Interplanetary satellite missions and also satellites orbiting the Earth carry instruments to measure fluxes of neutral atoms, which are plasma key parameters for the investigation of the planets' atmospheres. Neutral atoms entering the mass-spectrometry instrument have to be ionized to be able to guide them using electric and magnetic fields with intent to determine energy and velocity of the atoms and finally their mass. For low energy neutral atoms, the ionization process can be realized by implementing a charge state conversion surface, where-on the atoms are scattered in an angle of grazing incidence and getting ionized.The objective of this work is the characterization and analysis of two diamond-like carbon surface samples by measuring and determining ionization efficiencies and scattering properties and therefore their functionality as charge state conversion surfaces.First, a chemical vapor deposition (CVD) diamond sample is investigated. Furthermore the CVD diamond is compared to another diamond--like carbon surface manufactured by pulsed laser deposition (PLD) technique. All measurements have been accomplished at the ILENA (Imager for Low Energy Neutral Atoms) facility at the Physics Institute, University of Bern in the Department of Space Research and Planetary Sciences.It is discovered that the CVD surface gets electrostatically charged upon scattering of atomic ions. Though this charging effects, a qualitative characterization of the surface can be made. It is shown that the ionization efficiencies of the CVD and the PLD diamond surface are of comparable quality, where on the contrary the scattering properties of the CVD diamond charge state conversion surface are much better. It still has to be investigated in future experiments, if this brilliant scattering properties are due to charging effects or can be assigned to the very smooth surface of the CVD diamond surface. / <p>Validerat; 20120112 (anonymous)</p>

Neutral atom systems are an appealing platform for the development and testing of quantum control and measurement techniques. This dissertation presents experimental investigations of control and measurement tools using as a testbed the 16-dimensional hyperfine manifold associated with the electronic ground state of cesium atoms. On the control side, we present an experimental realization of a protocol to implement robust unitary transformations in the presence of static and dynamic perturbations. We also present an experimental realization of inhomogeneous quantum control. Specifically, we demonstrate our ability to perform two different unitary transformations on atoms that see different light shifts from an optical addressing field. On the measurement side, we present experimental realizations of quantum state and process tomography. The state tomography project encompasses a comprehensive evaluation of several measurement strategies and state estimation algorithms. Our experimental results show that in the presence of experimental imperfections, there is a clear tradeoff between accuracy, efficiency and robustness in the reconstruction. The process tomography project involves an experimental demonstration of efficient reconstruction by using a set of intelligent probe states. Experimental results show that we are able to reconstruct unitary maps in Hilbert spaces with dimension ranging from d=4 to d=16. To the best of our knowledge, this is the first time that a unitary process in d=16 is successfully reconstructed in the laboratory.

Venus does not have a strong intrinsic magnetic field as the Earth, and its magnetosphere is induced by the interaction of the solar wind with the ionosphere. The near-Venus space environment is characterized by the presence of a bow shock and of an induced magnetic boundary linked to the interplanetary magnetic field orientation. The interaction of the solar wind with the planetary atmosphere and exosphere is more direct than on Earth. This interaction energises ionospheric ions, leading to a loss of atmospheric compounds in space. Ions and energetic neutral atoms of solar wind or of planetary origin can precipitate onto the upper atmosphere of Venus, which is an important process of mass, momentum and energy transfer, and can lead to an increase of the loss of planetary constituents due to the atmospheric sputtering. The energetic neutral atoms are used as a diagnostic method, that gives a continuous and global imaging of the planetary magnetosphere. They are generated by multiple processes, as charge exchange, scattering and sputtering from the upper atmosphere of Venus. In this work, we study the precipitation of oxygen and hydrogen ions and energetic neutrals in the upper atmosphere of Venus. We use data produced with a global hybrid plasma model that simulated the interaction between Venus and the solar wind, and simulate the charge exchange process between the energetic ions and exospheric neutral particles to produce the energetic neutral atoms. Due to the low North-South asymmetry in the precipitation of oxygen planetary ions and energetic neutral atoms, we conclude that the effect of the finite gyroradius of oxygen ions is limited. Compared to the case of Mars, the fraction of the solar wind that precipitates as hydrogen energetic neutral atoms onto Venus is lower, consistently with the less extended exosphere of Venus. / Venus har inte ett starkt internt magnetfält som jorden, och dess magnetosfär induceras av solvindens växelverkan med jonosfären. Rymdmiljön nära Venus kännetecknas av närvaron av en bogchock och av en inducerad magnetisk gräns kopplad till den interplanetära magnetfältsorienteringen, genom en mer direkt växelverkan mellan solvinden och planetens exosfären och atmosfär än på jorden. Denna växelverkan aktiverar jonosfäriska joner, vilket leder till en förlust av atmosfär till rymden. Joner och energiska neutrala atomer i solvind eller av planetärt ursprung kankollidera med den övre atmosfären på Venus. Detta är en viktig typ av överföring av massa, rörelsemängd och energi och kan leda till en ökning av förlusten av planetära beståndsdelar på grund av sputtering. De energiska neutrala atomerna används som en diagnostisk metod, vilket ger en kontinuerlig och global avbildning av Venus magnetosfär. De är genererade av flera processer, som laddningsutbyte, spridning och sputtering från Venus övre atmosfär. I det här arbetet studerar vi precipitering av syre- och vätejoner och energiska neutraler i den övre atmosfären på Venus. Vi använder data som produceras med en global hybridplasmamodell som simulerar växelverkan mellan Venus och solvinden, och laddningsutbytesprocessen mellan de energiska jonerna och exosfäriska neutralpartiklar för att producera energiska neutrala atomer. På grund av den låga nord-sydliga asymmetrin i precipiteringen av planetära syrejoner och energiska neutrala atomer, drar vi slutsatsen att effekten av syrejonernas ändliga gyroradius är begränsad. Vi jämför precipitering väte och energiska neutralpartiklar på Venus med fallet på Mars. / A differenza della Terra, Venere non possiede un campo magnetico intrinseco. L’interazione del vento solare con la ionosfera del pianeta forma quella che è chiamata magnetosfera indotta. Questa struttura presenta un bow shock e un induced magnetic boundary (confine magnetico indotto) ed è fortemente legata all’orientamento del campo magnetico interplanetario. L’interazione tra il vento solare e l’atmosfera di Venere è più diretta in confronto a quanto accade per la Terra. Questa interazione è capace di energizzare ioni della ionosfera oltre alla loro velocità di fuga, portando a una perdita nello spazio di materiale di origine planetaria. Ioni o atomi neutri del vento solare o di origine planetaria possono precipitare nell’atmosfera del pianeta, trasferendo in questo modo energia, quantità di moto e massa dallo spazio a Venere. La precipitazione di ioni e atomi neutri può causare lo sputtering di materiale planetario e causare in questo modo un aumento della perdita di materia dall’atmosfera del pianeta. Gli atomi neutri energetici sono utilizzati come metodo di indagine per la magnetosfera, di cui possono fornire una rappresentazione globale e continua. Gli atomi neutri energetici sono generati da sputtering, backscattering e da processi di trasferimento di carica. In questa tesi è studiata la precipitazione nell’atmosfera di Venere di ioni e di atomi neutri, sia di idrogeno che di ossigeno. Sono utilizzati dati prodotti con un modello ibrido che simula l’interazione tra Venere e il vento solare. Gli atomi neutri energetici sono prodotti modellando il meccanismo di scambio di carica tra gli ioni e l’esosfera neutra di Venere. Si conclude che l’assimmetria calcolata nella precipitazione degli ioni di ossigeno è più bassa di quanto ci si sarebbe aspettato. La precipitazione di atomi neutri di idrogeno nell’atmosfera di Venere è confrontata con il caso di Marte.

Neste trabalho, mostramos que é possível suprimir a maioria dos processos inelásticos que podem causar perdas de átomos em armadilhas magneto-ópticas. Nossos resultados revelam que o processo de blindagem óptica (demonstrado pelo nosso grupo, pela primeira vez para o processo de ionização fotoassociativa – Phys. Rev. Lett. 73, 1911 (1994)) é bem mais geral do que se supunha. Permitindo, inclusive, a supressão de colisões entre átomos no estado fundamental. E provavelmente qualquer outro processo inelástico que ocorra a curtas distâncias internucleares. Para se chegar a esses resultados, foi necessário desenvolver uma nova técnica de aprisionamento, que permite o estudo de colisões frias, mesmo em armadilhas cujo potencial de confinamento é pequeno. Graças a essa técnica foi possível, pela primeira vez, observar perdas causadas por mudança de estrutura hiperfina, numa armadilha de átomos de sódio operando na linha D1 (carregada a partir de uma célula de vapor). Essa técnica ainda nos permitiu medir a taxa de colisões frias (&#61538;) no trap da linha D1, um dado que até então não existia na literatura. Para verificar a confiabilidade dos resultados obtidos por essa técnica, realizamos também medidas de &#61538; na linha D2 e comparamos esses resultados com outros existentes na literatura (obtidos por uma técnica diferente). A boa concordância entre esses resultados nos deixa confiantes em dizer que essa técnica, além de ser muito interessante, no estudo de armadilhas rasas (seja isso devido à intensidade dos lasers de aprisionamento, seja devido a natureza própria da armadilha), é também bastante confiável / In this work, we showed that is possible to suppress most of the inelastic processes that may cause losses of atoms in a magneto-optical trap. Our results reveal that the process of optical shielding (demonstrated by our group, for the first time to photoassociative ionization - Phys. Rev. Lett. 73, 1911 (1994)) is much more general than it was supposed. Even allowing the suppression of ground state collisions and probably any other inelastic process that happens at short internuclear distances. To achieve those results, it was necessary to develop a new trapping technique, which allows the study of cold collisions, even in traps whose confinement potential is small. Thanks to that technique it was possible, for the first time, to observe losses caused by hyperfine changing collisions, in a trap of sodium atoms operating in the D1 line (loaded from a vapor cell). That technique has still allowed us to measure the rate of cold collisions (&#61538;) for the D1 line trap, a result which, until now, did not exist in the literature. To verify the reliability of the results obtained by that technique, we also accomplished measures of &#61538; in the D2 line and compared those results with other existent ones in the literature (obtained by a different technique). The good agreement among those results, made us confident in saying that this technique, besides being very interesting in the study of shallow traps (due to the intensity of the trapping lasers, or due to the own nature of the trap), it is also quite reliable.

Devices that exploit the properties of quantum mechanics for their operation can offer unique advantages over their classical counterparts. Interference of matter waves can be used to dramatically increase the rotational sensitivity of gyroscopes. Complete control of the quantum evolution of a system could produce a new powerful computational device known as a quantum computer. Research into these technologies offers a deeper understanding of quantum mechanics as well as exciting new insights into many other areas of science. Currently, a limiting factor in many quantum devices using neutral atoms is accurate motional control over the atoms. This thesis describes two recent advancements in neutral atom motional control using both magnetic and electromagnetic confining fields. Part I reports on the demonstration of the first storage ring for neutral atoms. This storage ring may one day provide the basis for the world's most sensitive gyroscope. Part II describes the optical delivery of neutral atoms into the mode of a high-finesse cavity for applications in quantum computing and communication.

Neste trabalho, mostramos que é possível suprimir a maioria dos processos inelásticos que podem causar perdas de átomos em armadilhas magneto-ópticas. Nossos resultados revelam que o processo de blindagem óptica (demonstrado pelo nosso grupo, pela primeira vez para o processo de ionização fotoassociativa – Phys. Rev. Lett. 73, 1911 (1994)) é bem mais geral do que se supunha. Permitindo, inclusive, a supressão de colisões entre átomos no estado fundamental. E provavelmente qualquer outro processo inelástico que ocorra a curtas distâncias internucleares. Para se chegar a esses resultados, foi necessário desenvolver uma nova técnica de aprisionamento, que permite o estudo de colisões frias, mesmo em armadilhas cujo potencial de confinamento é pequeno. Graças a essa técnica foi possível, pela primeira vez, observar perdas causadas por mudança de estrutura hiperfina, numa armadilha de átomos de sódio operando na linha D1 (carregada a partir de uma célula de vapor). Essa técnica ainda nos permitiu medir a taxa de colisões frias (&#61538;) no trap da linha D1, um dado que até então não existia na literatura. Para verificar a confiabilidade dos resultados obtidos por essa técnica, realizamos também medidas de &#61538; na linha D2 e comparamos esses resultados com outros existentes na literatura (obtidos por uma técnica diferente). A boa concordância entre esses resultados nos deixa confiantes em dizer que essa técnica, além de ser muito interessante, no estudo de armadilhas rasas (seja isso devido à intensidade dos lasers de aprisionamento, seja devido a natureza própria da armadilha), é também bastante confiável / In this work, we showed that is possible to suppress most of the inelastic processes that may cause losses of atoms in a magneto-optical trap. Our results reveal that the process of optical shielding (demonstrated by our group, for the first time to photoassociative ionization - Phys. Rev. Lett. 73, 1911 (1994)) is much more general than it was supposed. Even allowing the suppression of ground state collisions and probably any other inelastic process that happens at short internuclear distances. To achieve those results, it was necessary to develop a new trapping technique, which allows the study of cold collisions, even in traps whose confinement potential is small. Thanks to that technique it was possible, for the first time, to observe losses caused by hyperfine changing collisions, in a trap of sodium atoms operating in the D1 line (loaded from a vapor cell). That technique has still allowed us to measure the rate of cold collisions (&#61538;) for the D1 line trap, a result which, until now, did not exist in the literature. To verify the reliability of the results obtained by that technique, we also accomplished measures of &#61538; in the D2 line and compared those results with other existent ones in the literature (obtained by a different technique). The good agreement among those results, made us confident in saying that this technique, besides being very interesting in the study of shallow traps (due to the intensity of the trapping lasers, or due to the own nature of the trap), it is also quite reliable.