Dissertations / Theses on the topic 'Particle Induced X-ray Emission (PIXE)'

Incident ions, from a Van de Graaff accelerator, in the MeV energy range, deposit their energy into the near surface of a sample. This, in turn, causes atomic, molecular, cluster and fragment ion species to be desorbed and ionized, while simultaneously emitting characteristic elemental X-rays. The multielemental X-rays provide qualitative elemental information, which may be deconvoluted and fit to a theoretical X-ray spectrum, generated by a quantitative analysis program, GUPIX, while the atomic, molecular, cluster, and fragment ion species are identified using a quadrupole mass spectrometer. This methodology directly links elemental determinations with chemical speciation.The development of this particle desorption ionization particle induced X-ray emission mass spectrometer, the PDI-PIXE-MS (or PIXE-MS) instrument, which has the ability to collect both qualitative multielemental X-rays and mass spectral data is described. This multiplexed instrument has been designed to use millimeter-sized MeV particle beams as a desorption ionization (PDI) and X-ray emission (PIXE) source. Two general methods have been employed, one simultaneous and the other sequential. Both methods make use of a novel X-ray/ion source developed for use with the quadrupole mass spectrometer used in these experiments. The first method uses a MeV heavy ion particle beam, typically oxygen, to desorb and ionize the sample, while simultaneously producing characteristic multielemental X-rays. The resulting molecular, cluster, and fragment ions are collected by the mass spectrometer, and the X-rays are collected using a Si-PIN photodiode detector in conjunction with a multichannel analyzer (MCA). Heavy ions of N+, O+, O+2, Ar+, and Kr+ have been investigated, although heavy ion X-ray and mass spectra have focused on the use of oxygen particle beams. The second method is performed by first collecting the X-ray data with a MeV ion beam of He+ ions, then desorbing and ionizing the sample species with a MeV particle beam of heavy ions, producing good ion yields, for mass spectral data collection. The potential development of a scanning microprobe instrument, that would provide micron-scale, imaged, multielemental, and molecular and fragment ion chemical information is being investigated through the development of this prototype PIXE-MS instrument.

Le travail concerne le developpement d'un programme informatique destine a l'analyse elementaire par l'intermediaire des rayons x induits lors du bombardement d'un echantillon par des protons d'energie comprise entre 1 et 4 mev. Les bases theoriques et experimentales sur lesquelles repose l'emission, la transmission et la detection des rayons x sont decrites en detail de meme que le modele utilise pour le calcul des concentrations elementaires a partir des intensites des raies x caracteristiques observees dans les spectres. Le programme est teste par l'intermediaire d'echantillons standards de compositions connues. L'influence de divers facteurs sur les resultats des calculs est examinee

Growth and element assimilation was investigated in post oak seedlings exposed to four different treatment combinations of fertilization and ectomycorrhizal inoculation. Element concentration in excised leaves was analyzed via particle induced X-ray emission spectrometry with a 1.8 MeV proton macrobeam. Mean growth was significantly different across the treatment groups as well as mean concentration of Mg, Al, S, K, Ca, Fe, Cu, and Zn. The data suggest that fertilization rather than mycorrhizal inoculation had a stronger influence on plant growth and nutrient uptake. A follow up study was conducted with a 3 MeV microbeam. A 850 μm2 scanned area of a post oak leaf produced topographical maps of 11 elements.

Les analyses par la methode pixe sont habituellement effectuees sous vide, ce qui limite cette technique a l'analyse de petits objets resistants au vide. Un faisceau extrait permet l'analyse de n'importe quel objet, meme de liquides. Pour cette raison, un dispositif permettant l'extraction, d'un faisceau de protons a ete construit et ses possibilites ont ete etudiees. La technique a ete appliquee a l'analyse qualitative de peinture et celle quantitative d'argile et de petrole

Le développement des techniques de microscopie 3D offrant une résolution spatiale de l'ordre du micromètre a ouvert un large champ de recherche en biologie cellulaire. Parmi elles, un avantage intéressant de la micro-tomographie par faisceau d'ions est de donner des résultats quantitatifs en termes de concentrations locales d'une manière directe, en utilisant une technique d'émission de rayonnement X (PIXET) combinée à la microscopie ionique en transmission (STIMT). Le traitement des données expérimentales constitue un point délicat. Après une brève introduction aux techniques de reconstruction existantes, nous présentons le principe du code DISRA, le plus complet écrit jusqu'à ce jour, qui nous a servi de base pour ce travail de thèse. Nous avons modifié et étendu le code DISRA en considérant les aspects spécifiques des échantillons biologiques. Un logiciel de traitement de données complet a ainsi été développé, avec une interface utilisateur permettant le contrôle de chaque étape de la reconstruction. Les résultats d'expériences de STIMT et/ou PIXET effectuées au CENBG sur des spécimens de référence et sur des cellules végétales ou humaines isolées sont présentés.

Cette thèse en cotutelle entre la France et le Canada étudie l’accélération d’ions dans l’interaction laser-plasma. La première partie, réalisée au CENBG et sur l’installation PICO2000 du laboratoire LULI à l'École Polytechnique de Palaiseau, présente des études expérimentales, complétées par des simulations numériques de type Particle-In-Cell, portant sur l’accélération d’ions dans l'interaction d'un laser infrarouge de haute puissance avec une cible gazeuse de haute densité. La seconde, réalisée avec le laser ALLS de l’institut EMT INRS, concerne le développement d'une application des faisceaux génerés par laser pour l’analyse élémentaire d’échantillons. Dans le manuscrit, les caractéristiques des deux lasers, des différents diagnostics de particules et d’X utilisés (paraboles de Thomson, films radiochromiques, CCD...) ainsi que les configurations expérimentales sont décrites.Les jets de gaz denses supersoniques utilisés comme cibles d'interaction laser au LULI, sont présentés en détail; depuis leur conception grâce à des simulations de dynamique des fluides, jusqu’à la caractérisation de leurs profils de densité par interférométrie Mach Zehnder. D'autres méthodes optiques comme la strioscopie ont été mises en œuvre pour contrôler la dynamique du jet de gaz et définir l’instant optimal pour effectuer le tir laser. Les spectres obtenus dans differentes conditions d’interaction sont présentés. Ils montrent, dans la direction du laser, des énergies maximales allant jusqu’à 6 MeV pour les protons et 16 MeV pour les ions hélium. Des simulations numériques effectuées avec le code PICLS sont utilisées pour discuter les différentes structures observées dans les spectres et les mécanismes d’interaction sous jacents.Des faisceaux de protons et d’X générés par le laser ALLS dans l’interaction avec des cibles solides d’aluminium, de cuivre et d’or ont été utilisés pour effectuer des analyses de matériaux par les méthodes Particle-induced X-ray emission (PIXE) et X-ray fluorescence (XRF). L’importance relative des deux techniques, XRF et PIXE, est étudiée en fonction de la nature de la cible d’interaction. Les deux diagnostics peuvent être implémentés simultanément ou individuellement, en changeant simplement la cible d'interaction. La double contribution des deux processus améliore l’identification des constituants des matériaux et permet une analyse volumétrique jusqu'à des dizaines de microns et sur de grandes surfaces (~cm2) jusqu'à un seuil de détection de quelques ppms
In this joint thesis, performed between the French Institute CENBG (Bordeaux) and the Canadian Institute INRS (Varennes), laser driven ion acceleration and an application of the beams are studied. The first part, carried out at CENBG and on the PICO2000 laser facility of the LULI laboratory, studies both experimentally and using numerical particle-in-cell (PIC) simulations, the interaction of a high power infrared laser with a high density gas target. The second part, performed at ALLS laser facility of the EMT-INRS institute, investigates the utilization of laser generated beams for elementary analysis of various materials and artifacts. In this work, firstly the characteristics of the two lasers, the experimental configurations, and the different employed particle diagnostics (Thomson parabolas, radiochromic films, etc.) employed are introduced.In the first part, a detailed study of the supersonic high density gas jets which have been used as targets at LULI is presented, from their conceptual design using fluid dynamics simulations, up to the characterization of their density profiles using Mach-Zehnder interferometry. Other optical methods such as strioscopy have been implemented to control the dynamics of the gas jet and thus define the optimal instant to perform the laser shot. The spectra obtained in different interaction conditions are presented, showing maximum energies of up to 6 MeV for protons and 16 MeV for Helium ions in the laser direction. Numerical simulations carried out with the PIC code PICLS are presented and used to discuss the different structures seen in the spectra and the underlying acceleration mechanisms.The second part presents an experiment using laser based sources generated by the ALLS laser to perform a material analysis by the Particle-induced X-ray emission (PIXE) and X-ray fluorescence (XRF) techniques. Proton and X-ray beams produced by the interaction of the laser with Aluminum, Copper and Gold targets were used to make these analyzes. The relative importance of XRF or PIXE is studied depending on the nature of the particle production target. Several spectra obtained for different materials are presented and discussed. The dual contribution of both processes is analyzed and indicates that a combination improves the retrieval of constituents in materials and allows for volumetric analysis up to tens of microns on cm^2 large areas, up to a detection threshold of ppms

Proton induced x-ray emission spectroscopy (PIXE) is a rapid and sensitive analytical technique for the non-destructive simultaneous determination of elemental concentrations above atomic number 11 (sodium) and is the only analytical technique that can determine 20-30 elements nondestructively in a single small sample (≈5 mg) with detection limits of 1- 5 ppm (dry weight). Part I of this dissertation outlines work done on the optimization of instrumental parameters and sample preparation for the analysis of biological tissue. Cultured rabbit renal slices were used as the biological system to demonstrate the use of PIXE analysis. The renal slices were exposed to HgCl₂, CdCl₂, K₂Cr₂0₇, or NaAsO₂ alone or in a mixture. The analysis of biological samples by PIXE provides information on inter-elemental interactions in tissue and body fluids. A computer program for spectrum processing and quantitation, which decomposes overlapped peaks, corrects for thick target matrix effects and calculates results without resorting to the use of standards, is explored. In part II of this dissertation, a convenient method of removing solvent from a benzene extract of graphitic soot containing fullerenes using sublimation, is outlined. Separation of macroscopic quantities of the fullerenes C₆₀ and C₇₀ has been accomplished using a combination of selective precipitation of C₆₀ and chromatography. C₆₀ is selectively crystallized by freezing and thawing a benzene solution of mixed fullerenes, then using the C₇₀ enriched supernatant as starting material in the chromatographic separation of C₆₀ and C₇₀. In the separation scheme, a bed of modified silica sorbent is charged with the fullerene mixture and the fullerenes are eluted using a hexanes/THF mobile phase. The methods of uv-Visible and infrared spectroscopy, as well as high performance liquid chromatography (HPLC) are evaluated for their ability to determine the purity of a C₆₀ or C₇₀ sample.

Trace elements within biological tissues are heterogeneously distributed. This complicates the task of deriving concentrations that represent an organ or specimen as a whole. The derivation of representative concentrations is important in the investigation of tissue health status or exposure to the individual from occupational or man-made pollution sources. Therefore, a knowledge of the elemental dispersions in biological tissues is required. Proton induced X-ray emission (PIXE) analysis is employed in the study of the elemental heterogeneity of porcine liver, kidney, heart and lung. Specimens are analysed in two different modes. One method involves the extraction of sub-samples that are dried, homogenised and manufactured into thick target pellets. This approach however limits the spatial resolution on which elemental distributions may be derived and hence thick specimen sections that can be irradiated directly may be preferred. This type of target though suffers in that surfaces are irregular and proton irradiation and X-ray take-off angles are ill defined. The effect of these surface imperfections upon X-ray yield in PIXE are investigated by the development of simple stylised models. The physical parameters of these models are varied and the elements most affected and dominant factors in modifying X-ray yield are identified. The trace element content for like tissues between targets in the form of pellets and freeze-dried sections are compared and mostly excellent correlation is found. The analysis of specimens in either of these modes stresses the high elemental inhomogeneity of biological samples. A quantitative determination of this elemental heterogeneity is made by the derivation of sampling factors, the minimum mass of material required to reduce elemental variations to a given level of precision. Those sampling factors derived by utilising the data from pelletised targets agree well with the limited values from the literature, whereas a large difference is found for those calculated from thick specimen target sections. This disagreement is thought to be due to the failure of sampling factor theory at the small sampling mass employed in the analysis of the latter targets. Photon transmission tomography was investigated for the ability of the technique to provide a measure of biological specimen heterogeneity, differentiate between different composite tissues and identify regions of interest. This may prove useful for the selection of sub-samples for subsequent trace element analysis. Biological specimens were scanned in fresh and dry states to ascertain the most favourable sample preparation technique to best achieve the above aims, the dry sample states were preferred. Freeze-dried specimens are imaged under differing scanning parameters and their data compared to theoretical values derived from PIXE and Rutherford backscattering (RBS) analysis. Good agreement is found. Regions of interest may be identified in tomographs, this being due to density variations rather than elemental variations, tissues of similar but different composition not being differentiatable due to image noise which is a product of finite counts in reconstructed images. However, with the improvement of photon counting statistics in images, these tissues may be more discernible from one another in tomographs thus making photon transmission tomography a viable technique for the selection of representative sub-samples for subsequent elemental analysis.

A novel experimental set-up was installed at the University of Surrey Ion Beam Centre for the purpose of producing 3D quantitative elemental maps of biological samples by combining simultaneous Proton Induced X-Ray Emission Tomography (PIXE- T), on/off-Axis Scanning Transmission Ion Microscopy-Tomography (STIM-T) and Rutherford Backscatter Spectrometry (RBS). A tomographic sample holder was designed and built and a scattering system developed for On/Off-Axis STIM. 2D PIXE and off-STIM analysis of leukocytes was performed to complement concurrent research and to identify problems with the very recently installed proton microbeam at the Ion Beam Centre. The other major aim was to see if a leukocyte would be a suitable sample for tomographic analysis and to study the damage induced by the beam on biological samples. Instrumental Neutron Activation Analysis (INAA) was performed on hair samples collected from MSc students at the University of Surrey and a database compiled of all elemental analysis of hair performed at the University. This complemented the tomographic analysis performed on a section of a strand of hair. Si, S, Cl, K, Ca, Fe and Zn were mapped using simultaneous PIXE-T, On/Off- Axis STIM-T and RBS.

Les composites de carbone renforcés de fibres de carbone (C/C) possèdent de nombreuses propriétés uniques, telles qu'une faible densité (< 2.0 g/cm3), une résistance/module spécifique élevé, un faible coefficient de dilatation thermique et une excellente résistance aux chocs thermiques. Ils ont été utilisés comme matériaux structurels dans les boucliers thermiques des véhicules et les freins des avions. Cependant, le carbone est sensible à l'oxydation à haute température. L'idée principale de cette thèse est de développer une technologie de protection contre l'oxydation/ ablation pour C/C, qui proposait une technologie de revêtement et une modification de la matrice. concevoir une interface de couplage revêtement/substrat. En outre, afin de mieux évaluer la fiabilité de service du revêtement, des interférences de Kossel d'émissions de rayons X induites par un proton combinées à une réflectivité des rayons X, en tant que nouvelle méthode de caractérisation non destructive, ont été développées. La faisabilité de cette méthode a été confirmée dans les films de guides d'ondes planaires. Cette méthodologie est prometteuse pour nous d’évaluer la fiabilité de service de multicouches HfC/SiC/HfC pour C/C en application réelle. Pour la technologie de modification de matrice, les céramiques HfB2 et HfB2-SiC ont été introduites dans un substrat C/C. Combinés à l'analyse thermogravimétrique et à la mesure des performances d'oxydation/ablation, le rôle des céramiques HfB2 et HfB2-SiC a été examiné
Carbon fiber reinforced carbon composites (C/C) possess many unique properties, such as low-density (< 2.0 g/cm3), high specific strength/modulus, low coefficient of thermal expansion and excellent thermal shock resistance. They have been used as the structural materials in vehicle heat shields and aircraft brakes. However, carbon is sensitive to oxidation at high temperature. The main idea of this thesis is to develop oxidation/ablation protection technology for C/C, where coating technology and matrix modification were proposed. To improve the adhesive strength and relieve the thermal expansion mismatch between the coating and the substrate, blasting treatment was proposed to design an interlock coating/substrate interface. Additionally, to better evaluate the service reliability of the coating, Kossel interferences of proton-induced X-ray emissions combined with X-ray reflectivity, as a novel non-destructive characterization method, were developed. The feasibility of this method was confirmed in planar waveguides films. This methodology is promising for us to evaluate the service reliability of HfC/SiC/HfC multilayer for C/C in actual application. For the matrix modification technology, HfB2 and HfB2-SiC ceramics were introduced into C/C substrate. Combined with thermogravimetric analysis and oxidation/ablation performance measurement, the role of HfB2 and HfB2-SiC ceramics were discussed

This master’s thesis is focused on the LIBS technique for compositional differentiation and relative hardness quantification of selected geological samples. The experimental part of this thesis was conducted at the National Institute of Laser Enhanced Sciences (NILES) in Cairo, Egypt where a simple LIBS system was constructed. In parallel to the experimental work, the literature review was surveyed with the aim to give a thorough view of the history, fundamentals and all the factors related to LIBS. LIBS is a developing analytical technique, which is used to perform qualitative and semi-quantitative elemental analysis of materials (solid, liquid and gas). The fast data collection and the lack of sample preparation made LIBS be an attractive technique to be used for geological samples. This study was done to improve analytical methods for geochemical analysis of samples during different exploration phases (Mining, filed analysis, etc.), as a real-time analysis method to save money and time spent in labs. For a generation of laser induced plasma, a Q-switched Nd: YAG laser operated at 10 Hz and wavelength of 1064 nm was employed on the surface of the samples. A spectrometer fitted with an intensified charge-coupled device (ICCD) was used to disperse and detect the spectrum; then fed to a computer for recording and further processing of the data. The sample set was compiled from samples collected from different areas (South Africa and Namibia). Using principal component analysis (PCA), it was found that LIBS was able to differentiate between the samples even those of the same area. The results from the LIBS technique were correlated with subsequent analysis of the same samples by Particle-induced X-ray emission (PIXE). The feasibility of relative hardness estimation using LIBS was done by measuring the plasma excitation temperature for different samples. LIBS with its advantages as an elemental analysis technique made it possible to estimate the hardness of geological samples. Based on theory and results, an analytical technique for compositional differentiation and quantification of relative hardness of geological samples is proposed.
National Research Foundation (South Africa)
Physics
M Sc. (Physics)

碩士
國立清華大學
物理學系
92
Abstract Hokutolite, a sediment on Andesite, is a radiative mineral. At present it is only found at Peitou Hot Spring in Taiwan and Tamagawa Hot Spring in Japan. The main composition of Hokutolite is a solid solution of barium sulfate and lead sulfate. Previous studies have shown that the weight ratio of Ba to Pb in Hokutolite from Taiwan is either 0.6-1.8 or 1.5-2.5. On the contrary, the weight ratio of Ba to Pb in Hokutolite from Japan is about 3.7-3.8. Using Particle Induced X-ray Emission, we obtained that the weight ratio of Ba and Pb in Hokutolite from Taiwan is about 0.7-1.45. However, Andesite and “Artificial Hokutolite” (Andesite sunk in Peito Hot Spring for one and a half months) are also be analyzed. The Ba/Pb weight ratio of Andesite and “Artificial Hokutolite” are 0.23 and 0.32, respectively. Thus, we hypothesize that Hokutolite has started to deposit on the “Artificial Hokutolite” in the month and half of our experiment. In addition, we analyzed theγ-ray of radionuclide 224Ra in the water issuing from the source and downstream. The radioactivities at these two locations are 3.5Bq/L and1.1Bq/L, respectively. From this we estimate that the Hot Spring is diluted to about 1/3 by domestic sewage and rainfall.

>Magister Scientiae - MSc
To study nuclear reactions and nuclear structures, target materials are bombarded with high-energy particles. The target material can either be in a form of a metal film or gas. A target material designed to study certain nuclear reactions or to produce nuclei to study their structure should yield as minimum as possible of competing reactions under ion bombardment. This requires a chemically and isotopically pure target material prepared as a self supporting thin film, or as alternative, prepared on a thin career foil. Additional requirement for lifetime measurement experiments are homogeneity and precise thickness of the target material. Some of the data obtained from the stopping power experiment where targets of 114Cd were used for lifetime measurement are presented. Moreover, a nuclear target should influence the spectroscopic resolution as little as possible. Thus, film thickness must be adjusted to the respective reaction under study while observing the optimum thickness homogeneity.