Neste trabalho apresentamos o estudo da variação da temperatura cinética de átomos aprisionados magneticamente bombeados por campos eletromagnéticos externos. Aprisionamos átomos de Sódio em uma armadilha magnética de quadrupolo e submetemos esses átomos a um campo magnético externo oscilante. Medimos a temperatura e o número dos átomos remanescentes na armadilha a partir de imagens de tempo de vôo. O processo de medida consiste em desligar a armadilha, deixando a nuvem atômica expandir balisticamente e então fazer uma imagem da fluorescência desses átomos gerada por um pulso de luz próximo da ressonância atômica. Do tamanho da nuvem e do número de fótons capturados podemos obter a temperatura e o número de átomos da amostra. Observamos um significativo resfriamento para algumas freqüências de oscilação do campo externo e posterior aquecimento para freqüências um pouco maiores. Observamos ainda simultaneamente ao resfriamento uma grande perda de átomos da armadilha. Por fim, apresentamos algumas simulações numéricas que reproduzem o fenômeno observado, bem como um modelo que explica os experimentos baseado em excitação seletiva dos átomos confinados pelo campo magnético externo. / In this work we present a study of the shift of the kinetic temperature of magnetically trapped atoms, excited by external electromagnetic fields. We trapped Sodium atoms in a quadrupole magnetic trap and applied an oscilating magnetic field to these atoms. We mesured the temperature and the number of the remaining atoms from time of flight images. The measure is done turning off the trap, leaving the cloud of atoms in a ballistic expansion and making an image of the fluorescence of these atoms after the shot of a near ressonant light. From the size of the cloud and the number of photons captured we can measure the temperature and number of atoms in the sample. We observed cooling of the atoms for some frequencies of the external field and heating for frequencies a bit larger. We observed that a high number of atoms were lost from the trap simultaneously with the cooling. Finally, we present numerical simulations that reproduce the observed phenomena and a model that explains the experiments\' results based on selective excitation of the trapped atoms by the external field.

Neste trabalho apresentamos o estudo da variação da temperatura cinética de átomos aprisionados magneticamente bombeados por campos eletromagnéticos externos. Aprisionamos átomos de Sódio em uma armadilha magnética de quadrupolo e submetemos esses átomos a um campo magnético externo oscilante. Medimos a temperatura e o número dos átomos remanescentes na armadilha a partir de imagens de tempo de vôo. O processo de medida consiste em desligar a armadilha, deixando a nuvem atômica expandir balisticamente e então fazer uma imagem da fluorescência desses átomos gerada por um pulso de luz próximo da ressonância atômica. Do tamanho da nuvem e do número de fótons capturados podemos obter a temperatura e o número de átomos da amostra. Observamos um significativo resfriamento para algumas freqüências de oscilação do campo externo e posterior aquecimento para freqüências um pouco maiores. Observamos ainda simultaneamente ao resfriamento uma grande perda de átomos da armadilha. Por fim, apresentamos algumas simulações numéricas que reproduzem o fenômeno observado, bem como um modelo que explica os experimentos baseado em excitação seletiva dos átomos confinados pelo campo magnético externo. / In this work we present a study of the shift of the kinetic temperature of magnetically trapped atoms, excited by external electromagnetic fields. We trapped Sodium atoms in a quadrupole magnetic trap and applied an oscilating magnetic field to these atoms. We mesured the temperature and the number of the remaining atoms from time of flight images. The measure is done turning off the trap, leaving the cloud of atoms in a ballistic expansion and making an image of the fluorescence of these atoms after the shot of a near ressonant light. From the size of the cloud and the number of photons captured we can measure the temperature and number of atoms in the sample. We observed cooling of the atoms for some frequencies of the external field and heating for frequencies a bit larger. We observed that a high number of atoms were lost from the trap simultaneously with the cooling. Finally, we present numerical simulations that reproduce the observed phenomena and a model that explains the experiments\' results based on selective excitation of the trapped atoms by the external field.

This dissertation details the development and experimental implementation of single-photon atomic cooling. In this scheme atoms are transferred from a large-volume magnetic trap into a small-volume optical trap via a single spontaneous Raman transition that is driven near each atom's classical turning point. This arrangement removes nearly all of an atomic ensemble's kinetic energy in one dimension. This method does not rely on a transfer of momentum from photon to atom to cool. Rather, single-photon atomic cooling achieves a reduction in temperature and an increase in the phase-space density of an atomic ensemble by the direct reduction of the system's entropy. Presented here is the application of this technique to a sample of magnetically trapped ⁸⁷Rb. Transfer efficiencies between traps of up to 2.2% are demonstrated. It is shown that transfer efficiency can be traded for increased phase-space compression. By doing so, the phase-space density of a magnetically trapped ensemble is increased by a factor of 350 by the single-photon atomic cooling process. / text

Made available in DSpace on 2016-12-12T20:15:53Z (GMT). No. of bitstreams: 1 parte1.pdf: 63647 bytes, checksum: f2fd5c831fcfe5e4d704fd18bec2cc27 (MD5) Previous issue date: 2010-03-11 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Laser cooling in high magnetic fields, presents a series of difficulties due to inhomogeneous broadening of the frequency due to Zeeman Effect. In the first part of this work we investigate the laser cooling of Li by a Monte Carlo simulation, the 2S(1/2)-> 2P(3/2) transition at 670.96 nm in a magnetic trap under the characteristics of trap operating at the LASER laboratory of the Institute of Physics, UFRJ. In the second part, we built a diode laser with extended Littrow cavity emitting in 972 nm using the configuration of extended cavity Littrow. The purpose of this laser is, after a double frequency doubling, to use it to study the hydrogen atom in the transition 1S -> 2S at 243 nm. / O resfriamento a laser em altos campos magnéticos, apresenta uma série de dificuldades devido ao alargamento inomogêneo da transição causado pelo efeito Zeeman. Na primeira parte desse trabalho investigamos o resfriamento a laser de Lítio através de uma simulação de Monte Carlo, na transição 2S1/2 -> 2P3/2 em 670.96 nm, em uma armadilha magnética com as características da armadilha em funcionamento no laboratório LASER do instituto de Física da UFRJ. Na segunda parte, foi construído um laser de diodo em cavidade estendida emitindo em 972 nm utilizando a configuração de Cavidade Estendida de Littrow. O propósito desse laser e após um duplo dobramento de freqüência, utilizá-lo para estudo do átomo de Hidrogênio na transição 1S -> 2S em 243 nm.

Le temps de vie du neutron libre joue un rôle important dans la physique des particules comme dans des modèles cosmologiques. Notre connaissance de la valeur précise du temps de vie du neutron est limitée par les incertitudes systématiques des deux méthodes expérimentales couramment utilisées, les méthodes dites de "faisceau" et de "bouteille matérielle". En outre une déviation systématique des valeurs de temps de vie obtenues par les deux méthodes s'est manifestée au cours des dernières décennies.Le projet HOPE fait parti d'une nouvelle génération d'expériences qui cherchent à mesurer le temps de vie du neutron en stockant des neutrons ultra-froids (UCN) dans un potentiel magnéto-gravitationnel. HOPE génère les champs magnétiques nécessaires par une combinaison d'aimants permanents puissants de terre rare, qui produisent des champs magnétiques maximaux d'environ 1.3 T, et un système de bobines supraconductrices. Dans cette thèse je donnerai une description détaillée de l'appareil, des effets systématiques possibles et comment nous envisageons d'étudier et de maîtriser ces effets. Ensuite les résultats d'un premier temps de faisceau, effectué à la source PF2, vont être présentés et discutés. Les résultats sont encourageants puisque nous avons atteint des constants de temps de stockages maximaux de 881(46) s, ce qui indique des pertes d'UCN très faibles pendant la phase du stockage. / The lifetime of the free neutron plays an important role in fundamental particle physics as well as cosmological models. Our knowledge of the precise value of the neutron lifetime is limited by the systematical inaccuracies of the two commonly used experimental approaches, the so called “beam” and “material bottle” methods. Moreover a systematic deviation of the lifetime-values extracted from both methods has become manifest over the past decades.The HOPE project is part of a new generation of experiments that aims to determine the neutron lifetime by storing ultra cold neutrons (UCN) in a combined magneto-gravitational potential. HOPE generates the necessary gradient magnet fields by a combination of highly potent rare-earth permanent magnets with a maximum B-field strength of about 1.3 T and a set of superconducting coils. In this thesis I give a detailed description of the apparatus, possible systematical effects and how we are planning to investigate and cope with those effects. Subsequently the results from a first beamtime at the PF2 source will be presented and discussed. The results are encouraging as we reached a maximum storage-time constants of 881(46) s, indicating a very small UCN loss rate during storage.

Usando a técnica de resfriamento evaporativo para átomos comprimidos numa armadilha magnética tipo QUIC, implementamos experimentos para observar Condensação de Bose-Einstein de átomos de sódio. Nessa armadilha magnética temos átomos advindos de uma armadilha magneto-óptica, a qual é carregada por um feixe desacelerado como etapa de pré-resfriamento. Nossas medidas foram baseadas em imagens de absorção fora de ressonância de um feixe de prova pela amostra atômica. Essas imagens foram feitas in situ, ou seja, na presença do campo da armadilha magnética, pelo fato do número de átomos ser baixo e a técnica de tempo de vôo não ser adequada a essa situação. Baseado no perfil de densidade e na temperatura medidos, calculamos a densidade de pico no espaço de fase D, a qual é seguida nas várias etapas de evaporação. Nossos resultados mostram que para uma freqüência final de evaporação de 1,65 MHz nós superamos o valor esperado para D (2,612) alcançar o ponto crítico, no centro da amostra, para obter a condensação. Devido ao baixo número de átomos restantes no potencial, a interação não produz efeitos consideráveis e dessa forma um modelo de gás ideal permite justificar essa observação. / Using a system composed of a QUIC trap loaded from a slowed atomic beam, we have performed experiments to observe the Bose-Einstein Condensation of Na atoms. In order to obtain the atomic distribution in the trap, we use an in situ out of resonance absorption image of a probe beam to determine the temperature and the density, which are use to calculate the phase space D. We have followed D as a function of the final evaporation frequency. The results show that at 1.65 MHz we crossed the critical value for D which corresponds to the point to start Bose-Condensation of the sample. Due to the low number of atoms remaining in the trap at the critical point, the interaction produce minor effects and therefore an ideal gas model explains well the observations.

Ultra-kalte atomare Gase werden in zahlreichen Laboren weltweit untersucht und finden unter anderem Anwendung in Atomuhren und in Atominterferometer. Die Einsatzgebiete erstrecken sich von der Geodäsie über die Metrologie bis hin zu wichtigen Fragestellungen der Fundamentalphysik, wie z.B. Tests des Äquivalenzprinzips. Doch die beispiellose Messgenauigkeit ist durch die irdische Gravitation eingeschränkt. Zum einen verzerrt die Schwerkraft das Fallenpotential und macht damit die Reduktion der atomaren Energie unter einem bestimmten Limit unmöglich. Zum anderen werden die aus einer Falle frei gelassenen Teilchen durch die Erdanziehung beschleunigt und so ist deren Beobachtungszeit begrenzt. Im Rahmen dieser Arbeit werden die Ergebnisse des Projektes QUANTUS (Quantengase Unter Schwerelosigkeit) dargestellt. Auf dem Weg zur Implementierung eines Quantengasexperimentes im Weltraum wurde innerhalb einer deutschlandweiten Zusammenarbeit eine kompakte, portable und mechanisch stabile Apparatur zur Erzeugung und Untersuchung eines Bose-Einstein-Kondensats (BEC) unter Schwerelosigkeit im Fallturm Bremen entwickelt. Sowohl die Abbremsbeschleunigung von bis zu 50 g als auch das begrenzte Volumen der Fallkapsel stellen hohe Ansprüche an die mechanische Stabilität und die Miniaturisierung von optischen und elektronischen Komponenten. Der Aufbau besteht aus einer im ultra-hoch Vakuum geschlossenen magnetischen Mikrofalle (Atomchip) und einem kompakten auf DFB-Dioden basierenden Lasersystem. Mit diesem Aufbau ließ sich das erste BEC unter Schwerelosigkeit realisieren und nach 1 Sekunde freier Expansion zu beobachten. Weder die schwache Krümmung des Fallenpotentials noch die lange Beobachtungszeit würden in einem erdgebundenen Experiment realisierbar. Die erfolgreiche Umsetzung des Projektes eröffnet ein innovatives Forschungsgebiet - degenerierte Quantengase bei ultratiefen Temperaturen im pK-Bereich, mit großen freien Evolutions- und Beobachtungszeiten von mehreren Sekunden. / Recently, cooling, trapping and manipulation of neutral atoms and ions has become an especially active field of quantum physics. The main motivation for the cooling is to reduce motional effects in high precision measurements including spectroscopy, atomic clocks and matter interferometry. The spectrum of applications of these quantum devices cover a broad area from geodesy, through metrology up to addressing the fundamental questions in physics, as for instance testing the Einstein’s equivalence principle. However, the unprecedented precision of the quantum sensors is limited in terrestial laboratories. Freezing atomic motion can be nowadays put to the limit at which gravity becomes a major perturbation in a system. Gravity can significantly affect and disturb the trapping potential. This limits the use of ultra-shallow traps for low energetic particles. Moreover, free particles are accelerated by gravitational force, which substantially limits the observation time. Targeting the long-term goal of studying cold quantum gases on a space platform, we currently focus on the implementation of a Bose-Einstein condensate (BEC) experiment under microgravity conditions at the drop tower in Bremen. Special challenges in the construction of the experimental setup are posed by a low volume of the drop capsule as well as critical decelerations up to 50g during recapture at the bottom of the tower. All mechanical and electronic components were thus been designed with stringent demands on miniaturization and mechanical stability. This work reports on the observation of a BEC released from an ultra-shallow magnetic potential and freely expanding for one second. Both, the low trapping frequency and long expansion time are not achievable in any earthbound laboratory. This unprecedented time of free evolution leads to new possibilities for the study of BEC-coherence. It can also be applied to enhance the sensitivity of inertial quantum sensors based on ultra-cold matter waves.

Usando a técnica de resfriamento evaporativo para átomos comprimidos numa armadilha magnética tipo QUIC, implementamos experimentos para observar Condensação de Bose-Einstein de átomos de sódio. Nessa armadilha magnética temos átomos advindos de uma armadilha magneto-óptica, a qual é carregada por um feixe desacelerado como etapa de pré-resfriamento. Nossas medidas foram baseadas em imagens de absorção fora de ressonância de um feixe de prova pela amostra atômica. Essas imagens foram feitas in situ, ou seja, na presença do campo da armadilha magnética, pelo fato do número de átomos ser baixo e a técnica de tempo de vôo não ser adequada a essa situação. Baseado no perfil de densidade e na temperatura medidos, calculamos a densidade de pico no espaço de fase D, a qual é seguida nas várias etapas de evaporação. Nossos resultados mostram que para uma freqüência final de evaporação de 1,65 MHz nós superamos o valor esperado para D (2,612) alcançar o ponto crítico, no centro da amostra, para obter a condensação. Devido ao baixo número de átomos restantes no potencial, a interação não produz efeitos consideráveis e dessa forma um modelo de gás ideal permite justificar essa observação. / Using a system composed of a QUIC trap loaded from a slowed atomic beam, we have performed experiments to observe the Bose-Einstein Condensation of Na atoms. In order to obtain the atomic distribution in the trap, we use an in situ out of resonance absorption image of a probe beam to determine the temperature and the density, which are use to calculate the phase space D. We have followed D as a function of the final evaporation frequency. The results show that at 1.65 MHz we crossed the critical value for D which corresponds to the point to start Bose-Condensation of the sample. Due to the low number of atoms remaining in the trap at the critical point, the interaction produce minor effects and therefore an ideal gas model explains well the observations.

Since Feynman's realization of using quantum systems to investigate quantum dynamics, interest in creating controllable quantum systems to simulate condensed matter phenomenon has been high. With the realization of BECs in 1995, the realization of a relatively clean testbed for simulating some of these phenomenon became a reality. My PhD research has been an exploration of the production and use of Bose-Einstein Condensates for the study of superfluidity. The first 3 years have been spent in the actual building of a Na BEC apparatus. During this time, we’ve implemented a distinct technique to trap ultra cold Na atoms, i.e. the Optically Plugged Trap. In the process, we have shown how atoms in a linear trap can show spin metastability and thus maintain a nonequilibrium state for long periods of time. In studying the interaction of ultra-cold atoms with light, we have developed a technique to measure the velocity distribution of atoms using a standing optical wave (Bragg Spectroscopy). Alongside this, we have also created optical traps for atoms in which we can change to shape of the trap itself to probe different condensed matter systems. The eventual goal being the investigation of condensed matter physics, specifically superfluidity, using ultra-cold atoms.

Le développement de différentes techniques pour contrôler les degrés de liberté internes et externes des molécules et pour produire (ultra-) froide, piège des moléculaire ensembles ouvrir des voies différentes à la physique et la chimie dans le régime de basse température. Il s'agit notamment de nombreux territoires en physique comme, phases quantiques de la matière, traitement de l'information quantique, les froides collisions moléculaires, les chimies froides et aussi de divers tests de haute précision pour la physique fondamentale. Cette thèse décrit diverses expériences de guidage et de décélération des faisceaux supersoniques d'atomes paramagnétiques à l’aide de champs magnétique inhomogène dépendent du temps. Ces champs magnétiques inhomogènes ont été utilisés pour exercer une force sur les atomes ou les molécules paramagnétiques, qui résultent de l'effet Zeeman. Le principe du ralentisseur Zeeman nouvellement développé est de produire un déplacement tridimensionnel du piège magnétique, à la vitesse initiale du faisceau. Le contrôle de la dépendance temporelle du champ magnétique nous permet de contrôler la vitesse du piège magnétique co-mobile, procurant ainsi une décélération d'une classe de vitesse du faisceau supersonique. Le piège magnétique co- mobile est déduit à partir d'une onde magnétique mobile, offrant un minimum de distorsion du piège lors de sa propagation. Les propriétés transverses du piège sont réglables grâce à un champ magnétique transversal quadrupolaire, qui peut être ajusté indépendamment des propriétés de vitesses et l'accélération du piège. Une grande part du travail de thèse a été consacrée à la conception, la réalisation et la construction du montage expérimental, consistant en un jet supersonique et en un dispositif complexe de bobines pour réaliser l’onde magnétique progressive, formant un piège magnétique mobile. Le jet froid pulsé d'atomes métastables est produit par expansion supersonique à travers une valve refroidie à l'azote liquide, excités dans l'état métastable par une décharge électrique. Nous avons guidé le jet d'argon au travers d’un tube capillaire le guidage et la décélération ont été démontrés. Le piège magnétique mobile est formé par la combinaison d'un champ magnétique quadrupolaire et d'un champ magnétique axial modulé spécialement. Le champ quadrupolaire est continu et un gradient de champ est dirigé seulement dans la direction transverse du jet. Le circuit plan produit une onde magnétique sinusoïdale avec un gradient de champ dans la direction axiale. Avec l'électronique fabriquée au laboratoire, ou peut produire une onde magnétique progressive d'amplitude 0.69T (avec un courant AC de 300A) et de fréquence 40 kHz. On obtient ainsi une onde qui se déplace à une vitesse de 464m/s. Plusieurs expériences de principe ont été réalisées en utilisant le jet froid pulsé d'argon métastable. Nous avons étudié les propriétés de guidage du quadrupole pour divers courants et pour différents atomes (hélium et argon) et comparé les résultats aux prédictions théoriques de simulations numériques. Le jet d'argon métastable a été guidé en 3D à des vitesses variées (464m/s, 400m/s, 392m/s) avec un décélérateur de 28cm de long. La température observée du paquet guidé est de 100mK. L'expérience de décélération a été réalisée avec le jet d'argon métastable depuis la vitesse de 400m/s jusqu’à 370m/s et depuis la vitesse de 392m/s jusqu’à 365m/s. Les résultats expérimentaux sont comparés avec les simulations numériques. / The development of various techniques to control both the internal and external degrees of freedom of molecules and to produce (ultra-) cold, trapped molecular ensembles open various avenues to physics and chemistry in the low temperature regime. These include many territories in physics like, quantum phases of matter, quantum information processing, cold molecular scattering, cold chemistry and also various high precision tests for fundamental physics.This thesis describes various guiding and deceleration experiments of supersonic beams of paramagnetic atoms using inhomogeneous time-dependent magnetic fields. Inhomogeneous magnetic fields have been used to exert a force on paramagnetic atoms or molecules, which derives from the Zeeman effect. The principle of the newly developed Zeeman decelerator is to produce a moving tridimensional magnetic trap, which moves at the initial velocity of the beam. The control of the time dependence of the magnetic field allows us to control the velocity of the so-called co-moving magnetic trap, thereby affording for a deceleration of a velocity class of the supersonic beam. The co-moving magnetic trap is inferred from a moving magnetic wave, offering a minimal distortion of the trap during its propagation. The transverse properties of the trap are tunable through a transverse quadrupolar magnetic field, which can be adjusted independently of the velocity and acceleration properties of the trap.Much of this thesis was devoted to the design, development and construction of the experimental setup consisting of a supersonic beam and complex coils to achieve a traveling magnetic wave. Using home-made electronics operating 300A AC currents at frequencies up to 40 kHz, the coils can produce a magnetic wave of amplitude 0.7T, moving at a controllable velocity up to 464m/s. Several proof-of-principle experiments have been carried out using a pulsed, cold beam of metastable atoms, excited in metastable states by an electric discharge during the supersonic expansion. We have studied the guiding properties of the quadrupolar magnetic field alone on two atomic beams (metastable helium and argon) and compared with the theoretical prediction of tridimensional numerical simulations. A supersonic beam of metastable argon atoms has been trapped in a co-moving trap at a constant velocity (464m/s, 400m/s, and 392m/s) using a 28cm-long prototype decelerator. The temperature of the guided beam packet is observed to be 100mK. Finally, Zeeman deceleration experiments have been done on metastable argon beams with an initial velocity of 400m/s, decelerated to various final velocities (392m/s, 370m/, and 365m/s). The experimental results are compared with tridimensional numerical simulations.Keywords: Supersonic beams, metastable atoms, cold molecules, atoms in inhomogeneous magnetic fields, transverse magnetic guide, co-moving magnetic trap, tridimensional guiding, Zeeman deceleration.