A ring trap for ultracold atoms

We propose a new kind of toroidal trap, designed for ultracold atoms. It relies on a combination of a magnetic trap for rf-dressed atoms, which creates a bubble-like trap, and a standing wave of light. This new trap is well suited for investigating questions of low dimensionality in a ring potential. We study the trap characteristics for a set of experimentally accessible parameters. A loading procedure from a conventional magnetic trap is also proposed. The flexible nature of this new ring trap, including an adjustable radius and adjustable transverse oscillation frequencies, will allow the study of superfluidity in variable geometries and dimensionalities.Comment: 4 figures, 10 pages ; the order of the sections has been changed ; to appear in Phys. Rev.

Evaporative cooling in a radio-frequency trap

A theoretical investigation for implementing a scheme of forced evaporative cooling in radio-frequency (rf) adiabatic potentials is presented. Supposing the atoms to be trapped by a rf field RF1, the cooling procedure is facilitated using a second rf source RF2. This second rf field produces a controlled coupling between the spin states dressed by RF1. The evaporation is then possible in a pulsed or continuous mode. In the pulsed case, atoms with a given energy are transferred into untrapped dressed states by abruptly switching off the interaction. In the continuous case, it is possible for energetic atoms to adiabatically follow the doubly-dressed states and escape out of the trap. Our results also show that when the frequencies of the fields RF1 and RF2 are separated by at least the Rabi frequency associated with RF1, additional evaporation zones appear which can make this process more efficient.Comment: 12 pages, 11 figure

RF spectroscopy in a resonant RF-dressed trap

We study the spectroscopy of atoms dressed by a resonant radiofrequency (RF) field inside an inhomogeneous magnetic field and confined in the resulting adiabatic potential. The spectroscopic probe is a second, weak, RF field. The observed line shape is related to the temperature of the trapped cloud. We demonstrate evaporative cooling of the RF-dressed atoms by sweeping the frequency of the second RF field around the Rabi frequency of the dressing field.Comment: 7 figures, 8 pages; to appear in J. Phys.

A micromanipulation setup for comparative tests of microgrippers

A micromanipulation setup allowing comparative tests of manipulation micro tools has been developed. Repeatability measurements of positioning as well as optimization of manipulation conditions can be run with parts of typically 5 to 50μm over a large set of parameters including environment conditions, substrate and tip specifications, and different strategies (robot trajectories at picking and releasing time). The workstation consists of a high precise parallel robot, the Delta3, to position the gripper, linear stages to place the parts in the field of view and two microscopes for the visual feedback and position measurement. The setup is placed in a chamber for controlling relative humidity and temperature. An interface was developed to integrate every kind of tool on the robot. Automated operations and measurement have been carried out based on localization and tracking of micro objects and gripper. Integration of micro tools was successfully accomplished and comparative tests were executed with micro tweezers. Sub micrometer position repeatability was achieved with a success rate of pick and pick operations of 95%

Automatic system for the renal and cancer segmentation in CT images

This article presents the concept of a complex system for automatic detection of kidneys and kidney tumors in computed tomography images. An effective treatment of cancer depends on a quick and effective diagnosis. Computer support for medical diagnostics is crucial in effective specialists’ analysis. Automatic and accurate location, together with precise detection of the kidney and/or tumor contour is a demanding task. In this article, authors present a complex system for automatic detection of kidneys and kidney tumors, based on machine learning techniques, using the U-Net network. Convolutional neural network recognition results are then processed in multiple stages, using morphological processing, 3D model analysis, geometric coefficients analysis and region-growth implementation. The results of the system detection were compared to the reference images marked by an expert. The system presented in the article is characterized by a very high efficiency of recognition and segmentation of kidney and tumor areas

Changeur d'outils pour station automatisée de micromanipulation

Une station de micromanipulation de haute précision, basée sur le robot Delta3 (3ddl, courses de 4mm), a été développée au LSRO. Elle permet des opérations automatiques de "pick and place", ainsi que la caractérisation des outils de manipulation dans des conditions spécifiques (environnement, matériaux, stratégies). Les outils utilisent différents principes de prise et de dépose. Un support standard a donc été développé et permet de les interfacer avec le robot. Dans le but d’une automatisation complète de ces opérations, il est nécessaire d’intégrer un changeur d’outils sur cette station. Un autre atout majeur est qu’il sera alors possible de tester différents outils dans des conditions identiques au niveau de l’environnement. Pour ce faire, une zone de stockage des outils devra être aménagée à l’intérieur de la boîte et le changement devra être possible sans ouverture de l’enceinte

In situ micro gripper shaping by electro discharge machining

A machining process based on Electro Discharge Machining (EDM) has been developed and allows producing flexible and low-cost tweezers-like grippers or grippers shaped for a specific application. It can be easily included in a micromanipulation setup and requires no additional hardware except the sparks generator: the machining is realized by the manipulator itself and due to this "in-situ" technique created grippers are exempt of misalignment errors. We have shown that precise micromachining of micro-parts or microstructures can be realized with a compact equipment. A microfactory concept has been introduced, in order to apply the "in-situ machining" technique to an automated and low cost clean-room manufacturing process. Issues for this application, particularly in term of contamination, have been discussed

Characterization of an inertial micro gripper based on adhesion forces

Adhesive forces become predominant in the micro world comparing to the gravity effect implying the development of new micro manipulation strategies. This paper presents the design and conception of a gripper that use the inertial principle for the release (applying a high acceleration, in the order of 10’000g) and the adhesion for catching a micro part of 50μm with the goal of precisely control the position after release. Experiments were conducted and showed a positioning repeatability of 2μm to 6μm depending on the relative humidity with a success rate of more than 90%

Micro-gripper à haute dynamique

Dans le monde microscopique, la force de gravité devient négligeable par rapport aux forces d’adhésion (capillarité, Van der Waals). Ce projet vise à utiliser ces forces pour la prise de bille d’une taille caractéristique de 50[μm]. La dépose quand à elle s’effectue de manière dynamique, en utilisant l’inertie de la bille soumise à une forte accélération. Le but de ce projet est de caractériser la prise (taux de succès) et la dépose (seuil d’accélération, taux de succès, précision et répétabilité). La prise dépend essentiellement du type de matériaux utilisés ; sa caractérisation a été faite pour un gripper en silicium et un gripper en verre dans l’air ambiant (20% humidité relative) et l’azote (3%). Pour fournir une accélération, un piézoélectrique est utilisé (cristal qui se déforme lorsqu’une tension est appliquée à ses bornes). L’avantage principal est que la déformation est bien contrôlable en intensité et direction. La dépose quand à elle a été caractérisée dans les mêmes conditions que la prise et en excitant le piézoélectrique avec des sinus continus ou en créant une seule impulsion Au final, il a été montré que cette technique est viable pour la micromanipulation. Toutefois des points clés nécessaires à un bon contrôle des opérations ont été identifiés, notamment au niveau de la rigidité du substrat pour éviter l’écrasement des objets et au niveau de la qualité des surfaces de contact