798 research outputs found
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
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
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
The CLIC Multi-Drive Beam Scheme
The CLIC study of an e+ / e- linear collider in the TeV energy range is based on Two-Beam Acceleration (TBA) in which the RF power needed to accelerate the beam is extracted from high intensity relativistic electron beams, the so-called drive beams. The generation, acceleration and transport of the high-intensity drive beams in an efficient and reliable way constitute a challenging task. An overview of a potentially very effective scheme is presented. It is based on the generation of trains of short bunches, accelerated sequentially in low frequency superconducting cavities in a c.w. mode, stored in an isochronous ring and combined at high energy by funnelling before injection by sectors into the drive linac for RF power production. The various systems of the complex are discussed
A Quantitative Comparison of Opacities Calculated Using the Distorted- Wave and -Matrix Methods
The present debate on the reliability of astrophysical opacities has reached
a new climax with the recent measurements of Fe opacities on the Z-machine at
the Sandia National Laboratory \citep{Bailey2015}. To understand the
differences between theoretical results, on the one hand, and experiments on
the other, as well as the differences among the various theoretical results,
detailed comparisons are needed. Many ingredients are involved in the
calculation of opacities; deconstructing the whole process and comparing the
differences at each step are necessary to quantify their importance and impact
on the final results. We present here such a comparison using the two main
approaches to calculate the required atomic data, the -Matrix and
distorted-wave methods, as well as sets of configurations and coupling schemes
to quantify the effects on the opacities for the and ions.Comment: 10 pages, 2 figure
CLIC Main Linac Beam-Loading Compensation by Drive Beam Phase Modulation
The CLIC final focus momentum acceptance of ± 0.5 % limits the bunch-to-bunch energy variation in the main beam to less than ± 0.1 %, since the estimated single-bunch contribution is ± 0.4 %. On the other hand, a relatively high beam-loading of the main accelerating structures (about 16 %) is unavoidable in order to optimize the RF-to-beam efficiency. Therefore, a compensation method is needed to reduce the resulting bunch-to-bunch energy spread of the main beam. Up to now, it has been planned to obtain the RF pulse shape needed for compensation by means of a charge ramp in the drive beam pulse. On the other hand, the use of constant-current drive beam pulses would make the design and operation of the drive beam injector considerably simpler. In this paper we present a possible solution adapted to the CLIC two-beam scheme with constant-current pulses, based on phase modulation of the drive beam bunches
Dark Matter detection via lepton cosmic rays
Recent observations of lepton cosmic rays, coming from the PAMELA and FERMI
experiments, have pushed our understanding of the interstellar medium and
cosmic rays sources to unprecedented levels. The imprint of dark matter on
lepton cosmic rays is the most exciting explanation of both PAMELA's positron
excess and FERMI's total flux of electrons. Alternatively, supernovae are
astrophysical objects with the same potential to explain these observations. In
this work, we present an updated study of the astrophysical sources of lepton
cosmic rays and the possible trace of a dark matter signal on the positron
excess and total flux of electrons.Comment: 6 pages and 3 figures. Proceedings for PASCOS 2010, Valencia, Spai
The NuMAX Long Baseline Neutrino Factory Concept
A Neutrino Factory where neutrinos of all species are produced in equal
quantities by muon decay is described as a facility at the intensity frontier
for exquisite precision providing ideal conditions for ultimate neutrino
studies and the ideal complement to Long Baseline Facilities like LBNF at
Fermilab. It is foreseen to be built in stages with progressively increasing
complexity and performance, taking advantage of existing or proposed facilities
at an existing laboratory like Fermilab. A tentative layout based on a
recirculating linac providing opportunities for considerable saving is
discussed as well as its possible evolution toward a muon collider if and when
requested by Physics. Tentative parameters of the various stages are presented
as well as the necessary R&D to address the technological issues and
demonstrate their feasibility.Comment: JINST Special Issue on Muon Accelerators. arXiv admin note: text
overlap with arXiv:1308.0494, arXiv:1502.0164
- …