Nuclear Reaction 1H Research Articles

Electron Screening in Nuclear Astrophysics

Electron screening in an important effect that cannot be neglected in nuclear astrophysics, since it influences nuclear reaction cross sections at low energies. We are trying to understand why most measurements in inverse kinematics on solid targets give electron screening potentials more than an order of magnitude above predictions. Below we report our latest results on electron screening in nuclear reactions 1H(14N,γ)15O and 2H(19F,ρ)2°F in both inverse and normal kinematics. The analysis is in progress.

Use of Radioactive Beams of 7Be Nuclei to Study the Wear Resistance of Materials

This work is devoted to the use of beams of radioactive nuclei for applied purposes – to study the wearresistance of materials used in different industries. The crux of the method is that the radioactive nuclei obtained in the nuclear reactions 1H(7Li, 7Be) and 1H(10B, 7Be) are implanted in the experimental sample. After implantation of the nuclei, the sample undergoes wear tests. The γ-radiation of the implanted nuclei is high-energy; the spectrum is comparatively simple and does not produce appreciable radiation damage in the test samples. The method has been successfully tested in determining the wear-resistance of machine parts and mechanisms.

Near-surface hydrogen depletion of diamond-like carbon films produced by direct ion deposition

Amorphous atomically flat diamond-like carbon (DLC) coatings were produced by direct ion deposition using a system based on a Penning ion source, butane precursor gas and post acceleration. Hydrogen depth profiles of the DLC coatings were measured with the 15N R-NRA method using the resonant nuclear reaction 1H(15N,αγ)12C (Eres=6.385MeV). The films produced at 3.0–10.5kV acceleration voltage show two main effects. First, compared to average elemental composition of the film, the near-surface region is hydrogen depleted. The increase of the hydrogen concentration by 3% from the near-surface region towards the bulk is attributed to a growth model which favours the formation of sp2 hybridised carbon rich films in the film formation zone. Secondly, the depth at which the maximum hydrogen concentration is measured increases with acceleration voltage and is proportional to the penetration depth of protons produced by the ion source from the precursor gas. The observed effects are explained by a deposition process that takes into account the contributions of ion species, hydrogen effusion and preferential displacement of atoms during direct ion deposition.

Site Change of Hydrogen Owing to Lattice Distortion in Niobium Alloys

The site occupancy of hydrogen in Nb alloyed with oversized Ta (atomic radius; \(r_{\text{Nb}}=1.43\) A and \(r_{\text{Ta}}=1.44\) A), Nb0.50Ta0.50H0.021 and Nb0.50Ta0.50H0.053, has been investigated at room temperature by the channelling method utilizing a nuclear reaction 1H(11B,α)αα with a 11B beam of an energy of 2.02 MeV. It was observed that, in both specimens, approximately 100% of H atoms are located at tetrahedral (\(T\)) sites. The half-widths of X-ray reflection lines have been measured for the non-hydrogen-doped Nb0.50Ta0.50 specimens. The half-widths for the Nb0.50Ta0.50 specimens are smaller than those for Nb alloyed with approximately the same concentration of undersized Mo atoms (\(r_{\text{Mo}}=1.36\) A), Nb0.52Mo0.48, and close to the value for pure Nb. This result indicates that, in the Nb0.50Ta0.50 specimens, the lattice is undistorted or very weakly distorted as compared with the Nb0.52Mo0.48 specimens. From the present results on the half-widths and the site occupancy of hydrogen in ...

The new 6 MV AMS-facility DREAMS at Dresden

A new 6MV electrostatic tandem accelerator has been put into operation at Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The system is equipped for accelerator mass spectrometry and opens a new research field at HZDR and the Helmholtz Association. It will be also used for ion beam analysis as well as for material modification via high-energy ion implantation. The research activity at the DREsden Accelerator Mass Spectrometry facility (DREAMS) based on a 6MV Tandetron is primarily dedicated to the long-lived radioisotopes of 10Be, 26Al, 36Cl, 41Ca, and 129I.DREAMS background levels have been found to be at 4.5×10−16 for 10Be/9Be, 8×10−16 for 26Al/27Al, 3×10−15 for 36Cl/35Cl and 8×10−15 for 41Ca/40Ca, respectively. The observed background of 2×10−13 for 129I/127I originates from intrinsic 129I from AgI produced from commercial KI. The introduction of quality assurance approaches for AMS, such as the use of traceable calibration materials and taking part in interlaboratory comparisons, guarantees high accuracy data for future DREAMS users.During first experiments an energy calibration of the accelerator has been carried out using the nuclear reaction 1H(15N,γα)12C yielding an energy correction factor of 1.019.

Atomistic State of Hydrogen Trapped by Vacancies and Formation of H-associated Vacancy Clusters in Nb as Observed by the Channelling Method

In order to study hydrogen-defect interactions, the effects of ion irradiation and annealing on the lattice location of hydrogen dissolved in Nb, NbH0.023, have been investigated at room temperature by the channelling method utilizing a nuclear reaction 1H(11B,α)αα with a 2 MeV 11B+ beam. By irradiation at room temperature with a dose of about 1.4 × 1016/cm2 of about 2 MeV 11B ions, the lattice location changes from the original tetrahedral (T) site (T-1 state) to the Ttr site, which is displaced from a T site by 0.45–0.55 A towards its nearest neighbour lattice point. The Ttr-site occupancy remains the same even for an approximately three times higher irradiation dose. On subsequent annealing at 523 K for 1 h, the site occupancy changes to the occupancy of (55–70)% of H atoms at T sites (T-2 state) and (30–45)% of them at random (R) sites. By additional irradiation with a dose of about 1.4 × 1016/cm2 at room temperature subsequent to the annealing, the site occupancy changes to the occupancy of (35–50)% at T + (50–65)% at R or (30–40)% at T + (10–20)% at Ttr + (50–60)% at R. It is concluded that the irradiation-induced site change to the Ttr site is a result of the trapping of hydrogen by monovacancies, i.e., the formation of H-vac. complex-1. Most of the H atoms in the T-2 state are not free hydrogen, but associated with more vacancies, for which hydrogen located at a T site in a tetrahedron consisting of four vacancies (tetravacancy), i.e., H-4vac. complex-2, is proposed. The R-site occupancy corresponds to hydrogen in a H-associated larger vacancy cluster complex-3. It is demonstrated that the complex-1 does not act as a nucleus, whereas the complex-2 acts as a nucleus for the growth to the H-associated larger vacancy cluster complex-3 by trapping more irradiation-introduced vacancies at room temperature.

Development of micro-beam NRA for 3D-mapping of hydrogen distribution in solids: Application of tapered glass capillary to 6 MeV 15N ion

A micro-beam NRA system, by means of a resonant nuclear reaction 1H(15N, αγ)12C, has been developed for the purpose of the 3D mapping of the hydrogen distribution in solids. To obtain the tens μm size of the beam spot, the combination of the newly proposed tapered glass capillary and a conventional quadrupole magnetic lens is employed. An Y patterned film on a substrate is prepared as an application of the developed system. The 6MeV 15N beam focused by glass capillaries down to 50μm successfully shows the hydrogen distribution. The in-plane NRA profile implies that the beam emitted from the glass capillary outlet is parallel, although the original beam has a considerable divergence. The NRA measurements in the 103Pa N2 atmosphere due to the low gas conductance of the glass capillary is also demonstrated.

Lattice location of hydrogen in β 1-V 2H (tetragonal)

In order to investigate the lattice location of hydrogen and its density distribution in a β 1-V 2H crystal with a tetragonal structure, channelling experiment has been performed at room temperature utilizing a nuclear reaction 1H( 11B, α)αα with a 11B beam of about 2 MeV. It has been demonstrated that hydrogen occupies an O z site, and the density distribution of hydrogen is anisotropic; the HWHM of the density distribution is about 0.35 Å in the [1 0 0] direction, while it is less than 0.2 Å in the [0 0 1] direction on the assumption of the Gaussian distribution.

Detection of hydrogen in hidden and spalled layers of turbine blade coatings

Gas turbine blades are covered with an outer ceramic top coat and an inner metallic bond coat, namely a thermal barrier coating system (TBC). The stability of the TBC is strongly influenced by the thermally growing oxide (TGO) which forms between the top and bond coat during turbine operation. This work is focused on the role of hydrogen in the adhesion of the top coat after oxidation at 1100°C in dry and wet air at various time steps between 75 and 1150h. To obtain the essential hydrogen information from the TGO the nuclear reaction 1H(15N, αγ)12C is used with a unique scattering chamber (SDIBA). This equipment combines the defined exfoliation of the top coat by using a 4-points bending mechanism followed by IBA. This allows the determination of hydrogen concentration depth profiles at the TGO and first results are presented.

Hydrogen analysis of BCN films with resonant nuclear reactions

Hydrogen is one of typical contaminants in carbon-based films. It can strongly influence the mechanical, physical and chemical properties of the films. The analysis of hydrogen is therefore a crucial problem in the course of preparing the films with the required properties. Ion beam techniques using nuclear reactions are effective for the quantitative determination of hydrogen concentration. A specially designed spectrometer is employed for the detailed determination of hydrogen concentrations by detecting 4.43 MeV γ-rays from the resonant nuclear reactions 1H( 15N,αγ) 12C at 6.385 MeV. In this study, the BCN films were formed on silicon substrate with ion-beam-assisted deposition (IBAD), in which boron and carbon were deposited by electron beam heating of B 4C solid and nitrogen was supplied by ion implantation simultaneously. The hydrogen depth profiling in the near surface region of BCN films were performed by employing RNRA. The mechanical properties of BCN films were evaluated using an ultra-micro-hardness tester. It has been confirmed that the hardness of BCN films becomes larger with the increase of the hydrogen concentration.

Laser Hydriding—a Novel Method to Store Hydrogen in Solids

Laser hydriding is a novel technique to incorporate large amounts of hydrogen into the surface layers of materials. The process consists of laser-irradiating the sample in hydrogen atmosphere at elevated hydrogen-gas pressures (1–3 bar). We used up to 256 pulses of a XeCl excimer laser (308 nm, 55 ns pulse duration, ≤ 5 J/cm2 laser fluence) to irradiate titanium, amorphous and single-crystalline silicon samples. The hydrogen depth profiles were measured with the 3 MV pelletron accelerator MaRPel, using the nuclear reaction 1H(15N, αγ)12C at the 6.385 MeV resonance. Titanium samples show hydrogen concentrations of up to 47 at.% after laser hydriding at a fluence of 4 J/cm2. The laser treatment leads to the formation of the TiH2 phase. Laser hydriding of crystalline silicon samples results in a damaged region near the sample surface and a hydrogen concentration of up to 8 at.%, much higher than the solubility limit in thermodynamic equilibrium. In the case of amorphous silicon, epitaxial recrystallization is observed after the laser treatment, with a smaller hydrogen take-up as compared to crystalline silicon. Thermodynamic simulations were carried out to elucidate the laser-material interaction. Similarities and differences relative to laser nitriding and carburization will be discussed briefly.

The State of Hydrogen in Nb-based Nb-Mo Alloys Analyzed by the Channelling Method

In order to locate hydrogen dissolved in metals a channelling method utilizing a nuclear reaction 1H(11B, α) αα with a 11B beam has been developed. This method has been applied to study the effect of metallic solutes on the state of hydrogen in metals. The lattice location of hydrogen in Nb-based Nb-Mo alloys with different concentrations (CMo) of undersized Mo atoms of 3, 10, 20 and 26 at% has hitherto been investigated. These results are summarized in this paper and the interaction of hydrogen with metal solutes is discussed. At low Mo concentrations less than 10 at% hydrogen is trapped by Mo atoms at room temperature due to attractive interaction to be located at sites displaced from tetrahedral (T) sites by about 0.6 Å toward the nearest neighbour Mo atom. In the case of CMo=3 at%, hydrogen is detrapped at 373 K and enter a T site. The number of H atoms trapped by one Mo atom is limited. It is 0.7-1.0 for CMo=3 at% and decreases with increasing CMo. The excess H atoms are located at T sites. For CMo=20 at% such trapped site occupancy is not observed, and 70-80% of the H atoms are located at T sites and the rest are at octahedral (O) sites at low H concentrations. For CMo=26 at%, most of the H atoms are located at T sites.

Thin hydroxyapatite surface layers on titanium produced by ion implantation

In medicine metallic implants are widely used as hip replacement protheses or artificial teeth. The biocompatibility is in all cases the most important requirement. Hydroxyapatite (HAp) is frequently used as coating on metallic implants because of its high acceptance by the human body. In this paper a process is described by which a HAp surface layer is produced by ion implantation with a continuous transition to the bulk material. Calcium and phosphorus ions are successively implanted into titanium under different vacuum conditions by backfilling oxygen into the implantation chamber. Afterwards the implanted samples are thermally treated. The elemental composition inside the implanted region was determined by nuclear analysis methods as (α,α) backscattering and the resonant nuclear reaction 1H( 15N,αγ) 12C. The results of X-ray photoelectron spectroscopy indicate the formation of HAp. In addition a first biocompatibility test was performed to compare the growing of marrow bone cells on the implanted sample surface with that of titanium.

Ｘ線材料強度 共鳴核反応分析法によるＢＣＮ膜の水素量測定

Hydrogen is a very common contaminant in carbon films. It can strongly influence on mechanical, physical and chemical properties of the films. The analysis of hydrogen is therefore a crucial problem produce the films with the properties required. Ion beam techniques using nuclear reactions are effective for the quantitative determination of hydrogen concentration. A specially designed spectrometer is employed for the detailed determination of hydrogen concentrations by detecting 4.43MeV γ-rays from the resonant nuclear reactions 1H(15N, αγ)12C at the 6.385MeV. In this study, the BCN films were formed on silicon substrate by ion beam assisted deposition (IBAD), in which boron and carbon were deposited by electron beam heating of B4C solid and nitrogen was supplied by ion implantation simultaneously. The concentrations of hydrogen in BCN films were measured using RNRA. The mechanical properties of BCN films were evaluated using an ultra-micro-hardness tester. It was confiremed that the hardness of BCN films increased with increasing the concentration of hydrogen.

Hydrogen in diamond-like carbon films

Properties of physical vapor deposited diamond-like carbon films and the migration of hydrogen in co-deposited samples were studied. Measurements utilizing Rutherford backscattering spectrometry and Doppler-shift-attenuation techniques were used to obtain the average mass density of the films. Distributions of co-deposited hydrogen and deuterium were measured by the nuclear resonance reaction 1H ( 15N,αγ) 12C, and the elastic recoil detection technique, respectively. Secondary ion mass spectrometry was also used in combination with these two methods. It was observed that in H and CH 4 co-deposited DLC films the temperature of H release varied between 950 and 1070°C depending on the H concentration.

Polyaniline, a conducting polymer, as a standard for hydrogen profiling on material surfaces

The behaviour of polyaniline, a conducting polymer, under 15N 3+ ions bombardment and its subsequent utility as a standard for hydrogen estimation using the nuclear resonance reaction 1H( 15N,αγ) 12C have been investigated. Polyaniline withstands higher doses of radiation compared to other polymeric materials like polyethylene, polypropylene etc. used as standards for hydrogen estimation without any special sample handling arrangements.

Hydrogen migration in diamond-like carbon films

Properties of physical vapor deposited diamondlike carbon (DLC) films and the migration of hydrogen in H+ and He+4 ion implanted and hydrogen co-deposited DLC films have been studied. Measurements utilizing Rutherford backscattering spectrometry showed that the films studied have an average mass density of 2.6±0.1 g/cm3. The bonding ratio sp3/sp2 is typically 70% measured with the electron spectroscopy for chemical analysis technique. Impurities and their depth distributions were deduced from the particle induced x-ray emission and secondary ion mass spectrometry (SIMS) measurements. Distributions of implanted and co-deposited hydrogen were measured by the nuclear resonance reaction H1(15N,αγ)12C and SIMS. It was found that annealing behavior of implanted H in DLC has a diffusion like character. The obtained diffusion coefficients resulted in the activation energy of 2.0±0.1 eV. It was observed that in H co-deposited DLC films the temperature of H release varied between 950 and 1070 °C depending on the H concentration.

Ion beam analysis of diamond-like carbon films

Diamond-like carbon films are deposited with a number of different methods. This results in a wide variety of different microstructures and even compositions of the films, which challenges characterization capabilities. Ion beam analysis can be used in many ways to probe the properties of the films. A classic application is the determination of hydrogen concentrations in hydrogenated amorphous carbon films, a-H : C. This is performed by using either a resonance of the nuclear reaction 1H( 15N, αγ) 12C or a forward recoiling technique. Diamond-like films have been doped with metals, Si, F, etc. in order to modify mechanical, tribological, or optical properties. Dopand concentrations can be qualitatively measured using either a backscattering or nuclear reaction analysis (NRA) method. A fairly trivial application is the utilization of either Rutherford or non-Rutherford backscattering to obtain the number of carbon atoms per square centimetre. Combined with other information on the chemical composition of the film and with the thickness obtained with a profilometer, for example, the density of the very thin films can be calculated. The density is an interesting parameter of the films and may vary considerably, depending on the hydrogen concentration and the structure of chemical bonding. If the thickness of the films is not constant or if a diamond-like material is just a deposition with an irregular shape, the above method cannot be utilized. The ion beam technique may still be useful and the Doppler shift attenuation of the resonance can be used. Resonance techniques are useful in analysing some other carbon related films, for example in analysing nitrogen in CN x films. In this paper, the most useful ion beam techniques for analysing diamond-like materials are given with examples.

Channelling study on the lattice location of hydrogen in metals utilizing a nuclear reaction

The behaviour of hydrogen in metals has been investigated by a channelling method utilizing a nuclear reaction1H(11B, α)αα. The results are briefly summarized.

Trapping of hydrogen impurities in helium-implanted niobium and tantalum

Trapping of hydrogen impurities at helium precipitates in helium-implanted niobium and tantalum has been studied. The samples were implanted at room temperature with 100 keV 4He+ ions to doses of (0.6–36)×1016 cm−2. Some of the samples were postirradiated with 60 keV and 4 MeV protons, and annealed at elevated temperatures up to 1070 K. The helium and hydrogen concentration distributions were characterized simultaneously using the elastic-recoil-detection-analysis technique. The hydrogen distributions were also measured by the nuclear resonance reaction 1H(15N,αγ) 12C. The observed hydrogen distributions show that defect-hydrogen complexes at He bubbles are built from the ion-irradiation-induced and pre-existing vacancies and pre-existing hydrogen impurities migrated to the associated internal surfaces and that the hydrogen impurities saturate the surfaces. Recovery energies of about 2.1 eV in Nb and about 2.7 eV in Ta were observed for the hydrogen trapping defects.