Дисертації з теми "Helium3"
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Piegay, Nathalie. "DYNAMIQUE DE L'AIMANTATION DANS LES SOLUTIONS HELIUM3-HELIUM4 HYPERPOLARISEES." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2002. http://tel.archives-ouvertes.fr/tel-00003086.
Повний текст джерелаDutay, Jean-Claude. "Influence du melange vertical et de la couche de melange sur la ventilation de l'ocean. Simulations numeriques des traceurs transitoires tritium-helium3 et cfcs avec le modele opa." Paris 6, 1998. http://www.theses.fr/1998PA066112.
Повний текст джерелаLea, Ramona. "Produzione di ipernuclei leggeri in collisioni Pb-Pb con l'esperimento ALICE a LHC." Doctoral thesis, Università degli studi di Trieste, 2013. http://hdl.handle.net/10077/8582.
Повний текст джерелаThe subject of the present PhD thesis is the study of the production of light hypernuclei in ultra-relativistic Pb-Pb collisions with ALICE (A Large Ion Collider Experiment), one of the four major experiments at the LHC (Large Hadron Collider). The main physics goal of the ALICE experiment is the investigation of the properties of the strongly interacting matter at high energy density ($>$ 10 GeV/fm$^3$) and high temperature ($\approx$ 0.2 GeV) conditions. According to the lattice Quantum Chromo Dynamics (QCD) calculations, under these conditions (i.e. high temperature and large energy density) hadronic matter undergoes a phase transition to a ``plasma'' of deconfined quarks and gluons (Quark Gluon Plasma, QGP). In the first chapter of the thesis a general introduction to the heavy-ion physics will be given. Then the main quantities related to QGP formation (i.e. \textit{probes}) will be described. Finally the most important results obtained at SPS, RHIC and LHC experiments will be shown and discussed. In the second chapter a short description of the LHC and its experimental conditions will be reported and an overview of the ALICE experiment will be given. A description of the different detectors and their performances during data taking will be described; in addition a description of the computing framework will be given. The third chapter will be devoted to an introduction of the (anti)(hyper)nuclei production in heavy-ion collisions. The two main approaches which are believed to govern nuclei production (i.e. coalescence and thermal models) will be described, and an overview on the results at different energies will be shown. A comparison of the theoretical results will be also shown, with particular regards to the energies at the LHC. The fourth chapter is devoted to the description of the analysis method used to get (anti)hypertriton production yield in \PbPb~collisions at $\sqrt{s_{\rm{NN}}}$ = 2.76~TeV with the ALICE experiment via its mesonic decay \hyp~$\rightarrow$ \he + \pim (\antihyp $\rightarrow$ \antihe + \pip). In the beginning of the chapter the analysis technique used for particle identification and for the determination of secondary vertices will be described. The analysis will be divided into two distinct parts: the first one based on the data sample collected by the ALICE experiment during the first LHC heavy-ion run held at the end of 2010, while the second one based on data collected at the end of 2011. A detailed description of the study on efficiency evaluation and signal extraction will be shown for both analysis, together with a study of the systematic uncertainties. The results on the production yield of (anti)hypertriton will also be shown. The estimation of the hypertriton lifetime will be provided in the final section of the chapter.\\ In the fifth chapter the method used to obtain the \pt~spectrum of \he~will be presented. The raw spectra, the efficiency evaluation, systematic errors and feed-down from \hyp~will be presented. The final spectrum will be used to evaluate the production yield of \he(\antihe) in the whole \pt~region, from 0 to $\infty$. \\ Finally, in the last chapter, the present experimental results will be compared with published relevant results and with the most recent theoretical findings. Moreover, the measurement of the ``Strangeness Population Factor'' [S$_{3}$= \hyp/\he/($\Lambda$/p)] at the LHC energies will be provided. This quantity is a valuable tool to probe the nature of dense matter created in high-energy heavy-ion collisions and to validate theoretical models.
-------------------------------------------------------------------------------------------------- Questa tesi è dedicata allo studio della produzione di ipernuclei leggeri in collisioni ultra-relativistiche di ioni piombo (Pb) con l'esperimento ALICE (A Large Ion Collider Experiment), uno dei quattro grandi esperimenti del Large Hadron Collider (LHC) del CERN. Il principale obiettivo scientifico dell'esperimenento ALICE è lo studio delle proprietà della materia in condizioni estreme di energia (> 10 GeV/fm^3) e di temperatura (~ 0.2 GeV) mediante lo studio di collisioni di ioni piombo. Calcoli di Cromo Dinamica Quantistica (QCD) su reticolo prevedono, infatti, che in condizioni di alta temparatura e grande energia la materia adronica subisca un transizione di fase verso un ``plasma'' di quark e gluoni deconfinati (Quark Gluon Plasma, QGP). Nel primo capitolo della tesi verranno descritte in maniera generale la fisica degli ioni pesanti e le grandezze caratterische usate per provare la formazione del QGP (probes). Verranno quindi mostrati e discussi i risultati sperimentali che possono provare l'esistenza di uno stato deconfinato della materia nucleare ottenuti agli esperimenti a SPS, RHIC e LHC. Nel secondo capitolo saranno brevemente presentati il Large Hadron Collider (LHC) e le condizioni sperimentali di lavoro durante i primi tre anni di presa dati; in seguito verrà data un'ampia panoramica dell'esperimento ALICE. Saranno descritti i differenti sotto-rivelatori che formano l'esperimento e verranno inoltre mostrate le loro performance durante l'acquisione dati; inoltre verrà fornita una descrizione del framework di calcolo utilizzato nell'analisi dei dati. Il terzo capitolo sarà dedicato alla descrizione dei maccanismi di produzione di (anti)(iper)nuclei in collisioni di ioni pesanti: verranno descritti i due meccanismi di produzione che si ritiene governino la loro produzione (coalescenza e modello termico) e verrà mostrata una panoramica sui risultati ottenuti a diverse energie. Inotre saranno presentati diversi calcoli teorici, ponendo particolare attenzione ai risultati aspettati all'energia di LHC. Il quarto capitolo contiene la descrizione del metodo di analisi utilizzato per valutare lo yield di pruduzione dell'(anti)ipertritone attraverso il suo canale di decadimento mesonico \hyp~$\rightarrow$ \he + \pim (\antihyp $\rightarrow$ \antihe + \pip) in collisioni \PbPb~con energia nel centro di massa $\sqrt{s_{\rm{NN}}}$ = 2.76~TeV. Inizialmente verrà descritta la tecnica di analisi utilizzata per l'identificazione di particelle e dei vertici secondari, quindi sarà fornita la descrizione dettagliata della tecnica di analisi. L'analisi dei dati è stata siddivisa in due distinte parti: la prima è dedicata alla descrizione della procedura utilizzata per l'analisi dei dati raccolti da ALICE durante la prima acquisizione di collisioni Pb--Pb alla fine del 2010; nella seconda parte, invece, verrà descritta la procedura di analisi dei dati raccolti durante la seconda presa dati nel Dicembre 2011. Verranno quindi descritte in modo dettagliato l'estrazione del segnale, lo studio del fondo combinatoriale e gli errori sistematici. Infine, nella parte finale del capitolo, varrà fornita una stima della vita media dell'ipertritone.\\ Nel quinto capitolo sarà presentato il metodo usato per ottenere lo spettro in pT di (anti-3He)3He. Verranno descritti: la procedura di estrazione del segnale, la stima dell'efficienza in funzione del momento trasverso, la valutazione degli errori sistematici e la procedure usata per sottrarre il feed-down dovuto al decadimento dell'ipertitone. Lo spettro verrà quindi utilizzato per valutare lo yield di produzione di (anti-3He) 3He. Infine, nel sesto e ultimo capitolo, i risultati sperimentali ottenuti verranno confrontati con i risultati teorici discussi nel Capitolo 3.
XXV Ciclo
1985
Yu, Nan. "The infrared spectrum of the helium molecular ion helium-3 positive helium-4." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184419.
Повний текст джерелаHjort, Hans H. "Helium-Helium scattering in vacuum and in liquid ³HE /." The Ohio State University, 1999. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488187049539918.
Повний текст джерелаJörder, Felix [Verfasser], and Andreas [Akademischer Betreuer] Buchleitner. "Dynamical localization in driven helium = Dynamische Lokalisierung in getriebenem Helium." Freiburg : Universität, 2015. http://d-nb.info/1119805643/34.
Повний текст джерелаTodd, Allan. "Helium-Antihydrogen Interactions." Thesis, University of Nottingham, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485533.
Повний текст джерелаSawkey, Daren Lewis. "Thermomechanical effect in normal liquid helium-3 with helium-4 pre-plating." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq22392.pdf.
Повний текст джерелаPorter, Ryan Lucian. "THEORY AND APPLICATION OF HELIUM AND HELIUM-LIKE IONS IN ASTROPHYSICAL ENVIRONMENTS." UKnowledge, 2006. http://uknowledge.uky.edu/gradschool_diss/430.
Повний текст джерелаBatey, G. J. "Thermal measurements in helium." Thesis, University of Nottingham, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376489.
Повний текст джерелаSteer, A. P. "Liquid helium acoustic microscope." Thesis, University of Exeter, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381340.
Повний текст джерелаTurner, Robert Paul. "Pumping helium 3 in a helium mixture with a magnetic field : thermal boundary resistance between liquid helium mixtures and silver sinters." Thesis, Lancaster University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242945.
Повний текст джерелаPetluri, Raghuram. "Angular dependent interaction of metastable helium molecules on the surfaces of helium nanodroplets /." View online ; access limited to URI, 2005. http://0-wwwlib.umi.com.helin.uri.edu/dissertations/dlnow/3186917.
Повний текст джерелаGspann, J. [Verfasser], and R. [Verfasser] Ries. "Wechselwirkung eines Caesiumatomstrahls mit Helium-3- und Helium-4-Clusterstrahlen / J. Gspann, R. Ries." Karlsruhe : KIT-Bibliothek, 2014. http://d-nb.info/1196577234/34.
Повний текст джерелаMendoza, Luna Luis Guillermo. "Free and hindered-rotation of helium excimers in liquid helium via a bulk experiment." Thesis, University of Leicester, 2015. http://hdl.handle.net/2381/35982.
Повний текст джерелаZhu, Jinzhen [Verfasser], and Armin [Akademischer Betreuer] Scrinzi. "Photoionization of the helium hydride ions and helium atoms / Jinzhen Zhu ; Betreuer: Armin Scrinzi." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2020. http://d-nb.info/1223849813/34.
Повний текст джерелаClaas, Patrick. "Femtosekundenspektroskopie an alkalidotierten Helium-Nanotröpfchen." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=978886488.
Повний текст джерелаWendler, Martin. "Helium- und Sauerstoffdiffusion in Glasschmelzen /." Clausthal-Zellerfeld : Papierflieger, 1996. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=007293193&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
Повний текст джерелаMatthias, John Robert. "Quantum evaporation from superfluid helium." Thesis, University of Exeter, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390167.
Повний текст джерелаKlingner, Nico. "Ionenstrahlanalytik im Helium-Ionen-Mikroskop." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-220036.
Повний текст джерелаThe present work describes the implementation of ion beam analysis methods in a helium-ion-microscope for the determination of sample compositions with a focused ion beam of < 1 nm size. Imaging in the microscope is realized by scanning the focused ion beam over the sample surface while measuring the local secondary electron yield. Although this procedure leads to a high topographical contrast, neither the yield nor the energy distribution of the secondary electrons deliver reliable information on the chemical composition of the sample. For this purpose, in this work different ion beam induced secondary particles were compared with respect to their suitability for the analysis of the chemical composition in the helium-ion-microscope. In particular the information content of the particles, their analysability and their yield were evaluated. As a result, the spectrometry of backscattered particles and the mass spectrometry of sputtered secondary ions were identified as the most promising methods and regarded in detail. The investigation focused on physical limitations and detection limits of the methods as well as their implementability into a helium-ion-microscope. Therefor various concepts of spectrometers were evaluated, tested and validated in terms of their efficiency, energy resolution and practicability in the microscope. Time-of-flight spectrometry by pulsing the primary ion beam could be identified as the most suitable technique and has been successfully implemented in a helium-ion-microscope. The measurement setup, signal processing and data handling as well as comparative simulations are described in detail. Further the spectrometer was characterized explicitly in terms of time, energy and mass resolution. Spatially resolved backscattering spectra will be shown demonstrating the feasibility of performing ion beam analysis in a helium-ion-microscope for the first time on a size scale of ≤ 60 nm. By pulsing the primary ion beam the technique of secondary ion mass spectrometry becomes automatically accessible. This method provides information on the molecular composition of samples and can reach higher detection limits than those from backscattering spectrometry. For the first time, in a helium-ion-microscope measured secondary ion mass spectra and spatially resolved elemental analysis by spectrometry of secondary ions, could be demonstrated. The results of this work are published 2016 in the scientific journal Ultramicroscopy, volume 162 on pages 91 to 971. In October 2016 there will be another publication as a book chapter in „Helium Ion Microscopy“ (publisher: Springer Verlag Heidelberg)
Haynes, S. R. "Condensed phases of confined helium." Thesis, University of Sussex, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372719.
Повний текст джерелаRorai, Cecilia. "Vortex reconnection in superfluid helium." Doctoral thesis, Università degli studi di Trieste, 2012. http://hdl.handle.net/10077/7868.
Повний текст джерелаLa presente tesi concerne la modellizzazione e simulazione numerica, attraverso l'equazione di Gross-Pitaevskii (chiamata anche equazione di Schroedinger non lineare), della dinamica dei vortici quantistici nell'elio superfluido e in particolare del fenomeno della riconnessione. La riconnessione si verifica qualora due vortici approssimativamente antiparalleli, si intersecano e si scambiano le estremità. Questo fenomeno è stato osservato sperimentalmente e risulta essere una caratteristica essenziale della turbolenza quantistica.
XXIII Ciclo
1983
Ludwig, Thorsten. "Anticrossing-Spektroskopie schnell bewegter Heliumatome nach Elektroneneinfang in 10 bis 50 keV HE+-He-Stössen." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=974015822.
Повний текст джерелаSchmidt, Lothar. "Effekte molekularer Symmetrien in der Elektronenemission bei langsamen He2+-He-Stössen eine kinematisch vollständige experimentelle Untersuchung /." [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=961247037.
Повний текст джерелаWalter, Michael. "Photo(doppel)ionisation von Helium und einfachen Molekülen." [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=961295074.
Повний текст джерелаCzasch, Achim. "Doppelt hoch angeregte Zustände von Helium partielle Wirkungsquerschnitte und Winkelverteilungen der Elektronenemission /." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972184260.
Повний текст джерелаGaiser, Christof. "Properties of helium and gas thermometry." Aachen Shaker, 2008. http://d-nb.info/990735125/04.
Повний текст джерелаGerlach, Stefan. "Dipol-Dipol-Wechselwirkungen ultrakalter Helium-Rydbergatome." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=981536980.
Повний текст джерелаBussiahn, René. "Laserabsorptionsspektroskopische Untersuchungen in Helium-Xenon-Glimmentladungen." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=98444811X.
Повний текст джерелаGuilleumas, Montserrat. "Nucleation and cavitation in liquid helium." Doctoral thesis, Universitat de Barcelona, 1995. http://hdl.handle.net/10803/667593.
Повний текст джерелаCai, Zhiming. "A study of global helium resources." Thesis, University of Cambridge, 2010. https://www.repository.cam.ac.uk/handle/1810/252193.
Повний текст джерелаPaetkau, Mark Jeffrey. "Helium mixtures in 87% porous aerogel." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq29088.pdf.
Повний текст джерелаHuang, Jiachang. "A helium high-temperature drift chamber." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0013/NQ38900.pdf.
Повний текст джерелаMiller, Jonathan I. "The design of robust helium aerostats /." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99000.
Повний текст джерелаLee, Richard Albert Marlor. "A cosmological experiment in liquid helium." Thesis, Lancaster University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239061.
Повний текст джерелаBuckland, J. R. "New methods in helium atom scattering." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597056.
Повний текст джерелаLusher, C. P. "Nuclear magnetic relaxation in gaseous helium." Thesis, University of Sussex, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356513.
Повний текст джерелаMarchalant, Pascale J. "(e, 2e) excitation-ionization of helium." Thesis, Queen's University Belfast, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337019.
Повний текст джерелаBoatwright, Adrian Lional. "Molecular behaviour in superfluid helium clusters." Thesis, University of Nottingham, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.478961.
Повний текст джерелаKlier, Jurgen. "Liquid helium on weak binding substrates." Thesis, University of Exeter, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337745.
Повний текст джерелаChristie, S. "Contrast in the helium acoustic microscope." Thesis, University of Exeter, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381299.
Повний текст джерелаTanner, Marc D. (Marc David) 1974. "Helium breath : an updated 6.111 curriculum." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/47585.
Повний текст джерелаIncludes bibliographical references (p. 85).
by Marc D. Tanner.
S.B.and M.Eng.
Hofmans, Marlous. "Experimental characterization of helium plasma jets." Thesis, Institut polytechnique de Paris, 2020. http://www.theses.fr/2020IPPAX062.
Повний текст джерелаThis thesis studies an atmospheric pressure helium plasma jet that is powered by positive, unipolar pulses at a kHz frequency. Experiments are performed that focus on the propagation dynamics, flow structure and temperature in a freely expanding jet, as well as the influence of a metallic target on the plasma.Stark polarization spectroscopy yields an axial electric field of around 10 kV/cm in the capillary of the jet and an increase up to 20 kV/cm in the plume, which is constant for different amplitudes and durations of the applied voltage pulse. Thomson and rotational Raman scattering are used to determine the electron density and electron temperature, at different axial and radial positions, as well as the gas temperature and the density of N2 and O2 that are mixed into the helium from the surrounding air.Quantitative comparison of these experimental results with results from a 2D fluid model show a good agreement and allow for a better understanding of the obtained results, namely that the electric field in the ionization front depends linearly on the flow composition at that location. Schlieren imaging shows the onset of turbulent structures at high applied flow rates and at the application of the voltage pulses. The gas temperature, as measured by a temperature probe, is found to increase by around 12 C when the plasma is ignited and by around 25 C when a metallic target is placed in front of the jet
Masuhara, Naoto. "Spin waves in liquid helium-3 /." The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487259580261871.
Повний текст джерелаAgarwal, Shradha. "Helium mobility in advanced nuclear ceramics." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112197/document.
Повний текст джерелаWhile the current second and third generation nuclear plant designs provides an economically, technically, and publicly acceptable electricity supply in many markets, further advances in nuclear energy system design can broaden the opportunities for the use of nuclear energy. The fourth generation of nuclear reactors is under development. These new reactors are designed with the following objective in mind: sustainability, safety and reliability, economics, proliferation resistance. Out of six Generation IV systems namely, Gas-Cooled Fast Reactor (GFR), Lead-Cooled fast reactor (LFR), Molten Salt Reactor (MSR), Sodium-Cooled Fast Reactor (SFR), Supercritical-Water-Cooled Reactor (SCWR), Very-High-Temperature Reactor (VHTR), this work is dedicated to identify specific fuel type that is compatible with gas-Cooled fast reactor (GFR) in-Core service conditions and could be extended to diagnose potential cladding material for SFR. The French strategy is mainly oriented towards the development of sodium-Cooled fast reactors (SFR) and very slightly focused on GFR. This dissertation is focused on the study of transition metal ceramics which are candidates for fuel coatings in GFR and have been considered as potential cladding materials for SFR. The specific fuel type in GFR should consists of spherical fuel particle made up of UC or UN, surrounded by a ceramic coating which provides structural integrity and containment of fission products. The most promising candidates for ceramic coatings are ZrN, ZrC, TiN, TiC & SiC due to a combination of neutronic performance, thermal properties, chemical behavior, crystal structure, and physical properties. It is obvious that these ceramics would be exposed to energetic fission products from fuel such as heavy ions and neutrons. These high-Energy neutron will knock the atoms in the surrounding materials and can induce (n, α) reactions, thus producing high concentration of helium atoms during and after reactor operation. The helium atoms produced are energetic and can easily penetrate into the surrounding material. Helium atoms are considered to be highly insoluble in previously studied structural nuclear materials. The accumulation of helium into solid matrix, can lead to the formation of bubbles, cavity, swelling, embrittlement etc. Helium can strongly induce grain boundary cavitation that can produce formation of inter-Granular channels, which may serve as pathways for release of radioactive elements to the environment or lead to grain-Boundary weakening and de-Cohesion. Particularly in ceramics, large quantities of helium can also lead to dimensional changes and cracks due to over-Pressurized helium bubbles. Therefore, study of helium behavior in advanced nuclear ceramics under high operating temperatures and extreme radiation conditions predicted for GFRs is viewed as crucial. In this thesis, ion-Implantation technique and material characterization techniques are used to study diffusion of helium in transition metal ceramics under thermal and extreme irradiation environments. Our main aim during this thesis is: 1) To calculate diffusion and migration energies of helium under different experimental conditions by applying theoretical models on experimental data.2) To investigate the role of microstructure such as grain boundaries, native vacancies and porosity on helium accumulation and its evolution after helium accumulation.3) To know the role of helium introduction conditions on helium diffusion. 4) To establish and validate an approach to calculate pressure built by helium gas inside the bubbles and to verify if the pressure approaches mechanical stability limit
Hoendervanger, Lynn. "A New Metastable Helium Machine : An Investigation into the Attributes of Trapping, Cooling and Detecting Metastable Helium." Thesis, Palaiseau, Institut d'optique théorique et appliquée, 2014. http://www.theses.fr/2014IOTA0006/document.
Повний текст джерелаThis thesis describes the work done over the past three and a half years on the new metastable helium experiment at the Institut d'Optique in Palaiseau. In the first chapter it describes a study to improve both the efficiency and the accuracy of the Microchannel Plate (MCP) detection system. We have experimented with adding a gold layer on the top of the input plate, something that we have found increases the efficiency but also decreases the accuracy. The addition of a voltage between the two stacked plates has been shown to both raise the efficiency and improve the accuracy in non-coated MCPs.The second chapter is devoted to the construction of the experimental apparatus. Here the excitation of ground state helium to its metastable state is described, as well as the subsequent collimation and cooling by Zeeman slower of the resulting hot atomic beam. The slowed beam is then captured in a Magneto-Optical Trap, in which we have captured 8x108 atoms.In the third chapter an original study on three-dimensional Doppler cooling in a red-detuned molasses and in the Magneto-Optical trap is presented. The metastable helium system is unique as there is no multiple scattering of photons and there are no sub-Doppler effects. This allows for a never before seen experimental realisation of pure Doppler cooling theory. The fourth chapter describes a study on collisions in a magneto-optical trap of metastable helium. Light-induced Penning collisions are responsible for high trap losses at high intensities and at frequencies close to the transition frequency. We measure the constant rate coefficient to Ksp = 2.8 ± 0.4 x 10-7cm3/s
Alahmade, Walaa. "EXPERIMENTAL INVESTIGATION AND MONTE CARLO SIMULATION OF QUASIELASTIC ELECTRON SCATTERING FROM HELIUM-3 CLUSTERS IN HELIUM-4." Kent State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=kent1619697731858548.
Повний текст джерелаWu, Huayou. "Convergent close-coupling calculations of positron-helium collisions." Thesis, Wu, Huayou (2004) Convergent close-coupling calculations of positron-helium collisions. PhD thesis, Murdoch University, 2004. https://researchrepository.murdoch.edu.au/id/eprint/416/.
Повний текст джерелаWu, Huayou. "Convergent Close-Coupling Calculations of Positron-Helium Collisions." Murdoch University, 2004. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20050107.101745.
Повний текст джерелаSchmiedeskamp, Jörg. "Weiterentwicklung einer Produktionsanlage und der Speicherungs- bzw. Transportkonzepte für hochpolarisiertes 3He Anwendungen in Kernspintomographie und physikalischer Grundlagenforschung /." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975909355.
Повний текст джерела