969 research outputs found
Prospects for direct cosmic ray mass measurements through the Gerasimova-Zatsepin effect
The Solar radiation field may break apart ultra high energy cosmic nuclei,
after which both remnants will be deflected in the interplanetary magnetic
field in different ways. This process is known as the Gerasimova-Zatsepin
effect after its discoverers. We investigate the possibility of using the
detection of the separated air showers produced by a pair of remnant particles
as a way to identify the species of the original cosmic ray primary directly.
Event rates for current and proposed detectors are estimated, and requirements
are defined for ideal detectors of this phenomenon. Detailed computational
models of the disintegration and deflection processes for a wide range of
cosmic ray primaries in the energy range of 10^16 to 10^20 eV are combined with
sophisticated detector models to calculate realistic detection rates. The
fraction of Gerasimova-Zatsepin events is found to be of the order of 10^-5 of
the cosmic ray flux, implying an intrinsic event rate of around 0.07 km^-2
sr^-1 yr^-1 in the energy range defined. Event rates in any real experiment,
however, existing or under construction, will probably not exceed 10^-2 yr^-1.Comment: 4 pages, 4 figure
Prospects for determining air shower characteristics through geosynchrotron emission arrival times
Using simulations of geosynchrotron radiation from extensive air showers, we
present a relation between the shape of the geosynchrotron radiation front and
the distance of the observer to the maximum of the air shower. By analyzing the
relative arrival times of radio pulses at several radio antennas in an air
shower array, this relation may be employed to estimate the depth of maximum of
an extensive air shower if its impact position is known, allowing an estimate
for the primary particle's species. Vice versa, the relation provides an
estimate for the impact position of the shower's core if an external estimate
of the depth of maximum is available. In realistic circumstances, the method
delivers reconstruction uncertainties down to 30 g/cm^2 when the distance to
the shower core does not exceed 7 km. The method requires that the arrival
direction is known with high precision.Comment: 7 pages, 9 figures. Accepted for publication in Astroparticle
Physics
Cosmic-ray energy spectrum and composition up to the ankle - the case for a second Galactic component
We have carried out a detailed study to understand the observed energy
spectrum and composition of cosmic rays with energies up to ~10^18 eV. Our
study shows that a single Galactic component with subsequent energy cut-offs in
the individual spectra of different elements, optimised to explain the observed
spectra below ~10^14 eV and the knee in the all-particle spectrum, cannot
explain the observed all-particle spectrum above ~2x10^16 eV. We discuss two
approaches for a second component of Galactic cosmic rays -- re-acceleration at
a Galactic wind termination shock, and supernova explosions of Wolf-Rayet
stars, and show that the latter scenario can explain almost all observed
features in the all-particle spectrum and the composition up to ~10^18 eV, when
combined with a canonical extra-galactic spectrum expected from strong radio
galaxies or a source population with similar cosmological evolution. In this
two-component Galactic model, the knee at ~ 3x10^15 eV and the second knee at
~10^17 eV in the all-particle spectrum are due to the cut-offs in the first and
second components, respectively. We also discuss several variations of the
extra-galactic component, from a minimal contribution to scenarios with a
significant component below the ankle (at ~4x10^18 eV), and find that
extra-galactic contributions in excess of regular source evolution are neither
indicated nor in conflict with the existing data. Our main result is that the
second Galactic component predicts a composition of Galactic cosmic rays at and
above the second knee that largely consists of helium or a mixture of helium
and CNO nuclei, with a weak or essentially vanishing iron fraction, in contrast
to most common assumptions. This prediction is in agreement with new
measurements from LOFAR and the Pierre Auger Observatory which indicate a
strong light component and a rather low iron fraction between ~10^17 and 10^18
eV.Comment: Added Table 4; Published in A&A, 595 (2016) A33 (Highlight paper
Central Acceptance Testing for Camera Technologies for CTA
The Cherenkov Telescope Array (CTA) is an international initiative to build
the next generation ground based very-high energy gamma-ray observatory. It
will consist of telescopes of three different sizes, employing several
different technologies for the cameras that detect the Cherenkov light from the
observed air showers. In order to ensure the compliance of each camera
technology with CTA requirements, CTA will perform central acceptance testing
of each camera technology. To assist with this, the Camera Test Facilities
(CTF) work package is developing a detailed test program covering the most
important performance, stability, and durability requirements, including
setting up the necessary equipment. Performance testing will include a wide
range of tests like signal amplitude, time resolution, dead-time determination,
trigger efficiency, performance testing under temperature and humidity
variations and several others. These tests can be performed on fully-integrated
cameras using a portable setup at the camera construction sites. In addition,
two different setups for performance tests on camera sub-units are being built,
which can provide early feedback for camera development. Stability and
durability tests will include the long-term functionality of movable parts,
water tightness of the camera housing, temperature and humidity cycling,
resistance to vibrations during transport or due to possible earthquakes,
UV-resistance of materials and several others. Some durability tests will need
to be contracted out because they will need dedicated equipment not currently
available within CTA. The planned test procedures and the current status of the
test facilities will be presented.Comment: 8 pages, 3 figures. In Proceedings of the 34th International Cosmic
Ray Conference (ICRC2015), The Hague, The Netherlands. All CTA contributions
at arXiv:1508.0589
Results from the KASCADE, KASCADE-Grande, and LOPES experiments
The origin of high-energy cosmic rays in the energy range from 10^14 to 10^18
eV is explored with the KASCADE and KASCADE-Grande experiments. Radio signals
from air showers are measured with the LOPES experiment. An overview on results
is given.Comment: Talk at The ninth International Conference on Topics in Astroparticle
and Underground Physics, TAUP 2005, Zaragoza, September 10-14, 200
Dissecting the knee - Air shower measurements with KASCADE
Recent results of the KASCADE air shower experiment are presented in order to
shed some light on the astrophysics of cosmic rays in the region of the knee in
the energy spectrum. The results include investigations of high-energy
interactions in the atmosphere, the analysis of the arrival directions of
cosmic rays, the determination of the mean logarithmic mass, and the unfolding
of energy spectra for elemental groups
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