Thick Target Research Articles

Modeling terahertz emissions from energetic electrons and ions in foil targets irradiated by ultraintense femtosecond laser pulses.

Terahertz (THz) emissions from fast electron and ion currents driven in relativistic, femtosecond laser-foil interactions are examined theoretically. We first consider the radiation from the energetic electrons exiting the backside of the target. Our kinetic model takes account of the coherent transition radiation due to these electrons crossing the plasma-vacuum interface as well as of the synchrotron radiation due to their deflection and deceleration in the sheath field they set up in vacuum. After showing that both mechanisms tend to largely compensate each other when all the electrons are pulled back into the target, we investigate the scaling of the net radiation with the sheath field strength. We then demonstrate the sensitivity of this radiation to a percent-level fraction of escaping electrons. We also study the influence of the target thickness and laser focusing. The same sheath field that confines most of the fast electrons around the target rapidly sets into motion the surface ions. We describe the THz emission from these accelerated ions and their accompanying hot electrons by means of a plasma expansion model that allows for finite foil size and multidimensional effects. Again, we explore the dependencies of this radiation mechanism on the laser-target parameters. Under conditions typical of current ultrashort laser-solid experiments, we find that the THz radiation from the expanding plasma is much less energetic-by one to three orders of magnitude-than that due to the early-time motion of the fast electrons.

An innovative approach for estimating energy absorption buildup factors (EABF) with HVL and TVL.

The current study proposes an empirical formula for absorption buildup factors as a function of target thickness. The present formula produces absorption buildup factors of compounds and mixtures with simple inputs of linear attenuation coefficient (μ), tenth value layer (TVL) and half value layer (HVL) of interacting target for the atomic number region 29<Z<92 for the energies 0.2MeV<E<1.5MeV. This method is used to compute the energy absorption buildup factors using HVL and TVL.

Fabrication and characterization of thin 94Zr target with gold backing for nuclear lifetime measurements using DSAM

For lifetime measurements of excited nuclear states in the sub-picosecond range, a thin target with a thick backing of high-Z material is required. To meet these specifications, a thin isotopic94Zr target of thickness 1.14 ± 0.05 mg/cm2, with backing of 4.7 ± 0.2 mg/cm2 thick Au layer, has been fabricated using the cost-effective cold rolling technique at the target laboratory of Inter-University Accelerator Centre (IUAC), New Delhi. The thickness verification and purity check of the fabricated target have been carried out by non-destructive Energy Dispersive X-ray Fluorescence (EDXRF) and Rutherford Backscattering Spectrometry (RBS) techniques. The results of these measurements are in good agreement with each other. The elemental composition, purity and surface morphology have been explored by Energy Dispersive X-ray Spectrometry (EDS) and Scanning Electron Microscopy (SEM) techniques. The fabricated target has been successfully used with a16O ion beam in a recent γ-ray spectroscopy experiment for lifetime measurements using the Doppler Shift Attenuation Method (DSAM) at IUAC, New Delhi.

Differential cross–section measurements for the proton-induced alpha and deuteron reactions and elastic scattering on 9Be, suitable for Ion beam analysis applications

In the current work the differential cross sections for the proton-induced 9Be(p,d0)8Be and 9Be(p,α0)6Li nuclear reactions (Q-values = 559 and 2125 keV respectively), as well as, the 9Be(p,p0)9Be elastic scattering were measured for 6 backscattering detection angles (θ = 120°, 130°, 140°, 150°, 160° and 170°) covering the Ep,lab = 300–3000 keV energy range with an energy step between 10 and 50 keV. The total estimated uncertainties of the determined cross-section values did not exceed 6.4 % for the elastic scattering, 7.0 % for the 9Be(p,α0)6Li and 9.9 % for the 9Be(p,d0)8Be reaction. Benchmarking measurements were also performed with a suitable thick target in order to validate the obtained cross-section values. The present experimental results constitute three coherent differential cross-section datasets suitable for IBA applications. The measurements were performed at the 4 MV Tandem Dynamitron Laboratory of the Ruhr University Bochum in Germany. The experimental, data analysis and benchmarking procedures are presented in detail.

The Effect of Zinc Oxide on DLP Hybrid Composite Manufacturability and Mechanical-Chemical Resistance.

The widespread use of epoxy resin (ER) in industry, owing to its excellent properties, aligns with the global shift toward greener resources and energy-efficient solutions, where utilizing metal oxides in 3D printed polymer parts can offer extended functionalities across various industries. ZnO concentrations in polyurethane acrylate composites impacted adhesion and thickness of DLP samples, with 1 wt.% achieving a thickness of 3.99 ± 0.16 mm, closest to the target thickness of 4 mm, while 0.5 wt.% ZnO samples exhibited the lowest deviation in average thickness (±0.03 mm). Tensile stress in digital light processed (DLP) composites with ZnO remained consistent, ranging from 23.29 MPa (1 wt.%) to 25.93 MPa (0.5 wt.%), with an increase in ZnO concentration causing a reduction in tensile stress to 24.04 MPa and a decrease in the elastic modulus to 2001 MPa at 2 wt.% ZnO. The produced DLP samples, with their good corrosion resistance in alkaline environments, are well-suited for applications as protective coatings on tank walls. Customized DLP techniques can enable their effective use as structural or functional elements, such as in Portland cement concrete walls, floors and ceilings for enhanced durability and performance.

High-velocity impact experiments and quantitative damage evaluation for finite ultra-high-performance concrete targets

In this work, we aim at improved characterization of target damage occurring as the result of projectile impact against ultra-high-performance concrete (UHPC). For this purpose, we present the results of high-velocity impact experiments with spherical steel projectiles and finite-thickness UHPC targets of approximately 115 MPa compressive cylinder strength in the impact velocity range from approximately 600 m/s to 1500 m/s. The data set obtained from these experiments includes residual projectile velocities as well as qualitative and quantitative information on damage. Quantitative damage information is mainly extracted from digital 3D post mortem targets, which are produced by 3D-scanning. For all damage quantities, a dependence on the impact velocity and the target thickness is discussed and used to provide possible explanations for the origin of the particular type of damage. The large data set presented in this work can constitute the basis for a comprehensive and quantitative verification and validation of analytical, empirical, and numerical models that describe the perforation of UHPC targets in the investigated impact velocity range.

Continuous and pulsed fast neutron beams at the CNA HiSPANoS facility

The characteristics of the fast neutron beams produced in the HiSPANoS facility at Centro Nacional de Aceleradores (CNA) are presented. The neutrons are generated by deuteron beams from a 3 MV tandem accelerator in either continuous (5 μA) or pulsed (2 ns width, 500 kHz and 4% duty cycle) mode. In this work, the pulsed mode was used in a time-of-flight characterization of the produced neutron beams in terms of yield, flux, energy resolution, and background. The results were then validated through their comparison with previously published data.Quasi-monoenergetic neutron beams between 2 and 6 MeV are produced by means of the 2H(d,n)3He reaction, featuring a neutron yield of 106 n/sr/μC at the target, with an energy resolution of about 7% at 150 cm. Neutron beams with broad energy distributions are produced by deuteron irradiation of thick beryllium and lithium targets, resulting in maximum neutron energies of 10 and 20 MeV, respectively. In this case, the neutron yields are significantly higher, reaching 1010 n/sr/μC.On the basis of these results, we consider that the HiSPANoS facility is now fully operational for the usage of fast neutrons by internal and external users of CNA.

High-Throughput Deposition of Recyclable SnO2 Electrodes toward Efficient Perovskite Solar Cells.

Chemical bath deposited (CBD) SnO2 is one of the most prevailing electron transport layers for realizing high-efficiency perovskite solar cells (PSCs) so far. However, the state-of-the-art CBD SnO2 process is time-consuming, contradictory to its prospect in industrialization. Herein, a simplified yet efficient method is developed for the fast deposition of SnO2 electrodes by incorporating a concentrated Sn source stabilized by the ethanol ligand with antimony (Sb) doping. The higher concentration of Sn source promotes the deposition rate, and Sb doping improves the hole-blocking capability of the CBD SnO2 layer so that its target thickness can be reduced to further save the deposition time. As a result, the deposition time can be appreciably reduced from 3-4h to only 5min while maintaining 95% of the maximum efficiency, indicating the power of the method toward high-throughput production of efficient PSCs. Additionally, the CBD SnO2 substrates are recyclable after removing the upper layers of complete PSCs, and the refurbished PSCs can maintain ≈98% of their initial efficiency after three recycling-and-fabrication processes.

Modeling of electron refluxing and TNSA fields in laser–target interactions based on analysis of K α emission

We analyze and model fast-electron-induced Kα emission from an experiment in which a high-intensity ultra-short laser irradiated foil and bulk titanium targets. The motion of electrons inside the targets is calculated allowing for multiple scattering and collisional energy loss, while outside the target, electric fields of arbitrary configurations are assumed. It is shown that both the radial Kα-intensity distributions and the somewhat non-intuitive dependence of the absolute Kα emission on the target thickness can be reproduced by taking into account the fast-electron refluxing with an electric field configuration based on the target normal sheath acceleration model. We infer the presence of a sheath electric field on the order of TV/m, extending to about 100μm in the radial direction. In addition, we obtain a temporal profile of the Kα radiation.

The relationship between Event‐Related Potentials and MRI cortical atrophy in a memory disorders clinic

AbstractBackgroundThere is a need for accessible and affordable ways to assess biomarkers of Alzheimer’s disease (AD). Event‐related potentials (ERPs) are associated with disease severity of AD (Fruehwirt et al., 2019) and are a candidate biomarker for AD (Olichney et al., 2022). There is, however, little understanding of how ERP components relate to neurodegeneration of specific brain structures in AD.MethodWe investigated the correlation between electrophysiology, as measured by ERPs and brain structure using quantitative structural MRI measurements using FreeSurfer. A dataset containing older veteran memory disorders patients (N = 25) from VA Boston Healthcare System was analyzed. Participants completed an MRI and an auditory oddball task ERP paradigm.ResultAn exploratory analysis was performed using a Pearson correlation coefficient to evaluate the relationship between ERPs and the thickness and volume of different cortical areas. There was a negative relationship between P300 target amplitude and inferior temporal volume (p &lt; .05), as well as P300 target latency and thickness of the superior temporal (p &lt; .05) and transverse temporal regions (p &lt; .01). P200 standard amplitude had a positive correlation with thickness in the middle temporal (p &lt; .01), and superior temporal regions (p ≤ .05), and P200 target latency had a negative correlation with thickness of the superior temporal region (p &lt; .05). N200 target amplitude had a negative correlation with the superior parietal volume (right hemisphere = p ≤ .05, left hemisphere = p ≤ .01), left inferior temporal volume (p ≤ .05), and the middle temporal volume (left = p ≤ .05, right = p ≤ .01). N200 target latency was negatively correlated with right superior parietal volume (p ≤ .05).ConclusionA correlation was found between ERP measures P200, N200 and P300 with cortical thickness and volume of areas that are commonly impacted by AD pathology, further substantiating use of ERPs as possible AD biomarkers. We conclude that ERPs provide insights as to structural changes of brain structures affected by AD pathology. ERPs could help inform areas of brain atrophy and related patterns of cognitive impairment.

Backward scattering of laser plasma interactions from hundreds-of-joules broadband laser on thick target

The use of broadband laser technology is a novel approach for inhibiting processes related to laser plasma interactions (LPIs). In this study, several preliminary experiments into broadband-laser-driven LPIs are carried out using a newly established hundreds-of-joules broadband second-harmonic-generation laser facility. Through direct comparison with LPI results for a traditional narrowband laser, the actual LPI-suppression effect of the broadband laser is shown. The broadband laser had a clear suppressive effect on both back-stimulated Raman scattering and back-stimulated Brillouin scattering at laser intensities below 1 × 1015 W cm−2. An abnormal hot-electron phenomenon is also investigated, using targets of different thicknesses.

Measurement of neutron spectra for various thicknesses of concrete and steel shielding at 24-GeV/c proton beam facility using Bonner sphere spectrometer

ABSTRACT Neutron energy spectra down to thermal energy were measured using a Bonner sphere spectrometer (BSS) for various thicknesses of concrete and steel shielding at the CERN/CHARM facility, where high-energy neutrons were produced by 24-GeV/c protons incident on a thick copper target. The thicknesses of the concrete and steel shielding blocks ranged from 40 cm to 200 cm and from 20 cm to 80 cm, respectively. The BSS consisted of a spherical 3He proportional counter and five polyethylene moderators with diameters of 7.62 cm, 10.2 cm, 12.7 cm, 17.8 cm, and 24.1 cm, respectively. In addition, polyethylene moderators combined with a lead or copper inner shell were used to increase the sensitivity to high-energy neutrons. The neutron energy spectra were deduced using an unfolding method. The initial guesses were obtained using the PHITS code for each experimental geometry. The response function for the BSS was determined using the MCNP6.2 code with JENDL-4.0/HE. The neutron energy spectra over the entire energy region from 10−4 eV to 10 GeV were successfully obtained for the different shielding conditions. The validity of the response function and the contribution of each moderator are discussed referring to previous studies and tests at the standard neutron fields of AIST.

Enhancement of Sn plasma EUV emission by double-sided laser illumination

Advancements in state-of-the-art nanolithography technology over the past decade have been raising an ongoing demand for improvement of the power and efficiency of extreme-ultraviolet (EUV) light sources that stand at its heart. This study introduces a double-sided laser illumination scheme aimed at enhancing EUV emission from such a laser-produced Sn plasma source. Using a solid-state laser, experiments were conducted with suspended solid Sn targets of varying thicknesses, evaluating the resulting effect on EUV output intensity. A significant increase in EUV emission to the collection side was observed due to the addition of illumination of the other side, particularly for thinner targets. For targets with thicknesses of 60 and 20 nm, an increase between 50% and 150% in EUV emission was detected in comparison with single-sided illumination. Extrapolating to a long laser pulse that burns through the target, the enhancement is projected to be 17% for a 300 nm thick target. These results highlight a promising way for further improvement of output power and energy efficiency in next-generation EUV light sources.

A data-driven approach for predicting the ballistic resistance of elastoplastic materials

Data-driven methods and machine learning methods provide efficient and accurate approaches for solving impact problems. In this paper, a data-driven approach is proposed for numerical simulations of ballistic impact behavior for elastoplastic materials. An enhanced rate-dependent scheme is employed for improving the predictability of the data-driven constitutive model. A new method that introduces a stress triaxiality indicator to three separate constitutive models is proposed to consider the discrepancy between the mechanical responses of materials under tension, compression, and shear. Additionally, a modified Bai-Wierzbicki fracture criterion considering the strain rate effect and the stress-state effect is used to evaluate the fracture behavior of the materials during impact simulations. Subsequently, a compatible numerical implementation algorithm that considers loading, unloading, and reverse loading is established to enable the application of the data-driven approach in finite element simulations. Numerical validation of the proposed data-driven approach is conducted through several simple loading examples, such as cyclic loading, torsional loading, and tension–torsion combined loading. The data-driven approach is then employed to simulate the ballistic impact behavior of Ti-6Al-4V targets of different thicknesses that are struck by blunt projectiles. Impact properties—including the relationship between residual velocity and impact velocity, ballistic limit velocities, and fracture paths—are comprehensively studied. The results demonstrate the reasonable predictability and accuracy of the data-driven approach when applied to ballistic impact simulations.

Experimental and numerical studies on the effectiveness of high-strength steels protecting against API BZ projectiles

ABSTRACT This paper uses numerical and experimental methods to look at how well Xar450 and Perform 700 high-strength steels protect against a 7.62 × 39 mm API BZ projectile. The numerical study of the target thicknesses varies from 3 mm to 4 mm and 6 mm. And they are struck at 0°, 15°, 30°, 45°, and 60° oblique angles. Numerical simulation results show that at a normal impact angle, the bullet can break through the Perform700 targets in all thicknesses; however, the resistance performance of the target plate increases with the rise of oblique angles. The Xar450 target plates of 4 mm and 6 mm can resist the bullet at any oblique angle, but the bullet can easily penetrate 3 mm thickness from 0° to 30° oblique angles. The experiment is based on the VPAM-APR 2006 standard. The experiment results showed that the bullet perforated through the Perform700 target plate with a thickness of 3 mm at 0° and 30° oblique angles. In contrast, the bullet cannot penetrate the Xar450 target thickness of 4 mm at a normal angle. The findings of this research are used in the formulation of the design methodology for a light armoured vehicle. Besides, they have considerable importance in the realm of calculating and developing anti-fracture structures for practical applications.

Microscopic hyperspectral imaging and an improved detection model based detection of Mycogone perniciosa chlamydospore in soil

The Mycogone perniciosa disease of Agaricus bisporus is highly contagious, with insignificant early symptoms and a long infestation period. Currently, there is a lack of a convenient and rapid means to detect the disease for early control. By using the transmission route of the disease, this paper focuses on M. perniciosa chlamydospore detection in contaminated soil. Microscopic hyperspectral images of M. perniciosa chlamydospore in contaminated soil were obtained to establish a detection model. Given a small target and a complex background, we proposed an improved spore detection model based on a faster regional convolutional neural network (Faster R-CNN). Furthermore, we combined the residual network Resnet50 and feature pyramid network (FPN) to extract thick spore target features at multiple scales. Meanwhile, we optimized the region proposal network (RPN) region proposal generation by adding two small scales to improve the performance of the detection model. The first three principal components (with 95% or more information) and RGB images were selected as model inputs, respectively, and the final average precision (AP) was 94.68% and 92.35%, respectively. This PC-based model also was compared to the VGG16 and Resnet50-based feature extraction networks of Faster R-CNN and Darknet53-based feature extraction network of the YOLOv3 model, and the AP was found to improve by 5.41%, 4.78%, and 6.34%, respectively. The results showed that micro-hyperspectral imaging combined with deep learning methods could accurately detect the chlamydospore in the soil, providing new methods and ideas for the early prevention and detection of M. perniciosa disease of A. bisporus.

Ionoacoustic monitoring of relativistic heavy ion beams

The performance of ionoacoustic detectors is investigated with respect to application of high-precision range and energy loss measurements for relativistic heavy ions. The technique is based on the generation of a pressure wave when a microsecond-pulsed relativistic ion beam is stopped in a water container. The acoustic signal from individual ion pulses is registered by a piezoelectric detector and analyzed in the time/frequency domain to identify the location of pressure wave generation. The experiments were performed at the SIS18 synchrotron at GSI Helmholtzzentrum (Darmstadt, Germany) with Xe, Pb and U ions of energies between 200 MeV/u and 1 GeV/u. We show that the signal amplitude of the acoustic pressure pulse has a linear correlation with the beam intensity within a range of at least 104 to 109 particles/spill.By determining the delay time of the primary and reflected acoustic signal in the water reservoir, the ionoacoustic technique provides information on ion ranges of 1 % accuracy. By an energy-range calibration in combination with a simulation code such as FLUKA, the range data can be used to determine the beam energy. As demonstrated, inserting targets of known thickness in front of the detector is a simple approach for measuring the energy loss of relativistic ions. The advantage of the ionoacoustic technique is the rather simple experimental setup, the huge dynamic range, the information available online by means of only a single pulse and its radiation hardness. Ionoacoustic detectors have great potential as intensity and energy monitor for short-pulsed light and heavy ion beams at existing or future high-energy ion facilities.

Fabrication and characterization of CaF2 target for multi-nucleon transfer reaction studies

Thin CaF2 targets with carbon backing are fabricated for the first time using physical vapour deposition technique at the target laboratory of IUAC, New Delhi to perform a multi nucleon transfer reaction on 10,11B＋40Ca systems using General Purpose Scattering Chamber (GPSC) facility. Ca being an oxidizing material, we have used molecular CaF2 as the target material instead of Ca. Using turbo-molecular pump based coating unit (TMPU), carbon is deposited on cleaned glass slide and then CaF2 is deposited on diffusion pump based coating unit (DPU). We are successful in fabricating CaF2 targets of thickness ≈264.4μg/cm2 on carbon backing of thickness ≈21.5μg/cm2. The thickness and purity measured by the crystal thickness monitor equipped with the vacuum chamber is verified by different techniques like alpha energy loss, Rutherford Back Scattering (RBS), Electron Diffraction Spectroscopy (EDS) and X-ray Diffraction (XRD). Small impurity level were smeared during the observation and the target is successfully used for nuclear reaction experiment. The fabrication of molecular Ca target is found to be more conducive to experimentation since they exhibit less oxidation and herewith we discuss about fabrication technique, experimentation and characterization.

Fabrication, swift heavy ion irradiation, and damage analysis of lanthanide targets

Abstract One limiting factor in progress in the discovery and study of new superheavy elements (SHE) is the maximum achievable thickness and irradiation stability of current generation actinide targets. The desired thickness of targets, using full excitation function widths, cannot be achieved with current target technology, especially the widely used molecular plating (MP). The aim of this study was to transfer progress in the electrochemistry of lanthanides and actinides to the production of targets. Here, we report on the production of lanthanide targets using anhydrous electrochemical routes. In a first irradiation series, thulium thin films with areal densities up to 1800 μg/cm2 were produced using anhydrous triflate compounds and subjected to irradiation tests, using 6.0 MeV/u 48Ca ions at a fluence of 3.9 × 1014 ions/cm2 and 8.6 MeV/u 197Au ions at fluences in the range of 3.0 × 1011 to 1.0 × 1013 ions/cm2. The thin films were characterised before and after the irradiations using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX).

Ballistic impact performance of hybrid composite armors made of aluminum foam containing the dispersion of shear thickening fluid made of various synthetic nano-fillers

Hybrid composites armors made of closed-cell aluminum foam are developed for intended use in ballistic protective plates. The manufacturing process involved impregnation of shear thickening containing different micro and nano-fillers into aluminum foam panels which are subsequently bonded two AA 5086-H32 aluminum sheets that surrounded the targets, by using compression molding techniques. The effects of the addition of different nano-fillers as colloidal silica, gamma alumina, silica carbide, and Kevlar micro-fibers to the aluminum foam plates on the ballistic response of the hybrid composites armors were investigated. Scanning electron micrographs were used to investigate the interfacial interaction between specimen layers, and the influence of the nanoparticles impregnated within closed aluminum foam cells before and after high-velocity impacts. The ballistic impact resistance of the produced hybrid composite cell aluminum foam laminates was tested according to NATO standards using a semiautomatic 9 mm Beretta Cx4 Storm Rifle Luger. The results indicated that the performance of the hybrid composite armors made of aluminum foam were enhanced by the deposition of micro and nano-fillers into the surface of the closed-cell aluminum foam.Therefore, the ballistic impact resistance and energy absorption of the specimens were improved. The highest impact energy absorption capacity was achieved by the deposition of Kevlar micro-fibers, but the resulting plates have the highest target weight and thickness. Silica carbide powder followed by gamma alumina, and colloidal silica powder in that order, enhanced the impact energy absorption capability with the least target weight and thickness average. These findings indicate that introduction of micro and nano-fillers coating on closed-cell aluminum foam, improved a range from 4.9 to 30.9 J in comparison with untreated samples, therefore, it could be a promising method for strengthening interfacial bonding between layers of the aluminum foam composites.