LORA: A scintillator array for LOFAR to measure extensive air showers

Thoudam, Satyendra; Buitink, S.; Corstanje, A.; Enriquez, J. E.; Falcke, H.; Frieswijk, W.; Hörandel, J. R.; Horneffer, A.; Krause, M.; Nelles, A.; Schellart, P.; Scholten, Olaf; Veen, S. ter; Akker, M. van den

doi:10.1016/j.nima.2014.08.021

Cited by 64 publications

(68 citation statements)

References 17 publications

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“…The systematic uncertainty on the energy reconstruction with the LORA particle detector array is 27%, which includes effects due to detector calibration, hadronic interaction models, and the assumed slope of the primary cosmic-ray spectrum in the CORSIKA simulations 33,39 Statistical analysis For each observed shower, we calculate:…”

Section: Systematic Effectsmentioning

confidence: 99%

A large light-mass component of cosmic rays at 1017–1017.5 electronvolts from radio observations

Buitink

Corstanje

Falcke

et al. 2016

Nature

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4Cosmic rays are the highest energy particles found in nature. Measurements of the mass composition of cosmic rays between 10 17 eV and 10 18 eV are essential to understand whether this energy range is dominated by Galactic or extragalactic sources. It has also been proposed that the astrophysical neutrino signal 1 comes from accelerators capable of producing cosmic rays of these energies 2 . Cosmic rays initiate cascades of secondary particles (air showers) in the atmosphere and their masses are inferred from measurements of the atmospheric depth of the shower maximum, X max 3 , or the composition of shower particles reaching the ground 4 .Current measurements 5 suffer from either low precision, and/or a low duty cycle. Radio detection of cosmic rays 6-8 is a rapidly developing technique 9 , suitable for determination of X max 10, 11 with a duty cycle of in principle nearly 100%. The radiation is generated by the separation of relativistic charged particles in the geomagnetic field and a negative charge excess in the shower front 6, 12 . Here we report radio measurements of X max with a mean precision of 16 g/cm 2 between 10 17 − 10 17.5 eV. Because of the high resolution in X max we can determine the mass spectrum and find a mixed composition, containing a light mass fraction of ∼ 80%. Unless the extragalactic component becomes significant already below 10 17.5 eV, our measurements indicate an additional Galactic component dominating at this energy range.Observations were made with the Low Frequency Array (LOFAR 13 ), a radio telescope consisting of thousands of crossed dipoles, with built-in air shower detection capability 14 . LOFAR records the radio signals from air showers continuously while running astronomical observations simultaneously. It comprises a scintillator array (LORA), that triggers the readout of buffers, stor-5 ing the full waveforms received by all antennas.We have selected air showers from the period June 2011 -January 2015 with radio pulses in at least 192 antennas. The total uptime was ∼150 days, limited by construction and commissioning of the telescope. Showers that occurred within an hour from lightning activity, or have a polarisation pattern that is indicative of influences from atmospheric electric fields are excluded from the sample 15 .Radio intensity patterns from air showers are asymmetric due to the interference between geomagnetic and charge excess radiation. They can be reproduced from first principles by summing the radio contributions of all electrons and positrons in the shower. We use the radio simulation code CoREAS 16 , a plug-in of CORSIKA 17 , which follows this approach.It has been shown that X max can be accurately reconstructed from densely sampled radio measurements 18 . We use a hybrid approach, simultaneously fitting the radio and particle data. The radio component is very sensitive to X max , while the particle component is used for the energy measurement.The fit contains four free parameters: the shower core position (x, y), and scaling factors for the partic...

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Section: Systematic Effectsmentioning

confidence: 99%

A large light-mass component of cosmic rays at 1017–1017.5 electronvolts from radio observations

Buitink

Corstanje

Falcke

et al. 2016

Nature

Self Cite

152

149

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“…Figure 1 shows the distribution of the 50 th percentile frequency as a function of distance to the shower axis in the shower plane for both one simulated event and the corrisponding real event. The detected event has a primary energy of (1.7 ± 0.8) · 10 17 eV as reconstructed by the LORA scintillator array, and a value of the atmospheric depth where the cascade reaches its maximum development X max = (763 ± 38) g/cm 2 as reconstructed by the Lateral Distribution Function method [11]. This real event has been compared with simulations, in particular with the one having the value of X max closest to the real one, i.e.…”

Section: Analysis and Resultsmentioning

confidence: 99%

“…Measurements of cosmic rays are performed mostly by using signals from the Low Band Antennas (LBAs) which operate in the frequency range 10 − 90 MHz. The LOFAR central array is instrumented with 20 scintillator detectors, the so-called LORA array [2], which provides triggers for cosmic ray data acquisition, and allows to reconstruct the arrival direction and the energy of primary particles. The LOFAR array detects cosmic rays in the energy range 10 16 − 10 18 eV.…”

Section: Introductionmentioning

confidence: 99%

A study of radio frequency spectrum emitted by high energy air showers with LOFAR

et al. 2017

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Abstract. The high number density of radio antennas at the LOFAR core in Northern Netherlands allows to detect radio signals emitted by cosmic ray induced air showers, and to characterize the geometry of the observed cascade in a detailed way. We present here a study of the radio frequency spectrum in the 30 − 80 MHz regime, and its correlation with some geometrical parameters of the extensive air shower. An important goal of this study is to find a correlation between the frequency spectrum and the primary particle type. Preliminary results on how the frequency spectrum changes as function of distance to the shower axis, and as function of primary particles mass composition are shown. The final aim of this study is to find a method to infer information of primary cosmic rays in an independent way from the well-established fluorescence and surface detector techniques, in view of affirming the radio detection technique as reliable method for the study of high energy cosmic rays.

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“…It produces extremely detailed air shower radio data, by using the dense core region, or superterp, where 384 antennas are located within a circle of 320 m diameter. A particle array, LORA [8], has been installed in the core and is used for triggering and reconstruction. Each antenna contains a ring buffer which is read-out in case of a trigger.…”

Section: Introductionmentioning

confidence: 99%

Cosmic Ray Mass Measurements with LOFAR

et al. 2017

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Abstract. In the dense core of LOFAR individual air showers are detected by hundreds of dipole antennas simultaneously. We reconstruct X max by using a hybrid technique that combines a two-dimensional fit of the radio profile to CoREAS simulations and a one-dimensional fit of the particle density distribution. For high-quality detections, the statistical uncertainty on X max is smaller than 20 g/cm 2 . We present results of cosmic-ray mass analysis in the energy regime of 10 17 -10 17.5 eV. This range is of particular interest as it may harbor the transition from a Galactic to an extragalactic origin of cosmic rays.

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LORA: A scintillator array for LOFAR to measure extensive air showers

Cited by 64 publications

References 17 publications

A large light-mass component of cosmic rays at 1017–1017.5 electronvolts from radio observations

A large light-mass component of cosmic rays at 1017–1017.5 electronvolts from radio observations

A study of radio frequency spectrum emitted by high energy air showers with LOFAR

Cosmic Ray Mass Measurements with LOFAR

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