non-Rutherford Cross Sections Research Articles

Quantitative light element analysis: Complementary IBA methods for H to O detection using an external proton beam

A new setup for quantitative light element analysis of thin films using a 2.50–2.72 MeV external proton beam under atmospheric conditions is described. This setup simultaneously performs backscattering spectrometry (BS) and p-p coincidence elastic recoil detection analysis (C-ERDA) in transmission. BS utilizes a highly non-Rutherford cross-section for profiling of e.g. C, N and O whereas C-ERDA is used to measure H concentration profiles in foils of up to 12.5 μm in thickness. To validate the method, thin Ti layers are deposited on 200 nm Si3N4 membranes and loaded with H. The method shows an expected increase of H concentration in the films with longer loading times. Nuclear reaction analysis (NRA) for Li detection in LiMn2O4 samples is undertaken to test the possibility of using complementary proton scattering techniques simultaneously. A Li depth resolution of around 250 nm can be achieved. Radiation damage to Mylar and Kapton films is investigated and the radiation resistance of Kapton demonstrated.

A model to simulate large angle Rutherford backscattering spectra in GEANT4

A model was developed to simulate RBS spectra of H, He and Li ions based on the GEANT4 simulation toolkit. The simulation consists of tracking particles inside the medium and collecting kinetic energy and momentum direction at each step of the particle track. With this information, a backscattering spectrum is simulated based on Rutherford and non-Rutherford cross sections, detection angle and energy loss in the sample and the detector. The simulation of impinging particles is governed by GEANT4 physics processes, while the backscattered particle kinetic energy at the detector is evaluated manually. The developed GEANT4 model supports up to five layers, includes evaluation of energy loss straggling and multiple scattering induced energy straggling, evaluation of detector energy resolution of heavier ions. The RBS spectra obtained by our GEANT4 model were compared with the most widely used tools, specifically, IBA Data Furnace WinDF and SIMNRA, and showed a good agreement. The current model lacks evaluation of plural scattering, surface roughness, material porosity influence, etc., however, as it is open source, the users and developers can add the lacking functions.

Status of Ion Beam Modification and Analysis of Materials at STU MTF

Abstract The new Ion Beam Centre (IBC) equipped with 6 MV tandem ion accelerator and 500 kV ion implanter systems was built at the Slovak University of Technology, Faculty of Materials Science and Technology (STU MTF). The facility provides Ion Beam Modification of Materials (IBMM) and Ion Beam Analysis (IBA), which includes Rutherford Backscattering Spectrometry (RBS), Particle Induced X-ray Analysis (PIXE), Elastic Recoil Spectrometry (ERDA) and Nuclear Reaction Analysis (NRA). Presented are selected experimental procedures carried out in the IBC during the first year of operation. They present examples of a typical IBA performed, such as thin film characterisation in nm to tens of µm range, elemental depth profiles and sensitivity to the light elements enhancement by non-Rutherford cross-section regime application along with the crystalline sample channelling spectra and boron content measurement.

Non-Rutherford cross-sections for alpha elastic scattering off Z = 28–38 elements in the energy range up to 10 MeV

Abstract The alpha elastic scattering cross-sections for Ni, Cu, and Y were measured at the energies above the onset of the non-Rutherford scattering. The obtained experimental data along with data from literature were incorporated into the theoretical analysis in the framework of the optical model. The optimization of the model parameters provided a basis for the calculations of the differential cross-sections for Z = 28–38 elements in the energy range up to 10 MeV. The obtained cross sections were made available for common use through the SigmaCalc web site at http://sigmacalc.iate.obninsk.ru/ .

X-ray production cross-sections measurements for high-energy alpha particle beams: New dedicated set-up and first results with aluminum

The “IPNAS” laboratory, in collaboration with the “Centre Européen d’Archéométrie” is partly focused on material analysis by means of IBA techniques: PIXE, PIGE and RBS. A new transport beam line has been developed at our CGR-520 MeV cyclotron to analyze Cultural Heritage objects using these techniques. This facility allows us to produce proton and alpha particle beams with energies up to 20 MeV. A vacuum chamber dedicated to X-ray production and Non-Rutherford cross-section measurements has been recently constructed. After determination of the chamber’s geometry for X-ray detection using thin foils of several elements (11 ⩽ Z ⩽ 82) and 3 MeV proton beams, the measurement of the X-ray production cross-sections in the 6–12 MeV energy range has started using alpha particle beams on light element targets. These experiments contribute to the filling a serious lack of experimental values for alpha particles of this particular energy range in databases. The recent decision to focus our work on the alpha particle interaction with light elements was taken because of the high interest of the low Z elements in the field of archaeometry.

Composition of Renaissance Paint Layers: Simultaneous Particle Induced X-ray Emission and Backscattering Spectrometry

Particle induced X-ray emission spectroscopy (PIXE) is now routinely used in the field of cultural heritage. Various setups have been developed to investigate the elemental composition of wood/canvas paintings or of cross-section samples. However, it is not possible to obtain information concerning the quantity of organic binder. Backscattering spectrometry (BS) can be a useful complementary method to overcome this limitation. In the case of paint layers, PIXE brings the elemental composition (major elements to traces) and the BS spectrum can give access to the proportion of pigment and binder. With the use of 3 MeV protons for PIXE and BS simultaneously, it was possible to perform quantitative analysis including C and O for which the non-Rutherford cross sections are intense. Furthermore, with the use of the same conditions for PIXE and BS, the experiment time and the potential damage by the ion beam were reduced. The results obtained with the external beam of the Accélérateur Grand Louvre pour l'Analyse Elementaire (AGLAE) facility on various test painting samples and on cross sections from Italian Renaissance masterpieces are shown. Simultaneous combination of PIXE and BS leads to a complete characterization of the paint layers: elemental composition and proportion of the organic binder have been determined and thus provide useful information about ancient oil painting recipes.

Evaluation of non-Rutherford cross sections for IBA: Theory and results

In order to meet the needs of the IBA community in nuclear data the evaluation of frequently used elastic scattering cross sections was made and the SigmaCalc web site (www-nds.iaea.org/sigmacalc/) was developed. A scheme of the evaluation procedure, theory and results are presented.

Precise measurement of the differential cross section from the O16(α,α)O16 elastic reaction at 165° and 170° between 2.4 and 6.0MeV

Non-Rutherford cross section for elastic scattering of α particles from oxygen has been measured for energies between 2.4 and 6.0MeV at commonly used backscattering angles of 165° and 170°. High precision in energy has been obtained with a 2MV Tandetron accelerator, with precise and stable energy calibration. The choice of a thin Ta2O5∕Ta∕C standard increased the sensitivity and reduced systematic errors due to the geometry. Precise data for energy, width, and ratio to Rutherford of the resonances have been extracted from nuclear shell models, and excitation levels of Ne20 have been deduced. The well-known resonance ER=3031.7±0.5keV and the narrow and intense resonance ER=5375.5±0.5keV, not included in cross-section libraries, have been applied for surface oxygen analysis in thin WCN∕SiO2∕Si multilayer samples, with improved depth resolution by optimizing the measuring geometry.

Cross sections for 165° backscattering of 8.0–11.7 MeV α from carbon

Non-Rutherford cross sections for carbon have been measured at the 165° backscattering angle for α beam energies ranging from 8.0 to 11.7MeV. Thin ∼42(±4)μg/cm2 amorphous freestanding carbon foils were measured at the 0° tilt angle. Also, ∼1.8×1018at/cm2 C films e-beam deposited onto Mo substrates were measured at the 75° tilt angle. The measured cross sections from these samples are discussed and compared with values from earlier work. The cross sections from all work are shown in graphic form and those not already available in tabular form will be submitted to the Ion Beam Analysis Nuclear Data Library (IBANDL).

Fast Monte Carlo simulation for elastic ion backscattering

A Monte Carlo method using ion packets is introduced. The method presented is optimal for the low probability scattering simulations of multiple and plural backscattering effects. Non-Rutherford cross sections are easily implemented in the framework of this model.

Measurement of non-Rutherford cross sections of [formula omitted]He ions on [formula omitted]N at a laboratory backscattering angle of 171° between 7.5 and 9.8 MeV

The ratio of the non-Rutherford to the Rutherford cross section of 14 N was measured using 4 He ions in the energy range between 7.5 and 9.8 MeV at a laboratory backscattering angle of 171° in order to complete the data published by Foster et al. (Nucl. Instr. and Meth. B 79 (1993) 454), who measured the ratio at a lower backscattering angle of 167°. This is important because of the interest in using high energy helium ion backscattering to determine the nitrogen content in heavy substrates. Non-Rutherford backscattering spectra and 14 N depth profiles of nitrogen-implanted titanium alloys, that serve as an application of the new cross sections, are shown in this work as well. The measurements were done at beam energies of 7.5–8.2 MeV and from 9 to 9.8 MeV. Results show a resonance around 9.3 MeV with cross sections that are about 100 times higher than the values for Rutherford backscattering.

Composition of NiTaC films on Si using neural networks analysis of elastic backscattering data

A neural network algorithm has been successfully used to analyse proton elastic backscattering (EBS) data. The composition of NiTaC films deposited on Si substrates was determined. We show that, after being trained, the neural network can analyse the spectra from these samples with an excellent accuracy. Although there are other methods to analyse these samples, this has the great advantage of being almost instantaneous and requiring no a priori knowledge from the user. This is particularly important in this case, as manual analysis is involved due to the presence of superimposed signals and strongly non-Rutherford cross-sections.

Composition of Ni–Ta–C thick films using simulated annealing analysis of elastic backscattering spectrometry data

Simulated annealing has been used successfully on elastic backscattering spectrometry data collected from tribological films of NiTa x C y on Si substrates. Manual analysis of the data was possible assuming that the films were well conditioned (homogeneous with depth). However, the C cross-section changes rapidly with beam energy, precluding manual analysis of more complex structures. We show that integrating the non-Rutherford cross-sections in the IBA DataFurnace leads to excellent fits, and analysis of compositional variation becomes trivial. We can demonstrate that the films have a very constant composition throughout their depth, that the precision of the analysis is about 2% and that the accuracy of the C determination approaches 10%. We demonstrate an error in the energy loss database (TRIM95) value of the ratio of Ni and Ta energy loss of 2%.

Elastic scattering cross sections of protons by copper, molybdenum, silver and tin near the Coulomb barrier

Cross sections for elastic scattering of protons by natural copper, molybdenum, silver and tin have been measured in the energy range of 2.3–6.5 MeV at typical Rutherford backscattering angles of 135° and 165°. The threshold energies have been determined above which the Rutherford cross sections become invalid. The threshold energies obtained are 3.5 and 3.4 MeV for copper, 5.1 and 5.0 MeV for molybdenum, 5.0 and 5.8 MeV for silver, and 6.1 and 6.2 MeV for tin at angles of 135° and 165°, respectively. Resonances or the rapid decrease of the cross sections above the thresholds render practical proton backscattering analysis impossible. A literature survey has been carried out to compile relevant energy threshold data for the present target mass and scattering angle regions. Considerable experimental and theoretical interest has recently been focused at the non-Rutherford cross sections. Comparing the experimental non-Rutherford threshold energies with theoretical calculations, we find the data clearly exceeding the predictions of simple classical formulations, while the optical model approach yields more realistic threshold energy values.

On the complementary use of ion beam techniques in the near surface analysis of implanted alloys

A combination of RBS, PIXE and resonant elastic backscattering was applied to determine the depth profiles and doses of Y implants in Cr and NiCr alloys, the mass contents of Cr and Ni respectively, and the oxygen composition in surface layers of these alloys before and after implantation. Only through the simultaneous use of PIXE analysis was a severe error in the alloy preparation revealed. A Fe content of about 5% was found in one of the nominal binary alloys, influencing the corrosion behaviour of this material significantly. This level of Fe content was undiscernible from the Ni and Cr continuum in the RBS spectra. For the analysis of the oxygen surface layers with the 3.03 MeV resonance of 4He ions, two evaluation programs were used and compared: GISA and RUMP in a modified form, enabling the use of non-Rutherford cross sections.

Cross sections for light element analysis by non-Rutherford scattering

The non-Rutherford cross sections of light elements, from Be to F, for θ lab = 165° are reviewed. New results for cross section measurements of Be, B and other light elements at θ lab = 165° in the energy range of 1.0–5.3 MeV are presented. Non-Rutherford backscattering for light elements and Rutherford backscattering for heavy elements were used to measure stoichiometries, depth profiles and light element contaminants in thin films of different compounds. The suitable energy range of the α-particles used for major light elements analysis is discussed. In the 3–10 MeV energy range, significant light element sensitivity enhancements were observed, while the heavy elements showed classical Rutherford behavior.

BSCAT: Code for simulation and for analysis of the RBS/NRA spectra

A beam of charged particles as a tool for non-destructive analysis of the structure and elemental composition of thin-surface layers is frequently used in material investigations. Nuclear methods such as RBS or NRA techniques have a good depth resolution and sufficient mass sensitivity. Many computer programs exist, like the RUMP [see L.R. Doolitle, Nucl. Instr. and Meth. B 9 (1985) 344] or DVBS [see V. Boháč and D.M. Shirokov, Nucl. Instr. and Meth. B 84 (1994) 497] codes, for simulation and for analysis of experimental results collected in measurements with beams of charged particles. A new computer code, called BSCAT (BackSCATtering), was created at the Institute of Nuclear Physics to analyze experimental spectra and to simulate new experiments. The BSCAT code, written in FORTRAN-77 and partially in C, can work on IBM personal computers or on larger computers such as CONVEX machines. As input for the program both Rutherford and non-Rutherford cross sections can be used and the stopping power function can be calculated by the Ziegler or the Montenegro formula. The program was used in the analysis of complex spectra of backscattered particles. Among other applications the BSCAT code was used for analysis of the spectrum of 2100 keV protons bombarding a thin carbon foil created by the IBAD technique on the surface of a Si {111} single crystal [ 12C(p, p) 12C and 28Si(p, p) 28Si resonance].

Simulation of RBS spectra for quantitative mapping of inhomogeneous biological tissue

A computational algorithm, capable to simulate RBS spectra recorded during scanning proton microprobe analysis of organic specimens with inhomogeneous thickness has been developed. This program is based on an enhancement of the RUMP source code. It allows us to normalize in terms of dry specimen mass the elemental concentrations obtained with simultaneous PIXE and RBS microanalysis. This code includes non-Rutherford cross sections for proton scattering from carbon, nitrogen and oxygen. It permits the computation of matrix correction factors for the analysis of low energy X-ray emitters. In this paper, the first version of the simulation algorithm is presented as also the application to the analysis of reference organic material.

Simultaneous analysis of light elements using non-Rutherford helium backscattering

Non-Rutherford backscattering has been recognized as a valuable analytical approach to profiling light elements with superior sensitivity and large depth accessibility. However in multielemental analysis the scattering cross sections of elements obtained under the same conditions and a proper computer simulation are preferable. Here a data base of non-Rutherford cross sections was determined precisely at the scattering angle of 165° with helium energy ranging from 2.0–9.0 MeV. The data for carbon and nitrogen have been published previously, and now the data for oxygen are presented. In addition, the results have been compiled into the computer simulation program RUMP, which is valid for simultaneously determining both the stoichiometry and depth profiles of light elements in a heavy element matrix. As examples of such application, the BS spectra of a Ti (C, N, O) film and a coated electrode material were measured with a number of incident energies, and consistent sample descriptions were assumed in the simulation.

The studies of non-Rutherford backscattering cross sections of 4 He from 16 O

In this article, we report the 170° backscattering cross sections of 4He from 16O in the energy range of 2.0-9.0 MeV. Our measurements show that the alpha-oxygen scattering remains Rutherford scattering up to Eα=2.35 MeV, and there exist two energy regions, namely 5.55-5.85 MeV and 8.50-8.80 MeV, where the cross sections are enhanced and show a smooth variation. The measured laboratory cross sections are 9.50-9.97 and 35.0-33.0 times greater than the Rutherford values, respectively. In the 8.50-8.80 MeV region, the cross sections at scattering angles of 160°, 165°, 170° and 175° were measured and found to be strongly angle-dependent. A most strong resonance occurred at 7.60 MeV, where the cross section is 200 times of its Rutherford value. This resonance has been used to measure the 16O concentration on a Cu surface, with a sensitivity of 1×1015 oxygen atoms/cm2. Besides, we have studied the backscattering angle dependence of the threshold energy, i. e., the energy at which the elastic cross section begins to deviate from its Rutherford value. The experimental result seems not in agreement with the prediction made from the analytical formula developed by Bozoian et al.