Fast accumulation of ions in a dual trap

Transporting charged particles between different traps has become an important feature in high-precision spectroscopy experiments of different types. In many experiments in atomic and molecular physics, the optical probing of the ions is not carried out at the same location as the creation or state preparation. In our double linear radio-frequency trap, we have implemented a fast protocol allowing to shuttle large ion clouds very efficiently between traps, in times shorter than a millisecond. Moreover, our shuttling protocol is a one-way process, allowing to add ions to an existing cloud without loss of the already trapped sample. This feature makes accumulation possible, resulting in the creation of large ion clouds. Experimental results show, that ion clouds of large size are reached with laser-cooling, however, the described mechanism does not rely on any cooling process

Correcting symmetry imperfections in linear multipole traps

Multipole radio-frequency traps are central to collisional experiments in cryogenic environments. They also offer possibilities to generate new type of ion crystals topologies and in particular the potential to create infinite 1D/2D structures: ion rings and ion tubes. However, multipole traps have also been shown to be very sensitive to geometrical misalignment of the trap rods, leading to additional local trapping minima. The present work proposes a method to correct non-ideal potentials, by modifying the applied radio-frequency amplitudes for each trap rod. This approach is discussed for the octupole trap, leading to the restitution of the ideal Mexican-Hat-like pseudo-potential, expected in multipole traps. The goodness of the compensation method is quantified in terms of the choice of the diagnosis area, the residual trapping potential variations, the required adaptation of the applied radio-frequency voltage amplitudes, and the impact on the trapped ion structures. Experimental implementation for macroscopic multipole traps is also discussed, in order to propose a diagnostic method with respect to the resolution and stability of the trap drive. Using the proposed compensation technique, we discuss the feasibility of generating a homogeneous ion ring crystal, which is a measure of quality for the obtained potential well

Two-step Doppler cooling of a three-level ladder system with an intermediate metastable level

Doppler laser cooling of a three-level ladder system using two near-resonant laser fields is analyzed in the case of the intermediate level being metastable while the upper level is short-lived. Analytical as well as numerical results for e.g. obtainable scattering rates and achievable temperatures are presented. When appropriate, comparisons with two-level single photon Doppler laser cooling is made. These results are relevant to recent experimental Doppler laser cooling investigations addressing intercombination lines in alkali-earth metal atoms and quadrupole transitions in alkali-earth metal ions.Comment: accepted by Phys Rev

Experimental Demonstration of a Terahertz Frequency Reference based on Coherent Population Trapping

A novel protocol of interrogation based on coherent population trapping in an N-level scheme atomic system leads to dark resonances involving three different photons. An ensemble of several hundreds of radiofrequency-trapped ions is probed by three lasers simultaneously locked onto the same optical frequency comb, resulting in high-contrast spectral lines referenced to an atomic transition in the THz domain. We discuss the cause of uncertainties and limitations for this method and show that reaching a sub-kHz resolution is experimentally accessible via this interrogation protocole

An ion ring in a linear multipole trap for optical frequency metrology

A ring crystal of ions trapped in a linear multipole trap is studied as a basis for an optical frequency standard. The equilibrium conditions and cooling possibilities are discussed through an analytical model and molecular dynamics simulations. A configuration which reduces the frequency sensitivity to the fluctuations of the number of trapped ions is proposed. The systematic shifts for the electric quadrupole transition of calcium ions are evaluated for this ring configuration. This study shows that a ring of 10 or 20 ions allows to reach a short term stability better than for a single ion without introducing limiting long term fluctuations

Terahertz frequency standard based on three-photon coherent population trapping

A scheme for a THz frequency standard based on three-photon coherent population trapping in stored ions is proposed. Assuming the propagation directions of the three lasers obey the phase matching condition, we show that stability of few 10$^{-14}$ at one second can be reached with a precision limited by power broadening to $10^{-11}$ in the less favorable case. The referenced THz signal can be propagated over long distances, the useful information being carried by the relative frequency of the three optical photons.Comment: article soumis a PRL le 21 mars 2007, accepte le 10 mai, version 2 (24/05/2007

Evaluation of the ultimate performances of a Ca+ single-ion frequency standard

We numerically evaluate the expected performances of an optical frequency standard at 729 nm based on a single calcium ion. The frequency stability is studied through the Allan deviation and its dependence on the excitation method (single Rabi pulse or two Ramsey pulses schemes) and the laser linewidth are discussed. The minimum Allan deviation that can be expected is estimated to $\sigma_y(\tau) \approx 2.5\times 10^{-15}/\sqrt{\tau}$ with $\tau$ the integration time. The frequency shifts induced by the environmental conditions are evaluated to minimize the uncertainty of the proposed standard by chosing the most suited environment for the ion. If using the odd isotope $^{43}$Ca$^{+}$ and a vessel cooled to 77 K, the expected relative shift is $-2 \times 10^{-16}$ with an uncertainty of $\pm 4\times10^{-16}$, mainly due to the quadrupole shift induced by the unknown static electric field gradient .Comment: soumis le 27/07/04 a Physics Letters

New Issues for Workers Safety in the Factory of the Future

Human in the factory is one of the main themes of the Factory of the Future, in this context the aim of this paper is to present the new issues for workers safety and the in-tegrated design concepts or methodologies which have to be taking into account. New paradigms come into being: the uncertainty of the demand in terms of products as well as production rate, product customization, integration product / service, the man-ufacturing processes are not fixed, so the manufacturing times cannot be foreseen, re-configuration of machine tools as manufacturing systems, space organization, auto-organization, planning …, new technologies are implemented: robots, plug and play devices, virtual / augmented reality, sensors, OPC standards, connected objects,… Several tasks are performed by the workers, the robots or in collaboration. The work-ers are place in the center of the Factory of the future but this concept introduce haz-ard events, problems of health and safety (physical or cognitive tasks, fatigue, stress, space or time organization, interfaces Human- robot, to take into account of the dif-ferent life situations…). So the aim of the paper is to present studies carrying out in order to propose to the machine or manufacturing systems designers as well as pro-duction managers structured methods, models, tools in order to get safe working sit-uations in the frame of the factory of the future paradigm