none

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.

Thesis (Ph. D.)--University of Washington, 1991. / Vita. Includes bibliographical references (leaves [131]-137).

abstract: Interpreting the petrogenesis of materials exposed on the surface of planets and asteroids is fundamental to understanding the origins and evolution of the inner Solar System. Temperature, pressure, fO2, and bulk composition directly influence the petrogenetic history of planetary surfaces and constraining these variables with remote sensing techniques is challenging. The integration of remote sensing data with analytical investigations of natural samples, lab-based spectroscopy, and thermodynamic modelling improves our ability to interpret the petrogenesis of planetary materials. A suite of naturally heated carbonaceous chondrite material was studied with lab-based spectroscopic techniques, including visible near-infrared and Fourier transform infrared reflectance spectroscopy. Distinct mineralogic, and thus spectroscopic, trends are observed with increasing degree of thermal metamorphism. Characterization of these spectral trends yields a set of mappable parameters that will be applied to remotely sensed data from the OSIRIS-REx science payload. Information about the thermal history of the surface of the asteroid Bennu will aid in the selection of a sampling site, ensuring OSIRIS-REx collects a pristine regolith sample that has not experienced devolatilization of primitive organics or dehydration of phyllosilicates. The evolution of mafic magma results in distinct major element chemical trends. Mineral assemblages present in evolved volcanic rocks are indicators of these processes. Using laboratory spectroscopic analyses of a suite of evolved volcanic rocks from the Snake River Plain, Idaho, I show that these evolutionary trends are reflected in the spectral signatures of ferromagenesian and feldspar minerals. The Athena science package on the Mars Exploration Rover Spirit allows for the in situ investigation of bulk chemistry, texture, and mineralogy on the surface of Mars. Using the bulk composition of the Irvine and Backstay volcanic rocks, thermodynamic modeling was performed to further constrain the formation conditions of Martian volcanics. Irvine and Backstay compositions exhibit dramatic variations in modal mineralogy with changing fO2. Using these results, I show that the observed Mini-TES spectra of Irvine and Backstay can be adequately reproduced, and additional constraints can be placed on their primary fO2. / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2018

Made available in DSpace on 2014-10-09T12:36:12Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:21Z (GMT). No. of bitstreams: 1 03663.pdf: 2365322 bytes, checksum: 0692ed0d4b16ccfb98d632cec8b1dc1d (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

La modélisation du rayonnement du CO2 à plus de 2000 K reste un défi pour la prédiction des transferts radiatifs à très haute température, en particulier pour le dimensionnement des protections thermiques des véhicules spatiaux entrant dans l’atmosphère de Mars. Le défi concerne aussi bien la constitution de bases de données que le développement de modèles permettant de réaliser des calculs couplés entre l’aérothermodynamique et les transferts radiatifs. Plusieurs bases de données spectroscopiques ont été développées dans les dernières décennies. Des simulations effectuées sur des mélanges CO2-N2 à l’équilibre ont montré que l’émission IR de CO2 reste importante, si ce n’est prédominante, jusqu’à 4000 K. Mais les données expérimentales permettant de vérifier leur précision à haute température sont peu nombreuses et limitées à la basse résolution spectrale, à des températures plus faibles, ou encore impliquent des incertitudes importantes. L’objectif principal de ces travaux est donc de fournir des données expérimentales à moyenne ou haute résolution spectrale et à haute température pour permettre de vérifier la précision des bases théoriques développées. Le mélange gazeux à très haute température dont nous mesurons les spectres d’émission est obtenu grâce à une décharge micro-ondes traversant un flux de CO2 pur. Aux températures atteintes (environ 6000 K), le mélange est à l’équilibre thermodynamique local (ETL) et contient principalement les espèces suivantes : CO2, CO, O2 et O. La mesure des spectres est effectuée grâce à un spectromètre à transformée de Fourier dans l’infrarouge. L’émission des bandes harmoniques de CO dans la région 3800-4400 cm puissance-1 permet la détermination précise du champ de température radial dans le plasma. L’émission théorique de CO2, que ce soit en coefficient d’émission ou en luminance intégrée sur un chemin optique, dans les régions de 2,7 _m et 4,3 _m, est alors calculée à partir des bases de données spectroscopiques et comparée aux mesures. Les bases de données spectroscopiques étudiées sont la base CDSD-4000 récemment publiée et EM2C-1994 qui est plus ancienne. Les résultats montrent que cette dernière est suffisante pour des applications classiques en combustion, nécessitant typiquement de faibles résolutions spectrales et des températures inférieures à 2500 K, pour lesquelles elle fut initialement développée. En revanche, la base CDSD-4000 est généralement en très bon accord avec les données expérimentales, en particulier dans les ailes de bandes ce qui indique sa fiabilité pour des applications à très haute température. Bien que des comparaisons aient révélé que les positions de raies pour les transitions à haute énergie manquent de précision dans cette base, le degré élevé de recouvrement des raies dans les régions 2,7 _m et 4,3 _m devrait grandement limiter l’impact de cette imprécision dans la pratique. L’autre objectif de ces travaux concerne la difficulté que pose la couplage entre les calculs d’aérothermodynamique et de transferts radiatifs. En effet, les calculs de transferts iv radiatifs impliquant des molécules polyatomiques doivent prendre en compte un nombre très important de transitions rovibroniques. Par conséquent, un modèle approché de propriétés radiatives (modèle Statistique à Bandes Etroites) a été développé et sa précision a été étudiée pour les systèmes électroniques optiquement épais des molécules carbonées diatomiques rencontrées dans les problèmes de rentrées atmosphériques martiennes. Ces systèmes sont CO 4eme positif, C2 Swan, et CN violet. Diverses conditions à l’ETL et hors ETL, ainsi que différents mélanges ont été étudiés pour différents régimes d’élargissement de raies. Les comparaisons effectuées avec les calculs "raie par raie" ont révélé d’excellents accords. Les paramètres de ce modèle ont été tabulés en fonction de deux températures, Tv (température vibrationnelle) et Tr (température rotationnelle). / Modeling of the radiation of CO2 above 2000 K remains a challenge for the prediction of radiative transfer at high temperatures, especially for the design of thermal protection of space vehicles entering the Martian atmosphere. The challenge for both the creation of databases that the development of models to perform calculations coupled between Aerothermodynamics and radiative transfer. Several spectroscopic databases have been developed in recent decades. Simulations of CO2-N2 mixtures at equilibrium showed that the IR emission of CO2 is important, if not predominant, up to 4000 K. But the experimental data to verify their accuracy at high temperature are few and limited to the low spectral resolution, at lower temperatures, or involve significant uncertainties. The main objective of this work is to provide experimental data at medium or high spectral resolution and high temperature in order to verify the accuracy of the theoretical foundations developed. The gas mixture at high temperature we measure the emission spectra is achieved through a microwave discharge through a stream of pure CO2. The temperatures reached (about 6000 K), the mixture is in local thermodynamic equilibrium (LTE) and mainly contains the following species: CO2, CO, O2 and O. The measurement of the spectra is carried out using a Fourier transform spectrometer in the infrared. The harmonic emission bands of CO in the region 3800-4400 cm-1 power allows accurate determination of the radial temperature field in the plasma. The theoretical CO2 emissions, both in emission coefficient or radiance integrated on an optical path, in the regions of 2.7 and 4.3 _m _m, is then calculated from the spectroscopic database and compared measures. The databases are based spectroscopic studied CDSD-4000 and recently published EM2C-1994 which is older. The results show that the latter is sufficient for combustion in conventional applications, typically requiring low spectral resolutions and temperatures below 2500 K, for which it was originally developed. However, based CDSD-4000 is generally in good agreement with experimental data, especially in the wings of bands indicating reliability for applications at very high temperatures. Although comparisons have revealed that the line positions for high energy transitions are unclear in this basis, the high degree of overlap of the lines in the regions 2.7 and 4.3 _m _m should greatly reduce the impact of this imprecision in practice. The other objective of this work concerns the difficulty of coupling between the calculations of radiative transfer and aerothermodynamics. Indeed, calculations of radiative transfer iv involving polyatomic molecules must take into account a large number of rovibronic transitions. Therefore, an approximate model of radiative properties (Statistics narrowband model) was developed and its accuracy has been studied for electronic systems optically thick carbon diatomic molecules encountered in problems of Martian atmospheric reentry. These systems are CO 4th positive, C2 Swan and CN violet. Various conditions to the non-LTE and LTE, and various mixtures have been studied for different regimes of line broadening. Comparisons with calculations "line by line" showed excellent agreement. The model parameters were tabulated in terms of two temperatures, Tg (vibrational temperature) and Tr (rotational temperature).

Made available in DSpace on 2014-10-09T12:36:12Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:21Z (GMT). No. of bitstreams: 1 03663.pdf: 2365322 bytes, checksum: 0692ed0d4b16ccfb98d632cec8b1dc1d (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Abstract In this thesis, different spectroscopic methods are used for studying metals. Electron spectroscopy is applied for the study of binding energy shifts between atomic vapor and solid metals. Photoionization and Auger decay of high temperature aluminum vapors are investigated. Ionization of atomic chromium metal vapor by light absorption is studied with synchrotron radiation and time-of-flight ion mass spectroscopy. Optical spectroscopy is used for studying light emission from electric arc furnace plasma in experimental apparatuses developed during this work. Experimental techniques and sample preparation methods are presented.

Le présent travail de thèse a consisté en un diagnostic d’une colonne de plasma d’un mélange d’argon et de CO2, créée par une décharge éclatant dans un réacteur cylindrique, entre deux électrodes pointues en tungstène, sous une tension d’amorçage de 10KV, un courant de 100 à 300mA, et à pression atmosphérique. Le diagnostic du plasma a été réalisé à l’aide d’un laser Hélium Néon (raie 632.8nm), d'un interféromètre de Mach-Zehnder et d’un spectromètre à fibre optique. Après calcul de la composition du mélange d’Argon et de CO2 en fonction de la température par la méthode de minimisation de l’enthalpie libre de Gibbs, on a déterminé la densité des espèces. Utilisant les propriétés des particules soumises à une onde électromagnétique, et la relation de Gladstone Dale qui lie l’indice de Réfraction d’un Gaz à sa densité et à sa température, nous avons calculé l’évolution de la réfractivité du milieu. Ensuite nous l’avons mesurée pour obtenir les profils radiaux de température par la transformée de Fourier et l’inversion d’Abel, des cartes de phase obtenues par interférométrie optique. Ce travail a été complété par une analyse par spectroscopie optique moléculaire d’émission. Utilisant le système de Swan de la molécule C2 (d3!g – a3!u) comme pyromètre, notamment les bandes 01(5635.2 Å) et 12 (5585.5 Å), nous avons déterminé les températures vibrationnelles et rotationnelles du plasma. Un programme en FORTRAN a été mis au point, pour la simulation des bandes moléculaires. Nous avons diagnostiqué la colonne de plasma sur toute sa largeur et dressé un profil de température radial. Les températures vibrationnelles et rotationnelles nous ont permis de calculer l’écart à l’équilibre thermodynamique. / This work of thesis consisted of a diagnosis of a column of plasma of a mixture of argon and CO2 created by a discharge bursting in a cylindrical engine, between two pointed tungsten electrodes, under a voltage of 10KV, a current of 100 to 300mA, at atmospheric pressure. The diagnosis of plasma was carried out using a laser Helium Neon (line 632.8nm), of an interferometer of Mach-Zehnder and a spectrometer with optical fibre. After calculation of the mix design of Argon and CO2 according to the temperature by the method of minimization of the free enthalpy of Gibbs, one determined the density of the species. Using the properties of the particles subjected to an electromagnetic wave, and the relation of Gladstone Dale which binds the index of Refraction of a Gas to its density and its temperature, we calculated the evolution of the refractivity of the medium. Then we measured it to obtain the radial profiles of temperature by the Fourier transform and the inversion of Abel, of the charts of phase obtained by optical interferometry. This work was supplemented by an analysis by molecular optical spectroscopy of emission. Using the system of Swan of the molecule C2 (d3!g – a3!u) like pyrometer, in particular the bands 01(5635.2 Å) and 12 (5585.5 Å), we determined the vibrational and rotational temperatures in the plasma. A Fortran program was developed, for the simulation of the molecular bands. We diagnosed the column of plasma over all its width and drew up a radial profile of temperature. The calculation of the vibrational and rotational temperatures enabled us to calculate the variation with thermodynamic balance.

The application of low-pressure low-temperature hydrogen plasma on artificial corrosion layers on bronze has been studied. For this purpose, three sets of bronze corroded samples were prepared. The first step of the model sample preparation was grinding of the bronze surface by using emery with 60, then 280 and finally by 600 grains density, in order to achieve the defined surface roughness. The next step of the work were optical and scanning electron microscopy observations with energy dispersive X-ray micro analysis (SEM-EDX) of the prepared bronze sample for purpose of surface structure characterization and element composition determination. Bronze samples with defined surface structure were corroded in different corrosion atmospheres. Three different model corrosion layers were formed by acidic atmospheres of hydrochloric acid, nitric acid and sulphuric acid. The element composition and structure of corrosion layer was determined by SEM-EDX again. The different amounts of oxygen, nitrogen, chlorine, sulfur, copper, tin and lead in the corrosion layer according to different types of corrosion atmospheres were determined. The next and also main part of the work was a plasma chemical reduction of corroded samples. The plasma reactor used the RF discharge (13.56 MHz) created in quartz tube with outer electrodes. The generation of capacitively coupled plasma in continuous or pulse mode by different supplied power was carried out. The plasma radiation emitted from the RF discharge during the sample treatment was measured by optical emission spectroscopy. The quantity of OH radical created in an active discharge by reactions of atomic hydrogen with the corrosion layer is a significant indicator of a reduction process. Therefore the OH radical band integral intensities observed as a function of the treatment time were used as a monitor for plasma chemical reduction process. The OH emission showed different behavior depending on corrosion layer composition during the plasma treatment. The transformations of the corrosion layer due to the plasma effect were investigated by means of SEM-EDX once again. Changes in the element composition of corrosion (or surface) layers in consequence of plasma chemical treatment are given. Generally, the element composition after the plasma chemical treatment showed explicitly that oxygen and chlorine content in the corrosion layer decreased, nitrogen was removed totally. Metal deposition on the reactor wall was observed occasionally. The SEM-EDX analyzes also showed that in some cases the tin content in sample surface layers was significantly decreased. For that reason, in case of bronze sample (artifacts) treatment, the sample and plasma temperature seem to be very important parameters for the process optimization. The acceptable conditions for plasma chemical treatment has been found in case of corrosion layer formed by nitric acid, only. The other corrosions will be a subject of further studies.