measurements. In addition, this new EOS has allowed us to refine the knowledge of the input electron beam parameters that have an impact on beam energy deposition.

Mechanics of ballistic impact with non-axisymmetric projectiles on thin aluminium targets. Part I: Failure mechanisms

The ballistic performance of thin aluminium targets under normal and oblique impacts with plate-like projectiles is investigated with emphasis on the local projectile-induced target response. Three projectiles of 5 mm thickness with decreasing bluntness were considered, with the ratio of the projectile’s equivalent diameter to the target’s thickness (deq/hT) within the range of 0 to 4.89. The obtained results suggest that defeat mechanisms, and target resistance measures were different from those observed in impact with equivalent axisymmetric projectiles, as a result of a high projectile’s cross-sectional aspect ratio. Projectiles with inclined nose sections inflicted a shear-dominant failure that was locally energetically expensive and depended on the product of length (LN) and half-angle (α) of the projectile’s nose. On the other hand, projectiles with blunt sections were associated with retardation of their penetration capacity due to dynamic effects, followed by a low-energy mechanism associated with membrane stretching and tensile failure of targets. A total of 48 experiments were performed at normal-impact conditions, to estimate the critical velocity of perforation/penetration and examine the real-time deformation patterns at sub-critical velocities, by employing the digital image correlation technique. Overall, the critical velocity showed a quadratic dependence on deq/hT, where the benefit of ballistic performance decreased with an increase in this ratio. The observed non-monotonic behaviour of the critical velocity with increasing impact obliquity in some cases and the distinction in failure mechanisms highlight the importance of the projectile’s geometrical parameters for the energy transfer mechanisms. Also, the lack of correlation between the critical velocity and the local work in the target defeat term suggests that the resultant energy transfer mechanisms considerably contributed to the dissipation of the projectile’s kinetic energy. Experimental data were utilised for calibrating the material model and separate experimental results for validating the numerical (finite-element) model. A total of 119 simulations were carried out for normal and oblique impact incidences to examine the role of the projectile’s (i) rotation, (ii) geometrical features, and (iii) obliquity on the target’s dynamic performance and induced defeat mechanisms. The conclusions of this study form the basis for considering the role of the projectile’s geometrical parameters on the energy transfer mechanisms in the target through statistical and semi-analytical approaches presented in the second part of this work.

Modeling laser interactions with aluminum and tantalum targets using a hybrid atomistic-continuum model

A hybrid atomistic-continuum method can model the microstructure evolution of metals subjected to laser irradiation. This method combines classical molecular dynamics (MD) simulations with the two-temperature model (TTM) to account for the laser energy absorption and heat diffusion behavior. Accurate prediction of the temperature evolution in the combined MD-TTM method requires reliable accuracy in electron heat capacity, electron thermal conductivity, and electron–phonon coupling factor across the temperatures generated. This study uses the electronic density of states (DOS) obtained from first-principle calculations. The calculated electron temperature-dependent parameters are used in MD-TTM simulations to study the laser metal interactions in FCC and BCC metals and the phenomenon of laser shock loading and melting. This study uses FCC Al and BCC Ta as model systems to demonstrate this capability. When subjected to short pulsed laser shocks, the dynamic failure behavior predicted using temperature-dependent parameters is compared with the experimentally reported single-crystal and nanocrystalline Al and Ta systems. The MD-TTM simulations also investigate laser ablation and melting behavior of Ta to compare with the ablation threshold reported experimentally. This manuscript demonstrates that integrating the temperature-dependent parameters into MD-TTM simulations leads to the accurate modeling of the laser–metal interaction and allows the prediction of the kinetics of the solid–liquid interface.

Impulse and Plasma Plume Generated By Ablating Aluminum Target with Nanosecond Laser in Double-Pulse Configuration

For laser ablation propulsion, the enhancement of the impulse is very challenging to realize without increasing the laser energy. In this paper, the enhancement of the impulse in vacuum is achieved by laser ablation in double-pulse mode. The impulse produced by irradiating the aluminum target for different energy combinations in double-pulse mode was measured with the torsion pendulum. The plasma plume was observed at the same time by fast photography to analyze the cause of the impulse characteristics. The effect of the energy combinations for double-pulse mode on the ablation impulse was investigated at typical interpulse delay time. When the delay time between the pulses is set to 80 ns, the maximum impulse is increased by approximately 11% compared to that of the single-pulse mode at the same total energy, wherein the energy of the first pulse is 125mJ in total energy of 200mJ. Therefore, the enhancement of the impulse can be achieved by choosing the suitable energy combination in the double-pulse configuration. However, when the time delay is 300ns, the difference in energy combinations has little influence on the impulse. The results reported here provide guidance for the application of laser ablation propulsion in space.

Compton scattering geometry: a tool to study radiation interaction characteristics of rare earth compounds doped in low-Z organic compound

Abstract The present measurements comprise of Compton scattering technique at six energies from 0.242 MeV to 0.402 MeV (not available from conventional radioisotopes) by scattering of primary gamma photon beam of 0.662 MeV energy from cylindrical aluminium target at different scattering angles. Two inorganic (rare-earth) compounds, Lanthanum (3+) nitrate hexahydrate and Samarium (3+) nitrate hexahydrate in a Low-Z organic solvent (acetone), have shown certain radiation interaction characteristics are the subject of study. The collimated beam of scattered gamma rays impinges on the plastic container having solution of rare earth compounds in the acetone of different concentrations. The transmitted gamma ray beam is detected by a well-collimated 2″ × 2″ NaI(Tl) scintillation detector and is analysed by a PC-based ORTEC Mastero-32 MCA. Attenuation coefficients along with some shielding parameters i.e. molar extinction coefficients, half value layer, tenth value layer and mean free path are evaluated. Besides this, Computed Tomography numbers and photon interaction cross-sections (photoelectric, coherent and incoherent) are also determined. The measured values of these parameters are compared with WinXCom software package’s values and are found to be in good agreement. The available data on rare earth salts’ solutions, in the current measurements, is scientifically important in nuclear and radiation physics, bridging the gap in which radiation workers do not have access to such data.

Supersonic water jets as point-like sources of extremely high pressure

Two interacting supersonic water jets and collisions of a water jet with an aluminum target are studied experimentally and by hydrodynamic simulations. Supersonic water jets form, when shocks generated by underwater electrical explosions of conical wire arrays converge. The arrays are supplied by a ∼250 kA, ∼1 μs rise time current pulse. Underwater explosion of two conical arrays placed face to face produces jets propagating in air with velocities of ∼2.5×103 m/s leading to hot plasma formation at a temperature of ∼2200–3000 K, pressure ∼1.7×1010 Pa, and density >1029 m−3. When a single array explodes underwater in front of an aluminum target, the collision of the jet with the target produces a local pressure of ∼3×1010 Pa on the surface of the target.

Towards a direct measurement of the 17O(p, γ)18F 65 keV resonance strength at LUNA

The 17O(p, γ)18F reaction plays a crucial role in the hydrogen burning phases of different stellar scenarios. At temperature of interest for AGB nucleosynthesis (20 MK < T < 80 MK) the main contribution to the astrophysical reaction rate comes from the poorly constrained 65 keV resonance. The strength of this resonance is presently determined only through indirect measurements, with a reported value of ωγ = (1.6 ± 0.3) 10−11 eV. With typical experimental quantities for beam current, isotopic enrichment and detection efficiency, this strength yields to an expected count rate of less than one count per Coulomb, making the direct measurement of this resonance extremely challenging. A new high sensitivity setup has been installed at LUNA (Laboratory for Underground Nuclear Astrophysics) of Laboratori Nazionali del Gran Sasso. The high performance LUNA 400kV accelerator underground location guarantees, indeed, a reduction of cosmic ray background by several orders of magnitude. The residual background was further reduced by a devoted shielding of lead and borated (5%) polyethylene. On the other hand, the 4π BGO detector efficiency was optimized installing aluminum target chamber and holder. With about 400 C accumulated on Ta2O5 targets, with nominal 17O enrichment of 90%, the LUNA collaboration has performed the first direct measurement of the 65 keV resonance strength.