195 research outputs found
Doppler cooling of calcium ions using a dipole-forbidden transition
Doppler cooling of calcium ions has been experimentally demonstrated using
the S1/2 to D5/2 dipole-forbidden transition. Scattering forces and
fluorescence levels a factor of 5 smaller than for usual Doppler cooling on the
dipole allowed S1/2 to P1/2 transition have been achieved. Since the light
scattered from the ions can be monitored at (violet) wavelengths that are very
different from the excitation wavelengths, single ions can be detected with an
essentially zero background level. This, as well as other features of the
cooling scheme, can be extremely valuable for ion trap based quantum
information processing.Comment: 4 pages, 4 figures, minor changes to commentary and reference
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
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
Parallel ion strings in linear multipole traps
Additional radio-frequency (rf) potentials applied to linear multipole traps
create extra field nodes in the radial plane which allow one to confine single
ions, or strings of ions, in totally rf field-free regions. The number of nodes
depends on the order of the applied multipole potentials and their relative
distance can be easily tuned by the amplitude variation of the applied
voltages. Simulations using molecular dynamics show that strings of ions can be
laser cooled down to the Doppler limit in all directions of space. Once cooled,
organized systems can be moved with very limited heating, even if the cooling
process is turned off
High contrast Mach-Zehnder lithium atom interferometer in the Bragg regime
We have constructed an atom interferometer of the Mach-Zehnder type,
operating with a supersonic beam of lithium. Atom diffraction uses Bragg
diffraction on laser standing waves. With first order diffraction, our
apparatus has given a large signal and a very good fringe contrast (74%), which
we believe to be the highest ever observed with atom interferometers. This
apparatus will be applied to high sensitivity measurementsComment: 6 pages, 3 figures, accepted by Appl. Phys.
Structural phase transitions in multipole traps
A small number of laser-cooled ions trapped in a linear radiofrequency
multipole trap forms a hollow tube structure. We have studied, by means of
molecular dynamics simulations, the structural transition from a double ring to
a single ring of ions. We show that the single-ring configuration has the
advantage to inhibit the thermal transfer from the rf-excited radial components
of the motion to the axial component, allowing to reach the Doppler limit
temperature along the direction of the trap axis. Once cooled in this
particular configuration, the ions experience an angular dependency of the
confinement if the local adiabaticity parameter exceeds the empirical limit.
Bunching of the ion structures can then be observed and an analytic expression
is proposed to take into account for this behaviour
Anharmonic contributions in real RF linear quadrupole traps
See also erratum at : http://www.sciencedirect.com/science/article/pii/S1387380610001004International audienceThe radiofrequency quadrupole linear ion trap is a widely used device in physics and chemistry. When used for trapping of large ion clouds, the presence of anharmonic terms in the radiofrequency potential limits the total number of stored ions. In this paper, we have studied the anharmonic content of the trapping potential for different implementations of a quadrupole trap, searching for the geometry best suited for the trapping of large ion clouds. This is done by calculating the potential of a real trap using SIMION8.0, followed by a fit, which allows us to obtain the evolution of anharmonic terms for a large part of the inner volume of the trap
Environmental assessment of bioethanol from onshore grown Ulva
PosterBesides biofuels from microalgae, an emerging interest in using macroalgae as feedstock for biofuel production is observable. Macroalgae have the advantage that they are much easier to harvest than microalgae so that the problem of low feedstock concentration does not arise. The environmental performance of bioethanol from onshore grown green algae is assessed using literature data and initial laboratory scale data. The optimized system model allows for producing an environmentally efficient biofuel in comparison to fossil fuel and bioethanol from sugar cane. Handling the co-product by substitution instead of energy allocation significantly reduced the environmental impacts of the system and resulted in environmental bonuses in several impact categories. Thus, the management of the co-product in the LCA model (energy allocation vs. substitution) is a key step in the LCA, as it highly influences the impact assessment results
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
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