Linear Paul trap design for an optical clock with Coulomb crystals

We report on the design of a segmented linear Paul trap for optical clock applications using trapped ion Coulomb crystals. For an optical clock with an improved short-term stability and a fractional frequency uncertainty of 10^-18, we propose 115In+ ions sympathetically cooled by 172Yb+. We discuss the systematic frequency shifts of such a frequency standard. In particular, we elaborate on high precision calculations of the electric radiofrequency field of the ion trap using the finite element method. These calculations are used to find a scalable design with minimized excess micromotion of the ions at a level at which the corresponding second- order Doppler shift contributes less than 10^-18 to the relative uncertainty of the frequency standard

Réseau à trois dimensions de quadrupôles électriques élémentaires pour le confinement d'ions

We propose a method to overcome the present limitations of the technique of storing ions in vacuum by electromagnetic fields. The method proposed uses a three dimensional lattice of quadrupoles, each microscopic in size, at whose centers the ions are kept in suspension. We show that the maximum number of confined ions in increased, the maximum kinetic energy of the ions is reduced, and the exchange of energy between the ions and the outside circuit more efficient in this arrangement.Nous proposons une méthode pour surmonter les limitations actuelles de la technique de stockage d'ions sous vide par des champs électromagnétiques. La méthode proposée utilise un réseau à trois dimensions de quadrupoles, chacun d'étendue microscopique, aux centres desquels les ions sont maintenus en suspension. Nous montrons que le nombre maximal d'ions confinés est augmenté, que l'énergie cinétique maximale des ions confinés est réduite, et que l'échange d'énergie entre les ions et le circuit extérieur est plus efficace dans cette méthode

La structure des raies de résonance hyperfine d'ions oscillant harmoniquement dans un champ électrique

The theory is developed for the structure of the microwave hyperfine spectrum observed for ions suspended harmonically in a quadrupole rf field. It is shown that the linear Doppler effect leads to a well resolved system of side bands whose relative amplitudes are sufficient to determine the energy distribution of the ions and hence evaluate the second order Doppler correction for the central line.Nous étudions la structure théorique du spectre hyperfin micro-onde observé sur des ions oscillant harmoniquement dans un champ quadrupolaire radio-fréquence. Nous montrons que l'effet Doppler du premier ordre se manifeste par la présence d'un ensemble de raies latérales bien résolues, dont l'amplitude relative permet de déterminer la distribution d'énergie des ions et d'évaluer la correction Doppler du second ordre pour la raie centrale

On bullshit in cultural policy practice and research : notes from the British case

In 2005, Harry G. Frankfurt, a retired professor of moral philosophy at Princeton University, made it into the best‐sellers chart with his book On Bullshit. Taking his essay as its starting point, this article explores the analysis of bullshit and the prevalence of bullshitting in the contemporary public sphere. Frankfurt’s short essay indeed provides an intellectual framework to interpret and understand contemporary rhetoric and practice in the cultural policy field, as well as recent trends in cultural policy research. Through a discussion of selected New Labour’s cultural policy documents in Britain, the article aims to show that many of the key actors in the cultural policy debate indeed display the ‘indifference to how things really are’ and the cultivation of vested interests which Frankfurt attributes to the activity of bullshitting. The final part of the text discusses the implications of the present status quo for ‘critical’ cultural policy research