arXiv subjects

Frank G. Schröder

Publications and source records attributed to Frank G. Schröder.

26 records · Page 2Linked to original sources

arXiv2017

Overview on the Tunka-Rex antenna array for cosmic-ray air showers (ICRC 2017)

Tunka-Rex is a $3\,$km$^2$ large antenna array for cosmic-ray air showers at the TAIGA observatory in Siberia close to Lake Baikal. In autumn 2016 Tunka-Rex has been extended to a total of 63 stations, each equipped with SALLA antennas for two polarization directions operating in the band of $30-80\,$MHz. All antenna stations are triggered by the other cosmic-ray detectors at the site, i.e., Tunka-Rex runs in coincidence with the Tunka-Grande array of scintillation detectors and during clear nights additionally in coincidence with the Tunka-133 non-imaging air-Cherenkov array. Compared to previous measurements, the day-time and bad-weather trigger increases the annual exposure by an order of magnitude, and the higher density of antennas is expected to increase the accuracy - in particular for the cosmic-ray mass composition. In addition to the status and potential of Tunka-Rex an overview of recently published results will be presented: by comparing the radio and the air-Cherenkov signals of the same air showers, the Tunka-Rex precision for the most important shower parameters has been determined. The direction precision is about $1^\circ$, the precision for the depth of the shower maximum, $X_\mathrm{max}$, is better than $40\,$g/cm$^2$ for high-quality events, and the energy precision is better than $15\,\%$. A rough estimation of the shower energy and of $X_\mathrm{max}$ is even possible with only a single antenna station when using the shower geometry measured by Tunka-133. Moreover, by using exactly the same external calibration source for the antennas as at the LOPES experiment we have shown that the absolute energy scale of different air-shower arrays can be compared with each other at $10\,\%$ precision. Thus, Tunka-Rex will improve the total accuracy of TAIGA for the energy as well as for the mass composition of cosmic rays of energy above $0.1\,$EeV.

astro-ph.HE↗

arXiv2017

Review on Cosmic-Ray Radio Detection (VULCANO 2016)

Extensive air showers still are our only access to the highest-energy particles in the universe, namely cosmic-ray nuclei with energies up to several 100 EeV. Studying open questions in cosmic-ray physics, like their yet unknown origin requires the reconstruction of the energy and mass of the primary particles from the air-shower measurements. Great progress has been achieved lately in the development of the radio detection technique for this purpose. There now is a consistent picture of the mechanisms behind the radio emission, which is in agreement with measurements. Several second-generation, digital antenna arrays are operating in different parts of the world not only aiming at the further development of the technique, but also contributing to cosmic-ray physics at energies above 100 PeV. Recently it has been demonstrated experimentally that radio detection can compete in precision with established techniques for air showers, like the measurement of secondary particles on ground, or fluorescence and Cherenkov light emitted by air showers. Consequently, cosmic-ray observatories can benefit from radio extensions to maximize their total measurement accuracy.

astro-ph.HE↗

arXiv2017

Ultimate precision in cosmic-ray radio detection --- the SKA

As of 2023, the low-frequency part of the Square Kilometre Array will go online in Australia. It will constitute the largest and most powerful low-frequency radio-astronomical observatory to date, and will facilitate a rich science programme in astronomy and astrophysics. With modest engineering changes, it will also be able to measure cosmic rays via the radio emission from extensive air showers. The extreme antenna density and the homogeneous coverage provided by more than 60,000 antennas within an area of one km$^2$ will push radio detection of cosmic rays in the energy range around 10$^{17}$ eV to ultimate precision, with superior capabilities in the reconstruction of arrival direction, energy, and an expected depth-of-shower-maximum resolution of 6~g/cm${^2}$.

astro-ph.IM↗

arXiv2017

Status of air-shower measurements with sparse radio arrays (ARENA 2016)

This proceeding gives a summary of the current status and open questions of the radio technique for cosmic-ray air showers, assuming that the reader is already familiar with the principles. It includes recent results of selected experiments not present at this conference, e.g., LOPES and TREND. Current radio arrays like AERA or Tunka-Rex have demonstrated that areas of several km^2 can be instrumented for reasonable costs with antenna spacings of the order of 200 m. For the energy of the primary particle such sparse antenna arrays can already compete in absolute accuracy with other precise techniques, like the detection of air-fluorescence or air-Cherenkov light. With further improvements in the antenna calibration, the radio detection might become even more accurate. For the atmospheric depth of the shower maximum, Xmax, currently only the dense array LOFAR features a precision similar to the fluorescence technique, but analysis methods for the radio measurement of Xmax are still under development. Moreover, the combination of radio and muon measurements is expected to increase the accuracy of the mass composition, and this around-the-clock recording is not limited to clear nights as are the light-detection methods. Consequently, radio antennas will be a valuable add-on for any air shower array targeting the energy range above 100 PeV.

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arXiv2017

Radio detection of Extensive Air Showers (ECRS 2016)

Detection of the mostly geomagnetically generated radio emission of cosmic-ray air showers provides an alternative to air-Cherenkov and air-fluorescence detection, since it is not limited to clear nights. Like these established methods, the radio signal is sensitive to the calorimetric energy and the position of the maximum of the electromagnetic shower component. This makes antenna arrays an ideal extension for particle-detector arrays above a threshold energy of about 100 PeV of the primary cosmic-ray particles. In the last few years the digital radio technique for cosmic-ray air showers again made significant progress, and there now is a consistent picture of the emission mechanisms confirmed by several measurements. Recent results by the antenna arrays AERA and Tunka-Rex confirm that the absolute accuracy for the shower energy is as good as the other detection techniques. Moreover, the sensitivity to the shower maximum of the radio signal has been confirmed in direct comparison to air-Cherenkov measurements by Tunka-Rex. The dense antenna array LOFAR can already compete with the established techniques in accuracy for cosmic-ray mass-composition. In the future, a new generation of radio experiments might drive the field: either by providing extremely large exposure for inclined cosmic-ray or neutrino showers or, like the SKA core in Australia with its several 10,000 antennas, by providing extremely detailed measurements.

astro-ph.HE↗

arXiv2017

Radio detection of Cosmic-Ray Air Showers and High-Energy Neutrinos

This review provides an introduction to the radio emission by particle cascades, an overview on the various experiments, and explains methods for the radio measurement of air-shower properties. Furthermore, potential applications of the radio technique in high-energy astroparticle physics are discussed. Due to the successful operation of digital radio experiments and due to the improved quantitative understanding of the emission, radio detection is back on the list of promising techniques for extensive air showers. With a threshold of about 100 PeV radio detectors are particularly useful to study the highest-energy galactic cosmic rays and ultra-high-energy extragalactic particles of all types. Various antenna arrays like LOPES, CODALEMA, AERA, LOFAR, and Tunka-Rex have shown that radio measurements can compete in precision with other techniques, in particular for the arrival direction, the energy, and the position of the shower maximum. The scientific potential of the radio technique seems to be maximum in combination with particle detectors, which increases the total accuracy for air-shower measurements. This is crucial for a better separation of different primary particles, like gamma-ray photons, neutrinos, or different types of nuclei. In addition to air-showers the radio technique can be used for particle cascades in dense media. Several pioneering experiments like ARA, ARIANNA, and ANITA are currently searching for cascades induced by ultra-high-energy neutrinos in ice. Moreover, several future projects aim at both, high-energy cosmic-rays and neutrinos. SKA will search for neutrino and cosmic-ray initiated cascades in the lunar regolith and provide unprecedented detail for air-shower measurements. Finally, radio detectors with huge exposure like GRAND, SWORD, or EVA are being considered to study the highest energy cosmic rays and neutrinos.

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arXiv2016

Radio detection of high-energy cosmic rays with the Auger Engineering Radio Array (PISA 2015)

The Auger Engineering Radio Array (AERA) is an enhancement of the Pierre Auger Observatory in Argentina. Covering about View the $17\,$km$^2$, AERA is the world-largest antenna array for cosmic-ray observation. It consists of more than 150 antenna stations detecting the radio signal emitted by air showers, i.e., cascades of secondary particles caused by primary cosmic rays hitting the atmosphere. At the beginning, technical goals had been in focus: first of all, the successful demonstration that a large-scale antenna array consisting of autonomous stations is feasible. Moreover, techniques for calibration of the antennas and time calibration of the array have been developed, as well as special software for the data analysis. Meanwhile physics goals come into focus. At the Pierre Auger Observatory air showers are simultaneously detected by several detector systems, in particular water-Cherenkov detectors at the surface, underground muon detectors, and fluorescence telescopes, which enables cross-calibration of different detection techniques. For the direction and energy of air showers, the precision achieved by AERA is already competitive; for the type of primary particle, several methods are tested and optimized. By combining AERA with the particle detectors we aim for a better understanding of cosmic rays in the energy range from approximately $0.3$ to $10\,$EeV, i.e., significantly higher energies than preceding radio arrays.

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arXiv2009

Time Calibration of the Radio Air Shower Array LOPES

LOPES is a digitally read out antenna array consisting of 30 calibrated dipole antennas. It is located at the site of the KASCADE-Grande experiment at Forschungszentrum Karlsruhe and measures the radio emission of cosmic ray air showers in the frequency band from 40 to 80 MHz. LOPES is triggered by KASCADE and uses the KASCADE reconstruction of the shower axis as an input for the analysis of the radio pulses. Thereby LOPES works as an interferometer when the signal of all antennas is digitally merged to form a beam into the shower direction. To be sensitive to the coherence of the radio signal, a precise time calibration with an accuracy in the order of 1 ns is required. Thus, it is necessary to know the delay of each antenna which is time and frequency dependent. Several calibration measurements are performed to correct for this delay in the analysis: The group delay of every antenna is measured regularly (roughly once per year) by recording a test pulse which is emitted at a known time. Furthermore, the delay is monitored continuously by the so called phase calibration method: A beacon (a dipole antenna) emits continuously two sine waves at 63.5 MHz and 68.1 MHz. By that a variation of the delay can be detected in a subsequent analysis of the radio events as a change of the phase at these frequencies. Finally, the dispersion of the analog electronics has been measured to account for the frequency dependence of the delay.

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