A double ion trap for large Coulomb crystals

While the linear radiofrequency trap finds various applications in high-precision spectroscopy and quantum information, its higher-order cousin, the linear multipole trap, is almost exclusively employed in physical chemistry. Recently, first experiments have shown interesting features by laser-cooling multipole-trapped ion clouds. Multipole traps show a flatter potential in their centre and therefore a modified density distribution compared to quadrupole traps. Micromotion is an important issue and will certainly influence the dynamics of crystallized ion structures. Our experiment tends to investigate possible crystallization processes in the multipole. In a more general way, we are interested in the study of the dynamics and thermodynamics of large ion clouds in traps of different geometry.Comment: 10th International Workshop on Non-Neutral Plasmas, Greifswald : Germany (2012

Fast and efficient transport of large ion clouds

The manipulation of trapped charged particles by electric fields is an accurate, robust and reliable technique for many applications or experiments in high-precision spectroscopy. The transfer of the ion sample between multiple traps allows the use of a tailored environment in quantum information, cold chemistry, or frequency metrology experiments. In this article, we experimentally study the transport of ion clouds of up to 50 000 ions. The design of the trap makes ions very sensitive to any mismatch between the assumed electric potential and the actual local one. Nevertheless, we show that being fast (100 $\mu$s to transfer over more than 20 mm) increases the transport efficiency to values higher than 90 %, even with a large number of ions. For clouds of less than 2000 ions, a 100 % transfer efficiency is observed

Experimental study of the recombination of a drifting low temperature plasma in the divertor simulator Mistral-B

In a new divertor simulator, an ultra-cold (Te<1 eV) high density recombining magnetized laboratory plasma is studied using probes, spectroscopic measurements, and ultra-fast imaging of spontaneous emission. The Mistral-B device consists in a linear high density magnetized plasma column. The ionizing electrons originate from a large cathode array located in the fringing field of the solenoid. The ionizing electrons are focused in a 3 cm diameter hole at the entrance of the solenoid. The typical plasma density on the axis is close to 2.10^18 m-3. The collector is segmented into two plates and a transverse electric field is applied through a potential difference between the plates. The Lorentz force induces the ejection of a very-low temperature plasma jet in the limiter shadow. The characteristic convection time and decay lengths have been obtained with an ultra-fast camera. The study of the atomic physics of the recombining plasma allows to understand the measured decay time and to explain the emission spectra.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France

Noise characterization of an Optical Frequency Comb using Offline Cross-Correlation

Using an offline cross-correlation technique, we have analyzed the noise behavior of a new type of optical frequency comb (OFC), which is carrier envelope offset (CEO) free by configuration, due to difference frequency generation. In order to evaluate the instrument's ultimate noise floor, the phase and amplitude noise of a stabilized OFC are measured simultaneously using two analog-to-digital converters. Carrier recovery and phase detection are done by post-processing, eliminating the need for external phase-locked loops and complex calibration techniques. In order to adapt the measurement noise floor and the number of averages used in cross correlation, an adaptive frequency resolution for noise measurement is applied. Phase noise results are in excellent agreement with measurements of the fluctuations of the repetition frequency of the OFC obtained from optical signal

Instabilités, turbulence et transport derrière un obstacle dans une colonne de plasma en champ magnétique

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Instabilités, turbulence et transport derrière un obstacle dans une colonne de plasma en champ magnétique

International audienc

Radial convection of plasma structures in a turbulent rotating magnetized plasma column

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Development of an aqueous two-phase emulsion using hydrophobized whey proteins and erythritol

International audienceFormation of aqueous two-phase (ATP) emulsions relies on the immiscibility of two (bio)polymeric phases. Herein, we report that hydrophobization of whey proteins via a pre-acetylation and succeeding acetylation/heating combined process makes solutions of whey protein isolate (WPI) immiscible with alginate solutions. Erythritol was also added at different concentrations (0, 52, 105, and 158 mg/g) into the hydrophobized WPI solution. Subsequently, emulsions at an alginate to WPI weight ratio of 0.1–0.9 were prepared. Erythritol supplementation facilitated emulsification and increased emulsion stability, so that at the erythritol concentration of 105 mg/g, the emulsion was stable for a minimum duration of 7 days. The droplet size evolved and reached to ≈5 μm during this period. The hydrophobized protein had a mean hydrodynamic diameter of 80 nm, ζ-potential of −39 mV, and intrinsic fluorescence emission peak of 335 nm. Erythritol addition did not influence any of the above-mentioned characteristics. However, the hydrophobized WPI solution changed from Newtonian to a more viscous and shear-thinning fluid by adding erythritol at concentrations ≥105 mg/g, due probably to the induction of interaction among protein particles. A diameter of 150 nm was calculated for the air-dried hydrophobized protein particles using atomic force microscopy images, supporting the assumption that exclusion of erythritol from the protein particles surface induced inter-particle interactions. Erythritol addition at 105 mg/g had a twofold larger influence on the surface tension of hydrophobized WPI compared to water. It decreased the surface tension of hydrophobized WPI to 45 mN/m after droplet ageing for 350 s

Dynamical control of the convective transport behind a limiter in a magnetized laboratory plasmas

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A plausible model of phyllotaxis

A striking phenomenon unique to the kingdom of plants is the regular arrangement of lateral organs around a central axis, known as phyllotaxis. Recent molecular-genetic experiments indicate that active transport of the plant hormone auxin is the key process regulating phyllotaxis. A conceptual model based on these experiments, introduced by Reinhardt et al. [Reinhardt, D., Pesce, E. R., Stieger, P., Mandel, T., Baltensperger, K., et al. (2003) Nature 426, 255–260], provides an intuitively plausible interpretation of the data, but raises questions of whether the proposed mechanism is, in fact, capable of producing the observed temporal and spatial patterns, is robust, can start de novo, and can account for phyllotactic transitions, such as the frequently observed transition from decussate to spiral phyllotaxis. To answer these questions, we created a computer simulation model based on data described previously or in this paper and reasonable hypotheses. The model reproduces, within the standard error, the divergence angles measured in Arabidopsis seedlings and the effects of selected experimental manipulations. It also reproduces distichous, decussate, and tricussate patterns. The model thus offers a plausible link between molecular mechanisms of morphogenesis and the geometry of phyllotaxis