455 research outputs found
Heteronuclear collisions between laser-cooled metastable neon atoms
We investigate heteronuclear collisions in isotope mixtures of laser-cooled
metastable 3P2 neon. Experiments are performed with spin-polarized atoms in a
magnetic trap for all two-isotope combinations of the stable neon isotopes
20Ne, 21Ne, and 22Ne. We determine the rate coefficients for heteronuclear
ionizing collisions to beta_{21,20}=(3.9+/-2.7) x 10^{-11} cm^3/s,
beta_{22,20}=(2.6+/-0.7) x 10^{-11} cm^3/s, and beta_{21,22}=(3.9+/-1.9) x
10^{-11} cm^3/s. We also study heteronuclear elastic collision processes and
give upper bounds for heteronuclear thermal relaxation cross sections. This
work significantly extends the limited available experimental data on
heteronuclear ionizing collisions for laser-cooled atoms involving one or more
rare gas atoms in a metastable state
Three level atom optics in dipole traps and waveguides
An analogy is explored between a setup of three atomic traps coupled via
tunneling and an internal atomic three-level system interacting with two laser
fields. Within this scenario we describe a STIRAP like process which allows to
move an atom between the ground states of two trapping potentials and analyze
its robustness. This analogy is extended to other robust and coherent transport
schemes and to systems of more than a single atom. Finally it is applied to
manipulate external degrees of freedom of atomic wave packets propagating in
waveguides.Comment: 14 pages, 6 figures; submitted to special issue 'Quantum Control of
Light and Matter' of Optics Communication
Switchable Magnetic Bottles and Field Gradients for Particle Traps
Versatile methods for the manipulation of individual quantum systems, such as
confined particles, have become central elements in current developments in
precision spectroscopy, frequency standards, quantum information processing,
quantum simulation, and alike. For atomic and some subatomic particles, both
neutral and charged, a precise control of magnetic fields is essen- tial. In
this paper, we discuss possibilities for the creation of specific magnetic
field configurations which find appli- cation in these areas. In particular, we
pursue the idea of a magnetic bottle which can be switched on and off by
transition between the normal and the superconducting phase of a suitable
material in cryogenic environments, for example in trap experiments in moderate
magnetic fields. Methods for a fine-tuning of the magnetic field and its linear
and quadratic components in a trap are presented together with possible
applications
Coherent injecting, extracting, and velocity filtering of neutral atoms in a ring trap via spatial adiabatic passage
We introduce here a coherent technique to inject, extract, and velocity
filter neutral atoms in a ring trap coupled via tunneling to two additional
waveguides. By adiabatically following the transverse spatial dark state, the
proposed technique allows for an efficient and robust velocity dependent atomic
population transfer between the ring and the input/output waveguides. We have
derived explicit conditions for the spatial adiabatic passage that depend on
the atomic velocity along the input waveguide as well as on the initial
population distribution among the transverse vibrational states. The validity
of our proposal has been checked by numerical integration of the corresponding
two dimensional Schr\"odinger equation with state-of-the-art parameter values
for Rb atoms and an optical dipole ring trap.Comment: To be published in European Physical Journal
Half-open Penning trap with efficient light collection for precision laser spectroscopy of highly charged ions
We have conceived, built and operated a 'half-open' cylindrical Penning trap
for the confinement and laser spectroscopy of highly charged ions. This trap
allows fluorescence detection employing a solid angle which is about one order
of magnitude larger than in conventional cylindrical Penning traps. At the same
time, the desired electrostatic and magnetostatic properties of a closed-endcap
cylindrical Penning trap are preserved in this congfiuration. We give a
detailed account on the design and confinement properties, a characterization
of the trap and show first results of light collection with in-trap produced
highly charged ions
Gaussian Process Regression for In-situ Capacity Estimation of Lithium-ion Batteries
Accurate on-board capacity estimation is of critical importance in
lithium-ion battery applications. Battery charging/discharging often occurs
under a constant current load, and hence voltage vs. time measurements under
this condition may be accessible in practice. This paper presents a data-driven
diagnostic technique, Gaussian Process regression for In-situ Capacity
Estimation (GP-ICE), which estimates battery capacity using voltage
measurements over short periods of galvanostatic operation. Unlike previous
works, GP-ICE does not rely on interpreting the voltage-time data as
Incremental Capacity (IC) or Differential Voltage (DV) curves. This overcomes
the need to differentiate the voltage-time data (a process which amplifies
measurement noise), and the requirement that the range of voltage measurements
encompasses the peaks in the IC/DV curves. GP-ICE is applied to two datasets,
consisting of 8 and 20 cells respectively. In each case, within certain voltage
ranges, as little as 10 seconds of galvanostatic operation enables capacity
estimates with approximately 2-3% RMSE.Comment: 12 pages, 10 figures, submitted to IEEE Transactions on Industrial
Informatic
Filtering of matter wave vibrational states via spatial adiabatic passage
We discuss the filtering of the vibrational states of a cold atom in an
optical trap, by chaining this trap with two empty ones and controlling
adiabatically the tunneling. Matter wave filtering is performed by selectively
transferring the population of the highest populated vibrational state to the
most distant trap while the population of the rest of the states remains in the
initial trap. Analytical conditions for two-state filtering are derived and
then applied to an arbitrary number of populated bound states. Realistic
numerical simulations close to state-of-the-art experimental arrangements are
performed by modeling the triple well with time dependent P\"oschl-Teller
potentials. In addition to filtering of vibrational states, we discuss
applications for quantum tomography of the initial population distribution and
engineering of atomic Fock states that, eventually, could be used for tunneling
assisted evaporative cooling.Comment: 7 pages, 6 figure
Modular converter system for low-cost off-grid energy storage using second life Li-ion batteries
Lithium ion batteries are promising for small off- grid energy storage
applications in developing countries because of their high energy density and
long life. However, costs are prohibitive. Instead, we consider 'used' Li-ion
batteries for this application, finding experimentally that many discarded
laptop cells, for example, still have good capacity and cycle life. In order to
make safe and optimal use of such cells, we present a modular power management
system using a separate power converter for every cell. This novel approach
allows individual batteries to be used to their full capacity. The power
converters operate in voltage droop control mode to provide easy charge
balancing and implement a battery management system to estimate the capacity of
each cell, as we demonstrate experimentally.Comment: Presented at IEEE GHTC Oct 10-14, 2014, Silicon Valle
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