26 research outputs found
Absolute calibration of the LOPES antenna system
Radio emission in extensive air showers arises from an interaction with the
geomagnetic field and is subject of theoretical studies. This radio emission
has advantages for the detection of high energy cosmic rays compared to
secondary particle or fluorescence measurement methods. Radio antennas like the
LOPES30 antenna system are suited to investigate this emission process by
detecting the radio pulses. The characteristic observable parameters like
electric field strength and pulse length require a calibration which was done
with a reference radio source resulting in an amplification factor representing
the system behavior in the environment of the KASCADE-Grande experiment.
Knowing the amplification factor and the gain of the LOPES antennas LOPES30 is
calibrated absolutely for systematic analyses of the radio emission.Comment: 5 pages, Proceedings of International Workshop on Acoustic and Radio
EeV Neutrino detection Activities: ARENA, May 17-19, 2005, DESY Zeuthe
Progress in Air Shower Radio Measurements: Detection of Distant Events
Data taken during half a year of operation of 10 LOPES antennas (LOPES-10),
triggered by EAS observed with KASCADE-Grande have been analysed. We report
about the analysis of correlations of radio signals measured by LOPES-10 with
extensive air shower events reconstructed by KASCADE-Grande, including shower
cores at large distances. The efficiency of detecting radio signals induced by
air showers up to distances of 700 m from the shower axis has been
investigated. The results are discussed with special emphasis on the effects of
the reconstruction accuracy for shower core and arrival direction on the
coherence of the measured radio signal. In addition, the correlations of the
radio pulse amplitude with the primary cosmic ray energy and with the lateral
distance from the shower core are studied.Comment: Accepted for publication in Astroparticle Physic
Detection and imaging of atmospheric radio flashes from cosmic ray air showers
The nature of ultrahigh-energy cosmic rays (UHECRs) at energies >10^20 eV
remains a mystery. They are likely to be of extragalactic origin, but should be
absorbed within ~50 Mpc through interactions with the cosmic microwave
background. As there are no sufficient powerful accelerators within this
distance from the Galaxy, explanations for UHECRs range from unusual
astrophysical sources to exotic string physics. Also unclear is whether UHECRs
consist of protons, heavy nuclei, neutrinos or gamma-rays. To resolve these
questions, larger detectors with higher duty cycles and which combine multiple
detection techniques are needed. Radio emission from UHECRs, on the other hand,
is unaffected by attenuation, has a high duty cycle, gives calorimetric
measurements and provides high directional accuracy. Here we report the
detection of radio flashes from cosmic-ray air showers using low-cost digital
radio receivers. We show that the radiation can be understood in terms of the
geosynchrotron effect. Our results show that it should be possible to determine
the nature and composition of UHECRs with combined radio and particle
detectors, and to detect the ultrahigh-energy neutrinos expected from flavour
mixing.Comment: Nature, May 19, 2005 issue (PDF, 14 pages),
http://www.astro.ru.nl/lopes/?loc=publication
Frequency spectra of cosmic ray air shower radio emission measured with LOPES
Aims. We wish to study the spectral dependence of the radio emission from cosmic-ray air showers around .Methods. We observe short radio pulses in a broad frequency band with the dipole-interferometer LOPES (LOFAR Prototype Station), which is triggered by a particle detector array named Karlsruhe Shower Core and Array Detector (KASCADE). LOFAR is the Low Frequency Array. For this analysis, 23 strong air shower events are selected using parameters from KASCADE. The radio data are digitally beam-formed before the spectra are determined by sub-band filtering and fast Fourier transformation.Results. The resulting electric field spectra fall off to higher frequencies. An average electric field spectrum is fitted with an exponential and , or alternatively, with a power law and a spectral index of . The spectral slope obtained is not consistent within uncertainties and it is slightly steeper than the slope obtained from Monte Carlo simulations based on air showers simulated with CORSIKA (Cosmic Ray Simulations for KASCADE). For the analyzed sample of LOPES events, we do not find any significant dependence of the spectral slope on the electric field amplitude, the azimuth angle, the zenith angle, the curvature radius, nor on the average distance of the antennae from the shower core position. But one of the strongest events was measured during thunderstorm activity in the vicinity of LOPES and shows the longest pulse length measured of and a spectral slope of .Conclusions. We show with two different methods that frequency spectra from air shower radio emission can be reconstructed on event-by-event basis, with only two dozen dipole antennae simultaneously over a broad range of frequencies. According to the obtained spectral slopes, the maximum power is emitted below 40 MHz. Furthermore, the decrease in power to higher frequencies indicates a loss in coherence determined by the shower disc thickness. We conclude that a broader bandwidth, larger collecting area, and longer baselines, as will be provided by LOFAR, are necessary to further investigate the relation of the coherence, pulse length, and spectral slope of cosmic ray air showers
Reconstruction of the energy and depth of maximum of cosmic-ray air showers from LOPES radio measurements
Contains fulltext :
132546.pdf (preprint version ) (Open Access
Thunderstorm observations by air-shower radio antenna arrays
Contains fulltext :
92498.pdf (publisher's version ) (Closed access)
Contains fulltext :
92498-1.pdf (preprint version ) (Open Access
Measuring the radio emission of cosmic ray air showers with LOPES
Contains fulltext :
83678.pdf (publisher's version ) (Closed access
Lateral distribution of the radio signal in extensive air showers measured with LOPES.
Contains fulltext :
83439.pdf (preprint version ) (Open Access)Scientific publicatio
Investigations of the radio signal of inclined showers with lopes
Contains fulltext :
93909.pdf (publisher's version ) (Closed access