Tantalum Target Research Articles

Experimental study of photoneutron spectra from tantalum, tungsten, and bismuth targets for 16.6 MeV polarized photons

ABSTRACT The double differential cross-sections (DDXs) of photoneutron production via the photonuclear reaction on tantalum, tungsten, and bismuth for 16.6 MeV linearly polarized photon beam were measured using the time-of-flight method at the NewSUBARU-BL01 facility. Polarized photons were obtained by the laser Compton backscattering (LCS) technique. Two distinct components were observed on the spectra: the low-energy component up to 4 MeV and the high-energy above 4 MeV. The angular distribution of the low-energy component was isotropic, whereas the high-energy was distributed anisotropically and affected by the polarized incident photons. These distributions were similar to the previous studies on the 197Au target. The low-energy component's data were fitted with the Maxwellian function. According to the fitting results, the slopes of low-energy neutrons’ distribution for natTa and natW are similar and steeper than that of 209Bi. The anisotropy of the high-energy component can be expressed as a function of cos 2 Θ   , where Θ is the angle between the direction of the photon polarization and neutron emission.The DDX energy integrations of the high-energy component were calculated and compared between the three targets. These integration values on natTa and natW were comparable and around 1.5 times smaller than those on 209Bi, regardless of the detection angles.

Development of an optical method for temperature measurements of the ISAC targets at TRIUMF

The temperatures of isotope separator on-line targets play an important role for the overall target performance, including the yield of the radioactive ion beams and the target lifetime. At TRIUMF an optical technique is being developed to obtain accurate real-time temperature feedback from ISAC and in the future ARIEL targets during beam delivery. The light emitted from within the hot tantalum target container is captured and transmitted into a spectrometer via an ionizer opening. For accurate results an absolute irradiance calibration of the spectrometer is performed to determine the spectral power density. Then, to analyze the light spectra and calculate the maximum temperature, two mathematical methods have been applied. These methods are first evaluated using the spectrum of a light source with a known colour temperature. One method is selected and applied to a tantalum target container heated off-line at nominal temperatures and cross-checked with a thermocouple. The results of the test are in close agreement with the temperatures read by the thermocouple. This paper describes the calibration of the optical system, the methods applied, along with their results and validations. This technique will be applied to the on-line targets and correlate isotope releases with target temperatures for optimizing the delivery of short-lived radioisotopes species.

Investigation of the effect of the TaC/α-C coating process on the properties of stainless steel bipolar plates

In this study, we present a series of innovative single-layer TaC/α-C coatings designed for integration into proton exchange membrane fuel cells (PEMFC). These coatings are fabricated on stainless steel (SS316L) substrates employing the magnetron sputtering technique. We systematically explore the influence of varying TaC content and the current applied to the tantalum target on the composition, morphology, and properties of these coatings. Notably, the investigation reveals that the coatings exhibit remarkably low values for interfacial contact resistance (ICR), amounting to 0.56 mΩ cm2, and corrosion current density, measuring at 10.7 nA cm−2. Subsequently, Single-cell performance of PEMFC test shows that the highest peak power density of TaC/α-C coated SS316L bipolar plates is 1003 mW cm−2 slightly higher than that of graphite bipolar plates, which is 948 mW cm−2. All the results show that the novel TaC/α-C coating is a prospective coating for PEMFC metal bipolar plates.

Trace-scale extraction of carrier-free tungsten radioisotope as a homolog of Sg using ionic liquid from acid solutions: Kinetic study

This study aimed to find a rapid extraction system for the preparation of a Seaborgium (Sg) aqueous chemistry experiment in the future. A new approach for extraction of 181W tracer as a lighter homolog of (Sg) by ionic liquids is explored. A natural tantalum target was activated by a beam of 9 MeV proton at Cologne University to produce carrier-free 181W. The preliminary batch extraction experiments of the carrier-free 181W from HCl and H2SO4 solutions have been evaluated. Different batch extraction parameters such as feed acidity, diluent type, ionic strength (KCl feed) and reducing agent as a function of time were explored. The obtained results demonstrated that the highest distribution of carrier-free 181W from 0.001 M acidic solutions using the used ionic liquid is observed. A significant rapid kinetic for the extraction of trace-scale using the used ionic liquid is achieved within 5 sec. The preliminary results are necessary to design the upcoming aqueous experiments of Sg. The next goal will be on-line experiments with the centrifuge system SISAK to develop the aqueous chemistry extraction of Sg using the most promising and adequate experimental setup.

The orientation dependence of stored energy and the evolution of texture of through-thickness tantalum targets during heating

In semiconductor integrated circuits, the orientation dependence of the stored energy and texture distribution uniformity of sputtering tantalum targets are critical to the properties of the deposited films which block the diffusion of Cu atoms into the storage cell Si. In this paper, the effect of heating rate on the recrystallization behavior was investigated with the aid of a differential scanning calorimeter (DSC). In addition, the texture and stored energy of deformed tantalum targets with different heat treatments along the thickness direction were characterized using electron backscatter diffraction (EBSD). The results show that the initial temperature of recrystallization rises but the temperature range reduces with the increase of the heating rates. The stored energy of deformed tantalum targets presents various orientation dependencies in different thickness layers. During the heating process, the stored energy difference among the grains with different orientations decreases, but the maximum difference of stored energy in different thicknesses increases inversely. The content of {101} oriented grains increases as the temperature increases, while the content changes of {111} and {001} present a waveform with an opposite trend.

178m2Hf isomer production cross-sections for Ta target irradiated by α-particles in the energy range from 36 to 92 MeV

178m2Hf isomer production cross-sections were measured when natural tantalum targets were irradiated by alpha particles in the energy range of 36–92 MeV. The simulations of these cross-sections in the TALYS-1.4 code showed that the main contribution to the 178m2Hf isomer production is given by (α, αp2n), (α, 3p4n) and (α, 3Hep3n) nuclear reactions. In the range of α-particle energies of 58–92 MeV, the theoretical results coincided well with the experimental ones, and based on this, the cross-sections of the 178gHf ground state production were estimated. allowing to calculate the isomer ratios as well. The obtained values are in good agreement with the trend of changes for the isomer ratios obtained in the nuclear reactions with lower-energy alpha particles and other targets.

Effect of Warm Crossing Rolling on the Microstructure, Texture and Annealing Behavior of High-Purity Tantalum

With advanced integrated circuit semiconductor chips, the uniformity of microstructure and texture is increasingly required for tantalum (Ta) targets. A combination of warm rolling and 135° cross rolling (CR) at the temperature of 500 °C and 800 °C, i.e., warm cross rolling (WCR), was carried out in tantalum (Ta) plates to investigate the evolution of deformed microstructure and texture. Subsequently, these rolled samples were annealed to analyze the recrystallized microstructure. Results exhibited that WCR samples formed a relatively uniform and weak texture distribution along the thickness direction. The reduction in the proportion of low-angle grain boundaries (LAGBs) was associated with the lower Peierls stresses to be overcome for dislocation motion due to thermal activation in the WCR sample. High grain boundary energy was observed in WCR samples, and WCR can promote dynamic recovery of samples to produce sub-crystals (thermodynamically unstable and serving as nuclei for subsequent recrystallization). Fine average grain size and high content of recrystallized grains with random orientation were obtained after annealing in the WCR sample. This study will provide a theoretical reference for the precise optimization of tantalum process parameters and the improvement in the target material’s performance.

Comparison of Radionuclide Impurities Activated during Irradiation of 18O-Enriched Water in Tantalum and Silver Targets during the Production of 18F in a Cyclotron.

During the production of 18F, as a result of the interaction of the beam of protons and secondary neutrons with the structural elements of the target body, many radionuclide impurities are created in the cyclotron. As part of this work, we theoretically predicted which isotopes would be activated in the target tantalum or silver bodies. Subsequently, we used gamma spectrometry analysis to verify these predictions. The results were compared with the work of other authors who studied titanium and niobium as materials for making the target body. Tantalum has been evaluated as the most favorable in terms of generating radionuclide impurities during the production of 18F by irradiation of 18O-enriched water in accelerated proton cyclotrons. Only three radionuclides were identified in the tested samples: 181W, 181Hf, and 182Ta with a half-life of fewer than 120 days. The remaining reactions led to the formation of stable isotopes.

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.

Radiological characterization of high-energy proton Tantalum targets from CERN-ISOLDE Facility

Radiological characterization of high-energy proton Tantalum targets from CERN-ISOLDE Facility

Spectral studies of soft x-ray radiation of laser-produced plasma of various target materials in a wide spectral range.

The work is devoted to experimental study of soft x-ray radiation spectra of laser-produced plasma in a wide spectral range of 5-100Å at the Kamerton facility (GPI) with pulse duration 70 ps, pulse energy 1-5J, and wavelength 0.53 microns at which the laser intensity (power flux density) of 7×10^{14}-3.5×10^{15}W/cm^{2} was achieved. A spectrograph was used, which had transmission diffraction gratings with a ratio of the elementary gap to the period of the structure of 0.25 and 0.41. Detection was performed on both UV-4 x-ray photo film and Fuji TR fluorescent imaging plate. Solid samples from Al, Si, Ti, Cu, Ta, and W were used as targets. The ionization states of the plasma corresponding to various electron temperatures were calculated, which made it possible to estimate the electron temperature by comparison of these calculation results with the experimentally obtained spectra. The estimated electron temperature, which depends on the laser pulse energy and the target material, varied within the range 100-450eV. To verify the correctness of the temperature estimations obtained by such comparison a numerical simulation of plasma radiation was carried out by the use of prismspect computer program. It was found that the results of this simulation are in good agreement with estimations on the base of experimentally obtained spectra. The analysis of these spectra showed that tantalum, tungsten, or titanium targets are the best candidates among the tested ones for the use of laser-produced plasma as a radiation source in the "water window" spectral range (23-44Å) for applications in biology and medicine.

An optimized microchannel Ta target for high-current accelerator-driven neutron sources

An optimized neutron producing tantalum target with an optimized internal microchannel cooling was developed for a 70 MeV proton beam with a peak current of 100 mA, a duty cycle of 1.43% and an average power of 100 kW on a target surface area of 100 cm 2. In this work a target with microchannel cooling structure is described which matches with the proton’s energy to minimize hydrogen implantation and to produce energy deposition with optimum homogeneity inside the target to minimize the thermal stresses. For the purpose of getting an optimal target design, the investigations of energy deposition, proton fluence, the spatial distribution of (p, n) reactions and the spatial distribution of stopping protons of the target with different microchannel geometries were performed with the particle transport code FLUKA. The resulting design produces a homogeneous proton fluence and energy deposition without hot spots. Furthermore, only 4.4% of the impinging protons accumulate in the metal target, which significantly decreases the risk of hydrogen embrittlement and blistering.

Rhodotron and rotating target: A solution towards micro-spot for high energy and high dose rate bremsstrahlung sources

High energy over MeV bremsstrahlung sources that employ normal conducting radio frequency linear accelerators have expanding applications in industrial computerized tomography (CT) for non-destructive inspection and evaluation. The X-ray spot size that mainly affects the imaging quality is yet limited by the electron beam width in the high resolution CT systems. In a short exposure time, high beam power is required to generate sufficient photons to improve the signal to noise ratio of imaging. However, with ∼kW level of average beam power these linear accelerators usually have a beam spot size over 1 mm since the temperature rising due to the beam energy deposition in the target should be far below its melting point. We propose a concept of using a Rhodotron-based accelerator to provide high power electron beams in a long duration pulse and a rotating target to mitigate the overheating issue, such that the gap between micro-spot and high dose rate can be bridged in the high energy bremsstrahlung sources. This article presents an in-depth simulation work to discuss and evaluate this scheme of X-ray source. The simulations of beam dynamics in the accelerator and bremsstrahlung process in the target predict the generated X-rays with a spot size as small as 68 μm at full-width half-maximum and a dose rate as high as 4700 cGy/min from a 9 MeV electron beam interacting with a 1 mm thickness tantalum target. Further thermal analysis in the rotating target indicates a significant improvement of beam power handling in comparison with the conventional stationary one.

Superior in vitro corrosion resistance of the novel amorphous Ta/TaxOy multilayer coatings on self-expanding nitinol stents

Magnetron sputtering method is used to coat a bi-phase Ta/TaxOy multilayer on NiTi shape memory alloy as a self-expandable stent. These coatings are created to improve the properties of the surface, such as radiopacity, in-vitro corrosion resistance, and biocompatibility. Thin films are formed by simultaneously sputtering the tantalum target in an ArO2 environment, to prevent target poisoning, the ratio of the volume percentage of oxygen to the total inlet gas is 16.6 (Vol%). In addition, the effect of substrate temperature has been studied in this gas composition.Atomic force microscopy has been used to analyze surface topography and roughness. Via potentiodynamic scanning and electrochemical impedance spectroscopy, the electrochemical behavior of the uncoated and coated samples is determined in SBF solution at 37 ± 0.5 °C. Also, the amount of Ni ions released has been analyzed using inductively coupled plasma-optical emission spectrometry. As a result, the Ta/TaxOy thin films deposited at 200 °C represent excellent corrosion resistance. These practical consequences provide a possible procedure to recover the efficiency of Ta/TaxOy coatings on NiTi alloys.

Growth Mechanisms of TaN Thin Films Produced by DC Magnetron Sputtering on 304 Steel Substrates and Their Influence on the Corrosion Resistance

In this work, thin films of TaN were synthesized on 304 steel substrates using the reactive DC sputtering technique from a tantalum target in a nitrogen/argon atmosphere. All synthesis parameters such as gas ratio, pressure, gas flow, and substrate distance, among others, were fixed except the applied power of the source for different deposited coatings. The effect of the target power on the formation of the resulting phases and the microstructural and morphological characteristics was studied using XRD and AFM techniques, respectively, in order to understand the growth mechanisms. Phase, line profile, texture, and residual stress analysis were carried out from the X-ray diffraction patterns obtained. Atomic force microscopy analysis allowed us to obtain values for surface grain size and roughness which were related to growth mechanisms in accordance with XRD results. Results obtained showed a strong correlation between the growth energy with the crystallinity of the samples and the formation of the possible phases since the increase in the growth power caused the samples to evolve from an amorphous structure to a cubic monocrystalline structure. For all produced samples, the δ-TaN phase was observed despite the low N2 content used in the process (since for low N2 content it was expected to be possible to obtain films with α-Ta or hexagonal ε-TaN crystalline structure). In order to determine the corrosion resistance of the coatings, electrochemical impedance spectroscopy and polarization resistance were employed in the Tafel region. The results obtained through this evaluation showed a direct relationship between the power used and the improvement of the properties against corrosion for specific grain size values.

Soft X-ray radiography for measurements of a dense metal plasma created by intense relativistic electron beam on a tantalum target

A radiographic diagnostic has been developed to quantify the plume of erosion products after the interaction between a target and a relativistic electron beam. The diagnostic is based on a point Z-pinch (PZ-pinch) with a metallic plasma jet. It creates an X-ray source with a typical size of 10 μm, a photon energy of up to 3 keV and a flash duration of 3 ns. The X-ray visualization system is based on a thin scintillator and a CCD camera. The spatial resolution of the diagnostic was evaluated experimentally. The spatial frequency limit was found to be about 1.5 line pairs per millimeter. The diagnostic was tested in an experiment performed using an LIA-5 linear induction accelerator. An electron beam with a current of 400 A, an energy of 3.5 MeV and a pulse duration of 80 ns was focused on a plane tantalum target 1 mm in thickness. The FWHM of the focal spot was ∼ 2 mm. Radiographs of the plume were taken with different delays after different accelerator pulses. According to our data, the plume most commonly propagates toward the beam. After 70 μs its length was about 70 mm, i.e. the plume expansion rate was about 1 km/s. The area density of the semi-transparent regions of the plume was estimated as lying in the range 3 · 10-16–2 · 1017 cm-2.

Superhard Ta–O–N coatings produced on titanium using induction physical vapor deposition

Due to simulation by the finite element method, the temperature fields in the “inductor – tantalum target – titanium product” system were calculated depending on the inductor current and exposure time during induction physical vapor deposition (IPVD). The conditions under which the tantalum target was heated to the evaporation temperature in vacuum were determined. It was experimentally established that after IPVD at an operating current IO = 500–800 A (inductor current IIND from 4.9 to 6.7 kA), electrical power consumption PC = 1.67–3.32 kW, and exposure time t = 30–300 s, there was an in increase in the content of tantalum C[Ta]= 21.6–42.1 at.%, oxygen C[O]= 16.5–43.5 at.%, and nitrogen C[N]= 2.6–9.4 at.% on the surfaces of titanium samples. According to the XRD data, the resulting thin-layered structure on the titanium samples was mainly presented by the following crystalline phases: tantalum oxides (Ta2O5, Ta2O), tantalum oxynitride/nitride (TaON, TaN), titanium oxides (TiO2, TiO), and metal phases (α-Ta, α-Ti). It was found that during IPVD hard H = 18.85–39.17 GPa and superhard H = 46.18–89.88 GPa tantalum-containing coatings were obtained on the surfaces of titanium samples. The highest resistance to plastic deformation (by 50–70%) and wear resistance of titanium samples with tantalum-containing coatings was observed in the case of short exposure t < 60 s during IPVD.

A study of the phase transformation of low temperature deposited tantalum thin films using high power impulse magnetron sputtering and pulsed DC magnetron sputtering

In this study, tantalum thin films were deposited on silicon substrates using high power impulse magnetron sputtering (HiPIMS) and pulsed DC magnetron sputtering (pulsed DC), investigating the texture transformation behavior of α-Ta and β-Ta tantalum films by changing the duty cycle of tantalum targets from 5% to 88% at the power of 150 W and 50 W. The surface, microstructure, and texture of sputtered tantalum films were measured by scanning electron microscopy (SEM), atomic force microscope (AFM) and X-ray diffraction spectroscopy (XRD). The hardness and resistivity were measured by nanoindentation and a four-point probe. The results reveal that the impulse power and voltage of the Ta target were increased because of the lower duty cycle. The higher the ion energy, resulting in a more efficient atomic mobility, the texture phase of tantalum film gradually changes from β-Ta-dominated to α-Ta-dominated, hardness and resistivity shift from β-Ta to the α-Ta property with the decreasing duty cycle. By adjusting the duty cycle and controlling the power, the texture transformation of tantalum film occurs. Different from the previously complicated transformation process, the tantalum thin film structure with high density and high quality deposited using this approach provides a broader range of applications.

Synthesis and characterization of Ta–B–C coatings prepared by DCMS and HiPIMS co-sputtering

This study reports on the deposition and properties of Ta–B–C coatings by the co-sputtering of tantalum, boron carbide, and graphite targets using High Power Impulse Magnetron Sputtering (HiPIMS). It was possible to affect the microstructure of the deposited coatings by altering the deposition temperature or by the application of RF induced self-bias on the substrates without changing their chemical composition. The only identified crystalline phase from the Ta–B–C system present was TaC. The boron content in the coatings shows that the TaC crystallite size can be changed by a factor of 10 by changing the power to the boron carbide target. Mechanical properties of the coatings measured directly after the synthesis yield hardness higher than 40 GPa. After the relaxation of internal stress in the coatings (after one year) and changes in the structure, the hardness of all coatings was close to 36 GPa. According to ab initio calculations, the B incorporation in the fcc lattice of TaC in combination with C vacancies lead to lower (higher) shear-to-bulk modulus ratio (Poisson’s ratio), providing a good basis for improved ductility. All in all, Ta–B–C system shows a good potential as a novel hard protective coating.

Expected yields ofTa181(e,e′)Ta*181in the multi-keV range with a plasma-cathode electron beam

Calculations of the cross sections of inelastic electron scattering $(e,e')$ on a nucleus in the multi-keV energy range strongly depend on the description of the screening of the nuclear Coulomb potential as well as on the deformation of the wave functions of the incoming and outgoing electron in the vicinity of the nucleus. These cross sections are evaluated at values lower than $10^{-30}$ cm$^2$ which vary by several orders of magnitude according to the models. Experimental measurements would be required to constrain the models but it is a real challenge to measure such low cross sections. In this study, we demonstrate that inelastic electron scattering is the main nuclear excitation mechanism in a $^{181}$Ta target irradiated with a new intense 10 - 30 keV electron beam produced with a biased laser-plasma. Calculations show that through the detection of conversion electrons, it should be possible to measure the nuclear excitation yields. The effect of electron beam heating and of plasma deposition on the tantalum target are quantified, thus allowing the dimensioning of a possible experimental configuration to study $(e,e')$ processes in this range of energy for the first time.