Characterisation of ferromagnetic magnetic storage media surfaces by complementary particle induced X-ray analysis and time of flight-energy dispersive elastic recoil detection analysis

Thin (10 nm–1 μm) films of ferromagnetic material constitute an important class of materials that are difficult to analyse by conventional ion beam analytical (IBA) techniques because they are based on the ferromagnetic elements (Co, Fe, Mn, Ni, and Cr). The similar or overlapping isotope masses makes it difficult to separate the elemental signals using time of flight and energy dispersive elastic recoil detection (ToF-E ERD). In this exploratory study we have investigated the use of Particle Induced X-ray Emission (PIXE) measurements to refine the mass dispersive depth profile information from ToF-E ERD. The surfaces of two commercial magnetic media were investigated. One sample was a double density diskette with a coating of ferrite particles in an organic binder. The other sample was a complex C/Co/Cr/Ni–P/Al multilayer structure taken from a standard hard disc. The Lund nuclear microprobe with a 2.55 MeV proton beam was used for PIXE analysis. ToF-ERD measurements were carried out using a 55 MeV ¹²⁷I¹⁰⁺ ion beam incident at 67.5° to the surface normal. The time of flight and kinetic energy of recoils ejected at 45° to the ion beam direction was measured in a detector telescope. The findings demonstrate that by detailed analysis of the PIXE spectra it is possible to remove the ambiguities in mass assignment of the ToF-ERD data associated with the ferromagnetic elements.     

微束背散射分析元素微区分布的研究

微束背散射分析元素微区分布的分析方法使上海原子核研究所的质子微探针能在微区内综合使用质子激发Ｘ射线荧光和背散射等多种核效应，为样品由轻元素到重元素的全面无损、双微（微区、微量）分析提供了依据。应用该方法还测量了Ｓｉ３Ｎ４／ＳｉＣ复合陶瓷材料，证明了该分析方法的可靠性。     

A new mapping acquisition and processing system for simultaneous PIXE-RBS analysis with external beam

The combination of ion beam analysis techniques is particularly fruitful for the study of cultural heritage objects. For several years, the AGLAE facility of the Louvre laboratory has been implementing these techniques with an external beam. The recent set-up permits to carry out PIXE, PIGE and RBS simultaneously on the same analyzed spot with a particle beam of approximately 20 μm diameter.A new mapping system has been developed in order to provide elemental concentration maps from the PIXE and RBS spectra. This system combines the Genie2000 spectroscopy software with a homemade software that creates maps by handling acquisition with the object position. Each pixel of each PIXE and RBS maps contains the spectrum normalised by the dose. After analysing each pixel of the PIXE maps (low and high energy X-ray spectra) with the Gupixwin peak-fitting software, quantitative elemental concentrations are obtained for the major and trace elements. This paper presents the quantitative elemental maps extracted from the PIXE spectra and the development of RBS data processing for light element distribution and thin layer characterization. Examples on rock painting and lustrous ceramics will be presented.     

Analysis of boron using the (p, α) reaction

The applicability of the strong and broad resonance of the reaction ${}^{11}\text{B(p}\text{, α)}{}^8\text{Be}$ at E_p = 675 keV to the elemental analysis of boron has been studied. To eliminate matrix effects and to optimize the measuring conditions a systematic study of the absolute thick-target yields of α-particles following proton bombardment has been carried out at E_p = 0.7 and 1.0 MeV for the elements Z = 3?9, 11?17s by. Summary spectra showing the α-peaks of light elements of interest in the elemental analysis of boron are given. An external beam measurement system has been developed to allow measurements to be carried out in He-gas at atmospheric pressure. Thus, problems arising in vacuo with insulating, medical and biological samples can be avoided. The detection limits of boron range from 0.1 ppm for biological samples containing nitrogen to below 0.01 ppm for samples with a low nitrogen concentration. An additional advantage of the method is that Li, F and N can be determined simultaneously with the boron analysis.     

Vaporisation characteristics and detection limits of ion beam thermography

Analytical properties of the chemical speciation method, Ion beam thermography (IBT), have been investigated. IBT combines the multi-elemental ion beam techniques PIXE, PESA, pNRA and cPESA with thermography. During thermography the sample temperature is gradually increased, causing vaporisation of chemical compounds at specific temperatures and the sample at the same time undergoes analysis by the above-mentioned techniques. The characteristic vaporisation temperature (CVT) and the stoichiometric relations between the elements vaporised at that temperature, identify the chemical compounds. This work describes the reproducibility of the method, the dependence of the rate of temperature increase, the dependence of the sample thickness and the influence from aerosol particle size on the CVT. In addition the minimum detectable mass changes for IBT analysis of marine and continental aerosols were estimated by calculation for major and minor elements.     

Development of a novel reaction chamber for ion beam analysis of large samples

A novel vacuum chamber for ion beam analysis of large-size industrial samples - whose analysis are not feasible in conventional ion beam analysis reaction chambers - has been designed, fabricated and successfully tested. Using the newly developed chamber, both PIXE and RBS analyses could be carried out at the same time and on the same point of the samples. Ion beam analysis using this novel chamber lacks the disadvantages of external beam analysis and benefits the advantages of in-vacuum analysis. This has been achieved by designing a tiny open port in the wall of the reaction chamber to be sealed with a small flat area of sample body where its analysis is of interest. As a case study, two samples of gas turbine blades, a corroded one at highly corrosive environment and a refurbished one after application of certain coatings are analysed using the novel chamber. Experimental results confirm the performance and capability of the reaction chamber.     

串列加速器-子注入机-射电镜联机系统的建立

建立了由2×1.7MV串列加速器、200kV离子注入机、H800型透射电子显微镜和联机传输系统组成的我国第1套串列加速器 离子注入机 透射电子显微镜联机装置。对主要设备进行了改造，并采取有效措施解决了联机装置的隔震问题。2台加速器和所有的真空泵都运行时，电镜仍可正常工作，观察到的图像质量不受振动影响。电镜室内样品倾斜角最大可达52°以上，离子注入不影响电镜观测，可进行离子注入的原位和实时结构研究。离子注入机输出的115keV氮离子在电镜入口测得的束流强度达100～180nA。初步实验已原位观察到氮离子注入导致单晶硅非晶化的过程，显示这套装置具有离子注入条件下的原位观测能力。     

Technical developments for computed tomography on the CENBG nanobeam line

The use of ion microbeams as probes for computed tomography has proven to be a powerful tool for the three-dimensional characterization of specimens a few tens of micrometers in size. Compared to other types of probes, the main advantage is that quantitative information about mass density and composition can be obtained directly, using specific reconstruction codes. At the Centre d’Etudes Nucléaires de Bordeaux Gradignan (CENBG), this technique was initially developed for applications in cellular biology. However, the observation of the cell ultrastructure requires a sub-micron resolution. The construction of the nanobeam line at the Applications Interdisciplinaires des Faisceaux d’Ions en Region Aquitaine (AIFIRA) irradiation facility has opened new perspectives for such applications.The implementation of computed tomography on the nanobeam line of CENBG has required a careful design of the analysis chamber, especially microscopes for precise sample visualization, and detectors for scanning transmission ion microscopy (STIM) and for particle induced X-ray emission (PIXE). The sample can be precisely positioned in the three directions X, Y, Z and a stepper motor coupled to a goniometer ensures the rotational motion. First images of 3D tomography were obtained on a reference sample containing microspheres of certified diameter, showing the good stability of the beam and the sample stage, and the precision of the motion.     

Internal elemental imaging by scanning X-ray fluorescence microtomography at the hard X-ray microprobe beamline of the SSRF: Preliminary experimental results

Synchrotron-based X-ray micro-fluorescence (μ-SXRF) is a non-destructive analytical technique and has been widely used to detect and quantify the elemental composition of samples in their natural state. To determine the internal elemental distributions within samples, X-ray fluorescence microtomography has been developed based on the hard X-ray microprobe at beamline BL15U1 of the Shanghai Synchrotron Radiation Facility (SSRF) in Shanghai, China. This technique was applied to image the cross-sectional distributions of multiple elements within a single human hair, and its validity was evaluated by comparing the results with the elemental maps of a thin hair section obtained using the well-established μ-SXRF mapping method. Elemental images of S, Ca, Mn, Fe, Cu, and Zn within a virtual slice of the hair were reconstructed after the tomographic measurements. The tomographic images of heavy elements like Fe, Cu, and Zn were found to be in good agreement with the corresponding μ-SXRF maps. Light elements, such as S, however, represented different patterns due to non-negligible self-absorption in the sample, and sophisticated correction algorithms accounting for such effects are required for obtaining qualitatively and quantitatively more accurate images. Compared to μ-SXRF mapping, X-ray fluorescence microtomography reduces the sample preparation requirements and has been demonstrated in this work as being a more ideal and effective imaging modality to non-destructively mapping out the internal distribution of heavy elements within samples at the micrometer scale at the SSRF.     

PIXE study on Chinese underglaze-red porcelain made in Yuan Dynasty

In China. the firing and glazed red techniques of producing underglaze-red porcelain began early in the Yuan Dynasty (AD1206-1368). This paper reports the results of the PIXE analysis of ancient Chinese underglaze-red porcelain produced at Kuan kiln (Jingdezhen, Jiangxi Province) in the Yuan Dynasty. In this work the elemental composition analysis of the obtained samples was carried out using the PIXE facility of a 3 MeV tandem accelerator at Fudan University. The major, minor and trace elements of the clay body, white and red glazes were determined,and details of the results are presented. The obtained data can be used for identification of precious Chinese Yuan underglaze-red porcelain,     

On the interpretation of micro-PIXE measurements on a prototype microstructured reference material

In order to determine the beam spot size and scanning properties of ion microbeam systems, a novel reference material has been developed, consisting of permalloy (81% Ni, 19% Fe) strip patterns on silicon substrate. Due to the choice of substrate and pattern materials, these samples exhibit a high elemental contrast suitable for analysis with X-ray detection and ion scattering techniques. The microlithographic production scheme is briefly described. A prototype chip of this material was investigated with PIXE and RBS analysis in a scanning nuclear microprobe. It proved to be extremely useful in the routine to focus the ion microbeam and to determine its spot size. Due to the microscopic structure of these samples, a geometric dependence of matrix effects in the production of Si X-rays from the substrate material could be shown. Even dead-time effects in the counting electronics, showing up as an apparent thickness gradient, could be observed. Besides its primary role in microbeam diagnostics, this reference material can serve an educational role in developing the analyst's ability to correctly identify and interpret such artefacts.     

Data acquisition and display system for a scanning proton probe

The usefulness of PIXE is considerably enhanced with the addition of a beam scanning facility allowing one to display images of elemental distributions of a sample's surface. The hardware and software of a system for data acquisition, storage and display of up to four images with a 32 × 32 pixels resolution is described.The system is built around a Signetics 2650 microprocessor. Data acquisition makes use of DMA techniques; element identification is made by comparing the ADC output with the limiting channels of predefined regions of interest. Sample scan is done by hardware but the beam can be made to irradiate a single chosen point of the sample. An example of the instrument's performance is given.     

Geochemical analysis of radiolarite samples from the Carpathian basin

A very important raw material of the prehistoric age, radiolarite was investigated in this work. Samples from geological and archaeological sites of the Carpathian basin, Greece and Austria were analyzed by ion beam methods, namely proton-induced gamma-ray emission (PIGE) and proton-induced X-ray emission (PIXE) techniques. Our aim was to study to what extent we are able to classify the specimens with various macroscopical features and different source areas. In order to answer this question, a cluster analysis was carried out on the concentration data set deduced from the analysis. Correlations between the elemental compositions and the source regions are established.     

Computer simulation of ion beam analysis: Possibilities and limitations

Quantitative application of ion beam analysis methods, such as Rutherford backscattering, elastic recoil detection analysis, and nuclear reaction analysis, requires the use of computer simulation codes. The different types of available codes are presented, and their advantages and weaknesses with respect to underlying physics and computing time requirements are discussed. Differences between different codes of the same type are smaller by about one order of magnitude than the uncertainty of basic input data, especially stopping power and cross section data. Even very complex sample structures with elemental concentration variations with depth or laterally varying structures can be simulated quantitatively. Laterally inhomogeneous samples generally result in an ambiguity with depth profiles. The optimization of ion beam analysis measurements is discussed, and available tools are presented.     

Improved resolution and sensitivity on the ANSTO microprobe and it’s application to μ-PIXE

We report on the improved spatial resolution of the ANSTO heavy ion microprobe, achieved through the use of a higher brightness ion source for hydrogen. The improved resolution will be demonstrated for applications of μ-PIXE.With the higher brightness source, a 3 μm resolution was achieved for μ-PIXE elemental analysis. This is illustrated in high resolution images of nickel (Ni)-hyperaccumulating Hybanthus floribundus subsp. floribundus leaf tissues, where individual cells were clearly visible in the acquired elemental images. The higher resolution images illustrated that Ni was localised in epidermal cell walls.     

External-beam PIXE characterization of volcanic material used in ancient Roman mortars

Volcanic deposits from two volcanic districts, Monti Sabatini (MSVD) and Colli Albani (CAVD), NW and SE of Rome, were analyzed using the particle-induced X-ray emission (PIXE) technique, in order to obtain chemical fingerprints that can be used for provenance studies of filler materials in ancient Roman mortars. The rock samples were mounted on an X-Y stage enabling scanning over the sample surface and irradiated in air with a collimated 3 MeV proton beam. The samples were either analyzed by scanning the beam over a polished surface or they were crushed, ground and homogenized prior to the irradiation. However, scanning over polished sample surfaces avoiding heterogeneities gave quite similar results as scanning over pellet surfaces, especially for the minor and trace elements. This study shows that the deposits of MSVD and CAVD can be distinguished from each other. Several elements or elemental ratios can be used to characterize the districts. Even the individual volcanic deposits of CAVD can be identified.     

Unique capabilities of heavy ion elastic recoil detection with gas ionization detectors

Specific aspects of heavy ion elastic recoil detection (ERD) with gas ionization detectors have been studied using representative measurements. A particular strength of the technique is the detection and direct quantification of elements with atomic numbers in the range Z=2–8, which are often not accessible with other ion beam techniques. Within the wider spectrum of analytical techniques in materials science, heavy ion ERD has unique capabilities, when the particular problem requires in addition the analysis of heavy elements or hydrogen detection. Whenever only heavy element analysis or only hydrogen profiling is of interest, alternative techniques tend to be superior.     

In situ characterization of micron-scale particles by nuclear microscopy

Nuclear microscopy is well suited for analyzing large particle populations as well as individual particles of interest in various types of collection samples. Unlike some commonly used in situ techniques, nuclear microscopy can quantitatively characterize particles embedded within the sample or particles that are too small to be reliably removed from their collection media. Additional advantages include its capability for the detection of minor and trace elements, its capability to simultaneously analyze multiple elements with little or no prior sample preparation, and its potential for automated analyses. Preliminary data are presented of particle size and composition measurements conducted on air filters. The potential of applying nuclear microscopy to the cataloging of micron-scale cometary remnants captured in low density aerogel collectors is also explored. Because of its importance to a variety of collection programs, an innovative high-throughput ion beam imaging and analysis system is being jointly developed by Sandia and Lawrence Livermore national laboratories for rapid quantitative particle characterization.     

Control of temperature in thin samples during ion beam analysis

The ability of ion beam analytical techniques such as proton induced X-ray emission (PIXE) to determine elemental content without damaging fragile objects is a key factor in their increasing use in the analysis of art and archaeological objects In this paper, we calculate the expected temperature rise in thin, planar samples with and without radiative, conductive and convective cooling The results show that the primary emphasis must be placed on minimizing energy input to the sample, and that forced convective cooling is by far the most effective method of energy removal in materials such as paper, parchment, and fabrics