Dissertations / Theses on the topic 'Diamond laser'
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1
Neff, Clayton. "Mechanical Properties of Laser-Sintered-Nylon Diamond Lattices." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/6001.
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Additive manufacturing offers a manufacturing technique to produce complex geometry prototypes at a rapid pace and low cost. These advantages advocate additive manufacturing for the design and production of cellular structures. Cellular structures are interesting because they contain a large amount of porosity (void space of air) to manifest a lightweight structure. Designs of cellular structures generate a periodic pattern; often of complex geometry, called a lattice.
There has been a significant amount of research to maximize specific stiffness of lattice structures but little to evaluate low-stiffness lattices. Low-stiffness structures benefit energy absorbance through bending of the lattice. This research seeks to assess diamond lattices as low stiffness, bending structures.
The research involves PA2200 (Nylon 12) laser sintered diamond lattices with experimental compression testing and direct FEA model comparison. A correction factor is applied for a design offset of laser sintered lattices. Once applied, the experimental and FEA data agree in validating the diamond lattice as a bending-dominated structure. Diamond lattices show a 4th order relationship between stiffness and parameters of thickness and unit cell length. For density, stiffness maintains a 2nd order relationship, as predicted by bending dominated structures. The resulting stiffness can be tuned over a stiffness range of four orders of magnitude. Further research shows the results for modifying the diamond lattice and scaling stiffness and density using other materials (like metals) to expand the range of stiffness and compare diamond lattices on material property charts. Lastly, the effective Poisson’s ratio varies from 0.5 to 0.4 depending on the (t/L) ratio.
2
Chen, Yu-Chen. "Laser writing of coherent colour centres in diamond." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:1b9fc247-3e35-457e-bfa5-d4ca474ac1ff.
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Optical active point defects in crystals have gained widespread attention as photonic systems that could be applied in quantum information technologies[1, 2]. However, challenges remain in the placing of individual defects at desired locations, an essential element of device fabrication. Here we report the controlled generation of single negatively charged nitrogen-vacancy (NV-) centres in diamond using laser writing[3]. Aberration correction in the writing optics allows precise positioning of the vacancies within the diamond crystal and subsequent annealing produces single NV- centres with a probability of success of up to 45%, located within about 200nm of the desired position in the transverse plane. A simple model was established to understand the mechanism of vacancies generation and estimate the success probability of NV- centres generation. Selected NV- centres display stable, coherent optical transitions at cryogenic temperatures, a prerequisite for the creation of distributed quantum networks of solid-state qubits. Strain measurement results of selected NV- centres show that the broadening of NV- optical transitions is due to local strain. The results illustrate the potential of laser writing as a tool for defect engineering in quantum technologies and extend laser processing to the single-defect domain.
3
Sharkey, Leo R. "Polishing of diamond films using an excimer laser." Connect to resource, 1996. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1192573096.
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Wills, Jonathan B. "Laser diagnostics of chemical vapour deposition of diamond films." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251103.
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5
Gottimukkala, Roja. "Growth and characterization of diamond and diamond like carbon films with interlayer." [Tampa, Fla] : University of South Florida, 2005. http://purl.fcla.edu/usf/dc/et/SFE0001405.
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Lamprecht, GH, HGC Human, and LW Snyman. "Detection of diamond in ore using pulsed laser Raman spectroscopy." Elsevier, 2007. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1000795.
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The viability of using pulsed laser excited Raman spectroscopy as a method for diamond detection from ore, has been
investigated. In this method the spontaneous Stokes Raman signal is used as indicator of diamond, and a dual channel system is
necessary for correcting for fluorescence of minerals and diamond itself. Various pulsed laser wavelengths from 266 to 1064nm
were used, as well as cw lasers for comparison. Wavelength scans of the regions of interest, indicated that pulsed lasers at 532, 355
and 308nm may be used with confidence for this purpose. Mineral fluorescence did not appear to pose a threat to the method, but
rather own fluorescence of some types of diamonds. In this respect, pulsed lasers offer a decided advantage above cw, due to nonlinear
increase of fluorescence with laser power, resulting in superior Raman to fluorescence signal ratios. An apparatus constructed
for discriminating diamond from ore was evaluated, and using minerals commonly occurring in diamond carrying ore as well as a
wide variety of diamonds, it proved to function effectively. A significant improvement in the capability for diamond detection was
found when pulsed lasers at 532 and 308nm were used, in comparison to the 532nm cw laser.
7
Lamprecht, GH, HGC Human, and LW Snyman. "Detection of diamond in ore using pulsed laser Raman spectroscopy." Elsevier, 2006. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1000856.
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The viability of using pulsed laser excited Raman spectroscopy as a method for diamond detection from ore, has been
investigated. In this method the spontaneous Stokes Raman signal is used as indicator of diamond, and a dual channel system is
necessary for correcting for fluorescence of minerals and diamond itself. Various pulsed laser wavelengths from 266 to 1064nm
were used, as well as cw lasers for comparison. Wavelength scans of the regions of interest, indicated that pulsed lasers at 532, 355
and 308nm may be used with confidence for this purpose. Mineral fluorescence did not appear to pose a threat to the method, but
rather own fluorescence of some types of diamonds. In this respect, pulsed lasers offer a decided advantage above cw, due to nonlinear
increase of fluorescence with laser power, resulting in superior Raman to fluorescence signal ratios. An apparatus constructed
for discriminating diamond from ore was evaluated, and using minerals commonly occurring in diamond carrying ore as well as a
wide variety of diamonds, it proved to function effectively. A significant improvement in the capability for diamond detection was
found when pulsed lasers at 532 and 308nm were used, in comparison to the 532nm cw laser.
8
Rebello, Jagdish Hilary Diago. "Synthesis of Diamond by Selective Laser Excitation of Gaseous Precursors /." The Ohio State University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487928649986997.
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9
Williams, Themistoklis. "Development of the diamond detector based real-time monitoring system for the ELI-NP gamma beam source." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS277/document.
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Cette thèse présente le développement d'un système de contrôle en temps réel basé sur un détecteur en diamant pour la nouvelle source de rayons gamma en cours de construction à Magurele, en Roumanie, pour le projet Extreme Light Infrastructure (ELI). La machine comprend un accélérateur linéaire d'électrons qui se sépare en deux lignes, une à basse énergie entre 80 et 320 MeV et l'autre à plus haute énergie pouvant atteindre 720 MeV. Sur les deux lignes, un recirculateur optique guide un laser haute puissance pour entrer en collision avec 32 paquets d'électrons afin de produire des rayons gamma par interaction Compton inverse. Cette machine est construite par le consortium européen EuroGammaS, dont le Laboratoire de l'Accélérateur Linéaire fait partie et qui a pour mission de développer la plupart des composants optiques. C'est aussi là où j'ai préparé le travail présenté dans ce manuscrit. Les paquets d'électrons séparés de 16 ns collisionneront avec une impulsion laser à une fréquence de 100 Hz. Pour s'assurer de la qualité et de la stabilité de ces interactions, le système du détecteur diamant a été mis en place. Cela a impliqué du travail de simulation sous GEANT4 ainsi que des expériences pour tester l'équipement à HiGS aux Etats-Unis et à newSubaru au Japon, deux établissements scientifiques qui proposent aussi des sources de rayons gamma produits par interaction Compton inverse. Les résultats obtenus démontrent l'efficacité de ce système en analysant l'efficacité de détection, la charge collectée ou encore la forme de faisceau. Ceci est encourageant en vue de l'installation et du commissioning qui sont attendus pour 2019This thesis discusses the development of a real-time monitoring system based on a diamond detector for the new gamma source being built in Magurele, Romania as part of the Extreme Light Infrastructure (ELI) project. The machine consists of an electron linear accelerator that branches into two lines, one at low energy between 80 and 320 MeV and one at higher energy going up to 720 MeV. On both lines, an optical recirculator leads a high power laser to collide with 32 electrons bunches to produce gamma rays by inverse Compton interaction. This machine is built by a European consortium named EuroGammaS, of which the "Laboratoire de l'Accélérateur Linéaire" is a member and tasked with developing most of the optical components. This is where I prepared the work presented in this manuscript. The electron bunches separated by 16 ns will collide with a circulating laser pulse at a rate of 100 Hz. To monitor the quality and stability of these interactions, the diamond detector system has been set-up. This involved simulation work on GEANT4 as well as two experiments to test the equipment at HiGS in the USA and newSubaru in Japan, two facilities that also offer gamma ray beams produced by inverse Compton scattering. The results obtained demonstrate the effectiveness of the system by analysing detection efficiency, charge collected or beam shape. This is promising in anticipation of the installation and commissioning expected for 2019
10
Lade, Robert James. "Pulsed ultraviolet laser ablation of carbon containing targets." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302156.
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Minami, Hideki. "Characterization of diamond-like carbon films produced by pulsed laser deposition." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0018/MQ47071.pdf.
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12
Reilly, Sean. "Characterisation and implementation of synthetic diamond as a Raman laser material." Thesis, University of Strathclyde, 2015. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=25764.
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Diamond's unrivalled thermo-mechanical and optical properties make the material an attractive material for use in laser systems. Improvements in growth techniques over the past decade have led to a surge of research employing diamond in optical systems. This thesis presents the characterisation of diamond and its implementation in Raman lasers, utilising the materials high Raman gain as well as its impressive thermal properties. Diamond's potential as both an extremely compact and robust method for frequency conversion, allowing access to relevant but otherwise hard to reach wavelengths, and also as a means to convert low brightness sources to near diffraction limited beams will also be discussed. A pump-probe measurement is used to conduct the first systematic study of the Raman gain in diamond over a wide range of wavelengths, from 355nm to 1450nm, with a dependence observed. Using the high Raman gain measured, both CW and pulsed Raman systems were designed and characterised. An 11-fold brightness enhancement was achieved in an Nd:YAG pumped intra-cavity diamond Raman laser, while record powers of 7.6W are presented using an Yb:LuAG pumped diamond Raman laser. Two monolithic diamond Raman lasers are discussed, achieving near quantum limited conversion efficiencies. An investigation of the laser induced damage threshold of diamond surfaces is conducted, with attempts made to improve the measured value of 25Jcm-2 discussed.
13
De, Feudis Mary. "Diamonds : synthesis and contacting for detector applications." Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCD005/document.
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Ce travail de doctorat a été réalisé dans le cadre d'un accord de cotutelle international entre l'Université de Salento (L3, Italie) et l'Université de Paris 13 (LSPM, France). L'objectif principal était la fabrication de contacts ohmiques sur des surfaces de diamant pour des applications telles que les détecteurs et les dispositifs de l’électronique. Les travaux au L3 ont été consacrés à l'étude du processus de graphitisation du diamant induit par laser afin de produire des électrodes de graphite sur des diamants intrinsèques. L'étude se concentre en particulier sur le développement d’un appareil expérimental pour l’écriture laser sur diamant tant sur les aspects matériel que logiciel, et un protocole a ainsi été développé pour la fabrication de contacts graphitiques segmentés sur de larges surfaces de diamant (cm²). Des travaux approfondis de caractérisation ont démontré la transition de phase diamant-graphite et le comportement ohmique pour les contacts électriques avec une résistivité de l'ordre de 10⁻⁵ Ω.m. Des détecteurs tout-carbone ont ainsi été développés et testés avec des faisceaux électroniques et positroniques de 450 MeV. Ils permettent d’ouvrir des perspectives en tant que cible active pour de nouvelles expériences de physique des hautes énergies (PADME) dans le cadre de l’étude de la matière noire. Le travail au LSPM a été consacré au développement d'un protocole permettant d'obtenir des contacts ohmiques sur des films diamant faiblement dopé au bore et terminé oxygène, élaborés par MPACVD. Les procédés de fabrication de contacts métalliques Ti/Au sur une structure mesa ainsi que l’implantation par des ions He, ont été développés afin d'induire une couche de graphite juste en dessous de la surface de diamant. Les mesures électriques sur des diamants légèrement dopés ([B] = 4 × 10¹⁷ cm⁻³) avec seulement des contacts métalliques ou graphitiques / métalliques ont montré que la présence de la couche graphitique rend les contacts ohmiques et conduisent à une résistance spécifique de contact égale à 3.3 × 10⁻⁴ Ω.cm²This PhD work has been carried out in international cotutelle agreement between the University of Salento (L3, Italy) and the University of Paris 13 (LSPM, France). The main aim was the manufacturing of ohmic contacts on diamond surface for detector and electronic device applications. The work at L3 was dedicated to the laser-induced diamond graphitization process in order to produce graphitic electrodes on intrinsic diamonds. An experimental set-up dedicated to the laser writing technique on diamond has been developed in both hardware and software aspects and a protocol for the manufacturing of segmented graphitic contacts on diamond surface of large scale (cm²) has been implemented. An extensive characterization work has demonstrated the diamond-graphite phase transition and an ohmic electrical behaviour for the contacts with a resistivity of the order of ≈ 10⁻⁵ Ω.m. Eventually, an all-carbon detector has been developed and tested with 450 MeV electron and positron beams proving to be a good candidate in the role of active target for a new high-energy experiment (PADME) in the framework of the dark matter. The work at LSPM has been dedicated to the development of a protocol allowing reaching ohmic contacts on lightly boron doped diamond with oxygenated surface grown by MPACVD. The fabrication of Ti/Au metallic contact above a mesa structure has relied on a He ion implantation treatment to induce a graphitic layer underneath the diamond surface. The electrical measurements on lightly doped diamonds ([B] = 4 × 10¹⁷ cm⁻³) with metal or graphite / metal contacts have shown that the graphitic layer makes ohmic the contacts leading to a specific contact resistance as low as 3.3 × 10⁻⁴ Ω.cm²
Questo dottorato di ricerca è stato svolto in convenzione di cotutela internazionale tra l’Università del Salento (L3, Italia) e l’Università di Parigi 13 (LSPM, Francia). Il principale obiettivo è stato la fabbricazione di contatti ohmici su superficie di diamante per applicazioni come rivelatori e dispositivi elettronici. Il lavoro a L3 è stato dedicato allo studio del processo di grafitizzazione del diamante indotto da laser al fine di produrre elettrodi grafitici su diamanti intrinseci. In particolare, è stato sviluppato un apparato sperimentale dedicato alla tecnica di scrittura laser su diamante sia nelle componenti hardware che software, ed è stato realizzato un protocollo per la fabbricazione di contatti grafitici segmentati su superfici di diamante di grande scala (cm²). Un ampio lavoro di caratterizzazione ha dimostrato la transizione di fase diamante-grafite e il comportamento ohmico per i contatti elettrici con una resistività dell’ordine di 10⁻⁵ Ω.m. Pertanto, un rivelatore costituito solo di carbonio è stato sviluppato e testato con fasci elettronici e positronici di 450 MeV risultando essere un buon candidato nel ruolo di bersaglio attivo per un nuovo esperimento di fisica delle alte energie (PADME) nel contesto della materia oscura. Il lavoro a LSPM è stato dedicato allo sviluppo di un protocollo che ha consentito di ottenere contatti ohmici su diamanti leggermente drogati con boro e con superficie terminata con ossigeno, cresciuti mediante MPACVD. I processi di fabbricazione di contatti metallici Ti/Au sopra una struttura mesa sono stati sviluppato così come un trattamento di impiantazione a base di ioni di He al fine di indurre uno strato grafitico appena sotto la superficie del diamante. Le misure elettriche su diamanti leggermente drogati ([B] = 4 × 10¹⁷ cm⁻³) con contatti o solo metallici o grafitici / metallici hanno dimostrato che la presenza dello strato grafitico rende i contatti ohmici e comporta una resistenza specifica di contatto pari a 3.3 × 10⁻⁴ Ω.cm²
14
Smith, James Anthony. "Laser diagnostics of a diamond depositing chemical vapour deposition gas-phase environment." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247541.
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Alameer, Maryam. "Polarization Dependent Ablation of Diamond with Gaussian and Orbital Angular Momentum Laser Beams." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39850.
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The vectorial nature (polarization) of light plays a significant role in light-matter interaction
that leads to a variety of optical devices. The polarization property of light
has been exploited in imaging, metrology, data storage, optical communication and
also extended to biological studies. Most of the past studies fully explored and dealt
with the conventional polarization state of light that has spatially symmetric electrical
field geometry such as linear and circular polarization. Recently, researchers
have been attracted to light whose electric field vector varies in space, the so-called
optical vector vortex beam (VVB). Such light is expected to further enhance and
improve the efficiency of optical systems. For instance, a radially polarized light
under focusing condition is capable of a tighter focus more than the general optical
beams with a uniform polarization structure, which improves the resolution of the
imaging system [1].
Interaction of ultrafast laser pulses with matter leads to numerous applications
in material processing and biology for imaging and generation of microfluidic systems.
A femtosecond pulse, with very high intensities of (10^{12} - 10^{13} W/cm^2), has
the potential to trigger a phenomenon of optical breakdown at the surface and therefore
induce permanent material modification. With such high intensities and taking
into account the fact that most materials possess large bandgap, the interaction is
completely nonlinear in nature, and the target material can be modified locally upon the surface and even further in bulk. The phenomenon of optical breakdown can be
further investigated by studying the nonlinear absorption. Properties like very short
pulse duration and the high irradiance of ultrashort laser pulse lead to more precise
results during the laser ablation process over the long pulsed laser. The duration of
femtosecond laser pulse provides a high resolution for material processing because
of the significant low heat-affected zone (HAZ) beyond the desired interaction spot
generated upon irradiating the material. Under certain condition, the interaction
of intense ultrashort light pulses with the material gives rise to the generation of
periodic surface structures with a sub-micron periodicity, i.e., much smaller than the
laser wavelength. The self-oriented periodic surface structures generated by irradiating
the material with multiple femtosecond laser pulses results in improving the
functionality of the material's surface such as controlling wettability, improving thin
film adhesion, and minimizing friction losses in automobile engines, consequently,
influences positively on many implementations.
In this work, we introduced a new method to study complex polarization states
of light by imprinting them on a solid surface in the form of periodic nano-structures.
Micro/Nanostructuring of diamond by ultrafast pulses is of extreme importance because
of its potential applications in photonics and other related fields.
We investigated periodic surface structures usually known as laser-induced periodic surface
structures (LIPSS) formed by Gaussian beam as well as with structured light carrying
orbital angular momentum (OAM), generated by a birefringent optical device
called a q-plate (QP). We generated conventional nano-structures on diamond
surface using linearly and circularly polarized Gaussian lights at different number
of pulses and variable pulse energies. In addition, imprinting the complex polarization state of different orders of optical vector vortex beams on a solid surface was fulfilled in the form of periodic structures oriented parallel to the local electric field of optical light. We also produced a variety of unconventional surface structures by superimposing a Gaussian beam with a vector vortex beam or by superposition of different order vector vortex beams.
This thesis is divided into five chapters, giving a brief description about laser-matter
interaction, underlying the unique characterization of femtosecond laser over
the longer pulse laser and mechanisms of material ablation under the irradiation of
fs laser pulse. This chapter also presents some earlier studies reported in formation
of (LIPSS) fabricated on diamond with Gaussian. The second chapter explains the
properties of twisted light possessing orbital angular momentum in its wavefront, a
few techniques used for OAM generation including a full explanation of the q-plate
from the fabrication to the function of the q-plate, and the tool utilized to represent
the polarization state of light (SoP), a Poincar'e sphere. Finally, the experimental details and results are discussed in the third and fourth chapters, respectively,
following with a conclusion chapter that briefly summarizes the thesis and some
potential application of our findings.
16
Murphy, Steven. "An investigation of processing techniques and characterisation methods for 3D diamond detectors." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/an-investigation-of-processing-techniques-and-characterisation-methods-for-3d-diamond-detectors(186f03ff-d923-4fe7-bc27-dffd71e6bb36).html.
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In this thesis 3D diamond detectors were fabricated using an ultrafast femtosecond (120 fs) pulse length laser, with a 800nm wavelength, to induce a phase change of diamond to graphite to form electrodes in the diamond bulk. Graphitic electrodes, with diameters of O(um), were fabricated using a known processing technique and were enhanced further through the use of a Spatial Light Modulator (SLM), which is a new technology in this field. These detectors were subsequently characterised through the use of particle beams, and this work also presents methods for characterising such detectors: A pair of crossed polarisers to determine the stress induced by the electrodes on the diamond bulk; Raman spectroscopy to assess the relative quantity of diamond:graphite formed; Scanning Electron Microscopy (SEM) to image the starting (seed) and finishing (exit) sides of electrode formation; and current-voltage (I-V) measurements to calculate the electrical properties of the electrodes. These characterisation methods (alongside the use of particle beams) serve as a means to compare the two fabrication techniques and to determine the optimum fabrication parameters to produce 3D diamond detectors for use as tracking detectors in high luminosity environments such as those in the Large Hadron Collider (LHC). This work shows that using a higher beam energy and translation speed of the focal spot results in electrodes of lower electrical resistivity, which is an ideal characteristic for a tracking detector. These higher processing parameters also result in more graphitic structure on the seed and exit sides of the diamond, determined separately via Raman spectroscopy and SEM. An increased beam energy also results in larger electrode diameters, reducing the active area of the detector and inducing more stress in the diamond bulk. These measurements therefore indicate an upper limit on the fabrication parameters. A further study into these processing parameters shows the translation speed scales with the pulse repetition rate of the laser and allows for fast fabrication of 3D diamond detectors. Two devices were fabricated with and without the use of an SLM, with a more uniform detector response (through characterisation by particle beams), lower electrical resistivity, and more graphitic material observed for SLM-fabricated electrodes. The benefits of square and hexagonal cell structures were also investigated with both structures showing a similar response to particle beams. A lower charge sharing region is observed in hexagonal cells and indicates potentially different applications for these cell geometries. Transient Current Technique (TCT) measurements were also taken on both detectors, where faster charge collection and higher quality data were seen for the SLM-fabricated device. These measurements indicate a preference in the use of an SLM for the future fabrication of 3D diamond tracking detectors. These TCT measurements were then compared to simulations to extract the charge carrier properties in diamond. Only qualitative agreement was obtained, motivating further work in this area to fully understand the charge carrier dynamics and demonstrate the future viability of 3D diamond detectors.
17
Sikora, Aurélien. "Incorporation de bore dans des films minces de « diamond-like carbon » : élaboration par ablation laser pulsé et caractérisations." Saint-Etienne, 2009. http://www.theses.fr/2009STET4018.
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Ce travail concerne l’étude de couches minces de « Diamond-Like Carbon » dopés au bore élaborées par ablation laser femtoseconde et nanoseconde. Un des objectifs de cette étude est d’identifier les applications potentielles de ces films en tant qu’élément actif de capteur (par exemple de température). Le deuxième objectif est de corréler la structure et les propriétés des films minces obtenus avec les procédés de dépôt employés. Le premier chapitre présente les éléments constitutifs des couches minces étudiées : le bore et le carbone. Ce chapitre propose également un état de l’art sur les films de DLC purs et dopés et les méthodes d’élaboration existantes. Le deuxième chapitre traite des méthodes expérimentales adoptées pour l’élaboration et l’étude des films. Le troisième chapitre traite des différentes caractérisations structurales et morphologiques réalisées. Il met en avant la nette différence de structure des films obtenus par les deux procédés de dépôt. De plus, il met en évidence la modification structurale due au bore. Le quatrième chapitre présente l’étude des propriétés électriques et mécaniques, ainsi que du comportement tribologique des films. La différence de structure des couches se traduit par de grandes différences de résistivité mais affecte peu le coefficient de frottement. Le dernier chapitre met en évidence l’hétérogénéité structurale des films de DLC purs et se focalise notamment sur les particularités de leur extrême surface. Celle-ci se révèle moins dense et plus conductrice que le reste du filmThis work deals with the study of boron doped diamond-like carbon thin films elaborated by femtosecond and nanosecond laser ablation. The first aim of this work consists in identifying the potential applications of these films for sensors (for example thermometers). The second aim consists in correlating the films structure and properties with the deposition processes. The first chapter focused on the constitutive elements of the films: boron and carbon. Moreover, it presents a “state of the art” about DLC thin films and the different elaboration techniques. The second chapter deals with the experimental methods used for the elaboration and the study of the thin films. The third chapter deals with the structural and morphological characterizations. It highlights the important difference of structure of the films deposited by ns and fs PLD. Moreover, it underlines the structural modification due to the boron. The fourth chapter presents the study of the electrical and mechanical properties, as well as the tribological behaviour of the films. The structure difference of the films results in large variations of resistivity but does not change much the friction coefficient. The last chapter underlines the structural heterogeneity of the pure DLC films and focuses on the specificities of their extreme surface. This one turns out to be less dense and more conductor than the global film
18
Nikitin, Sergey. "Laser ultrasonics in a diamond anvil cell for investigation of simple molecular compunds at ultrahigh pressures." Thesis, Le Mans, 2015. http://www.theses.fr/2015LEMA1005/document.
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Le travail que j’ai effectué durant ce doctorat est dédié à l’utilisation de l’ultrason des lasers sous haute pression physique. La recherche est construite en utilisant les récentes techniques de mesure de laser ultrasonique dans une enclume de diamant, conduisant à l’exploration de la propagation du son et de sa détermination suivant la vitesse de l’onde acoustique sous ultra-hautes pressions. La diffusion Brillouin a été appliquée ici pour déterminer l’épaisseur de la glace polycristalline compressée dans l’enclume à diamant sous pressions de mégabars. La technique permet d’examiner les caractéristiques des dimensions des inhomogénéités élastiques et la texture de la glace polycristalline, de ce fait ce processus est commun pour les surfaces de l’enclume à diamant avec des sous micromètres de résolution spatiale via les mesures des variations résolues dans le temps sur la vitesse de propagation du pouls acoustique voyageant dans l’échantillon compressé. Ceci a été appliqué pour mesurer la vitesse acoustique dans du H2O à l’état de glace jusqu’à 84 Gpa. La technique d’imagerie développée contient, pour chaque cristallite (ou groupe de cristallites) dans un ensemble homogène chimique transparent, des informations utiles sur son orientation ainsi que sur sa valeur élastique modulée par rapport à la direction de la propagation du son. Cela répand les bases pour une application réussite sur la déformation de solides sous haut-développement de modèles micromécaniques sous la pression à mégabars. Pour une plus longue durée, ce genre d’expériences répandus sur les minéraux de la terre et avec des températures basses ou hautes, assurerait un progrès important dans la compréhension de la construction de la cape terrestre, son évolution ainsi que celle d’autres planètesThis PhD research work is devoted to the use of laser ultrasound in high-pressure physics. The research is done using the recently established technique of laser ultrasonic measurements in a diamond anvil cell which allows investigation of the sound propagation and determination of the acoustic wave velocities at ultrahigh pressures. Time domain Brillouin scattering was applied here to depth-profiling of polycrystalline aggregate of ice compressed in a diamond anvil cell to megabar pressures. The technique allowed examination of characteristic dimensions of elastic inhomogeneities and texturing of polycrystalline ice in the direction, normal to the diamond anvil surfaces with sub-micrometer spatial resolution via time-resolved measurements of variations in the propagation velocity of the acoustic pulse travelling in the compressed sample. It was applied to measure the acoustic velocities in H2O ice up to 84 Gpa. The developed imaging technique provides, for each crystallite (or a group of crystallites) in chemically homogeneous transparent aggregate, usable information on its orientation as well as on the value of the elastic modulus along the direction of the sound propagation. This extends the basis for a successful application of highly developed micromechanical models of solids deformation at mbar pressure. On long term, such experiments extended to earth’s minerals and high or low temperatures would insure a significant progress in understanding of convection of the earth’s mantle and thus evolution of this and other planets
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Cadot, Guillaume Bastien Jérémy. "Experimental and numerical investigations of diamond and related materials controlled-depth machining using pulsed laser ablation." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/46409/.
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Pulsed laser ablation is a non-conventional machining technique that is used to machine complex parts in ultra-hard materials and for minute part geometry, which are otherwise not readily accessible with conventional tooling. The constant development of new materials with enhanced properties, as well as the demand for products with improved functionality have led to a renewed interest for alternative machining. Pulsed laser ablation is regarded as a promising technology with potential to machine a wide range of materials and shapes. The use of non-mechanical methods is advantageous due to the reduced tool-wear for ultra-hard materials and minute geometry. However, these advantages pose significant challenges since the removal rate of the material in term of shape and amount is controlled through a set of operating parameters. It is therefore necessary to have a comprehensive understanding of the process and the relation between such parameters and the effect of the laser on the surface. Furthermore, the process itself is hard to monitor online due to the short temporal and small spatial space it occurs within, and this makes it more complex to establish a detailed understanding of the process, and the optimum parameters to control the machining. The main objective of this thesis is to develop mathematical frameworks that have the capability to predict the removal rate of pulsed laser ablation for the main operating parameters (feed speed, power, position, etc.) and the physical processes occurring during pulsed laser ablation of diamond and related materials for nanosecond laser pulses at 1064 nm and 248 nm. This is addressed using two modelling approaches: a physical model that simulates the mass and heat conservation in the system coupled with a collisional radiative model for the plasma, and a simplified approach based on geometrical aspect built on the idea that trenches represent the simplest element of the machining method enabling quantification of the relation between the control parameters and the removal rate. In the physical approach, the system is modelled using the conservation of mass and energy with the capability to accurately predict the position of the interfaces (graphitisation front and surface), and the amount of material removed. The model is validated against boron doped diamond and is used to estimate the activation energy and rate of graphitisation for tetrahedral amorphous carbon. The framework developed provides accurate results for two different carbon allotropes with a high content of sp$^3$ bounds for a range of fluence. A geometrical approach for the prediction of the material removal during large pulsed laser ablation machining task has been developed. Since, the objective of this model is for it to be integrated into CAD/CAM packages, the model needs to be computationally efficient and should require as little empirical data as possible to be accurately calibrated. This framework has been validated against three materials, graphite POCO AF-5, a mechanical polycrystalline diamond CVD Mechanical, and a metal-matrix poly-crystalline diamond CMX850. The model enables the prediction of material removal for large machining tasks and is being used with an optimisation procedure for the machining parameters (power, feed speed, etc.) for CAD/CAM packages. Finally, the physical model is coupled with a collisional radiative model for the plasma, and it enables the prediction of the pressure over the crater. Experimental investigations have confirmed that melting of the graphite only occurs for a fluence over 30 J.cm$^{-2}$. TEM analysis and Raman spectroscopy also show an increase in the disorder of the graphite lattice with an increase of fluence which is coherent with thermal damage and constraint growth of the graphite crystal at the graphitisation front. The fluence threshold for the melting of the graphite lattice is in agreement with the prediction of the model. The work developed in this thesis contributes to the understanding of the ablation process and graphitisation process during pulsed laser ablation of diamond and related material, and demonstrates how a simplified modelling approach can be used to improve current capabilities of this technology for large micro-machining tasks.
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Koivusaari, J. (Jarmo). "Structural, mechanical, and electronic properties of pulsed laser deposited carbon thin films and C-Si-heterojunctions." Doctoral thesis, University of Oulu, 2000. http://urn.fi/urn:isbn:9514257499.
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Sikora, Aurélien. "Incorporation de bore dans des films minces de "Diamond-Like Carbon" : élaboration par ablation laser pulsée et caractérisation." Phd thesis, Université Jean Monnet - Saint-Etienne, 2009. http://tel.archives-ouvertes.fr/tel-00751337.
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Ce travail concerne l'étude de couches minces de " Diamond-Like Carbon " dopés au bore élaborées par ablation laser femtoseconde et nanoseconde. Un des objectifs de cette étude est d'identifier les applications potentielles de ces films en tant qu'élément actif de capteur (par exemple de température). Le deuxième objectif est de corréler la structure et les propriétés des films minces obtenus avec les procédés de dépôt employés. Le premier chapitre présente les éléments constitutifs des couches minces étudiées : le bore et le carbone. Ce chapitre propose également un état de l'art sur les films de DLC purs et dopés et les méthodes d'élaboration existantes. Le deuxième chapitre traite des méthodes expérimentales adoptées pour l'élaboration et l'étude des films. Le troisième chapitre traite des différentes caractérisations structurales et morphologiques réalisées. Il met en avant la nette différence de structure des films obtenus par les deux procédés de dépôt. De plus, il met en évidence la modification structurale due au bore. Le quatrième chapitre présente l'étude des propriétés électriques et mécaniques, ainsi que du comportement tribologique des films. La différence de structure des couches se traduit par de grandes différences de résistivité mais affecte peu le coefficient de frottement. Le dernier chapitre met en évidence l'hétérogénéité structurale des films de DLC purs et se focalise notamment sur les particularités de leur extrême surface. Celle-ci se révèle moins dense et plus conductrice que le reste du film.
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Constantin, Loic. "Fabrication additive assisté laser de matériaux composites 3D et revêtement diamant par CVD." Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0066.
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L'augmentation constante de la fréquence de travail des dispositifs à base de semi-conducteurs avec leur miniaturisation a conduit à une surchauffe sévère, qui affecte leur durée de vie et leur fiabilité. Par conséquent, la gestion thermique est devenue une préoccupation importante dans le domaine microélectronique et doit être abordée. Le diamant (D) est connu pour être un excellent matériau pour la dissipation thermique car il possède l'une des conductivités thermiques les plus élevées de tous les matériaux naturels et possède une résistivité électrique élevée. D peut refroidir les puces électroniques de deux manières. Lorsqu'il est utilisé sous forme de film, D agit comme un diffuseur de chaleur. Lorsqu'ils sont utilisés sous forme de poudre, les Ds peuvent être introduits dans les métaux pour améliorer leur conductivités thermiques (TC) et apporter une stabilité dimensionnelle à des températures élevées. Les matériaux composites métal / D résultants sont ainsi d'excellents composants pour former des dissipateurs thermiques. Naturellement, les performances thermiques des dissipateurs thermiques sont étroitement liées à leur surface. Malgré l'attrait des matériaux à base de D en termes de performances thermiques, ils présentent souvent une géométrie simple, principalement en raison de la complexité d’usiner des matériaux à base de D dans des formes complexes. L'impression laser 3D est une méthode émergente de fabrication de géométrie sophistiquées et a donné des résultats prometteurs pour divers métaux et alliages. Dans cette étude, l'impression 3D laser de matériaux composites cuivre / D est proposée pour fabriquer des structures complexes de Cu / D qui pourraient remodeler leurs applications. Avant de fabriquer des matériaux composites Cu / D de manière additive, plusieurs défis doivent être relevés. Premièrement, la fabrication additive de Cu pur est optimisée et caractérisée. Puis, faute d'une affinité chimique entre Cu et D, une interphase est introduite dans le matériau composite. Plus tard, un procédé de revêtement de sel fondu est étudié pour produire un revêtement gradué et multicouche d'oxyde / carbure et de carbure / carbure, respectivement, sur des matériaux carbones. Ensuite, la fabrication additive de structures composites Cu / D est présentée. Enfin, le dépôt des films D est réalisé avec une flamme oxyacétylénique assistée laser. Les effets de l'introduction de lasers ultraviolets dans la flamme sont caractérisés en termes de réaction chimique, de qualité du film D et de taux de croissanceThe constant increase of the working frequency of semiconductor-based devices with their miniaturization led to severe overheating, which affect their lifetime and reliability. Hence, thermal management has become a significant concern for the microelectronic area and needs to be addressed. Diamond (D) is known to be an excellent material for thermal dissipation as it possesses one of the highest thermal conductivity (TC) of any natural material and has a high electrical resistivity. D can cool electronic chips in two ways. When used in the form of a film, D acts as a heat spreader. When utilized in powder-form, Ds can be introduced into metals to enhance their TC and bring dimensional stability at elevated temperatures. The resulting metal/D composite materials are thus, excellent component to form heat sinks. Naturally, the thermal performances of heat sinks are closely related to their surface area. Although the attractiveness of D-based materials in term of thermal performance, they often exhibit simple geometry mostly due to the complexity of machining D-based materials into intricated designs. Laser 3D printing is an emerging method of manufacturing sophisticated designs and has shown promising results for various metal and alloys. In this study, the laser 3D printing of copper/D composite materials is proposed to fabricate highly complex Cu/D structures which could remodel their applications. Before additively manufactured Cu/D composite materials, several challenges need to be addressed. First, the additive manufacturing of pure Cu is optimized and characterized. Then, due to a lack of a chemical affinity between Cu and D, the Cu-D interfacial zone is introduced in the composite material. Later, a molten salt coating process is studied to produced graded and multilayer coating of oxide/carbide and carbide/carbide, respectively, on carbon materials. Next, the additive manufacturing of highly sophisticated Cu/D composite structures is presented. Finally, the deposition of D films is performed by laser-assisted combustion flame. The effects of introducing ultraviolet lasers into the combustion flame are characterized in terms of chemical reaction and D film quality and growth rate
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Lord, Oliver T. "Experimental Constraints on the Chemistry of the Earth's Core : Novel approaches using the Laser-Heated Diamond Anvil Cell." Thesis, University of Bristol, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520173.
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Aprilis, Georgios [Verfasser], and Natalia [Akademischer Betreuer] Dubrovinskaia. "Pulsed laser heating in the diamond anvil cell : applications in geo- and material sciences / Georgios Aprilis ; Betreuer: Natalia Dubrovinskaia." Bayreuth : Universität Bayreuth, 2021. http://d-nb.info/1227444648/34.
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Garrelie, Florence. "Ablation laser femtoseconde pour le dépôt de couches minces." Habilitation à diriger des recherches, Université Jean Monnet - Saint-Etienne, 2008. http://tel.archives-ouvertes.fr/tel-00356315.
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Ce mémoire concerne l'élaboration de couches minces par ablation laser femtoseconde (Pulsed Laser Deposition, PLD) et la caractérisation du panache plasma. Les résultats obtenus pour le dépôt de couches minces de Diamond-Like Carbon (DLC) sont présentés avec l'objectif de déposer des couches à grande dureté et faible coefficient de frottement, avec de bonnes propriétés d'adhérence sur divers substrats d'intérêt biomédical. Des couches minces ont pu être déposées avec succès sur une tête fémorale de prothèse de hanche. Les propriétés des DLC élaborés par PLD femtoseconde et nanoseconde PLD ont été comparées au travers des propriétés optiques des films et d'une caractérisation du plasma.Des nanoparticules ont été déposées par PLD femtoseconde, et incluses dans une matrice DLC. Des films de DLC dopés au nickel ou tantale (en raison de leur différente affinité chimique avec le carbone) ont été synthétisés. Deux différentes phases cristallines sont obtenues dans le cas du DLC dope Ta, avec la présence surprenante d'une phase métastable β-Ta, qui est corrélée aux propriétés du plasma. La présence de carbure de tantale est également mise en évidence sur les bords des clusters de tantale.
Les films de DLC pur et de DLC dopé aux métaux sont caractérisés pour l'application aux électrodes pour biocapteurs, avec une sensibilité élevée et une faible limite de détection. L'optimisation avec l'incorporation d'un autre dopant, tel que le bore est discutée.
La possibilité d'utiliser ces couches de DLC dopé au bore pour des capteurs thermiques et nanocalorimétriques est étudiée dans le cadre d'un projet ANR. Les thermomètres à base de DLC avec un fort TCR (Coefficient de Température de Resistance) sont intégrés dans des structures suspendues, et montrent de bonnes propriétés.
Dans la dernière partie de ce mémoire, les perspectives envisagées pour ce travail sont présentées, avec l'introduction d'une mise en forme temporelle de l'impulsion laser femtoseconde et d'une boucle adaptative d'optimisation. Ces premiers travaux mettent bien en évidence les potentialités de cette technique, pour le dépôt couches minces et la synthèse de nanoparticules, permettant un contrôle de la nature et de l'énergie cinétique des particules du plasma. La suite de ce travail envisage donc de mieux comprendre les effets d'une mise en forme temporelle de l'impulsion laser femtoseconde sur les propriétés des produits d'ablation et donc des couches minces élaborées.
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Bourquard, Florent. "Ablation laser femtoseconde assistée d’une mise en forme temporelle pour le dépôt de couches minces et la synthèse de nanoparticules." Thesis, Saint-Etienne, 2013. http://www.theses.fr/2013STET4022/document.
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Ce travail explore le contrôle de la composition et la cinétique du panache d’ablation laser en régime ultrabref par mise en forme temporelle des impulsions laser femtoseconde. L’objectif est l’optimisation du dépôt de couches minces et de nanoparticules. Le chapitre 1 est une synthèse de la littérature sur le dépôt de couches minces par ablation laser femtoseconde, en particulier de films de Diamond-Like Carbon et de nanoparticules. L’influence de la mise en forme temporelle du laser sur les mécanismes d’ablation est développée, ainsi que le diagnostic du panache d’ablation. Le chapitre 2 présente les dispositifs expérimentaux de mise en forme temporelle et de diagnostic du panache d’ablation par spectroscopie d’émission résolue en temps et espace et spectroscopie d’extinction. Le chapitre 3 rapporte l’impact de l’utilisation d’impulsions doubles et élargies sur les panaches de l’aluminium et du bore. L’augmentation de la composante ionique du plasma d’aluminium est expliquée au travers de simulations hydrodynamiques. Dans le chapitre 4, différentes formes temporelles sont employées pour l’ablation du graphite et le dépôt de couches de Diamond-Like Carbon. Le contrôle de la cinétique du panache est atteint en peuplant plus ou moins ses différentes composantes de vitesse : molécules, atomes et ions. Si la structure du Diamond-Like Carbon déposé n’est pas affectée, une amélioration de la surface des couches est observée. Le chapitre 5 montre l’efficacité et la sensibilité de la spectroscopie d’extinction optique pour la mesure in situ de la distribution en taille des nanoparticules métalliques dans le panache d’ablation laser femtosecondeThis work explores the control of ultrafast laser ablation plume composition and kinetics by temporal shaping of femtosecond laser pulses. The goal is the optimization of thin films and nanoparticles deposition. Chapter 1 is a synthesis of the literature on femtosecond laser deposition of thin films. The focus is on Diamond-Like Carbon films and nanoparticles. The impact of laser temporal pulse shaping on the ablation mechanisms is developed. Ablation plume diagnostic methods are detailed. Chapter 2 describes the experimental setup for temporal pulse shaping and plasma diagnostic. The latter is done through space and time-resolved optical emission spectroscopy and extinction spectroscopy. Chapter 3 reports on the impact of doubles pulses and long pulses on aluminium and boron ablation plumes. Ion yield enhancement in aluminium ablation plasma is explained through hydrodynamics simulations. In chapter 4, various temporal pulse shapes are used for graphite ablation and Diamond-Like Carbon thin films deposition. The control of the plume kinetics is reached by selectively populating the various plume speed components: molecules, atoms, ions. Even though the deposited Diamond-Like Carbon structure is unaffected, it has been observed an improvement of the thin films surface. Chapter 5 shows the efficiency and sensitivity of optical extinction spectroscopy for in situ measurement of nanoparticles size distribution in femtosecond laser ablation plumes
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Kelly, Mark. "Laser diagnosis and computer modelling of C/H/O and C/H/N plasmas used in diamond chemical vapour deposition." Thesis, University of Bristol, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.653079.
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Laser and optical emission spectroscopies have been employed to study the gas phase chemistry in the growth environment for diamond chemical vapour deposition (CVO) in a microwave (MW) reactor. Computational investigations have also been used to explore the energetics of elementary reactions on a diamond surface, to give insight into which species are likely to incorporate into a growing diamond film. The focus of this thesis is on 0 and N containing CIH plasmas.
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Coleman, Amy Louise. "Studies of dynamically and statically compressed antimony." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31334.
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Physics at extreme conditions is not a young field; there have been decades of developments that have allowed us to generate high-pressure and high-temperature conditions in a vast array of materials. Conventionally, these extreme conditions were generated using static compression techniques; compressing a material in a diamond anvil cell which could then be heated or cooled, with structural information deduced using synchrotron radiation. These techniques are still invaluable for extreme conditions research although the pressures and temperatures that are accessible to them are limited by the strength of the diamond anvil cells and their ability to withstand extreme temperatures. The necessity for access to pressure-temperature states that are beyond the scope of the conventional diamond anvil cell is driven by the need to characterise extreme environments such as planetary interiors. It was long believed that materials in high pressure-temperature states would exhibit relatively simple, high-symmetry crystal structures, but recent research has proven that, conversely, there is an abundance of complex structural behaviour at these extreme conditions. One means of attaining pressure-temperature states beyond those accessible using static compression techniques is to impart a large amount of energy into a material in a comparatively short period of time (milliseconds to nanoseconds); this is known as dynamic compression. Dynamic compression can be generated using impact techniques or, alternatively, via laser ablation. Access to the most extreme conditions is commonly achieved by generating a shockwave which compresses the sample with the fastest achievable compression wave. Not only does this type of compression facilitate access to the most extreme states, it also allows us to explore the physics of impact phenomena and other such situations involving rapid energy transfer. Dynamic compression occurs on short timescales and, as such, there is a considerable challenge in implementing diagnostics to study the behaviour of compressed materials. Furthermore, because complexity is commonplace in extreme conditions, it is vital that any diagnostics should be able to provide data of high enough quality that this complexity may be resolved. The advent of 4th generation light sources (x-ray free electron lasers) has afforded us the opportunity to obtain extraordinarily high quality data on dynamic compression timescales. In the interest of refining analytical techniques when utilising this novel technology, materials exhibiting complex crystal structures should be investigated. Antimony is an element which is known, under static compression, to transform from a Peierls-distorted rhombohedral phase (R-3m) to an incommensurately modulated host-guest structure (I'4=mcm(00γ)000s), a structure with an incredibly high level of complexity. The complexity of this host-guest phase, and the relatively low pressure at which it forms, makes antimony an ideal candidate for testing the resolution achievable using these 4th generation light sources. Furthermore, it is interesting to observe whether such a complex phase can form on the short timescales of dynamic compression. In this work antimony is both statically and dynamically compressed and the results of both experiments are compared. A static phase diagram is constructed for antimony up to 31 GPa and 835 K, confirming the location of a previously theorised triple point and suggesting the location of an additional triple point. Three solid phases are characterised and data are found to agree with the pre-existing static compression studies. The nature of the host-guest phase is investigated and the guest 'chains' are found to remain intact even at the highest temperatures and pressures, a result which has not previously been observed in high pressure-temperature host-guest structures. Dynamic data from shock-compression experiments at pressures up to 59.3 GPa are plotted alongside the static data and contrasting phase behaviour is discussed. Four solid phases are identified along with one liquid phase. Observation of the host-guest phase in shock-compressed antimony confirms that highly complex crystal structures are able to form on the nanosecond timescale.
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Cayzac, Witold. "Ion energy loss at maximum stopping power in a laser-generated plasma." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2013. http://tel.archives-ouvertes.fr/tel-00949958.
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In the frame of this thesis, a new experimental setup for the measurement of the energy loss of carbon ions at maximum stopping power in a hot laser-generated plasma has been developed and successfully tested. In this parameter range where the projectile velocity is of the same order of magnitude as the thermal velocity of the plasma free electrons, large uncertainties of up to 50% are present in the stopping-power description. To date, no experimental data are available to perform a theory benchmarking. Testing the different stopping theories is yet essential for inertial confinement fusion and in particular for the understanding of the alpha-particle heating of the thermonuclear fuel. Here, for the first time, precise measurements were carried out in a reproducible and entirely characterized beam-plasma configuration. It involved a nearly fully-stripped ion beam probing a homogeneous fully-ionized plasma. This plasma was generated by irradiating a thin carbon foil with two high-energy laser beams and features a maximum electron temperature of 200 eV. The plasma conditions were simulated with a two-dimensional radiative hydrodynamic code, while the ion-beam charge-state distribution was predicted by means of a Monte-Carlo code describing the charge-exchange processes of projectile ions in plasma. To probe at maximum stopping power, high-frequency pulsed ion bunches were decelerated to an energy of 0.5 MeV per nucleon. The ion energy loss was determined by a time-of-flight measurement using a specifically developed chemical-vapor-deposition diamond detector that was screened against any plasma radiation. A first experimental campaign was carried out using this newly developed platform, in which a precision better than 200 keV on the energy loss was reached. This allowed, via the knowledge of the plasma and of the beam parameters, to reliably test several stopping theories, either based on perturbation theory or on a nonlinear T-Matrix formalism. A preliminary analysis suggests that the energy deposition at maximum stopping power is significantly smaller than predicted, particularly, by perturbation approaches.
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Makela, Mark F. "Polarized Ultracold Neutrons: their transport in diamond guides and potential to search for physics beyond the standard model." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/26194.
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Experiments with polarized "ultracold neutrons" (UCN) offer a new way to measure the decay correlations of neutron beta decay; these correlations can be used to test the completeness of the Standard Model and predict physics beyond it. Ultracold neutrons are very low energy neutrons that can be trapped inside of material and magnetic bottles. The decay correlations in combination with the neutron and muon lifetimes experimentally find the first element (Vud) of the Cabibbo-Kobayashi-Maskawa (CKM) quark mixing matrix. The CKM matrix is a unitary transform between the mass and weak eigenstates of the d, s and b quarks; if the matrix is not unitary this would imply that the Standard Model is not complete. Currently the first row of the CKM matrix is over 2 sigma from unitarity and Vud is the largest component of the row.
The UCNA experiment looks at the correlation between the polarization of the neutron and the momentum of the electron resulting from the beta decay of the neutron (the A-correlation). The keys to making a high precision measurement of A-correlation are a near 100% polarization of the neutrons that decay, low"backscatter electron detectors, and small, well characterized backgrounds. UCN can be 100% polarized by passing them through a seven Telsa magnetic field. The key to the UCNA experiment is keeping them polarized until they decay or are lost.
This dissertation covers the development of guides that are minimally depolarizing and efficient transporters of UCN and their use in the UCNA experiment. The entire guide development process is covered from conception to manufacturing and testing. This process includes development of a pulsed laser deposition, diamond-like carbon coating system and materials studies of the resulting coatings. After the initial studies of the guide coating, meter"long sections of guide are tested with UCN to determine their depolarization and transport properties.
The guide technology developed in this dissertation has been used in the entire UCNA experiment. Also, this technology is currently the state of the art for polarized and non-polarized UCN guide systems and it is being implemented in several new UCN experiments.Ph. D.
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Torresin, Olivier. "Etude comparée de l'émission d'électrons de nanopointes de tungstène et de diamant : émission de champ et photoémission induite par laser femtoseconde." Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30253.
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Cette thèse s'intéresse à l'émission d'électrons à partir de nanopointes métalliques et diélectriques sous illumination laser femtoseconde. Les différents types d'émission sont étudiés dans les cas spécifiques de nanopointes de tungstène et de diamant. Les nombreuses études précédentes sur le tungstène, permettent une comparaison des phénomènes d'émission bien connus, à ceux, nouveaux, observés dans le cas du diamant. Dans la première partie de l'étude, nous reprenons les résultats expérimentaux de l'émission statique et de la photoémission à partir de nanopointes de tungstène. Des simulations numériques, faites à partir d'un modèle à éléments finis (utilisant le logiciel commercial) COMSOL du dispositif expérimental, permettent un calcul des coefficients d'amplification statique et optique du champ électrique, due à la forme particulière de ces pointes. Les résultats sont alors comparés à des cartographies spatiales de l'émission, ce qui permet de conclure sur la relation directe entre la zone d'amplification du champ à l'apex de la pointe et la zone d'arrivée des électrons sur le détecteur. Dans la deuxième partie de l'étude, nous reprenons les études expérimentales faites sur le tungstène pour le cas du diamant. Les premières mesures de l'énergie des électrons mettent en évidence la présence d'une chute de tension le long de la pointe de diamant, venant de sa faible conductivité. Le courant de conduction des électrons dans la pointe est alors modélisé par un mécanisme Poole-Frenkel dépendant directement de cette chute de tension. Nous modélisons l'émission statique de ces pointes par un circuit électrique simple composé de deux résistances en série. Dans le régime de photoémission, induit par un laser femtoseconde, les résultats sont très différents du cas du tungstène. Les impulsions laser induisent l'émission d'électrons jusqu'à un courant de saturation tel que l'émission statique entre les impulsions disparait. Nous avons mesuré le temps nécessaire (de l'ordre de la microseconde) permettant à l'émission statique de réapparaitre entre les impulsions laser. Ces mesures sont interprétées par un effet capacitif de déplétion des charges disponibles pour la photoémission. En complétant le modèle électrique précédant avec l'ajout d'un condensateur, il est possible de modéliser quantitativement l'ensemble des résultats obtenus pour l'émission statique et la photoémission de nanopointe de diamant. La dernière partie de l'étude propose une introduction à la mesure du temps de vol et des statistiques temporelles des électrons émis. Nous présentons les changements opérés sur le dispositif expérimental afin de permettre de telles mesures ainsi que les résultats préliminaires obtenus sur une nanopointe de tungstène sous illumination laserThis thesis presents electron emission from metallic (tungsten) and dielectric (diamond) nanotips under femtosecond laser illumination. The behavior of DC emission and laser induced photoemission from tungsten nanotips has been widely studied and we use it to benchmark diamond measurements. In the first part, we study DC emission and photoemission from tungsten nanotips. Numerical simulations made from a finite element model (using COMSOL) of our experimental setup, allow the computation of static and optical field enhancement coefficients linked to the tip geometry. Results are compared with the spatial profile of electron emission, which links the field enhancement area at the tip apex and the electron detection area. In the second part, we study DC emission and photoemission from diamond nanotips. Electron energy measurements highlight the presence of a voltage drop along the diamond tip, due to the low conductivity of this material. Electron emission current inside the tip and at the apex obeys Poole-Frenkel conduction, coupled with Fowler-Nordheim field emission observed commonly for metallic surfaces. We propose a macroscopic model to combine conduction and emission mechanisms for DC emission. Under laser illumination, emission measurements are very different from the metallic case. Electron emission saturates under intense laser illumination. In this regime, we show that the DC current cannot reach its DC value between pulses. By lowering laser repetition rate, we are able to measure the dynamics of the DC current in between laser pulses. We adapt the DC macroscopic model for laser induced photoemission using an effective capacitance, and we show very good quantitative agreement with experimental measurement obtained on diamond nanotips. The last part is an introduction to electron time-of-flight measurements to measure the temporal statistics of electron arrival times. We present the modifications made on the experimental setup to be able to make these kinds of measurements, as well as preliminary results obtained on DC and laser-induced emission from tungsten nanotip
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Borz, Mario. "Propriétés d'émission et de conduction de nano-pointes de diamant sous éclairement laser ultra-bref : Etude par microscopies à effet de champ et spectroscopie en énergie." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMR117.
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Le but de cette thèse est de comprendre les changements dans les propriétés électriques et optiques des matériaux à large bande interdite à l'échelle nanométrique par rapport au matériau massif et en présence d'un champ électrique statique intense. Le diamant en forme de nano-aiguille a été choisi comme matériau d'étude en raison de sa large bande interdite, sa haute résistance aux contraintes externes et sa conduction thermique élevée. Le diamant présente également une résistance électrique élevée, ce qui en fait un bon candidat pour l'étude des modifications de conduction électrique sous des champs électriques et optiques forts. Afin d'étudier les propriétés de conduction électrique, deux différentes techniques expérimentales ont été utilisées : la microscopie ionique à effet de champ et la microscopie électronique à effet de champ avec et sans éclairement laser. Les observations expérimentales ont été couplées à des modèles de conduction électrique qui décrivent qualitativement et quantitativement les résultats obtenus. Pour l'étude des propriétés optiques, une microscopie électronique à émission de champ assistée par laser a été réalisée. Dans ce cas, l'étude a été menée dans deux configurations expérimentales : l'une en éclairant l'ensemble de l'échantillon par le faisceau laser et l'autre en focalisant le laser uniquement sur le sommet de la nano-pointe où le champ électrique est augmenté et les électrons sont émis dans le vide. Les résultats décrivent les propriétés de conduction électrique et d'émission d'électrons des nano-aiguilles de diamant dans l'obscurité et sous un éclairement laser. En tant qu'émetteurs d'électrons, les nano-aiguilles de diamant présentent des avantages par rapport aux pointes métalliques telles qu'une stabilité d'émission et un seuil de dommage plus élevés sous éclairement laser. Les résultats sont prometteurs pour le développement d'une nouvelle source de photo- électrons pour la microscopie électronique résolue en tempsThe aim of this thesis is to understand the changes in the electrical and optical properties of large band-gap materials at the nanoscale in the presence of a huge static electric _eld. Diamond nano-needle has been chosen as a study material, thanks to its wide band gap, high resistance to external stress and high thermal conduction. Diamond presents also high electrical resistance, making it a good candidate for the study of electrical conduction modi_cations under high electric and optical _elds. In order to study the electrical conduction properties, two di_erent experimental tech- niques were used: Field Ion microscopy and Field Emission Microscopy with and without laser illumination. The experimental observations were coupled with electrical conduction models which describe qualitatively and quantitatively the obtained results. For the study of the optical properties, laser-assisted Field Emission Microscopy was performed. In this case, the study was performed in two experimental con_gurations: one by illuminating the whole sample by the laser beam and the other by focusing the laser beam only on the apex of the nano-tip where the electric _eld is enhanced and the electrons are emitted into vacuum. The results describe the electrical conduction and electron emission properties of the diamond nano-needles in dark and under laser illumination. As _eld emitters, diamond nano-needles show advantages compared to metallic tips such as: higher emission stability and higher damage threshold under laser illumination. The results are promising for the development of novel photo-electron sources for time- resolved electron microscopy
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Kupenko, Ilya [Verfasser], and Leonid [Akademischer Betreuer] Dubrovinsky. "Portable laser-heating system for experiments with diamond anvil cells and its application to studies of geophysically important materials / Ilya Kupenko. Betreuer: Leonid Dubrovinsky." Bayreuth : Universität Bayreuth, 2014. http://d-nb.info/1063995558/34.
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Konôpková, Zuzana. "Thermal Conductivity of Materials under Conditions of Planetary Interiors." Doctoral thesis, Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-150396.
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The presented thesis focuses on study of transport and thermoelastic properties of materials under conditions of planetary interiors by means of high-pressure experimental tools and finite element modeling, and their role in the dynamics and states of cores of terrestrial planets. Experiments in laser-heated diamond anvil cell (LHDAC) in combination with numerical simulations of heat transfer in DAC are shown to yield information on thermal conductivity of a pressurized sample. The novel technique consists of one-sided laser heating and double-sided temperature measurements and utilizes a precise determination of several parameters in course of the experiment, including the sample geometry, laser beam power distribution, and optical properties of employed materials. The pressure-temperature conditions at the probed portion of the sample are, however, not uniform. To address this problem, thermal pressure in the laser-heated diamond anvil cell and anisotropic thermal conductivity originating from the texture development upon uniaxial compression have been studied by means of numerical simulations. The method for determination of thermal conductivity is applied to iron at pressures up to 70 GPa and temperatures of 2000 K, meeting the Earth’s lower mantle conditions and covering Mercury’s entire core. The obtained results are extrapolated to the conditions of the Earth’s core-mantle boundary using a theoretical model of the density dependence of thermal conductivity of metals and published values on Grüneisen parameter and bulk modulus. After considering the effect of minor core elements, the obtained value at these conditions supports case for the downward revision of the thermal conductivity in the core. From the point of view of core dynamics and energy budget, the lower thermal conductivity implies more favorable conditions to drive the dynamo. Similar scenario applies for Mercury where, for high values of thermal conductivity, heat flux conducted along the iron-core adiabat exceeds the actual heat flux through the core-mantle boundary. This leads to a negative rate of entropy production in the core that makes it impossible to sustain the dynamo process presumably responsible for the observed magnetic field of Mercury.
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Fedotenko, Timofey [Verfasser], and Natalia [Akademischer Betreuer] Dubrovinskaia. "Laser heating setup with high-magnification imaging for studies of physical and chemical phenomena up to ultra-high pressures in diamond anvil cells / Timofey Fedotenko ; Betreuer: Natalia Dubrovinskaia." Bayreuth : Universität Bayreuth, 2021. http://d-nb.info/1240309643/34.
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Hrubiak, Rostislav. "Exploring Thermal and Mechanical Properties of Selected Transition Elements under Extreme Conditions: Experiments at High Pressures and High Temperatures." FIU Digital Commons, 2012. http://digitalcommons.fiu.edu/etd/696.
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Transition metals (Ti, Zr, Hf, Mo, W, V, Nb, Ta, Pd, Pt, Cu, Ag, and Au) are essential building units of many materials and have important industrial applications. Therefore, it is important to understand their thermal and physical behavior when they are subjected to extreme conditions of pressure and temperature. This dissertation presents: An improved experimental technique to use lasers for the measurement of thermal conductivity of materials under conditions of very high pressure (P, up to 50 GPa) and temperature (T up to 2500 K). An experimental study of the phase relationship and physical properties of selected transition metals, which revealed new and unexpected physical effects of thermal conductivity in Zr, and Hf under high P-T. New phase diagrams created for Hf, Ti and Zr from experimental data. P-T dependence of the lattice parameters in α-hafnium. Contrary to prior reports, the α-ω phase transition in hafnium has a negative dT/dP slope. New data on thermodynamic and physical properties of several transition metals and their respective high P-T phase diagrams. First complete thermodynamic database for solid phases of 13 common transition metals was created. This database has: All the thermochemical data on these elements in their standard state (mostly available and compiled). All the equations of state (EoS) formulated from pressure-volume-temperature data (measured as a part of this study and from literature). Complete thermodynamic data for selected elements from standard to extreme conditions.
The thermodynamic database provided by this study can be used with available thermodynamic software to calculate all thermophysical properties and phase diagrams at high P-T conditions. For readers who do not have access to this software, tabulated values of all thermodynamic and volume data for the 13 metals at high P-T are included in the APPENDIX. In the APPENDIX, a description of several other high-pressure studies of selected oxide systems is also included.
Thermophysical properties (Cp, H, S, G) of the high P-T ω-phase of Ti, Zr and Hf were determined during the optimization of the EoS parameters and are presented in this study for the first time. These results should have important implications in understanding hexagonal-close-packed to simple-hexagonal phase transitions in transition metals and other materials.
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Benchikh, Épouse Sbaï Nadia. "Couches minces nanostructurées de carbone amorphe dopées ou alliées : Elaboration par ablation laser femtoseconde et Caractérisations." Phd thesis, Université Jean Monnet - Saint-Etienne, 2005. http://tel.archives-ouvertes.fr/tel-00142211.
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Amélioration des propriétés des couches minces de carbone amorphe (appelé Diamond Like Carbon, DLC) et recherche de nouvelles fonctionnalités pour ce type de couches minces en dopant les films DLC par des métaux comme le nickel et le tantale.L'ablation laser en régime femtoseconde est la technique utilisée pour la synthèse des couches minces de DLC dopées ou alliées. Ce sujet met également en évidence l'apport de cette technique sur les propriétés morpho-structurales et physiques des DLC dopés ou alliés.
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Bourquard, Florent. "Ablation laser femtoseconde assistée d'une mise en forme temporelle pour le dépôt de couches minces et la synthèse de nanoparticules." Phd thesis, Université Jean Monnet - Saint-Etienne, 2013. http://tel.archives-ouvertes.fr/tel-01063802.
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Ce travail explore le contrôle de la composition et la cinétique du panache d'ablation laser en régime ultrabref par mise en forme temporelle des impulsions laser femtoseconde. L'objectif est l'optimisation du dépôt de couches minces et de nanoparticules. Le chapitre 1 est une synthèse de la littérature sur le dépôt de couches minces par ablation laser femtoseconde, en particulier de films de Diamond-Like Carbon et de nanoparticules. L'influence de la mise en forme temporelle du laser sur les mécanismes d'ablation est développée, ainsi que le diagnostic du panache d'ablation. Le chapitre 2 présente les dispositifs expérimentaux de mise en forme temporelle et de diagnostic du panache d'ablation par spectroscopie d'émission résolue en temps et espace et spectroscopie d'extinction. Le chapitre 3 rapporte l'impact de l'utilisation d'impulsions doubles et élargies sur les panaches de l'aluminium et du bore. L'augmentation de la composante ionique du plasma d'aluminium est expliquée au travers de simulations hydrodynamiques. Dans le chapitre 4, différentes formes temporelles sont employées pour l'ablation du graphite et le dépôt de couches de Diamond-Like Carbon. Le contrôle de la cinétique du panache est atteint en peuplant plus ou moins ses différentes composantes de vitesse : molécules, atomes et ions. Si la structure du Diamond-Like Carbon déposé n'est pas affectée, une amélioration de la surface des couches est observée. Le chapitre 5 montre l'efficacité et la sensibilité de la spectroscopie d'extinction optique pour la mesure in situ de la distribution en taille des nanoparticules métalliques dans le panache d'ablation laser femtoseconde
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Ćmiel, Milan. "VÝVOJ NÁSTROJŮ S PKD, CVD VRSTVOU A CVD POVLAKEM PRO DOKONČOVÁNÍ DĚR." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228661.
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The aim of the thesis is to design, conduct and assess an experiment seeking to look into the utility properties of recent tools manufactured by HAM-FINAL. The tools include polycrystalline diamond (PCD) and CVD diamond cutting edges. In the theoretical part, the attention is devoted to cutting materials with an emphasis on diamond materials, as well as to issues associated with the wearing of the cutting tools, requirements specified for precision of bores and tools used in the manufacture of precision bores. The paper further provides an overview of a selection of world’s leading manufacturers of PCD blanks, CVD diamond coatings, CVD diamond layers and reamers with PCD cutting edges.
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Mammei, Russell Rene. "Thin Films for the Transport of Polarized Ultracold Neutrons for Fundamental Symmetry Study." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/28714.
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The use of ultracold neutrons (UCN) to study fundamental parameters such as the neutron lifetime and decay correlations in polarized neutron beta decay are poised to make significant contributions to our understand of the Standard Model and its extensions. To this end, the UCNA experiment is pursuing a precision measurement (0.2%) of the angular correlation between the neutron spin and the direction of emission of the electron in polarized neutron decay (the ``A'' asymmetry). The UCNA experiment makes use of the spallation-driven solid deuterium (SD2) UCN source at the Los Alamos Neutron Science Center (LANSCE). The UCN leave the source and are 100% polarized by passing through a strong magnetic field before their decay is observed by a very sensitive electron spectrometer.
UCN guides facilitate the transfer of UCN from the source to the spectrometer. Common guide materials include stainless steel, copper, aluminum, and quartz. Often a thin film is applied to these components to increase their ability to transport/bottle and preserve the polarization of UCN. In the region of the SD2 UCN source, nickel-58 films are applied, whereas once the UCN are polarized, diamond-like carbon (DLC) films are employed. This dissertation covers the application, process developments, and characterization of these coatings. In addition a study concerning the surface finish resulting from the mechanical polishing and electropolishing of the guides that make up the UCNA beamline is presented.
Ph. D.
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Hamad, Hassan. "Détermination des coefficients d'ionisation de matériaux à grand gap par génération multi-photonique." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0017/document.
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L’utilisation des semi-conducteurs à large bande interdite (wide bandgap ou WBG) tels que le carbure de silicium SiC, le nitrure de gallium GaN, le diamant, etc… s’est répandue dans le domaine de l’électronique de puissance ces dernières décennies. Leurs caractéristiques électroniques et mécaniques font des WBGs des solutions alternatives pour remplacer le traditionnel silicium. Cependant, des études supplémentaires sont indispensables pour améliorer la tenue en tension, les pertes statiques et dynamiques et les performances en fonctionnement à haute température des composants WBGs. Dans ce cadre, deux bancs expérimentaux OBIC (Optical Beam Induced Current) spécifiques « en cours de développement » sont mis en place pendant cette thèse. L’OBIC consiste à éclairer avec un faisceau laser de longueur d’onde appropriée une jonction polarisée en inverse, des porteurs de charge sont alors créés par absorption photonique. On peut alors mesurer un courant induit par faisceau optique (OBIC) lorsque les porteurs sont générés dans la zone de charge d’espace. Après une première phase de préparation et d’adaptation de l’environnement expérimental, des essais ont mené à la démonstration du principe de génération multi-photonique en éclairant une jonction SiC avec un faisceau vert (532 nm). L’analyse des différentes mesures OBIC nous a permis de construire une image du champ électrique à la surface de la diode : une analyse non destructive pour étudier l’efficacité des protections périphériques des jonctions et pour détecter les défauts dans la structure cristalline. Egalement, la durée de vie des porteurs minoritaires a été déduite par l’analyse de la décroissance du courant OBIC au bord de la jonction. Les coefficients d’ionisation sont également déterminés par la méthode OBIC, ces coefficients sont des paramètres clés pour la prévision de la tension de claquage des composants. Nous avons réalisé des mesures OBIC dans le GaN, et nous avons observé un effet d’absorption bi-photonique dans le diamant avec un faisceau UV (349 nm)In the last few decades, the use of wide bandgap (WBG) semiconductors (silicon carbide SiC, gallium nitride GaN, diamond, etc…) has become popular in the domain of power electronics. Their electronic and mechanical characteristics made of the WBGs a good alternative to the traditional silicon. However, additional studies are mandatory to improve the breakdown voltage, static and dynamic losses, and the performance at high temperature of the WBG devices. In this context, two specific experimental benches OBIC (Optical Beam Induced Current) -under development- are set up during this thesis. OBIC method consists to generate free charge carriers in a reverse biased junction by illuminating the device with an appropriate wavelength. An OBIC signal is measured if the charge carriers are generated in the space charge region. After a first phase of preparation and adaptation of the experimental environment, OBIC measurements led to demonstrate the multi-photonic generation by illuminating a SiC junction with a green laser (532 nm). OBIC measurements allowed giving an image of the electric field at the surface of the diode: OBIC presents a non-destructive analysis to study the efficiency of the peripheral protection and to detect the defects in the semi-conductor. Minority carrier lifetime was also deduced by studying the OBIC decrease at the edge of the space charge region. Ionization rates were extracted using OBIC method; these coefficients are key parameters to predict the breakdown voltage of the devices. OBIC measurements were also realized on the GaN, and two-photon generation was highlighted by measuring an OBIC current in the diamond when illuminating it with a UV laser beam (349 nm)
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Mashhadikarimi, Meysam. "Obtaining triple layer polycrystalline diamond compact by HPHT method." PROGRAMA DE P?S-GRADUA??O EM CI?NCIA E ENGENHARIA DE MATERIAIS, 2017. https://repositorio.ufrn.br/jspui/handle/123456789/23749.
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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES)
Neste trabalho de pesquisa, foi obtido um compacto de diamante policristalino (PDC), constitu?do de uma camada superior de diamante policristalino sob um substrato de WC-10% em peso de Co e uma interface de WC-20% em peso de Nb/Ni entre as camadas, atrav?s de m?todo de sinteriza??o de alta press?o e alta temperatura (HPHT). Para alcan?ar esse objetivo, foram realizadas tr?s etapas distintas. Na primeira etapa, foi sinterizado o corpo de diamante com um ligante adequado, e foram obtidos os melhores par?metros de sinteriza??o. Na segunda etapa, foi realizado o estudo de diferentes condi??es de sinteriza??o para o substrato de metal duro WC-10% p.Co. E, na terceira e ?ltima etapa, foi produzido, de acordo com os resultados alcan?ados nas etapas anteriores, o compacto de diamante policristalino de camada tripla (PDC). Na primeira etapa, quatro ligantes diferentes foram usados para sinterizar o diamante atrav?s do m?todo HPHT. Os ligantes utilizados foram o Nb/Fe, Nb/Co, Nb/Ni e Nb puro, sendo 10% em peso de ligante utilizado para cada composi??o. A sinteriza??o foi realizada a diferentes temperaturas e sob diferentes press?es e tempos. As amostras obtidas foram analisadas atrav?s das medidas de densidade relativa e dureza, al?m das imagens eletr?nicas de varredura, para encontrar os melhores par?metros de sinteriza??o e ligante. Os estudos mostraram que o Nb apresentou o melhor comportamento, e que os melhores par?metros de sinteriza??o foram: T = 1750 ?C, P = 7,7 GPa, t = 6 minutos. Na segunda etapa, uma mistura em p? de WC-10% em peso de Co foi sinterizado atrav?s de HPHT sob press?o de 7,7 GPa, variando temperatura (1500 ?C, 1600 ?C, 1700 ?C, 1800 ?C, 1900 ?C) e tempo (2 e 3 minutos). As an?lises microestruturais e estruturais foram realizadas atrav?s de MEV/EDS e DRX. Ensaios de dureza, tenacidade (ITF) e de resist?ncia ? compress?o, tamb?m, foram realizados para entender os efeitos de diferentes par?metros de sinteriza??o nas propriedades dos sinterizados, verificando-se densifica??o total das amostras sinterizadas a altas temperaturas. Entretanto, foi observado um crescimento anormal de gr?os para estas mesmas temperaturas. Altos valores de dureza foram observados, aproximadamente, entre 1250 a 1650 HV para todas as amostras sinterizadas. Na terceira etapa, para a obten??o do PDC, uma camada fina de WC-20% em peso de Nb/Ni foi utilizada para a forma??o da interface entre a camada superior de diamante com ligante de Nb pura e o substrato de WC 10% em peso de Co. A sinteriza??o foi feita atrav?s do m?todo HPHT ? temperatura de 1750 ?C sob 7,7 GPa de press?o. Foram utilizados dois tempos diferentes, de 6 min. (tr?s sucessivos 2 minutos) e 9 min. (tr?s sucessivos 3 minutos). A dureza foi medida e os estudos estruturais/microestruturais foram realizados atrav?s de an?lises de MEV/EDS. Em suma, os resultados mostraram que este novo tipo de PDC pode ser produzido com sucesso, usando um novo ligante, o niobio puro, para o diamante, sem qualquer presen?a de grafitiza??o. Verificou-se tamb?m que o uso de uma interface com os mesmos elementos constituintes do substrato e do corpo de diamante sinterizado resultou numa boa ades?o entre as camadas, o que pode resultar em melhor desempenho e melhorar a durabilidade do PDC.
The primary objective of this thesis was to obtain a triple layer polycrystalline diamond compact (PDC) containing a polycrystalline diamond as top layer, a WC 10 wt% Co substrate, and a WC 20 wt% Nb/Ni interface to bond these two layers via high pressure high temperature (HPHT) sintering. To achieve this objective, the project has been done in three different stages. The first stage was producing diamond sintered body with a suitable binder, and finding the best sintering parameters. The second stage of project was done to study the WC 10 wt% Co hardmetal substrate at different sintering conditions, and the third and last stage was done according to the results achieved from previous stages to obtain a triple layer PDC. At the first stage, four different binders were used to sinter diamond under HPHT condition. Binders were Nb/Fe, Nb/Co, Nb/Ni and pure Nb and 10 wt% binder was used. Sintering was carried out at different temperature and under different pressure and holding time. Obtained samples were studies according to relative density, microstructure, and hardness to find the optimum binder and sintering parameters. Studies at this stage showed that Nb is the best binder and T=1750 ?C, 7.7 GPa with holding time more than 6 minutes are the best sintering parameters. At the second stage a powder mixture of WC 10 wt% Co was sintered via HPHT at 1500, 1600, 1700, 1800, and 1900?C under 7.7 GPa pressure for 2 and 3 minutes. Microstructural/structural analyses were performed by SEM/EDS and XRD and hardness, Indentation Fracture Toughness (ITF) and compression tests were also carried out to understand effects of different sintering parameters. At this stage, it was found that full density can achieved for high sintering temperature along with abnormal grain growth. High hardness was observed in range starting from 1250 up to 1650 HV. At the third stage, to obtain PDC, a thin layer of WC 20 wt% Nb/Ni was used as an interface between top layer of diamond with pure Nb binder and WC 10 wt% Co substrate. Sintering was done via HPHT method at 1750?C under 7.7 GPa of pressure. Two different holding time of 6 (three successive 2 minutes) and 9 (three successive 3 minutes) were used. Hardness was measured and microstructural/structural studies were done via SEM/EDS. The overall results showed that this new kind of PDC can successfully produce using a new pure Niobium binder for diamond without any graphitization. It was also found that using an interface having the resemblance to both substrate and sintered diamond body caused good adhesion between layers that can results in enhanced performance and improving durability of PDC.
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Kitabayashi, Hiroyuki. "Surface acoustic wave filters on diamond layered structures /." *McMaster only, 2001.
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De, vecchy Jon. "Réalisation de substrats innovants à partir de diamant." Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALT022.
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Au sein d'un objectif global de réduction de la consommation énergétique, les composants de microélectronique se doivent d'être plus performants tout en étant moins énergivores. L'électronique de puissance, dont la fonction est la conversion de l'énergie électrique, est particulièrement concernée puisque ses composants doivent fonctionner à haute intensité, tension et température. Dans ces conditions, le silicium qui les constitue atteint ses limites et la conception de composants faits de matériaux plus adaptés est en plein essor. Parmi les matériaux candidats, le diamant et ses propriétés hors du commun est particulièrement étudié. Son excellente conductivité thermique (2200 W/m/K) combinée à son très fort champ de claquage (10 MV/cm) et à la grande mobilité des trous (2000 cm²/V/s) sont promesses de composants plus petits et plus performants.Cependant, les méthodes de synthèse limitent la taille des substrats de diamant monocristallin à environ 15 x 15 mm² et empêchent encore son industrialisation. L'approche développée dans cette thèse est le report de film de diamant sur un autre substrat en adaptant le procédé Smart Cut^TM. Ce procédé repose sur la combinaison d'une implantation ionique et d'un collage du substrat implanté sur un substrat receveur. Un recuit permet la fracture du substrat implanté et le détachement d'un film d'épaisseur contrôlée qui se retrouve reporté sur le substrat receveur. Cette approche permettrait de réduire les coûts du composant en diminuant la consommation de diamant tout en ouvrant la voie à l'industrialisation grâce à des reports successifs sur substrat grand format.Le Smart Cut^TM doit être intégralement adapté au cas du diamant, des études de chaque brique technologique seront donc présentées. L'obtention de bulles à la surface du substrat implanté après recuit traduit l'adaptation des conditions d'implantation. Le procédé de bullage par plusieurs combinaisons d'implantation ionique d'hydrogène et de recuit sera donc d'abord présenté. Les transformations du diamant durant le procédé seront caractérisées. Des essais complets de transfert en utilisant du collage seront ensuite présentés. Enfin, des perspectives d'optimisation et de réalisation seront donnéesWithin a global aim of reducing energy consumption, microelectronics components must be more efficient and less energy-consuming. Power electronics, which converts electric power, is particularly concerned because its component must operate at high intensity, voltage and temperature. Silicon, the base material of these components, is reaching its limits and the conception of components made with other materials is currently being studied. Among the candidate materials, diamond and its outstanding properties is of great interest. Its excellent thermal conductivity (2200 W/m/K) combined with high breakdown field (10 MV/cm) and high hole mobility (2000 cm²/V/s) are attractive for making smaller and more efficient components.However, monocrystalline diamond synthesis methods are limiting substrate size to about 15 x 15 mm², thus preventing its industrialization. The approach developed in this thesis is the diamond layer transfer to another substrate by adapting the Smart Cut^TM process. This process is based on a combination of ion implantation and bonding of the implanted substrate to a receiving substrate. Annealing then causes the fracture of the implanted substrate and the detachment of a film (with controlled thickness) which is transferred to the receiving substrate. This approach would make it possible to reduce component cost by decreasing diamond consumption and to open the way to industrialization thanks to successive transfers on a large substrate.Smart Cut^TM must be fully adapted to the diamond case, studies of each step will thus be presented. Blistering observation on the implanted substrate surface after annealing is the very first step of ion implantation parameters adaptation. A blistering process using combinations of hydrogen ion implantation and annealing will be presented.Diamond transformations occurring during the process will be characterized. Full layer transfer studies using substrate bonding will then be presented. Finally, prospects for optimization and realization will be given
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Hallock, Samuel H. "Viability of using diamond field emitter array cathodes in free electron lasers." Thesis, Monterey, California : Naval Postgraduate School, 2010. http://edocs.nps.edu/npspubs/scholarly/theses/2010/Jun/10Jun%5FHallock.pdf.
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Thesis (M.S. in Applied Physics)--Naval Postgraduate School, June 2010.Thesis Advisor(s): Lewellen, John ; Swent, Richard. "June 2010." Description based on title screen as viewed on July 13, 2010. Author(s) subject terms: Free Electron Lasers, Field Emitter Arrays, Cathode Test Cell, FEL, Diamond Field Emitter Array, Cathode. Includes bibliographical references (p. 71-72). Also available in print.
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Sprague, Michael R. "Raman memory for entanglement in diamonds and light storage in optical fibres." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:7f3d03f3-d47d-4871-8d59-268b301e1b8d.
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Light, when reduced to the level of individual quanta, can possess, besides its familiar properties of wavelength, direction, and polarization, a set of correlations irreducible to classical correlations, among other peculiar behaviour. These correlated states are intrinsically interesting, and are also useful for quantum-enhanced information processing. In this thesis, I use a high-bandwidth, far-off-resonant Raman memory to implement two quantum information primitives -- entanglement generation and light storage -- at room temperature and ambient conditions. Specifically, I show, for the first time, the entanglement of two solid-state objects at room temperature and, also, the storage of light in a hollow-core optical fibre. In the first part, I show that the optical phonon modes of two diamonds can be entangled -- the prototypical non-classical correlation -- at room temperature. The entanglement was generated by spontaneous Raman scattering with projective measurements using single-photon detectors. The degree of entanglement was rigorously quantified by measuring the concurrence -- an entanglement monotone -- of the joint state of the scattered optical fields. In the second part, I store light in the coherent superposition of cesium atoms confined within a kagome-structured hollow-core photonic crystal fibre at room temperature using a far-off-resonant stimulated Raman interaction. The storage efficiency of the memory was 27$pm$1% and the noise level was sufficiently low such that single-photon-level pulses could be stored. Taken together, these results highlight the potential of Raman memories for quantum information tasks in noisy systems with short coherence times.
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Birch, Rolf. "Progress towards high power, high brightness microchip lasers : multi-watt operation using diamond heatspreaders." Thesis, University of Strathclyde, 2011. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=16841.
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The microchip laser – a sub-millimetre thick slice of laser gain material onto which cavity mirrors are directly coated – offers a robust, compact laser design; however, this design both inhibits heat removal and is sensitive to thermally induced distortions. This limits power scaling and degrades beam quality at higher powers. This thesis describes progress towards achieving a high power, high brightness microchip laser using diamond heatspreaders. Diamond, silicon carbide (SiC) and sapphire heatspreaders are examined in a selection of dopeddielectric microchip lasers using finite element analysis (FEA). This suggests that diamond is the heatspreader of choice for most applications. The role of gain material thickness with respect to temperature gradients within Nd:YVO4, Nd:GdVO4 and Yb:KYW microchip lasers incorporating diamond heatspreaders is explored. Operation in the thin-disk regime is predicted to provide improved thermal management. At lower thicknesses, diamond is likely to outperform SiC at reducing thermal lensing and improving the overlap between the pump and fundamental cavity modes. This offers the potential for better beam quality. The same heatspreader materials examined using FEA are also investigated experimentally in extended cavity and quasi-microchip Nd:YVO4 lasers. It is found that diamond gives rise to the best performance. The performance of Nd:GdVO4 and a 1060nm semiconductor disk laser in an extended cavity format incorporating an intra-cavity diamond heatspreader is compared with that of Nd:YVO4. Finally, initial characterisation of a Yb:KYW extended cavity laser is presented. Over 3W of output power is achieved using Nd:YVO4 microchip lasers in novel configurations incorporating intra and extra-cavity diamond heatspreaders. Routes to achieving higher brightness are discussed. Finally, thoughts are given on how to best achieve high brightness, high power microchip lasers in the future by moving to smaller gain thicknesses and using Yb:KYW which is well suited to efficient operation in this configuration.
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Rémy, Benjamin. "Mesure de propriétés thermophysiques de matériaux minces et de dépôts par méthode Flash : application aux films polycristallins de diamant." Vandoeuvre-les-Nancy, INPL, 1998. http://www.theses.fr/1998INPL020N.
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L’objet de cette étude est de caractériser par une méthode impulsionnelle des matériaux minces et bons conducteurs dans le sens de l'épaisseur. Dans une première partie, nous présentons une méthode de bicouche permettant de mesurer les propriétés thermophysiques d'un dépôt solidaire de son substrat. L’approche méthodologique mise en oeuvre consiste tout d'abord, à étudier dans quelles conditions l'hétérogénéité du matériau bicouche peut être détectée (détectivité). Nous cherchons ensuite à déterminer par une étude de sensibilité, quel paramètre peut être estimé par cette technique (identifiabilité). Dans une seconde partie, nous développons un modèle semi-analytique pour la caractérisation de milieux semi-transparents en prenant en compte le couplage des transferts conductif et radiatif dans le matériau. Ce modèle est ensuite étendu aux cas de matériaux bicouche et multicouche à interfaces et parois semi-transparentes. Une simplification est également proposée pour des échantillons minces, à faible coefficient d'absorption, comme les films diamant. Dans une troisième partie, nous décrivons le banc laser aux temps courts qui a été conçu pour la mesure de diffusivité thermique de films minces. Une attention particulière est portée à la préparation de l'échantillon (revêtement utilisé pour opacifier le matériau), à la qualité du faisceau excitateur (profil plat ou gaussien), ainsi qu'au signal réellement mesuré (choix d'un amplificateur adapté et mesure locale/non-locale de température par détecteur infrarouge). Finalement, dans une quatrième partie, nous présentons différents résultats expérimentaux obtenus par méthode "Flash" sur des films non-diamant et diamant autoportés d'une épaisseur de 200 à 700 µm. Les valeurs mesurées sont ensuite comparées à celles données par effet "Mirage". Ceci nous permet alors, de valider le dispositif expérimental mis en place et de mettre en évidence l'anisotropie des films de diamant de type C. V. D.
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Brygoo, Stéphanie. "Chocs laser sur le diamant, l'hélium et l'hydrogène : une étude expérimentale de la Warm Dense Matter." Palaiseau, Ecole polytechnique, 2006. http://www.theses.fr/2006EPXX0037.
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Silva, Vlamir Oliveira da [UNESP]. "Influência da técnica de preparo cavitário na microinfiltração marginal em restaurações de dentes decíduos." Universidade Estadual Paulista (UNESP), 2000. http://hdl.handle.net/11449/104285.
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silva_vo_dr_arafo.pdf: 540803 bytes, checksum: 7326794dd51a361dd48b2e7c4b355170 (MD5)O objetivo desse trabalho foi avaliar a influência da forma do preparo cavitário na microinfiltração marginal em restaurações em dentes decíduos. Foram preparadas canaletas medindo 2,0 mm nas faces vestibular e lingual de molares decíduos que foram divididas aleatoriamente em 3 grupos de acordo com a técnica de preparo cavitário: Grupo I - alta rotação associado à ponta diamantada; Grupo II - sistema de abrasão a ar; e Grupo III - laser Er:YAG. Após o condicionamento com ácido fosfórico por 15 segundos, foi utilizado o adesivo Single Bond (3M) e a resina Filtek Flow (3M) para restaurar as canaletas. Os espécimes foram então mantidos em estufa a 37ºC por 6 dias, termociclados (500 ciclos com temperatura variando entre 5 e 55ºC), isolados e colocados em solução de fucsina básica à 0,5% durante 24 horas. Após serem seccionados a microinfiltração foi avaliada em microscópio ótico ligado a uma câmera de vídeo com 10 X de aumento. Para se avaliar a forma das cavidades medimos os ângulos oclusal, cervical e de abertura das cavidades, bem como a largura e a profundidade das mesmas por meio de fotomicrografias obtidas em MEV. Os resultados demonstraram semelhança estatística entre as larguras dos preparos cavitários, porém os ângulos oclusal, cervical e de abertura das cavidades apresentaram-se diferentes estatisticamente e que não houve microinfiltração marginal em nenhum dos grupos avaliados e que a diferença na forma de preparo das cavidades não influenciou na microinfiltração marginal dos espécimes estudados.
The aim of this research was the evaluation of the cavity prepare technique on the marginal microleakage in deciduous teeth. Cavities measuring 2.0 mm were prepared on the buccal and lingual faces and were divided into three groups according to the cavity prepare technique: Group I - High speed associated to diamond bur; Group II - air abrasion system; and Group III - Er:YAG laser. After the phosphoric acid etching for 15 seconds, the Single Bond (3M) adhesive and te Filtek Flow (3M) were used for the restoration of the cavities. Then the sample was stored at 37ºC for 6 days, termocycled (500 cycles with temperature varying from 5 to 55º C), isolated and immersed in a 0.5% funcsin solution for 24 hours. After being sectioned the microleakage was examined with a magnification optical microscope connected to a color video camera. In order to evaluate the shape of the cavities the occlusal, cervical and cavity opening angles were measured, as well as the width and depth of then, using SEM photographs. The results showed that there was no marginal microleakage in any of the evaluated groups and that the difference in the cavity shape did not influence the marginal infiltration on the studied samples.