1,644 research outputs found
Extending the applicability of an open-ring trap to perform experiments with a single laser-cooled ion
An open-ring ion trap, also referred to as transparent trap was initially
built up to perform - correlation experiments with radioactive
ions. This trap geometry is also well suited to perform experiments with
laser-cooled ions, serving for the development of a new type of Penning trap,
in the framework of the project TRAPSENSOR at the University of Granada. The
goal of this project is to use a single Ca ion as detector for
single-ion mass spectrometry. Within this project and without any modification
to the initial electrode configuration, it was possible to perform Doppler
cooling on Ca ions, starting from large clouds and reaching single
ion sensitivity. This new feature of the trap might be important also for other
experiments with ions produced at Radioactive Ion Beam (RIB) facilities. In
this publication, the trap and the laser system will be described, together
with their performance with respect to laser cooling applied to large ion
clouds down to a single ion.Comment: 9 pages, 13 figure
Ipopv2: Photoionization of Ni XIV -- a test case
Several years ago, M. Asplund and coauthors (2004) proposed a revision of the
Solar composition. The use of this new prescription for Solar abundances in
standard stellar models generated a strong disagreement between the predictions
and the observations of Solar observables. Many claimed that the Standard Solar
Model (SSM) was faulty, and more specifically the opacities used in such
models. As a result, activities around the stellar opacities were boosted. New
experiments (J. Bailey at Sandia on Z-Pinch, The OPAC consortium at LULI200) to
measure directly absorbtion coefficients have been realized or are underway.
Several theoretical groups (CEA-OPAS, Los Alamos Nat. Lab., CEA-SCORCG, The
Opacity Project - The Iron Project (IPOPv2)) have started new sets of
calculations using different approaches and codes. While the new results seem
to confirm the good quality of the opacities used in SSM, it remains important
to improve and complement the data currently available. We present recent
results in the case of the photoionization cross sections for Ni XIV (Ni13+ )
from IPOPv2 and possible implications on stellar modelling.Comment: 10 pages, 3 figures, Conf. on New Advances in Stellar Physics: From
Microscopic to Macroscopic Processe
Control of Coulomb blockade in a mesoscopic Josephson junction using single electron tunneling
We study a circuit where a mesoscopic Josephson junction (JJ) is embedded in
an environment consisting of a large bias resistor and a normal metal -
superconductor tunnel junction (NIS). The effective Coulomb blockade of the JJ
can be controlled by the tunneling current through the NIS junction leading to
transistor-like characteristics. We show using phase correlation theory and
numerical simulations that substantial current gain with low current noise
( fA/) and noise temperature (
0.1 K) can be achieved. Good agreement between our numerical simulations and
experimental results is obtained.Comment: 5 pages, 4 figures, RevTE
Radiological examination of the spine and fitness for work as a helicopter pilot
On the matter of spinal fitness for piloting, standards are proposed that suit the critical spinal segments proper to different jobs. Involved here are primarily pilots of combat airplanes and of helicopters. Fitness for one of these does not necessarily mean fitness for the other
Vertebral pain in helicopter pilots
Pathological forms of spinal pain engendered by piloting helicopters were clinically studied. Lumbalgia and pathology of the dorsal and cervical spine are discussed along with their clinical and radiological signs and origins
Design Issues of TeV Linear Colliders
Within the frame work of a world-wide collabora-tion, various possible approaches for Linear Colliders in the TeV energy range (TLC) and high luminosity (~ 1034 cm-2 sec-1) are explored in different laboratories and periodically compared in international workshops. The main accelerator physics issues required to meet the requested performance improvement by three orders of magnitude in luminosity and by a factor 10 in beam energy with respect to the unique linear collider presently operational, the SLC at SLAC, are reviewed, pointing out the main challenges common to all designs as well as the possible technological choices. Corresponding designs based on the improve-ment of present standard or the development of new tech-nologies are presented, emphasizing their main issues and specific challenges. The main goals of ambitious test facilities presently set-up to study the feasibility and cost of the various schemes in the next few years are introduced
A Review of Possible Future High-Energy Colliders for the Post-LHC Era
A review of the studies being conducted by various laboratories and collaborations in order to determine and optimise the next generation of particle accelerators for physics at the high energy frontier beyond HERA1) at DESY, LEP2) and LHC3) at CERN, SLC4) at SLAC and the TEVATRON5) at FNAL is presented. The relative advantages of the Very Large Hadron Colliders, Electron Positron Colliders and Muon Colliders are compared pointing out their main challenges and key issues both in beam dynamics and technology. The present status and future plans of the studies are summarised outlining the research and development of key components and their tests in ambitious test facilities. Finally, the schedules presently assumed and the possible scenarios for the post-LHC-era around 2010 are presented
Positrons from dark matter annihilation in the galactic halo: uncertainties
Indirect detection signals from dark matter annihilation are studied in the
positron channel. We discuss in detail the positron propagation inside the
galactic medium: we present novel solutions of the diffusion and propagation
equations and we focus on the determination of the astrophysical uncertainties
which affect the positron dark matter signal. We show that, especially in the
low energy tail of the positron spectra at Earth, the uncertainty is sizeable
and we quantify the effect. Comparison of our predictions with current
available and foreseen experimental data are derived.Comment: 4 pages, 4 figures, Proc. of the 30th International Cosmic Ray
Conference, July 3 - 11, 2007, Merida, Yucatan, Mexico (ICRC07
A Graphical Language for Proof Strategies
Complex automated proof strategies are often difficult to extract, visualise,
modify, and debug. Traditional tactic languages, often based on stack-based
goal propagation, make it easy to write proofs that obscure the flow of goals
between tactics and are fragile to minor changes in input, proof structure or
changes to tactics themselves. Here, we address this by introducing a graphical
language called PSGraph for writing proof strategies. Strategies are
constructed visually by "wiring together" collections of tactics and evaluated
by propagating goal nodes through the diagram via graph rewriting. Tactic nodes
can have many output wires, and use a filtering procedure based on goal-types
(predicates describing the features of a goal) to decide where best to send
newly-generated sub-goals.
In addition to making the flow of goal information explicit, the graphical
language can fulfil the role of many tacticals using visual idioms like
branching, merging, and feedback loops. We argue that this language enables
development of more robust proof strategies and provide several examples, along
with a prototype implementation in Isabelle
Positrons from dark matter annihilation in the galactic halo: theoretical uncertainties
Indirect detection signals from dark matter annihilation are studied in the
positron channel. We discuss in detail the positron propagation inside the
galactic medium: we present novel solutions of the diffusion and propagation
equations and we focus on the determination of the astrophysical uncertainties
which affect the positron dark matter signal. We find dark matter scenarios and
propagation models that nicely fit existing data on the positron fraction.
Finally, we present predictions both on the positron fraction and on the flux
for already running or planned space experiments, concluding that they have the
potential to discriminate a possible signal from the background and, in some
cases, to distinguish among different astrophysical propagation models.Comment: 22 pages, 15 figures. A few comments and references adde
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