5,997 research outputs found
The Electrostatic Ion Beam Trap : a mass spectrometer of infinite mass range
We study the ions dynamics inside an Electrostatic Ion Beam Trap (EIBT) and
show that the stability of the trapping is ruled by a Hill's equation. This
unexpectedly demonstrates that an EIBT, in the reference frame of the ions
works very similar to a quadrupole trap. The parallelism between these two
kinds of traps is illustrated by comparing experimental and theoretical
stability diagrams of the EIBT. The main difference with quadrupole traps is
that the stability depends only on the ratio of the acceleration and trapping
electrostatic potentials, not on the mass nor the charge of the ions. All kinds
of ions can be trapped simultaneously and since parametric resonances are
proportional to the square root of the charge/mass ratio the EIBT can be used
as a mass spectrometer of infinite mass range
Shape in an Atom of Space: Exploring quantum geometry phenomenology
A phenomenology for the deep spatial geometry of loop quantum gravity is
introduced. In the context of a simple model, an atom of space, it is shown how
purely combinatorial structures can affect observations. The angle operator is
used to develop a model of angular corrections to local, continuum flat-space
3-geometries. The physical effects involve neither breaking of local Lorentz
invariance nor Planck scale suppression, but rather reply on only the
combinatorics of SU(2) recoupling. Bhabha scattering is discussed as an example
of how the effects might be observationally accessible.Comment: 14 pages, 7 figures; v2 references adde
About the dynamics and thermodynamics of trapped ions
This tutorial introduces the dynamics of charged particles in a
radiofrequency trap in a very general manner to point out the differences
between the dynamics in a quadrupole and in a multipole trap. When dense
samples are trapped, the dynamics is modified by the Coulomb repulsion between
ions. To take into account this repulsion, we propose to use a method,
originally developed for particles in Penning trap, that model the ion cloud as
a cold fluid. This method can not reproduce the organisation of cold clouds as
crystals but it allows one to scale the size of large samples with the trapping
parameters and the number of ions trapped, for different linear geometries of
trap.Comment: accepted for publication in the "Modern Applications of Trapped Ions"
special issu
Penning traps as a versatile tool for precise experiments in fundamental physics
This review article describes the trapping of charged particles. The main
principles of electromagnetic confinement of various species from elementary
particles to heavy atoms are briefly described. The preparation and
manipulation with trapped single particles, as well as methods of frequency
measurements, providing unprecedented precision, are discussed. Unique
applications of Penning traps in fundamental physics are presented.
Ultra-precise trap-measurements of masses and magnetic moments of elementary
particles (electrons, positrons, protons and antiprotons) confirm
CPT-conservation, and allow accurate determination of the fine-structure
constant alpha and other fundamental constants. This together with the
information on the unitarity of the quark-mixing matrix, derived from the
trap-measurements of atomic masses, serves for assessment of the Standard Model
of the physics world. Direct mass measurements of nuclides targeted to some
advanced problems of astrophysics and nuclear physics are also presented
Quantum Dynamics without the Wave Function
When suitably generalized and interpreted, the path-integral offers an
alternative to the more familiar quantal formalism based on state-vectors,
selfadjoint operators, and external observers. Mathematically one generalizes
the path-integral-as-propagator to a {\it quantal measure} on the space
of all ``conceivable worlds'', and this generalized measure expresses
the dynamics or law of motion of the theory, much as Wiener measure expresses
the dynamics of Brownian motion. Within such ``histories-based'' schemes new,
and more ``realistic'' possibilities open up for resolving the philosophical
problems of the state-vector formalism. In particular, one can dispense with
the need for external agents by locating the predictive content of in its
sets of measure zero: such sets are to be ``precluded''. But unrestricted
application of this rule engenders contradictions. One possible response would
remove the contradictions by circumscribing the application of the preclusion
concept. Another response, more in the tradition of ``quantum logic'', would
accommodate the contradictions by dualizing to a space of
``co-events'' and effectively identifying reality with an element of this dual
space.Comment: plainTeX, 24 pages, no figures. To appear in a special volume of {\it
Journal of Physics A: Mathematical and General} entitled ``The Quantum
Universe'' and dedicated to Giancarlo Ghirardi on the occasion of his 70th
birthday. Most current version is available at
http://www.physics.syr.edu/~sorkin/some.papers/ (or wherever my home-page may
be
Spatial Hypersurfaces in Causal Set Cosmology
Within the causal set approach to quantum gravity, a discrete analog of a
spacelike region is a set of unrelated elements, or an antichain. In the
continuum approximation of the theory, a moment-of-time hypersurface is well
represented by an inextendible antichain. We construct a richer structure
corresponding to a thickening of this antichain containing non-trivial
geometric and topological information. We find that covariant observables can
be associated with such thickened antichains and transitions between them, in
classical stochastic growth models of causal sets. This construction highlights
the difference between the covariant measure on causal set cosmology and the
standard sum-over-histories approach: the measure is assigned to completed
histories rather than to histories on a restricted spacetime region. The
resulting re-phrasing of the sum-over-histories may be fruitful in other
approaches to quantum gravity.Comment: Revtex, 12 pages, 2 figure
Particle Motion in Rapidly Oscillating Potentials: The Role of the Potential's Initial Phase
Rapidly oscillating potentials with a vanishing time average have been used
for a long time to trap charged particles in source-free regions. It has been
argued that the motion of a particle in such a potential can be approximately
described by a time independent effective potential, which does not depend upon
the initial phase of the oscillating potential. However, here we show that the
motion of a particle and its trapping condition significantly depend upon this
initial phase for arbitrarily high frequencies of the potential's oscillation.
We explain this novel phenomenon by showing that the motion of a particle is
determined by the effective potential stated in the literature only if its
initial conditions are transformed according to a transformation which we show
to significantly depend on the potential's initial phase for arbitrarily high
frequencies. We confirm our theoretical findings by numerical simulations.
Further, we demonstrate that the found phenomenon offers new ways to manipulate
the dynamics of particles which are trapped by rapidly oscillating potentials.
Finally, we propose a simple experiment to verify the theoretical findings of
this work.Comment: 9 pages, 8 figures, published in PR
High-accuracy Penning trap mass measurements with stored and cooled exotic ions
The technique of Penning trap mass spectrometry is briefly reviewed
particularly in view of precision experiments on unstable nuclei, performed at
different facilities worldwide. Selected examples of recent results emphasize
the importance of high-precision mass measurements in various fields of
physics
Sympathetic and swap cooling of trapped ions by cold atoms in a MOT
A mixed system of cooled and trapped, ions and atoms, paves the way for ion
assisted cold chemistry and novel many body studies. Due to the different
individual trapping mechanisms, trapped atoms are significantly colder than
trapped ions, therefore in the combined system, the strong binary ionatom
interaction results in heat flow from ions to atoms. Conversely, trapped ions
can also get collisionally heated by the cold atoms, making the resulting
equilibrium between ions and atoms intriguing. Here we experimentally
demonstrate, Rubidium ions (Rb) cool in contact with magneto-optically
trapped (MOT) Rb atoms, contrary to the general expectation of ion heating for
equal ion and atom masses. The cooling mechanism is explained theoretically and
substantiated with numerical simulations. The importance of resonant charge
exchange (RCx) collisions, which allows swap cooling of ions with atoms,
wherein a single glancing collision event brings a fast ion to rest, is
discussed.Comment: 10 pages, 3 figure
A semiclassical tetrahedron
We construct a macroscopic semiclassical state state for a quantum
tetrahedron. The expectation values of the geometrical operators representing
the volume, areas and dihedral angles are peaked around assigned classical
values, with vanishing relative uncertainties.Comment: 10 pages; v2 revised versio
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