Heavy Impurities Research Articles

Complex-valued in-medium potential between heavy impurities in ultracold atoms

Complex-valued in-medium potential between heavy impurities in ultracold atoms

High-n Rydberg transition spectroscopy for heavy impurity transport studies in W7-X (invited).

Here, we present a novel spectroscopy approach to investigate impurity transport by analyzing line-radiation following high-n Rydberg transitions. While high-n Rydberg states of impurity ions are unlikely to be populated via impact excitation, they can be accessed by charge exchange (CX) reactions along the neutral beams in high-temperature plasmas. Hence, localized radiation of highly ionized impurities, free of passive contributions, can be observed at multiple wavelengths in the visible range. For the analysis and modeling of the observed Rydberg transitions, a technique for calculating effective emission coefficients is presented that can well reproduce the energy dependence seen in datasets available on the OPEN-ADAS database. By using the rate coefficients and comparing modeling results with the new high-n Rydberg CX measurements, impurity transport coefficients are determined with well-documented 2σ confidence intervals for the first time. This demonstrates that high-n Rydberg spectroscopy provides important constraints on the determination of impurity transport coefficients. By additionally considering Bolometer measurements, which provide constraints on the overall impurity emissivity and, therefore, impurity densities, error bars can be reduced even further.

Contaminants, biochemical methane potential, and biodegradability of different bio-waste categories: guidance for anaerobic digestion

This study evaluated the anaerobic digestion suitability of bio-waste from different sources by comparing their biochemical methane potential (BMP), biodegradability (BI), and content of contaminants (heavy metals and physical impurities) − an often-overlooked factor but one of particular concern in bio-waste. Predominant heavy metals included Cu and Zn, while recurring physical impurities comprised plastics and organic non-biodegradable matter. Food waste from food processing plants were most suitable, exhibiting low contamination and high biogas conversion (BMP > 549 NmLCH4/gVS and BI > 86 %). Conversely, organic fractions from mechanical biological treatment were highly contaminated, while green waste displayed low biogas conversion (BMP < 368 NmLCH4/gVS and BI < 72 %). Food waste from households and medium/large-sized producers also demonstrated high biogas conversion, but variable contamination levels could compromise their suitability. Assessing contaminants alongside BMP and BI provides a comprehensive approach for selecting suitable bio-waste feedstocks that can be introduced in biogas plants.

Thermometry with a dissipative heavy impurity

Improving the measurement precision of low temperature is significant in fundamental science and advanced quantum technology application. However, the measurement precision of temperature T usually diverges as T tends to zero. Here, by utilizing a heavy impurity to measure the temperature of a Bose gas, we obtain the Landau bound to precision δ2T∝T2 to avoid the divergence. When the initial momentum of the heavy impurity is close to be fixed and nonzero, the measurement precision can be δ2T∝T3 to break the Landau bound. We derive the momentum distribution of the heavy impurity at any moment and obtain the optimal measurement precision of the temperature by calculating the Fisher information. As a result, we find that increasing the expectation value P0 and reducing the variance Δ/2 of the initial momentum can help to improve the measurement precision. Moreover, under certain conditions, Δ/P0 is a relevant parameter, the smallness of which helps improve the thermometric precision of the probe. In addition, the momentum measurement is the optimal measurement of the temperature in the case that the initial momentum is close to be fixed and not equal to zero. The kinetic energy measurement is the optimal measurement in the case that the expectation value of the initial momentum is close to zero. Finally, we obtain that the temperatures of two Bose gases can be measured simultaneously. The simultaneous measurement precision is proportional to T2 when two temperatures are close to T. Published by the American Physical Society 2024

Impurity transport study based on measurement of visible wavelength high-n charge exchange transitions at W7-X

A recently installed high-speed charge exchange diagnostic at the W7-X stellarator has been used to identify several high-n Rydberg emission lines near 500 nm following impurity injections. The wavelengths of observed high-n Rydberg transitions are independent of the impurity species and originate from ions with ionization states ranging from 14+ to 45+ suggesting that this approach can be applied to a variety of heavy impurities. Moreover, little to no passive signal is observed since the high-n energy levels are unlikely to be populated by electron impact excitation. The combination of the newly developed diagnostic and the observation of high-n Rydberg states provides spatially resolved, high-speed measurements of multiple charge states which are analyzed in a Bayesian inference framework to determine both impurity diffusion and convection profiles. Measurements from the 2023 experimental campaign conclusively show high diffusion and an inward pinch in the core, well above predictions by neoclassical theory.

First observation of edge impurity behavior with n = 1 RMP application in EAST L-mode plasma

High-Z impurity accumulation suppression and mitigation in core plasma is frequently observed in EAST edge localized mode mitigation experiments by using resonant magnetic perturbations (RMP) coils. To study the individual effects of the RMP field on impurity transport, based on high-performance extreme ultraviolet impurity spectroscopic diagnostics, the effect of the n = 1 (n is the toroidal mode number) RMP field on the behavior of intrinsic impurity ions at the plasma edge, e.g. He+, Li2+, C2+–C5+, O5+, Fe8+, Fe15+, Fe17+, Fe22+, Cu17+, Mo12+, Mo13+ and W27+, is analyzed for the first time in L-mode discharges. Based on the evaluation of the location of these impurity ions, it is found that with the increase in RMP current (I RMP), an impurity screening layer inside the last closed flux surface is formed, e.g. at ρ = 0.74–0.96, which is also the region that the RMP field affects. Outside this screening layer, the impurity ion flux of He+, Li2+, C2+, C3+, O5+, Fe8+, Mo12+ and Mo13+ ions increases gradually, while inside this screening layer, the impurity ion flux of C4+, C5+, Cu17+, W27+, Fe15+, Fe17+ and Fe22+ ions decreases gradually. When I RMP is higher than a threshold value, RMP field penetration occurs, accompanied with m/n = 2/1 mode locking, and the position of this screening layer moves to the plasma core region, i.e. ρ = 0.66–0.76, close to the q = 2 surface, and the opposite behavior of the impurity ion flux at two sides of the screening layer is strengthened dramatically. As a result, significant decontamination effects in the plasma core region, indicated by the factor of ((Γ Imp Z+)w/o–(Γ Imp Z+))/(Γ Imp Z+)w/o (where (Γ Imp Z+)/(Γ Imp Z+)w/o denotes the impurity ion flux ratio with and without RMP), is observed, i.e. 30%–60% for heavy impurity (Fe, Cu, Mo, W), and ∼27% for light impurity of C. In addition, the analysis of the decontamination effects of C and Fe impurities under four different RMP phase configurations shows that it may be related to the strength of the response of the plasma to RMP. These results enhance the understanding of impurity accumulation suppression by the n = 1 RMP field and demonstrate a candidate approach using RMP coils for W control in magnetic confinement devices.

Fabrication of 208Pb and 193Ir targets on Al-backing using high/ultra-high vacuum deposition technique for low-energy nuclear reaction experiments

Aiming to study the interplay of different nuclear reactions at low incident energies, thin targets of enriched stable isotopes, 208Pb and 193Ir, have been fabricated at the target development laboratory of the Inter-University Accelerator Centre (IUAC), New Delhi. As a means of preparing a large number of thin isotopically pure targets, physical vapour deposition techniques, (a) resistive heating, for fabrication of 208Pb targets of mass thickness 160-340μg/cm2, and (b) electron-gun evaporation technique, for fabrication of 193Ir targets of mass thickness 17-60μg/cm2, have been employed. The fabricated targets were characterized using Rutherford Backscattering Spectrometry (RBS) and Field Emission Scanning Electron Microscopy (FE–SEM). The thickness of targets was estimated based on the evaporation rate and measured by RBS. The RBS was employed to analyse the samples for trace- and heavy impurities, provided the measurements and analysis suggest that the targets prepared in the present work do not contain any impurities. FE-SEM was employed to examine the surface morphology and microstructure in high resolution. This technique enables the detection of any morphological changes induced by the irradiation process, offering insights into the effects of irradiation on the target films. The targets have been successfully deployed to measure complete and incomplete fusion excitation functions, mass distribution of fission fragments, and forward ranges of target-like recoils in 12C + 208Pb, 193Ir reactions from sub- to above barrier energies. Preliminary data analysis suggests the achievement of high-quality 208Pb and 193Ir target foils.

Концентрационная конвекция в замкнутой области пористой среды при заданном вертикальном перепаде концентрации и учете иммобилизации примеси

This work is devoted to the study of stability of horizontal filtration flow of a mixture through a closed porous domain taking into account impurity immobilization. The instability arises due to the vertical concentration difference of heavy impurities, which creates unstable density stratification. A general mathematical model describing the transport of an impurity through a porous medium is presented. The equations are simplified for the case of low impurity concentration. Simplification made it possible to analytically obtain the solution corresponding to homogeneous horizontal filtration and to study its stability. It is known that, in the narrow regions of porous medium and at weak intensities of the external flow, convection is excited in a monotonous manner. On the contrary, in the case of an infinite horizontal layer, oscillatory instability is observed. A study of the transition between the instability modes is presented. It is shown that the oscillatory regime is observed in long regions or at significant intensity of the external horizontal flow. At low flow intensities, convective cells do not move relative to the region and, hence, there is no reason for oscillations. It has been established that the range of flow intensity values, in which oscillations are observed, grows with increasing length of the domain. Impurity immobilization leads to the stabilization of horizontal filtration with respect to convective perturbations. Critical curves and stability maps are obtained in a wide range of problem parameters and then analyzed. For limiting cases, a comparison is made with the known results obtained for an infinite layer.

Simulation of neoclassical heavy impurity transport in ASDEX Upgrade with applied 3D magnetic fields using the nonlinear MHD code JOREK

Accumulation of heavy impurities in the tokamak core is detrimental for its performance and can lead to disruption of the plasma. In small to medium-sized tokamaks the effective neoclassical transport in the pedestal is typically oriented radially inward. In larger tokamaks—e.g., ITER—where the temperature gradient is higher and density gradients are lower due to the need to operate in a radiative divertor regime, the neoclassical transport is predicted to be outwards. The models are derived for axisymmetric quasi-steady-state plasmas. Applied 3D magnetic fields, i.e., Resonant Magnetic Perturbation (RMPs) as they are used to suppress Edge Localized Modes (ELMs), have experimentally been observed in AUG to enhance the outflow of heavy impurities in the pedestal. There is no model that can predict neoclassical heavy impurity transport in these ergodized 3D magnetic fields self-consistently. In this contribution, we present our kinetic tungsten transport simulation for an ASDEX Upgrade plasma with applied RMPs. Our model based on Hoelzl et al. [Nucl. Fusion 61, 065001 (2021)], van Vugt et al. [Phys. Plasmas 26, 042508 (2019)], and Korving et al. [Phys. Plasmas 30, 042509 (2023)] utilizes a full-orbit pusher, ionization, recombination, effective line, and continuum radiation and neoclassical collisions with the background plasma. The effective collisional radiative rates are from the OpenADAS database, the neoclassical collision operator uses the framework of Homma et al. [J. Comput. Phys. 250, 206–223 (2013)] and Homma et al. [Nucl. Fusion 56, 036009 (2016)]. We show that the adopted collision operator produces neoclassical transport within a satisfactory degree of accuracy. A sufficiently high RMP current causes an increase in tungsten diffusion in the pedestal by a factor of 2. We compare the average radial transport between axisymmetric and 3D RMP scenarios in the pedestal region. RMPs enhance the pedestal permeability for impurities, which results in enhanced transport. In addition to the enhanced transport, some of W is found to be trapped in 3D potential wells in the scrape-off layer. Due to the lack of suitable diagnostics for W in the pedestal, we investigate and suggest that argon can be an adequate substitute in experiments for model validation and further understanding impurity transport in scenarios with applied 3D magnetic fields. With the newly developed neutral model [Korving et al., Phys. Plasmas 30, 042509 (2023)], we can combine the interaction in the divertor with the 3D RMPs to model the tungsten transport from the divertor toward the core of the plasma.

Spectroscopic Analysis of Lipsticks for the Traces of Heavy Metals: A Comprehensive Review

Abstract: Heavy metal impurities are typically discovered in cosmetic products since they are abundant naturally. Lipstick's metal concentration has raised health concerns across the globe. This is so because applying cosmetics to the face always starts with lipstick. Since they are a potential source of daily, widespread, and frequently longterm exposure to a range of chemicals, the safety of cosmetic and personal care products has come under increased scrutiny in recent years. Hazardous heavy metals are included in cosmetics and other products in general, which can cause a multitude of health issues. Therefore, they ought to be kept to a minimum use wherever it is technically feasible. Analysing the levels of harmful heavy metals present in commercially available cosmetic products is important for reducing exposure to those substances. In this study, we investigated the levels of a few harmful heavy metals in lipsticks, such as lead, cadmium, nickel, arsenic, and chromium. For this purpose, we have studied around 50 research articles that explain the spectroscopic analysis of lipsticks for the traces of heavy metals. This article includes the determination of levels of these toxic heavy metals by Atomic Absorption Spectroscopy. Due to its hyphenated nature, low cost, quick analysis time, and reliable results, the atomic absorption spectroscopic (AAS) methodology is currently the one that is most frequently employed for metal ion detection despite the availability of a number of other methods.

Phonon vortices at heavy impurities in two-dimensional materials.

The advent of monochromated electron energy-loss spectroscopy has enabled atomic-resolution vibrational spectroscopy, which triggered interest in spatially localized or quasi-localized vibrational modes in materials. Here we report the discovery of phonon vortices at heavy impurities in two-dimensional materials. We use density-functional-theory calculations for two configurations of Si impurities in graphene, Si-C3 and Si-C4, to examine atom-projected phonon densities of states and display the atomic-displacement patterns for select modes that are dominated by impurity displacements. The vortices are driven by large displacements of the impurities, and reflect local symmetries. Similar vortices are found at phosphorus impurities in hexagonal boron nitride, suggesting that they may be a feature of heavy impurities in crystalline materials. Phonon vortices at defects are expected to play a role in thermal conductivity and other properties.

Atomic models for description of high-Z impurities dynamics in tokamak plasmas – summary of HARMONIA project

Since the year 2019, the project entitled „Study of the mutual dependence between Lower Hybrid current drive and heavy impurity transport in tokamak plasmas ”has been jointly executed by Polish (IFJ PAN) and French (CEA-IRFM) research teams. A particularly crucial topic studied within this project is the influence of not fully ionized high-Z impurities (e.g. tungsten ions) on suprathermal electrons dynamics. The influence can be studied using a Fokker-Planck solver. However, in this case, it is necessary to modify the electron-ion collision operator, in order to incorporate the efect of partially ionized high-Z atoms, arising from uncontrolled influxes of impurities. This, in turn, requires atomic models that are accurate enough but allow preforming fast and efficient calculations for all elements present in the plasma, regardless their local level of ionization. For this purpose, a few simple atomic models for elastic and inelastic collisions of electrons with high-Z ions have been proposed and implemented into a Fokker-Planck solver – LUKE code and DREAM (Disruption and Runaway Electron Analysis Model) code. Those semi-empirical atomic models have been calibrated and optimized using results of Density Functional Theory (DFT) calculations, Dirac-Fock-Slater (DFS) method, relativistic multiconfiguration Dirac-Hartree-Fock (MCDHF) method or available reference experimental data. This paper introduces to the achievement of the whole project, with a special emphasis placed on eforts to incorporate the physics of partially ionized high-Z elements in kinetic calculations.

Resistive drift wave turbulence and anomalous transport of multi-species plasma

Anomalous transport of multi-species plasma is considered with the generalized Hasegawa–Wakatani model. It is shown that the transport of all plasma species is described by fractional diffusion equations with the same effective diffusion coefficient. Strongly enhanced perturbations of heavy impurity density are found in long-living plasma flow vortices.

Zinc removal from metallurgical dusts with iron- and sulfur-oxidizing bacteria

The generation of currently partially recyclable metallurgical dusts during the steel production represents a challenge for the realization of a circular economy in this industrial sector. Due to a high iron concentration, the reutilization of blast furnace and cast house dusts in internal crude steel processes, is state of the art. However, heavy metal impurities such as zinc, act as an interference due to diverse negative effects. The aim of this study is to utilize Acidithiobacillus ferrooxidans, an iron- and sulfur-oxidizing bacteria, to solubilize zinc whilst retaining iron in the dust residue intended for reuse. To achieve this, the biooxidation of elemental sulfur is of crucial relevance. Two different strains of A. ferrooxidans (DSM 583 and CCM 4253) were cultivated and their leaching performances were compared to each other using a stirred tank reactor operated in a fed batch set-up, with a working volume of 3 L, at an operation temperature of 30 °C. The dust concentration was gradually increased until a maximum of 125 g/L, after which the reactors were left to run for three additional cycles to ensure replicability of results. For both strains, at a cast house dust concentration of 125 g/L paired with a leaching duration of two weeks, an average zinc removal of 56 % was achieved whereas solely an average of 4 % of iron was leached.

Interplay among turbulence, flow and impurities for sustaining magnetic island

As ubiquitous structures in magnetized fusion plasmas, magnetic islands (MIs) would short-circuit adjacent magnetic flux surfaces and result in a reduced pressure gradient and fluctuations inside the island; it is widely accepted that due to the stabilizing of drift wave instability, the turbulence intensity inside MIs is much lower for larger islands. Here, we provide the first observations that strong turbulence could be generated inside a large radiation MI, which is probably driven by the electron temperature dip due to strongly localized impurity radiation. Moreover, the flow velocity inside the MI is strongly correlated with the turbulence intensity, and the impurity concentration rate suddenly increases as the flow velocity reaches a threshold value, strongly suggesting that turbulence and flow inside the island play important roles in trapping heavy impurities and sustaining radiative MIs.

Dissipative Dynamics of a Heavy Impurity in a Bose Gas in the Strong Coupling Regime.

We study the motion of a heavy impurity in a one-dimensional Bose gas. The impurity experiences the friction force due to scattering off thermally excited quasiparticles. We present detailed analysis of an arbitrarily strong impurity-boson coupling in a wide range of temperatures within a microscopic theory. Focusing mostly on weakly interacting bosons, we derive an analytical result for the friction force and uncover new regimes of the impurity dynamics. Particularly interesting is the low-temperature T^{2} dependence of the friction force obtained for a strongly coupled impurity, which should be contrasted with the expected T^{4} scaling. This new regime applies to systems of bosons with an arbitrary repulsion strength. We finally study the evolution of the impurity with a given initial momentum. We evaluate analytically its nonstationary momentum distribution function. The impurity relaxation towards the equilibrium is a realization of the Ornstein-Uhlenbeck process in momentum space.

Thermoelectric properties of B-doped nanostructured bulk diamond with lowered thermal conductivity

Diamond exhibits high wear resistance and high chemical resistance. If diamond exhibits high thermoelectric performance, the thermoelectric application will be expanded for various situations such as the use of friction heat on turbines. However, bulk diamond exhibits low electrical conductivity and high thermal conductivity, leading to the low thermoelectric performance. In this study, to solve the above problem, we propose a strategy of heavy impurity doping in nanostructured bulk diamond which brings two things: (1) higher thermoelectric power factor, and (2) phonon scattering enhancement at impurities and nanostructure interfaces reducing the thermal conductivity drastically. We investigate the thermoelectric properties of heavily B-doped nanostructured bulk diamonds prepared by direct conversion sintering under ultra-high pressure and temperature using B-doped graphite as a starting material. This nanostructured bulk diamond exhibited high electrical conductivity due to heavy B doping, resulting in high power factor of 4 μWcm−1 K−2 at 1050 K. Furthermore, we found that this nanostructured bulk diamond exhibited drastic thermal conductivity reduction, resulting in quite low thermal conductivity among bulk diamond ever reported. This comes from phonon scattering both at nanostructure interfaces and by substitutional B atoms. From these results, the present study would be informative for expanding thermoelectric application to various situations such as the use of friction heat.

Chromium removal from chromium gypsum through microwave hydrothermal crystal phase regulation.

Chromium gypsum (CG) is a common hazardous waste formed in chromium salt or electroplating industries. The trapped or lattice-doped CrO42- in gypsum crystals are difficult to be reduced or removed by traditional methods, which will be re-oxidized or slowly released during long-term hypaethral storage. In this study, microwave hydrothermal treatment was applied to remove chromium in CG. Under optimal conditions (solid-liquid ratio of 1:5, 0.1M sulfuric acid as liquid media, and 110°C), over 99% of the chromium in CG can be removed within 10min. XRD spectra indicated that 59.8% gypsum was transformed to from dihydrate gypsum to hemihydrate gypsum. The toxicity leaching test shows that chromium in CG is 377.0mg/L before detoxification and 0.55mg/L after detoxification, which proves that chromium in CG lattice can be efficiently removed. This work enables to significantly advance the dehydration phase transformation process of gypsum and release the heavy metal impurities within it more quickly and provides new possibilities to treat similar solid waste containing gypsum or minerals with hydration water.

The toxicological assessment of hazardous elements (Pb, Cd and Hg) in low-cost jewelry for adults from Chinese E-commerce platforms: In situ analysis by portable X-ray fluorescence measurement

This article focusses on the environmental implications of low-cost jewelry for adults from Chinese e-commerce platforms ((n = 8) with heavy metal impurities (Pb, Cd and Hg) and their potential impact on human health and the environment. The study highlights the advantages of using portable X-ray fluorescence (pXRF) analysis for rapid, non-destructive, and in situ analysis of heavy metals in jewelry. The results reveal that all products (n = 106) contained heavy metals at varying levels, Hg being the most commonly detected heavy metal. The fact that 71% of the samples exceeded the EU limit for Pb and 51% exceeded the EU limit for Cd is alarming and highlights the need for stricter regulations and monitoring of the jewelry industry to mitigate the risks posed by heavy metals in the environment. The study emphasizes the importance of using pXRF analysis to identify heavy metals in jewelry and address the literature gap in environmental risk assessments of Pb, Cd, and Hg in low-cost jewelry for adults from China. In general, the findings call for urgent action to ensure the safety of consumers and prevent environmental pollution by strengthening regulations and monitoring the jewelry industry.

Implementation and verification of a model linearized multi-species collision operator in the COGENT code

We implement the multi-species linearized model collision operator, based on the approach proposed by Kolesnikov [1], in the full-f continuum gyrokinetic code COGENT [2]. We describe the operator and use it in several COGENT simulations of highly collisional plasmas. We analyze simulation results with the Braginskii fluid model [3] to illustrate that COGENT recovers both friction and thermal forces. Finally, we simulate the neoclassical transport of heavy impurities with COGENT and illustrate agreement with previously published [4] theoretical results.