The angular distribution of Cherenkov light in an air shower is closely linked to that of the shower electrons and positrons. As charged particles in extensive air showers are deflected by the ...magnetic field of the Earth, a deformation of the angular distribution of the Cherenkov light, that would be approximately symmetric about the shower axis if no magnetic field were present, is expected. In this work we study the variation of the Cherenkov light distribution as a function of the azimuth angle in the plane perpendicular to shower axis. It is found that the asymmetry induced by the geomagnetic field is most significant for early stages of shower evolution and for showers arriving almost perpendicular to the vector of the local geomagnetic field. Furthermore, it is shown that ignoring the azimuthal asymmetry of Cherenkov light might lead to a significant under- or overestimation of the Cherenkov light signal especially at sites where the local geomagnetic field is strong. Based on CORSIKA simulations, the azimuthal distribution of Cherenkov light is parametrized in dependence on the magnetic field component perpendicular to the shower axis and the local air density. This parametrization provides an efficient approximation for estimating the asymmetry of the Cherenkov light distribution for shower simulation and reconstruction in cosmic ray and gamma-ray experiments in which the Cherenkov signal of showers with energies above 1014eV is observed.
The discrepancies in the results produced by the two most commonly used Monte Carlo programs for simulation of propagation of ultra-high energy cosmic ray photons in the presence of the geomagnetic ...field are presented. Although photons have not yet been discovered in the cosmic ray flux at highest energies, the capabilities of the present cosmic ray detectors make their discovery possible, according to the predictions of conventional models, within the next few years. It is therefore necessary to have a reliable and well maintained software for relevant simulations. The results of this paper are important for simulations of propagation of photons at energies above 1019eV. Photons of such high energies might interact with the geomagnetic field giving rise to a cascade of particles even above the atmosphere. This effect is called a “preshower effect”. The preshower effect is important for air shower evolution and has to be accounted for in full Monte Carlo simulations of propagation of highest energy cosmic-ray photons. In this paper we compare the two most frequently used Monte Carlo codes for preshower simulations: PRESHOWER, used as a stand-alone program or as a part of CORSIKA, and MaGICS, used as a part of AIRES.
The identification of primary photons or specifying stringent limits on the photon flux is of major importance for understanding the origin of ultra-high energy (UHE) cosmic rays. UHE photons can ...initiate particle cascades in the geomagnetic field, which leads to significant changes in the subsequent atmospheric shower development. We present a Monte Carlo program allowing detailed studies of conversion and cascading of UHE photons in the geomagnetic field. The program named PRESHOWER can be used both as an independent tool or together with a shower simulation code. With the stand-alone version of the code it is possible to investigate various properties of the particle cascade induced by UHE photons interacting in the Earth's magnetic field before entering the Earth's atmosphere. Combining this program with an extensive air shower simulation code such as CORSIKA offers the possibility of investigating signatures of photon-initiated showers. In particular, features can be studied that help to discern such showers from the ones induced by hadrons. As an illustration, calculations for the conditions of the southern part of the Pierre Auger Observatory are presented.
Title of program:PRESHOWER 1.0
Catalogue identifier:ADWG
Program summary URL:
http://cpc.cs.qub.ac.uk/summaries/ADWG
Program obtainable: CPC Program Library, Quen's University of Belfast, N. Ireland
Computer on which the program has been thoroughly tested:Intel-Pentium based PC
Operating system:Linux, DEC-Unix
Programming language used:C, FORTRAN 77
Memory required to execute with typical data:<100 kB
No. of bits in a word:32
Has the code been vectorized?:no
Number of lines in distributed program, including test data, etc.:2567
Number of bytes in distributed program, including test data, etc.:25 690
Distribution format:tar.gz
Other procedures used in PRESHOWER
:IGRF N.A. Tsyganenko, National Space Science Data Center, NASA GSFC, Greenbelt, MD 20771, USA,
http://nssdc.gsfc.nasa.gov/space/model/magnetos/data-based/geopack.html, bessik, ran2 Numerical Recipes,
http://www.nr.com.
Nature of the physical problem:Simulation of a cascade of particles initiated by UHE photon passing through the geomagnetic field above the Earth's atmosphere.
Method of solution: The primary photon is tracked until its conversion into
e
+
e
−
pair or until it reaches the upper atmosphere. If conversion occurred each individual particle in the resultant preshower is checked for either bremsstrahlung radiation (electrons) or secondary gamma conversion (photons). The procedure ends at the top of atmosphere and the shower particle data are saved.
Restrictions on the complexity of the problem: Gamma conversion into particles other than electron pair has not been taken into account.
Typical running time: 100 preshower events with primary energy
10
20
eV
require a 800 MHz CPU time of about 50 min, with
10
21
eV
the simulation time for 100 events grows up to 500 min.
Rutile TiO
2
and Eskolaite Cr
2
O
3
powders were mechanically mixed and fed into the plasma jet simultaneously. The influence of the ratio of components on behavior of the plasma-sprayed coatings was ...observed using two different compositions, both at two different feeding distances. The produced coatings were analyzed by XRD, SEM, XPS, and light microscopy. Electrical resistivity was measured at voltages from 1 to 100 V. Photocatalytic decomposition of butane on the coatings was studied using visible light together with a setup typically used for UV-light tests. For the coatings with high TiO
2
content, besides rutile, low anatase content was identified. The coatings with predominant Cr
2
O
3
exhibited lower porosity and higher hardness. All coatings are relatively efficient photocatalysts for butane decomposition. Moreover, they have good mechanical properties governed predominantly by Cr
2
O
3
content as the harder component. It was proven that the spray process led to obtaining of robust photocatalytically active coatings.
The light intensity distribution in a shower image and its implications to the primary energy reconstructed by the fluorescence technique are studied. Based on detailed CORSIKA energy deposit ...simulations, a universal analytical formula is derived for the lateral distribution of light in the shower image and a correction factor is obtained to account for the fraction of shower light falling into outlying pixels in the detector. The expected light profiles and the corresponding correction of the primary shower energy are illustrated for several typical event geometries. This correction of the shower energy can exceed 10%, depending on shower geometry.
Accumulative roll bonding (ARB) allows production of large amounts of ultra-fine grained materials. Therefore, ARB is suitable for industrial applications. Refinement efficiency is improved when the ...input materials contain fine particles, such as in twin-roll cast (TRC) alloys. The effect of the ARB temperature on bond strength, microstructure, properties and thermal stability of a TRC Al–Fe–Mn–Si alloy was studied. After two cycles at 200
°C, grain sizes of 0.4–0.8
μm are achieved along with areas of grain sizes of 0.08–0.3
μm. The hardness increases significantly during first two ARB cycles and afterwards it increases less. Processing at higher temperatures produces a better bonding but smaller hardness increments. Partial recrystallization during heating above 250
°C results in a less effective grain refinement depending on the annealing temperature and on the number of cycles. The thermal stability of the samples processed at 250
°C is better as compared to higher temperatures and to conventional cold rolling.
An ultra-fine grained (UFG) material was prepared from a twin-roll cast (TRC) Al–Fe–Mn–Si (AA8006) sheet using accumulative roll-bonding (ARB) process. After initial failures to achieve good sheet ...bonding, five cycles of ARB at 200
°C were successfully performed. Scanning electron microscopy (Electron Backscatter Diffraction) and transmission electron microscopy (TEM) were used for the characterization of subgrain and grain structures of ARB processed samples. The strength of ARB sheets was evaluated by microhardness measurements. Very fine grain structure (0.4–0.8
μm) with large disorientation was observed after two cycles of ARB. In two samples, areas with extremely fine grains 0.1–0.3
μm in diameter were found. The hardness of the alloy increased from 28 to 60 HV1 after the first two cycles, but during subsequent ARB processing it rose only very slightly.
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