88 research outputs found
Cosmic rays studied with a hybrid high school detector array
The LORUN/NAHSA system is a pathfinder for hybrid cosmic ray research
combined with education and outreach in the field of astro-particle physics.
Particle detectors and radio antennae were mainly setup by students and placed
on public buildings. After fully digital data acquisition, coincidence
detections were selected. Three candidate events confirmed a working prototype,
which can be multiplied to extend further particle detector arrays on high
schools.Comment: 10 pages, 6 figures. Nigl, A., Timmermans, C., Schellart, P.,
Kuijpers, J., Falcke, H., Horneffer, A., de Vos, C. M., Koopman, Y., Pepping,
H. J., Schoonderbeek, G., Cosmic rays studied with a hybrid high school
detector array, Europhysics News (EPN), Vol. 38, No. 5, accepted on
22/08/200
VLBI observations of jupiter with the initial test station of LOFAR and the nancay decametric array
AIMS: To demonstrate and test the capability of the next generation of
low-frequency radio telescopes to perform high resolution observations across
intra-continental baselines. Jupiter's strong burst emission is used to perform
broadband full signal cross-correlations on time intervals of up to hundreds of
milliseconds. METHODS: Broadband VLBI observations at about 20 MHz on a
baseline of ~50000 wavelengths were performed to achieve arcsecond angular
resolution. LOFAR's Initial Test Station (LOFAR/ITS, The Netherlands) and the
Nancay Decametric Array (NDA, France) digitize the measured electric field with
12 bit and 14 bit in a 40 MHz baseband. The fine structure in Jupiter's signal
was used for data synchronization prior to correlation on the time-series data.
RESULTS: Strong emission from Jupiter was detected during snapshots of a few
seconds and detailed features down to microsecond time-scales were identified
in dynamic spectra. Correlations of Jupiter's burst emission returned strong
fringes on 1 ms time-scales over channels as narrow as a hundred kilohertz
bandwidth. CONCLUSIONS: Long baseline interferometry is confirmed at low
frequencies, in spite of phase shifts introduced by variations in ionospheric
propagation characteristics. Phase coherence was preserved over tens to
hundreds of milliseconds with a baseline of ~700 km. No significant variation
with time was found in the correlations and an estimate for the fringe
visibility of 1, suggested that the source was not resolved. The upper limit on
the source region size of Jupiter Io-B S-bursts corresponds to an angular
resolution of ~3 arcsec. Adding remote stations to the LOFAR network at
baselines up to thousand kilometers will provide 10 times higher resolution
down to an arcsecond.Comment: 6 pages, 4 figures. Nigl, A., Zarka, P., Kuijpers, J., Falcke, H.,
Baehren, L., VLBI observations of Jupiter with the Initial Test Station of
LOFAR and the Nancay Decametric Array, A&A, 471, 1099-1104, accepted on
31/05/200
Air Shower Measurements with LOFAR
Air showers from cosmic rays emit short, intense radio pulses. LOFAR is a new
radio telescope, that is being built in the Netherlands and Europe. Designed
primarily as a radio interferometer, the core of LOFAR will have a high density
of radio antennas, which will be extremely well calibrated. This makes LOFAR a
unique tool for the study of the radio properties of single air showers.
Triggering on the radio emission from air showers means detecting a short
radio pulse and discriminating real events from radio interference. At LOFAR we
plan to search for pulses in the digital data stream - either from single
antennas or from already beam-formed data - and calculate several parameters
characterizing the pulse shape to pick out real events in a second stage. In
addition, we will have a small scintillator array to test and confirm the
performance of the radio only trigger.Comment: Proceedings of the ARENA 2008 workshop, to be published in NIM
The LOPES experiment - recent results, status and perspectives
The LOPES experiment at the Karlsruhe Institute of Technology has been taking
radio data in the frequency range from 40 to 80 MHz in coincidence with the
KASCADE-Grande air shower detector since 2003. Various experimental
configurations have been employed to study aspects such as the energy scaling,
geomagnetic dependence, lateral distribution, and polarization of the radio
emission from cosmic rays. The high quality per-event air shower information
provided by KASCADE-Grande has been the key to many of these studies and has
even allowed us to perform detailed per-event comparisons with simulations of
the radio emission. In this article, we give an overview of results obtained by
LOPES, and present the status and perspectives of the ever-evolving experiment.Comment: Proceedings of the ARENA2010 conference, Nantes, Franc
Air Shower Measurements with the LOPES Radio Antenna Array
LOPES is set up at the location of the KASCADE-Grande extensive air shower
experiment in Karlsruhe, Germany and aims to measure and investigate radio
pulses from Extensive Air Showers. Since radio waves suffer very little
attenuation, radio measurements allow the detection of very distant or highly
inclined showers. These waves can be recorded day and night, and provide a
bolometric measure of the leptonic shower component. LOPES is designed as a
digital radio interferometer using high bandwidths and fast data processing and
profits from the reconstructed air shower observables of KASCADE-Grande. The
LOPES antennas are absolutely amplitude calibrated allowing to reconstruct the
electric field strength which can be compared with predictions from detailed
Monte Carlo simulations. We report about the analysis of correlations present
in the radio signals measured by the LOPES 30 antenna array. Additionally,
LOPES operates antennas of a different type (LOPES-STAR) which are optimized
for an application at the Pierre Auger Observatory. Status, recent results of
the data analysis and further perspectives of LOPES and the possible large
scale application of this new detection technique are discussed.Comment: 8 pages, 10 figures, Contribution to the Arena 2008 conference, Rome,
June 200
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
Radio Emission in Atmospheric Air Showers: First Measurements with LOPES-30
When Ultra High Energy Cosmic Rays interact with particles in the Earth's
atmosphere, they produce a shower of secondary particles propagating toward the
ground. LOPES-30 is an absolutely calibrated array of 30 dipole antennas
investigating the radio emission from these showers in detail and clarifying if
the technique is useful for largescale applications. LOPES-30 is co-located and
measures in coincidence with the air shower experiment KASCADE-Grande. Status
of LOPES-30 and first measurements are presented.Comment: Proceedings of ARENA 06, June 2006, University of Northumbria, U
Radio detection of cosmic ray air showers with LOPES
In the last few years, radio detection of cosmic ray air showers has
experienced a true renaissance, becoming manifest in a number of new
experiments and simulation efforts. In particular, the LOPES project has
successfully implemented modern interferometric methods to measure the radio
emission from extensive air showers. LOPES has confirmed that the emission is
coherent and of geomagnetic origin, as expected by the geosynchrotron
mechanism, and has demonstrated that a large scale application of the radio
technique has great potential to complement current measurements of ultra-high
energy cosmic rays. We describe the current status, most recent results and
open questions regarding radio detection of cosmic rays and give an overview of
ongoing research and development for an application of the radio technique in
the framework of the Pierre Auger Observatory.Comment: 8 pages; Proceedings of the CRIS2006 conference, Catania, Italy; to
be published in Nuclear Physics B, Proceedings Supplement
Radio emission of highly inclined cosmic ray air showers measured with LOPES
LOPES-10 (the first phase of LOPES, consisting of 10 antennas) detected a
significant number of cosmic ray air showers with a zenith angle larger than
50, and many of these have very high radio field strengths. The most
inclined event that has been detected with LOPES-10 has a zenith angle of
almost 80. This is proof that the new technique is also applicable
for cosmic ray air showers with high inclinations, which in the case that they
are initiated close to the ground, can be a signature of neutrino events.Our
results indicate that arrays of simple radio antennas can be used for the
detection of highly inclined air showers, which might be triggered by
neutrinos. In addition, we found that the radio pulse height (normalized with
the muon number) for highly inclined events increases with the geomagnetic
angle, which confirms the geomagnetic origin of radio emission in cosmic ray
air showers.Comment: A&A accepte
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