Aluminum Target Research Articles

Interactions of microwaves with alumina surface in microwave-enhanced laser-induced breakdown spectroscopy

In laser-induced breakdown spectroscopy (LIBS), when the target material is radioactive, the total amount of ablated materials presents a challenge. High-efficiency particulate air (HEPA) filters prevent the release of the fumes of radioactive materials into the atmosphere. Microwave enhances LIBS without increasing the number of laser shots, potentially reducing the production of fumes. In this study, we analyzed the interaction of microwaves with an alumina target surface during laser ablation. Time-series images of the plasma evolution on the surface of an alumina target were captured. Moreover, the ablation crater characteristics and temporal temperature profiles were measured to evaluate the non-equilibrium plasma characteristics of the microwave-enhanced laser-induced plasma. The results show no direct correlations of the ablation crater depth and volume with the microwaves, and the number of laser shots primarily influences the volume of the crater. The absorption of microwaves by the plasma took 100 µs after the laser shot, suggesting that microwaves did not contribute to the ablation process. Although laser ablation was not influenced by the microwave input, it is the primary cause of the volume expansion of the plasma.

OCT-guided Robotic Subretinal Needle Injections: A Deep Learning-Based Registration Approach.

Subretinal injection (SI) is an ophthalmic surgical procedure that allows for the direct injection of therapeutic substances into the subretinal space to treat vitreoretinal disorders. Although this treatment has grown in popularity, various factors contribute to its difficulty. These include the retina's fragile, nonregenerative tissue, as well as hand tremor and poor visual depth perception. In this context, the usage of robotic devices may reduce hand tremors and facilitate gradual and controlled SI. For the robot to successfully move to the target area, it needs to understand the spatial relationship between the attached needle and the tissue. The development of optical coherence tomography (OCT) imaging has resulted in a substantial advancement in visualizing retinal structures at micron resolution. This paper introduces a novel foundation for an OCT-guided robotic steering framework that enables a surgeon to plan and select targets within the OCT volume. At the same time, the robot automatically executes the trajectories necessary to achieve the selected targets. Our contribution consists of a novel combination of existing methods, creating an intraoperative OCT-Robot registration pipeline. We combined straightforward affine transformation computations with robot kinematics and a deep neural network-determined tool-tip location in OCT. We evaluate our framework's capability in a cadaveric pig eye open-sky procedure and using an aluminum target board. Targeting the subretinal space of the pig eye produced encouraging results with a mean Euclidean error of 23.8μm.

Analysis of the characteristics of microwave-enhanced laser-induced atmospheric air plasma and ablation plasma for Al target

The investigation and comparison of air plasma generated directly in the absence as well as in the presence of solid target along with microwave enhancement were reported. The plasma characteristics including emissions, size, duration, and temperature were measured using high-speed camera, optical emission spectroscopy, and temperature approximation through spectral fitting. The laser energy required for ablation is much lower than the air breakdown energy but, the minimum energy density for air and alumina breakdown is inversely proportional to the focal lengths. The size and volume of the air plasma generated by the microwave and ablation plasma interactions were less than those of the microwave-enhanced laser-induced air plasma but was similar with standard laser-induced air plasma. When comparing the plasma lifetimes, both air plasmas (with and without a solid target) exceeded the duration of the microwave pulse input (approximately 1 ms). As the plasma lifetime is a function of electron density, shorter lifespan with the target ∼1500 ± 150 µs compared with the lifetime of the plasma without the target at ∼1800 ± 150 µs were observed. Similar results were observed for the time-series measurements of the OH and N2 second positive (N2PS) molecular emissions. OH and N2PS were not observed within the first 300 µs in the presence of the solid target; these air plasma components were only generated as a “by-product” of the microwave and ablation plasma. The rotational and vibrational temperatures were approximated by spectral fitting of simulated OH and N2PS spectra and the experimentally acquired spectra. The microwave increased the vibrational temperature in a constant rotational temperature during the expansion of the air plasma. The same trend is observed with the presence of the alumina target.

Expansion Dynamic and Characterization of Stagnation Layer in Laterally Colliding Plasmas: Dependence of Observation Bandwidth and Plasma Plume Separation

The colliding laser-produced plasma (CLPP) has a wide range of applications in various contexts, that might start with astrophysical applications or pulsed laser deposition or Laser-Induced Breakdown Spectroscopy (LIBS), which is a powerful analytical technique for elemental analysis and material identification.In CLPP experiments, the stagnation layer might form at the interface region when two dense laser-induced plasmas collide, and the degree of stagnation can be diagnosed by the collisionality parameter that is used to determine what kind of interaction will take place, i.e., soft or hard stagnation.Our experimental work presents the results of the temporal, spatial and semi-spectrally imaging of colliding plasmas of aluminium and silicon targets. The analysis is focused on describing the velocity of the expanding plasma front for the interaction zone. The aim of the work presented here is to further advance and study colliding plasma techniques, as well as other methods to realize and control species density and expansion, with a view to a deep understanding of these complex mechanisms and optimising emission in the visible wavelength range.All investigation sequences were based on a similar experimental setup, where two different focusing lenses were used with an effective focal length (EFL) of approx. 100mm or 125mm to achieve seed separation around 1.66mm or 2.16mm, respectively. Time-resolved emission imaging was employed to track the stagnation layer‛s size and shape, which might act as a signature of hard versus soft stagnation.The study provides a considerable amount of detailed data related to the expansion velocity of the interaction zone which extends the understanding of the behaviour of particular species within colliding laser-produced plasmas.

Mechanical and Tribological Properties of NbTiAlx, NbTiAl0.5Ny, and NbTiAl0.5N14-CHz Coatings with Various Aluminum Target Currents and Nitrogen and Acetylene Flow Rates

Mechanical and Tribological Properties of NbTiAlx, NbTiAl0.5Ny, and NbTiAl0.5N14-CHz Coatings with Various Aluminum Target Currents and Nitrogen and Acetylene Flow Rates

Influential Factors of a Reactive Materials Projectile’s Damage Evolution Behavior

To determine the mechanism of penetration of multi-layer aluminum targets (MLAT) by a reactive materials projectile (RMP), AUTODYN-3D numerical simulations and experimental tests were carried out. The Powder Burn equation of the state ignition model was introduced for the reactive core activation under different projectile–target interaction conditions, which effectively simulated the deflagration reaction damage effects behavior of the RMP and the damage evolution behavior of the MLAT. The activation rate of the reactive core increased significantly when the thickness of the steel target was 8–15 mm; a significant combined destructive effect of kinetic and chemical energy was produced on the MLAT. The initial velocity was proportional to the penetration and destruction effect of the front-layer aluminum target. For the rear-layer aluminum target, the detonation damage showed a tendency to increase and then decrease. If the head metal block was too thick, the penetration ability would be improved at the same time, and the deflagration reaction damage effects ability of the steel target would be significantly reduced. In order to achieve good battlefield damage efficacy, all of the influencing factors should be comprehensively considered.

Research on the penetration characteristics of elliptical cross-section projectile into semi-infinite metal targets

To better understand the penetration characteristics of the elliptical cross-section projectile (ECSP) into metal targets, a series penetration experiments of projectiles with different shape cross-section to semi-infinite aluminum target were carried out. The shape ratios of typical ECSPs were 1.25 and 1.56, respectively, and another was circular cross-section projectile (CCSP) which has the same cross-section area in accordance with ECSP. In the penetration experiments, the projectiles were launched with striking velocities ranged from 400 m/s to 1000 m/s, and strain sensors were arranged on the impact surface of the aluminum target to catch the dynamic response during the penetration process. Then, characteristics of cracks on the impact surface of targets, penetration depths and penetration trajectory were measured after the penetration experiments. The results indicated that the dynamic response and damage behavior of targets showed obvious asymmetry under the penetration of ECSPs. Strain data had a decreasing trend from the major axis to the minor axis of the ellipse, and the length and number of cracks of the ECSP were larger than that of the CCSP. Besides, a theoretical model was developed to explain the asymmetric deformation and failure behavior of targets based on the conformal mapping theory and the strain path method. Calculation results showed that the asymmetric deformation of targets was directly caused by the displacement boundary conditions of the ellipse.

Studies on target-induced enhancement in pre-ablation orthogonal double-pulse laser-induced breakdown spectroscopy

To investigate the signal enhancement of pre-produced target plasma on the optical emissions of sample plasma in air under atmospheric pressure and its mechanisms, target-enhanced orthogonal double-pulse laser-induced breakdown spectroscopy (TEODP-LIBS) in pre-ablation scheme was studied. The signal enhancement factors with respect to single pulse LIBS were compared while using KHCO3 target and aluminum target in pre-ablation TEODP-LIBS. It was demonstrated that KHCO3 target could provide higher signal enhancement than aluminum target. Two orders signal enhancement could be observed at short inter-pulse delay from −0.4 to −0.6 μs when KHCO3 target was used. Both plasma temperature and electron density in pre-ablation TEODP-LIBS were increased if compared with those in pre-ablation orthogonal double-pulse laser-induced breakdown spectroscopy (ODP-LIBS) without solid target. Significant improvement on the detection limits of lead and iron in brass sample caused by the target-induced signal enhancement have also been experimentally demonstrated. This technique is especially useful for in-situ sensitive elemental analysis under minimal sample ablation or high spatial resolution.

Mechanics of ballistic impact with non-axisymmetric projectiles on thin aluminium targets. Part II: Energy considerations

In Part I of this study, the ballistic performance and failure mechanisms of a thin aluminium target impacted by plate-like, non-axisymmetric projectiles with three different geometries, were considered using the gas-gun experiments. Failure mechanisms of the target material were found to depend strongly on the projectile’s geometrical features. Also, the local target’s response was not a reliable predictor of the critical kinetic energy for perforation or penetration. In order to improve the prediction of ballistic performance of thin targets, a nonlocal target behaviour should also be accounted for. In this part of the study, the global target response is examined, and a heuristic approach is introduced for the energy balance. The approach involves a new factor that represents additional energy-dissipating mechanisms between the projectile’s critical energy and the local work in target defeat. The methodology is based on the identified strong correlation of the normalised impact-induced peak kinetic energy in the target, KE¯Tmax, and the normalised target impact-induced nonlocal internal energy, U¯TPL+KE, associated with plastic deformation and increase in kinetic energy. A physically-based semi-analytical formulation for KE¯Tmax is developed by decomposition of the contributions by the inclined and blunt projectile sections, succeeding statistical analysis of key projectile’s geometrical and impact parameters. The developed approach was assessed for 17 projectile geometries implementing a total of 119 finite-element simulations with experimentally validated numerical models at subcritical (50) and critical/supercritical (69) projectile velocities. The obtained predictions had an average absolute error of less than 6.5% for impact velocities at and above the ballistic limit, while at subcritical velocities a higher scatter was observed as a result of secondary interaction effects between the projectile and the target. Overall, the methodology yielded results for the ballistic limit with an error below 5%, improving the otherwise derived results nearly twofold. The method was proven to be a practical and accurate way to improve the projectile’s critical energy prediction for thin targets, and, even though developed for non-axisymmetric projectile cases, its framework is directly transferable to axisymmetric projectiles.

A Primary-Auxiliary Coupled Neural Network for Three-Dimensional Holographic Particle Field Characterization

Particle field measurement is an important topic in many industrial branches. However, there are always complex imaging scenes in the engineering experiments, resulting in severe imaging artifact, noise, and blur, such as the optical holography. In this article, we propose a primary-auxiliary coupled neural network (PANet) for 3-D holographic particle field characterization, which can obtain a comprehensive particle measurement, including the identification, focus determination, segmentation, and size estimation. PANet is constituted by two subnets that are arranged in a coupled architecture, i.e., a Primary-Net (PNet) and an AuxiliaryNet (ANet). As the main frame, PNet is designed to accomplish the detection of most particles, while ANet aims to detect the tiny particles that PNet cannot identify. We exploit an alternative training method to realize their functional differentiation and complementation. PANet is evaluated on two kinds of holographic particle field data, i.e., high-energy laser shock aluminum target and droplet breakup in high Mach shock wave. By means of semisupervised learning and a specific loss function, the effect of deficient particle labeling can be alleviated. Experimental results demonstrate that PANet can achieve excellent performance in particle field characterization, especially for those with a wide size span and complex image background.

Thermal conductivity of Al2O3 irradiated with swift heavy ions

• Comprehensive study of thermal conductivity under swift heavy ion irradiation. • Very strong effect of a narrow highly damaged track core on heat propagation. • Classical thermal transport model may be not valid for nanometric SHI tracks. Thermal transport in α -Al 2 O 3 irradiated with 167 MeV Xe ions is studied within direct method based on the Fourier law implemented into classical molecular dynamics. Formation of defective regions as a result of ion passages is described using the original multiscale approach developed in previous works. Degradation of the thermal conductivity coefficient of single-crystalline alumina with ion fluence shows reasonable agreement with the experimental thermoreflectance data. The applied method demonstrated good applicability in the considered case and allowed to distinguish effects of discontinuous crystalline tracks on thermal conductivity of the alumina target. It was surprisingly observed that a nanometric highly damaged core of swift heavy ion tracks strongly affect the heat transport in the irradiated material, which is in contradiction with classical Rayleigh model.

Exciton-mediated surface-enhanced Raman studies of Aluminum doped platinum nano colloids

In this article, we report the fabrication of Aluminum doped Platinum bimetallic nanoparticles (NPs) by ultrafast laser ablation (using femtosecond laser pulses of duration ∼50 fs, central maximum 800 nm) of Aluminum (Al) target immersed in Platinum (Pt) colloidal solutions in Isopropanol. Colloidal solutions of Pt NPs at a concentration of 0.5 mM, 1 mM, 3 mM, and 7 mM were prepared in Isopropyl alcohol and exhibited localized surface plasmon resonances (LSPR) at ∼292 nm. However, the LSPRs of Al-doped Pt colloids were modified to ∼283 nm (0.5 mM Pt), ∼226 nm (1 mM Pt) ∼226 nm (3 mM Pt) ∼228 (7 mM Pt). Average sizes of Al-doped Pt colloidal NPs synthesized by the ablation of Al metal targets immersed in 0.5 mM Pt, 1 mM Pt, 3 mM Pt, and 7 mM Pt colloids were estimated to be ∼19.5 nm, ∼11 nm, ∼12 nm, and ∼13.5 nm, respectively. These Al-doped Pt NPs are employed in surface-enhanced Raman scattering (SERS) studies of Methylene Blue (MB) dissolved in IPA at 0.5 μM, 5 μM, and 50 μM concentrations. Although the SPR strength of Pt and Al are moderate, the annihilation of the excitons created in Al-doped Pt NPs might lead to the formation of the charge carriers, enhancing the population in the conduction band and strengthening the SPR, finally leading to a significant SERS enhancement. The estimated enhancement factors for the mode 1623 cm−1 correspond to MB's highly elevated vibrational mode are ∼105. This article is the first report of its kind on SERS of Al-doped Pt NPs to the best of our knowledge.

Spatially and temporally resolved plasma formation on alumina target in microwave-enhanced laser-induced breakdown spectroscopy

Microwave energy was applied to the laser-induced breakdown spectroscopy (LIBS) of laser-ablated Al plasma using a helical antenna. The process of generating an enhanced laser ablation plasma was visualized with a high-speed camera. The time and space evolution of the plasma were investigated by changing the laser power, microwave energy, and microwave energy duration. The obtained raw images were converted into 8-bit 255 grayscale and binary black and white (BW) images and were analyzed using Matlab. Three major periods of plasma evolution were established based on the key physical process involved. Laser energy was the primary parameter involved in period 1, where laser ablation and initial plasma formation occurred. The microwaves had little significance at the beginning of the ablation process, as suggested by the minimal changes in plasma size and intensity. The microwaves controlled the expansion of the plasma and sustained breakdown in period 2. The post ablation breakdown of the material by microwaves sustained the enlargement of the plasma. The events leading to plasma dissipation comprised period 3, where the nonthermal plasma was sustained for 500 μs after the microwave was turned off. The effects of the laser and microwave parameters in the timeline of these periods were discussed. Complementary emission intensity measurements were also presented.

Investigating laser ablated plume dynamics of carbon and aluminum targets

Recently acquired high-resolution images of nanosecond laser ablation plumes suggest a strong correlation between the internal plume structure and the type of material being ablated. However, the details of this relation are currently not well understood. In this work, we attempt to explore this correlation using a 2D radiation hydrodynamics model to study the dependence of internal plume structure formation on the ablation material. Spatio-temporal emission maps and plume expansion velocities from experimental measurements are compared with the model predictions, including synthetic emission maps. The shape and expansion rate of an outer air plume region are found to be in good agreement for both carbon and aluminum, as are the inner material plume dynamics for carbon ablation. The largest disagreement is observed in the case of a polished aluminum target, where the chaotic inner plume features seen in the experimental images are not observed in the model. The possible physical mechanisms responsible for this discrepancy are discussed. This effort constitutes a continued development toward a predictive model of ablation plume dynamics and chemistry for various materials in extreme environments.

Plasma and Light Flash Radiant Features Generated by Al/PTFE Projectile High-Velocity Impact Thin Aluminum Target

To reveal the characteristic parameters and the evolutionary rules of plasma and light flash radiation produced by aluminum powder/polytetrafluoroethylene (Al/PTFE) projectile hypervelocity impacting on 2A12 thin aluminum plate, the Al/PTFE projectile was obtained by the improved sintering process of the sample, which is based on the process of the traditional Al/PTFE (mass percentage ratio of aluminum powder and PTFE is 26.5%/73.5%). The dynamic compressive strength of the sample was characterized by the self-constructed split Hopkinson pressure bar (SHPB) system. Meanwhile, the experiments, enhanced Al/PTFE projectile (mass 0.22 g, size <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5\times5$ </tex-math></inline-formula> mm) impacting on 2A12 aluminum targets with the thicknesses of 2 and 3 mm at different impact speeds (1.95–2.45 km/s), have been performed using a two-stage light gas gun loading system combining with a high-speed camera acquisition system, a transient fiber pyrometer measurement system, and a plasma characteristic parameter diagnostic system. The electron temperature, electron density of plasma, and the radiant temperature (in the range of visible light wavelength) of light flash have been experimentally studied. The results show that the dynamic compressive strength of the Al/PTFE specimen with rapid cooling was significantly improved at the strain rate of 4000 s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> comparing with the traditional Al/PTFE projectile (the dynamic compressive strength was 32–44 MPa), which can reach more than 100 MPa. The maximum electron temperature, electron density, and visible light radiant temperature produced by the hypervelocity impact increase with an increase in impact velocities and target thicknesses, respectively.

An improvement on the Florence analytical equation for predicting the ballistic limit velocity of ceramic–aluminum targets and its development to ceramic–aluminum–polyurea panels

An improvement on the Florence analytical equation for predicting the ballistic limit velocity of ceramic–aluminum targets and its development to ceramic–aluminum–polyurea panels

Micro-impulse and plasma plume produced by irradiating aluminum target with nanosecond laser pulses in double-pulse scheme

The micro-impulse generated by ablating an aluminum target in double-pulse laser bursts with different interpulse delays was investigated using a torsion pendulum. The plasma plume was simultaneously visualized using high-speed photography to analyze the coupling mechanism of the ablation impulse. The experiment was carried out using a pulsed laser with a pulse width of 8 ns and a wavelength of 1064 nm. The experimental results show that an impulse with an interpulse delay of 60 ns is roughly 60% higher than that with no delay between the two pulses, when the energy of both laser pulses is 50 mJ. Therefore, double-pulse schemes could enhance the ablation impulse under certain conditions. This is because the ablation of the first laser pulse changes the optical properties of the aluminum target surface, increasing the absorptivity. However, the ablation impulse is reduced with a time delay of 20 ns when the energy of both laser pulses is 100 mJ or 150 mJ. It can be concluded that the plasma produced by ablating the aluminum with the first pulse shields the second laser pulse. To summarize, the experimental results show that different delay times in a double-pulse scheme have a significant effect on the ablation impulse. The study provides a reference for the optimization of the parameters when laser ablation propulsion with a double-pulse scheme is applied in the fields of space debris removal, laser ablation thrusters, and so on.

Production of High-Transverse-Momentum Deuterons and Tritons at an Angle of 40{{}^{circ}} in Proton–Nucleus Interactions at a Beam Energy of 50 GeV

Data on the production of positively charged particles emitted at an angle of 40{}^{circ} (in the laboratory frame) with transverse momenta of up to 2.7 GeV/c in the interaction of 50-GeV/c protons with carbon, aluminum, copper, and tungsten nuclear targets are presented. Particular attention is given to studying the production of light nuclear fragments, such as deuterons (d) and tritons (t). An analysis of data on d and t particles gives grounds to state that these fragments arise via a local mechanism of their direct knockout from nuclei. The results were obtained in the SPIN experiment at the Institute for High Energy Physics (IHEP, Protvino).

Cross-Section Measurement of In-coherent Scattering from Annular 241Am Gamma Ray Source

Compton scattering of gamma- rays has been carried out with the aluminum target at a fixed angle of 650± 2.50. 241Am gamma ray source, having 59.57 KeV energy and a long half-life of 432.2 years has been used to carry out the scattering. The strength of the source is 1000 mCi and it has an annular geometry. Scintillation detector NaI (Tl) of type 708 having a crystal size 1 3^"/4 × 2^" connected to a Multichannel Analyzer (MCA) has been used for this study. MCA was calibrated using 133Ba, and 137Cs sources through ACCUSPEC software. The data accumulated was used to estimate the energy of the backscattered peak of the said sources and compared with their respective theoretical value. Spectrums were accumulated directly from 241Am and the shift in the photo-peak of 241Am with the aluminum scatterer. Data was used to calculate the scattering cross-section and compared with its theoretical value using Kline and Nishina’s equation. A good agreement is found in theoretical and experimental values.

Dependence on the Lens-to-Target Distance and with the Laser Energy at Constant Irradiance of the Laser-Induced Breakdown Spectroscopy Signal.

The emission signal-to-noise ratio (S/N) of a laser-produced plasma on an aluminum target at different focusing distances and at fixed irradiances was investigated. The plasma was produced by a 1064nm nanosecond-pulsed laser and the energy and irradiances were varied in the 6-110mJ and 0.4-700GWcm-2 ranges, respectively. Regardless of the applied laser energy, adjusting the lens-to-target distance, best emission values were obtained for an irradiance of nearly 8GWcm-2. At lower irradiances, the signal decreases due to less matter removal, while at higher values, the plasma shielding effect prevents the laser from reaching the sample. This mechanism is surpassed when the lens-to-sample distance is close to the nominal focusing value at about 100GWcm-2. The enhancement of the signal with the focusing distance is due to a combination of an increment of the plasma temperature, electron density, and atomized mass. When the irradiance is kept fixed changing simultaneously the laser energy and the ablated area, an increment of the emission was observed. This is basically due to an increment of the ablated mass while both electron density and temperature do not show significant changes, even though the laser energy increased by more than one order of magnitude.