Penetration Of Deuterium Research Articles

Crystallographic and temperature effects in low-energy collisions for plasma–material interactions

The interaction of plasma with materials is critical for the fundamental understanding of non-equilibrium processes and their wide application. Recent achievements in fusion energy research emphasize the importance of this problem. Because modelling and predicting plasma–material interactions (PMI) require considering a tremendous number of single plasma particle–surface interaction events, this type of modelling was, until recently, possible only within a binary collision approximation (BCA). The BCA approach considers materials as uniform temperature-insensitive media. The research presented here addresses the PMI problem within an atomistic-based approach for the first time at a statistically significant level. Approximately 105 molecular dynamics trajectories were generated for 100 eV deuterium ions interacting with a tungsten surface. The research demonstrated the critical importance of incorporating the discrete lattice structure of matter into the model. Deuterium penetration depth and fraction of backscattered deuterium ions strongly depend on the surface orientation, the impact incident ion directions, and the ions’ initial positions. On average, the BCA-based calculations underestimate the penetration depth by a factor of two or more, and the fraction of backscattered atoms is overestimated by a factor of two or more. Furthermore, increasing the material temperature from 500 to 3000 K reduces penetration depth by about 30% and increases the fraction of backscattered atoms by 250%.

Penetration of deuterium into neutron-irradiated tungsten under plasma exposure

Hydrogen isotope trapping at lattice defects in neutron-irradiated tungsten (W), a leading candidate as plasma facing material, is an important problem determining tritium (T) inventory in a vacuum vessel of a future fusion reactor. In this study, W samples were irradiated with neutrons in the Belgium Reactor 2 at 563 K to 0.06 or 0.016 displacement per atom (dpa). After characterizing defects by positron lifetime measurements, deuterium (D) penetration under exposure to D plasma was examined at 563–773 K. Positron lifetime showed the presence of dislocations, monovacancies and relatively large vacancy clusters. These defects trapped D atoms with different values of binding energy. Dependence of D retention on plasma exposure temperature and damage level indicated that the concentrations of weak traps with smaller binding energy increased more significantly with damage level than those of strong traps.

Multiple-isotope pellet cycles captured by turbulent transport modelling in the JET tokamak

For the first time the pellet cycle of a multiple-isotope plasma is successfully reproduced with reduced turbulent transport modelling, within an integrated simulation framework. Future nuclear fusion reactors are likely to be fuelled by cryogenic pellet injection, due to higher penetration and faster response times. Accurate pellet cycle modelling is crucial to assess fuelling efficiency and burn control. In recent Joint European Torus tokamak experiments, deuterium pellets with reactor-relevant deposition characteristics were injected into a pure hydrogen plasma. Measurements of the isotope ratio profile inferred a deuterium penetration time comparable to the energy confinement time. The modelling successfully reproduces the plasma thermodynamic profiles and the fast deuterium penetration timescale. The predictions of the reduced turbulence model QuaLiKiz in the presence of a negative density gradient following pellet deposition are compared with GENE linear and nonlinear higher fidelity modelling. The results are encouraging with regard to reactor fuelling capability and burn control.

The study of deuterium permeability of film-forming inhibitors with the addition of fullerenes

In this work, the results of the hydrogen permeability study of a composite film-forming inhibitor are considered. Film-forming inhibitor consists of polyether urethane and synthesized fullerenes C60 and C70 in pure form. Two types of samples were used: uncoated and coated stainless steels with composite polyether urethane/fullerene varnish. The experimental work was based on the study of the dependence of the permeation reduction factor on the temperature in the reactor. For the coated sample, the minimum temperature was 623 K at which the deuterium flux was registered. Here we assume that at temperatures below 573 K the output pressure caused by the deuterium flow through the sample is less than 10−10 Pa. The rate of steady-state flow through a coated sample is significantly lower than for an uncoated one at temperatures 573–673 K. The deuterium penetration rates through the two samples increase and reach similar stationary values starting at 723 K.

Temporal Evolution of Corrosion Film Nano-Porosity and Magnesium Alloy Hydrogen Penetration in NaCl Solution

Exposures of 0.5, 1, 4, 8, and 24 h were conducted for Mg-3Al-1Zn (AZ31B) and Mg-1.5Zn-0.3Zr-<0.5Nd (ZE10A, ZEK100 type) alloys in D2O with 5 weight% (wt%) NaCl. Multiple techniques including small angle neutron scattering (SANS) and scanning transmission electron microscopy (STEM) were used to follow the growth of nano-porous oxide-hydroxide corrosion films. On the same samples, time of flight mass spectrometry (ToF SIMS) was used to study the penetration of deuterium into the alloys in advance of the films. The SANS scattering invariants, which are proportional to the number of nanoscale features, increased approximately linearly with time for both alloys. Analysis with the polydisperse hard sphere model for fractal systems suggests that the nano-porous structures grew at all length scales assessed, but that the size distribution did not change significantly with reaction time, i.e., the film thickness increased while the nano-porosity structures remained essentially constant. Extensive penetration of deuterium into the underlying alloy was observed by ToF-SIMS for ZE10A, but not AZ31B despite similar corrosion film growth behavior. The depth profiles suggest an alloy diffusion-controlled deuterium penetration over time, which is of similar extent to that previously observed in water without NaCl. Implications for the corrosion mechanism(s) are discussed.

Modeling of H/D isotope-exchange in crystalline beryllium

Abstract A reaction-diffusion model with surface occupation dependent desorption [D. Matveev et al., Nucl. Instr. Meth. B 430 (2018) 23–30] has been updated to handle multiple hydrogen species to simulate hydrogen/deuterium isotope-exchange experiments performed on polycrystalline beryllium samples under ultra-high vacuum laboratory conditions. In the experiments subsequent exposures of a sample to hydrogen and deuterium ion beams in direct and reverse implantation order were followed by thermal desorption spectroscopy measurements under a constant heating rate of 0.7 K/s. The recorded signals of masses 2 to 4 (H2, HD and D2) indicate that the second implanted isotope dominates clearly the low temperature release stage ( ≈ 450 K), while both isotopes show a comparable contribution to the high temperature desorption stage ( ≈ 700 K) with only minor effect of the implantation order attributed to a slightly deeper penetration of deuterium compared to hydrogen. Simulations of the implantation and subsequent thermal desorption of hydrogen isotopes are performed to assess the atomic processes behind the isotope-exchange. Simulations were performed under the assumption that the low temperature release stage is attributed to hydrogen/deuterium atoms retained on effective open surfaces (e.g. interconnected porosity) represented in the simulations by a surface with an effective surface area exceeding the nominal exposed surface area by a factor up to 100. Kinetic de-trapping from vacancies with multiple trapping levels and enhanced desorption at surface coverages close to saturation are addressed in the model as possible mechanisms promoting the isotope-exchange. Simulation results suggest the applicability of the model to describe isotope-exchange processes in crystalline beryllium and give a qualitative explanation of the observed experimental facts.

Estimation and Mode Selection of Deuterium Flux Supply into Ampoule Device Through Diffusion Filter in Experiments with Pb15.7Li Eutectic at the IVG1.M Reactor

One of the most promising materials to produce tritium in fuel cycle of fusion facilities is the lead-lithium eutectic Pb15.7Li. Tritium will be generated in nuclear reactions in a lithium-containing material under the influence of neutron irradiation. However, nowadays a limited number of studies have been conducted with the eutectic of such a composition (with a lithium content of 15.7%) and consequently, there is a lack of data on mechanisms of tritium generation and release from Pb15.7Li. In this regard, there is an urgent necessity for research of tritium generation and release from Pb15.7 Li directly under neutron irradiation conditions. For these studies a differential method will be used, which consists in follows: a controlled flux of spectrally pure deuterium will be continuously fed into the experimental cell with the eutectic sample during the reactor experiment. The regulated flux of deuterium will be fed to the experimental cell with the Pb15.7Li sample using diffusion palladium-silver filter. The article describes the process of determination of deuterium flux supply modes into the experimental cell. The temperature dependences of deuterium penetration through diffusion palladium-silver filter are presented. The coefficients of diffusion, solubility and permeability of deuterium through a palladium-silver filter are estimated and the activation energies of these processes as well as the Arrhenius dependence are presented.

Mitigated blistering and deuterium retention in tungsten exposed to high-flux deuterium–neon mixed plasmas

Surface morphology and deuterium retention in tungsten exposed at surface temperature of ~550 K to mixed deuterium–neon plasmas of different neon concentrations are investigated. It is found that the addition of neon up to 20% mitigates blistering on the surface. Cross-section view of the surface shows the formation of pores near the surface in the depth less than 100 nm. Deuterium depth profile is featured by an enhanced deuterium concentration within a depth of 16 nm but a mitigated penetration in depth larger than 1 µm. Deuterium retention is reduced by up to a factor of four. It is suggested the open pores formed in the surface serves as an escaping channel, mitigates deuterium penetration towards bulk and retention in the bulk.

Interaction of atomic and low-energy deuterium with tungsten pre-irradiated with self-ions

Polycrystalline tungsten (W) specimens were pre-irradiated with self-ions to create identical samples with high density of defects up to ∼2.5 μm near the surface. Then, W specimens were exposed to either thermal atomic deuterium (D) beam with an incident energy of ∼0.2 eV or low energy D plasma with the incident energy varied between 5 and 200 eV at different sample temperatures. Each sample was exposed once at certain temperature and fluence. The D migration and accumulation in W were studied post-mortem by nuclear reaction method. It was shown that the rate of the D to occupy radiation-induced defects increases with increasing the incident energy, ion flux, and temperature. Experimental investigation was accompanied by modelling using the rate-equation model. Moreover, the analytical model was developed and benchmarked against numerical model. The calculations of the deuterium diffusion with trapping at radiation-induced defects in tungsten by analytical model are consistent with numerical calculations using rate-equation model. The data of reflection and penetration of atomic and low-energy D were taking from calculations using molecular dynamics (MD) with Juslin interatomic potentials and a binary collision code TRIM. MD calculations show an agreement with a binary collision code TRIM only in a very narrow range of deuterium energies between 1 and 20 eV. Incorporation of the data of reflection and penetration of deuterium in the macroscopic modelling has been done to verify the range of validity of calculations using MD and binary collision code TRIM by comparison of modelling results with experimental data. Modelling results are consistent with experiments using reflection and penetration data of D obtained from TRIM code for incident ion energy above 1 eV. Otherwise, the parameters obtained from MD should be incorporated in the rate-equation model to have a good agreement with the experiments.

Strongly Reduced Penetration of Atomic Deuterium in Radiation-Damaged Tungsten

Radiation-damaged tungsten is exposed to high-flux, low-energy deuterium plasmas at self-bias conditions. We observe that the fraction of deuterium that penetrates is only 10(-5)-10(-7) of the plasma flux and strongly dependent on the local surface temperature. We propose that deuterium does not directly penetrate bulk tungsten but that it thermalizes at the surface, where it forms a protective chemisorbed layer. We find an energy barrier of 1-2 eV between the surface and bulk, causing the influx of deuterium to be low as compared to the number of defects and leading to slow filling of the damaged layer.

Preparation and characterization of enamel coating on pure titanium as a hydrogen penetration barrier

The enamel coating with a thickness of 90–110×10−6m was prepared on TA1 substrate by spin-coating and enameling to solve the problems of hydrogen isotope penetration for commercial pure titanium TA1. The microstructure and the interfacial morphology of the samples were characterized respectively by X-ray diffraction, optical and scanning electron microscopy. The profiles of main elements at the interface were analyzed by EDS line-scanning. The experimental results indicated that the dense enamel coatings were chemically bonded with TA1 substrate, and possessed better thermal shock resistance and ball-dropping impact properties. It was concluded from the results of hydrogen charging test with Vickers microhardness measurement and deuterium penetration experiments that the as-prepared dense enamel coating exhibited a good barrier effect to hydrogen isotope penetration.

Hydrogen Absorption into Titanium under Cathodic Polarization: An In-Situ Neutron Reflectometry and EIS Study

Hydrogen (deuterium) absorption into sputter-coated titanium (Ti) film electrodes during cathodic polarization in heavy water (D2O) was monitored using in-situ neutron reflectometry (NR) and electrochemical impedance spectroscopy (EIS). The scattering length density (SLD) of Ti metal increased with increasing cathodic polarization, due to the penetration of deuterium through the surface oxide and into the underlying metal. The rate of D absorption estimated from the NR data showed a pattern with four distinctive regions separated by potential boundaries between −0.35 and −0.4 VSCE and around ∼−0.6 VSCE. EIS results support division of the behavior into these potential ranges. Hydrogen absorption by Ti was observed at potentials <∼−0.35 VSCE, where the capacitance and resistance of the TiO2 layer dramatically changed. At this point, the D content of the film quickly achieved a level of ∼900 ppm by weight (atom ratio D:Ti ∼ 0.04). Decreased absorption kinetics were observed over the potential region from ∼−0.40 VSCE to −0.6 VSCE, indicating that D absorption was controlled either by a diffusion process through the TiO2 layer or by the formation of blocking hydrides at the Ti/TiO2 interface, at the base of the defective locations in the oxide through which the hydrogen was entering. Significant increases in the current density and SLD of the Ti film at potentials more negative than −0.6 VSCE were assigned to widespread hydrogen absorption and TiHx growth within the metal. These observations are consistent with hydrogen ingress through the oxide film, probably via weak points containing electronic defects and disorder, such as grain boundaries and triple points, at potentials as mild as ∼−0.4 VSCE, and with hydrogen penetration through continuous, intact oxide via the previously published redox transformation mechanism, at potentials more negative than −0.6 VSCE.

Anomalously deep penetration of hydrogen and deuterium in assemblies from Nb foils and deuterated polyethylene (CD2) n under the pulse high temperature hydrogen plasma

Studies of the storage and redistribution of hydrogen atoms under pulse high temperature hydrogen plasma that was obtained using a PF-4 Plasma Focus facility in a multilayered structure (sandwich) which consists of two high-purity niobium foils and a deuterium polyethylene film pressed between them have been carried out using the method for elastic recoil detection (ERD). It was established that, with an increase in pulses of the PF-4 facility, the redistribution of implanted hydrogen atoms for large depths occurs in the two Nb foils and deuterated polyethylene. The depths substantially exceed the projective range of paths of hydrogen ions (at their maximum velocity of ∼108 cm/s). A maximum hydrogen concentration of 45 at % is reached in the nearest surface of the second Nb foil to the PF-4 at 20 pulses of hydrogen plasma. An X-ray diffraction analysis showed the presence of a niobium hydride phase in both Nb foils. The redistribution of deuterium atoms from the bound state of deuterated polyethylene into the near-surface layer and the bulk material of the second Nb foil was detected as well. This phenomenon can be attributed to the transfer of implanted hydrogen atoms through the foil assembly and the transfer of deuterium from deuterated polyethylene into the near-surface layer of the second foil under the effect of powerful shock waves that are created by pulse hydrogen plasma and by acceleration in the diffusion of hydrogen and deuterium in the strain field induced by the shock wave.

Superdeep hydrogen and deuterium penetration into metals upon exposure to high-temperature hydrogen and deuterium plasma

Superdeep hydrogen and deuterium penetration into metals upon exposure to high-temperature hydrogen and deuterium plasma

Penetration of Hydrogen and Deuterium into Si and Hydrogen States in Si

We review recent works on 1) an isotope effect of penetration of Hydrogen(H) and Deuterium(D) into Silicon through Si/SiO2 interface and 2) H effects for Si nanostructures, as well as summary of hydrogen states in crystal Si. In particular, a new filtering effect of H and D isotope atoms was found for penetration process into crystal silicon (Si) through the interface between a Si and SiO2 native oxide layer. More H atoms are introduced into Si than D for mixing gases. This phenomenon can be tentatively explained in terms of an isotope filtering model of H and D via an intermediate cluster state formed at the interface between the native SiO2 layer and crystal Si. Hydrogen passivation of interface defects is shown to be needed for knowing proper impurity doping effects, and electronic, optical, and magnetic properties in Si nanostructures.

Isotope Effect of Penetration of Hydrogen and Deuterium into Silicon through Si/SiO2 Interface

We found a new filtering effect of hydrogen (H) and deuterium (D) isotope atoms for penetration process into crystal silicon (Si) through the interface between a Si and SiO2 native oxide layer. More H atoms are introduced into Si than D for mixing gases. It was determined from H and D mixed-atom treatment of Si wafer with the native oxide and the systematic measurements of Raman scattering of hydrogen molecules (H2, HD, or D2) and secondary ion mass spectrometry. This phenomenon can be tentatively explained in terms of an isotope filtering model of H and D via an intermediate cluster state formed at the interface between the native SiO2 layer and crystal Si.

Changes of internal properties of vanadium and structure of its surface under the effect of pulsed high-temperature deuterium plasma

The work presents experimental research of the influence of a pulse of high-temperature dense plasma on materials, which as are supposed, will be used in future thermonuclear power stations. The experiments were made on 4 kJ Plasma Focus installation. Such type of installations is capable to form pulse of axial plasma flows moving with velocity approximately 108 cm/s and plasma density is about 1018 cm−3. Pure vanadium was chosen in our researches, because it can be used as a basic element at the creation of low-activated alloys. We found that due to a pulse irradiation of vanadium by deuterium plasma, shock waves arises, which result in super-deep penetration of deuterium into a volume of the studied sample. This process is accompanied with the change of vanadium structure, the occurrence of pores in it, and changes of its mechanical properties. The break-away of vanadium particles from the backside surface of the sample and forming of craters were also observed.

Comparison of CW-EPR and ESEEM technique for determination of water permeability profile in liposome membranes

The hydrophobicity profile across a membrane is an important parameter of biological membranes as it defines the barrier for permeation of polar molecules into the cell interior and of the stability of transmembrane proteins. In this work, the hydrophobicity profile was measured by conventional continuos-wave electron paramagnetic resonance (CW-EPR) and by electron spin echo envelope modulation (ESEEM) in two liposome suspensions with different ionic strengths in order to compare the sensitivity of both methods for the determination of the water penetration depth into the liposome membrane. Multilamellar liposomes from egg-phosphatidylcholine, cholesterol and dicetyl phosphate were prepared in deuterium oxide, buffered with phosphate buffer with or without NaCl at the phosphate concentrations 0.1 or 0.01 M. Liposomes were spin labeled with stearic acids spin probes with the nitroxide group at different positions on the acyl chain. The deuterium penetration depth was measured by the ESEEM technique and the signal was analyzed in the frequency domain (Fourier transform [FT]-ESEEM). The ratio of the intensities of FT-ESEEM lines at deuterium and hydrogen Larmor frequencies was used as a measures of the water penetration depth. It was also indirectly determined from the hyperfine splitting constants in frozen and in fluid state, measured by CW-EPR, as they depend on the polarity of the nitroxide group environment. The comparison of the two techniques demonstrated that FT-ESEEM is more sensitive to the changes on the surface of the membrane and thus more appropriate for the determination of the hydrophobic barrier than the conventional CW-EPR method.

Palladium isotope separation under high mechanical stresses induced in Pd foils upon loading with deuterium

The effects of a significant decrease in the sputtering rate and of the symmetrical separation of the isotope pairs 108Pd-105Pd and 110Pd-104Pd at depths up to 500 A are experimentally detected in Pd specimens saturated with deuterium during electrolysis (i.e., having a high concentration of internal stresses). These effects are shown to be qualitatively explained using the concepts of isotope separation by centrifugation and diffusion with allowance for defects and mechanical stresses that appear in the near-surface Pd layer during deuterium penetration.

Preliminary results for the diffusion of water into fibre optic oil well sensors

Preliminary results are presented on a measurement technique for determination of water penetration into fibre optic sensors under high pressure, high temperature conditions. Both fibre optic sensors and communication fibres were subjected to prolonged treatment in heavy water at temperatures up to 250°C and pressures of 40 bar. Deuterium penetration is measured by a nuclear reaction technique based on a 3 He micro-focussed ion beam, which permits two-dimensional mapping of the deuterium penetration into cleaved fibres. Water penetration can be detected whilst still confined to the cladding, well before any optical effects become apparent, permitting prediction of likely fibre lifetime under down-hole conditions after realistic experimental times.