109 research outputs found
Axions and Photons In Terms of "Particles" and "Anti-Particles"
The axion photon system in an external magnetic field, when for example
considered with the geometry of the experiments exploring axion photon mixing
(which can be represented by a 1+1 effective model) displays a continuous
axion-photon duality symmetry in the limit the axion mass is neglected. The
conservation law that follows from this symmetry is obtained. The magnetic
field interaction is seen to be equivalent to first order to the interaction of
a complex charged field with an external electric potential, where this
ficticious "electric potential" is proportional to the external magnetic field.
This allows one to solve for the scattering amplitudes using already known
scalar QED results. Axion photon oscillations can be understood as violations
of a charge symmetry in the scalar QED language. Going beyond the linear
theory, the axion photon system in a self consistent magnetic field is shown,
using this formalism, to have interesting soliton solutions that represent new
non gravitational ways of trapping light. Finally, generalizing the scalar QED
formalism to 2+1 dimensions makes it clear that a photon and an axion splitt
into two components in an inhomogeneous magnetic field, an effect that reminds
us of the Stern Gerlach experiment.Comment: Talk given at the 4th Patras workshop on axions, WIMPs and WISPs,
Hamburg, Gemany, 18-21 Jun 2008. Corrected reference in version
Stabilization of Neutral Thin Shells By Gravitational Effects From Electric Fields
We study the properties of a system consisting of an uncharged spherically
symmetric two dimensional extended object which encloses a stationary point
charge placed in the shell's center. We show that there can be a static and
stable configuration for the neutral shell, using only the gravitational field
of the charged source as a stabilizing mechanism. In particular, two types of
shells are studied: a dust shell and a string gas shell. The dynamical
possibilities are also analyzed, including the possibility of child universe
creation.Comment: 5 pages, 1 figur
Axions Scattering From a Quadrupole Magnetic Field
We study the 2D scattering of axions from an accelerator like quadrupole
magnet using the eikonal approximation in order to learn whether or not such a
setup could serve as a new possible method for detecting axions on terrestrial
experiments. The eikonal approximation in 2D is introduced and explained. We
also apply the eikonal approximation to two known cases in order to compare it
with previous results, obtained using Born's approximation, and discuss its
correctness
New Superconducting Toroidal Magnet System for IAXO, the International AXion Observatory
Axions are hypothetical particles that were postulated to solve one of the
puzzles arising in the standard model of particle physics, namely the strong CP
(Charge conjugation and Parity) problem. The new International AXion
Observatory (IAXO) will incorporate the most promising solar axions detector to
date, which is designed to enhance the sensitivity to the axion-photon coupling
by one order of magnitude beyond the limits of the current state-of-the-art
detector, the CERN Axion Solar Telescope (CAST). The IAXO detector relies on a
high-magnetic field distributed over a very large volume to convert solar
axions into X-ray photons. Inspired by the successful realization of the ATLAS
barrel and end-cap toroids, a very large superconducting toroid is currently
designed at CERN to provide the required magnetic field. This toroid will
comprise eight, one meter wide and twenty one meter long, racetrack coils. The
system is sized 5.2 m in diameter and 25 m in length. Its peak magnetic field
is 5.4 T with a stored energy of 500 MJ. The magnetic field optimization
process to arrive at maximum detector yield is described. In addition,
materials selection and their structure and sizing has been determined by force
and stress calculations. Thermal loads are estimated to size the necessary
cryogenic power and the concept of a forced flow supercritical helium based
cryogenic system is given. A quench simulation confirmed the quench protection
scheme.Comment: Accepted for publication in Adv. Cryo. Eng. (CEC/ICMC 2013 special
issue
Conceptual Design of a New Large Superconducting Toroid for IAXO, the New International AXion Observatory
The International AXion Observatory (IAXO) will incorporate a new generation
detector for axions, a hypothetical particle, which was postulated to solve one
of the puzzles arising in the standard model of particle physics, namely the
strong CP problem. The new IAXO experiment is aiming at achieving a sensitivity
to the coupling between axions and photons of one order of magnitude beyond the
limits of the current state-of-the-art detector, represented by the CERN Axion
Solar Telescope (CAST). The IAXO detector relies on a high-magnetic field
distributed over a very large volume to convert solar axions into x-ray
photons. Utilizing the designs of the ATLAS barrel and end-cap toroids, a large
superconducting toroidal magnet is currently being designed at CERN to provide
the required magnetic field. The new toroid will be built up from eight, one
meter wide and 20 m long, racetrack coils. The toroid is sized about 4 m in
diameter and 22 m in length. It is designed to realize a peak magnetic field of
5.4 T with a stored energy of 500 MJ. The magnetic field optimization process
to arrive at maximum detector yield is described. In addition, force and stress
calculations are performed to select materials and determine their structure
and sizing. Conductor dimensionality, quench protection and the cryogenic
design are dealt with as well.Comment: 5 pages, 5 figures. To be published in IEEE Trans. Appl. Supercond.
23 (ASC 2012 conference special issue
The Superconducting Toroid for the New International AXion Observatory (IAXO)
IAXO, the new International AXion Observatory, will feature the most
ambitious detector for solar axions to date. Axions are hypothetical particles
which were postulated to solve one of the puzzles arising in the standard model
of particle physics, namely the strong CP (Charge conjugation and Parity)
problem. This detector aims at achieving a sensitivity to the coupling between
axions and photons of one order of magnitude beyond the limits of the current
detector, the CERN Axion Solar Telescope (CAST). The IAXO detector relies on a
high-magnetic field distributed over a very large volume to convert solar
axions to detectable X-ray photons. Inspired by the ATLAS barrel and end-cap
toroids, a large superconducting toroid is being designed. The toroid comprises
eight, one meter wide and twenty one meters long racetrack coils. The assembled
toroid is sized 5.2 m in diameter and 25 m in length and its mass is about 250
tons. The useful field in the bores is 2.5 T while the peak magnetic field in
the windings is 5.4 T. At the operational current of 12 kA the stored energy is
500 MJ. The racetrack type of coils are wound with a reinforced Aluminum
stabilized NbTi/Cu cable and are conduction cooled. The coils optimization is
shortly described as well as new concepts for cryostat, cold mass, supporting
structure and the sun tracking system. Materials selection and sizing,
conductor, thermal loads, the cryogenics system and the electrical system are
described. Lastly, quench simulations are reported to demonstrate the system's
safe quench protection scheme.Comment: To appear in IEEE Trans. Appl. Supercond. MT 23 issue. arXiv admin
note: substantial text overlap with arXiv:1308.2526, arXiv:1212.463
The influence of the Al stabilizer layer thickness on the normal zone propagation velocity in high current superconductors
The stability of high-current superconductors is challenging in the design of
superconducting magnets. When the stability requirements are fulfilled, the
protection against a quench must still be considered. A main factor in the
design of quench protection systems is the resistance growth rate in the magnet
following a quench. The usual method for determining the resistance growth in
impregnated coils is to calculate the longitudinal velocity with which the
normal zone propagates in the conductor along the coil windings.
Here, we present a 2D numerical model for predicting the normal zone
propagation velocity in Al stabilized Rutherford NbTi cables with large cross
section. By solving two coupled differential equations under adiabatic
conditions, the model takes into account the thermal diffusion and the current
redistribution process following a quench. Both the temperature and magnetic
field dependencies of the superconductor and the metal cladding materials
properties are included. Unlike common normal zone propagation analyses, we
study the influence of the thickness of the cladding on the propagation
velocity for varying operating current and magnetic field.
To assist in the comprehension of the numerical results, we also introduce an
analytical formula for the longitudinal normal zone propagation. The analysis
distinguishes between low-current and high-current regimes of normal zone
propagation, depending on the ratio between the characteristic times of thermal
and magnetic diffusion. We show that above a certain thickness, the cladding
acts as a heat sink with a limited contribution to the acceleration of the
propagation velocity with respect to the cladding geometry. Both numerical and
analytical results show good agreement with experimental data.Comment: To be published in Physics Procedia (ICEC 25 conference special
issue
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