The Auger Engineering Radio Array (AERA) is an enhancement of the Pierre Auger Observatory in Argentina. Covering about 17km2, 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 10EeV, i.e., significantly higher energies than preceding radio arrays.
The Auger Engineering Radio Array (AERA) is currently detecting cosmic rays of energies at and above 1017 eV at the Pierre Auger Observatory, by triggering on the radio emission produced in the ...associated air showers. The radio-detection technique must cope with a significant background of man-made radio-frequency interference, but can provide information on shower development with a high duty cycle. We discuss our techniques to handle the challenges of self-triggered radio detection in a low-power autonomous array, including triggering and filtering algorithms, data acquisition design, and communication systems.
In this paper we present first results of the efficiency of the adaptive FIR filter based on the linear prediction (LP) for a suppression of radio frequency interference (RFI), deployed in real AERA ...(Auger Engineering Radio Array) station on pampas, with a comparison to the currently used IIR notch filter with constant coefficients. The filter has been installed in several radio stations in the AERA experiment. AERA observes coherent radio emission from extensive air showers induced by ultra-high-energy cosmic rays to make a detailed study of the development of the electromagnetic part of air showers. Radio signals provide complementary information to that obtained from Auger surface detectors, which are predominantly sensitive to the particle content of an air shower at the surface. The radio signals from air showers are caused by the coherent emission due to geomagnetic and charge-excess processes. These emissions can be observed in the frequency band between 10 - 100 MHz. However, this frequency range is significantly contaminated by narrow-band RFI and other human-made distortions. A FIR filter implemented in the FPGA logic segment of the front-end electronics of a radio sensor significantly improves the signal-to-noise ratio. Theoretical calculations show a high efficiency of this filter for mono-carrier as well as for standard FM radio contaminations. The laboratory tests, performed on an Altera development kit confirmed the theoretical expectations. The coefficients for the linear predictor are dynamically refreshed and calculated in a Voipac PXA270M ARM processor, which is implemented on a daughter-board placed in the same digital unit as the FPGA. Laboratory tests confirms the stability of the filter. Using constant LP coefficients the suppression efficiency remains the same for hours, which corresponds to more than 10 12 clock cycles. We compare in real conditions several variants of the LP FIR filter with various lengths and various coefficients widths (due to fixed-point representations in the FPGA logic) with the aim to minimise the power consumption for the radio station while keeping sufficient accuracy for noise reduction.
We present a trigger based on a pipelined artificial neural network implemented in a large FPGA which after learning can recognize different types of waveforms from the Pierre Auger surface ...detectors. The structure of an artificial neural network algorithm being developed on a MATLAB platform has been implemented into the fast logic of the largest Cyclone V E FPGA used for the prototype of the Front-End Board for the Auger-Beyond-2015. Several algorithms were tested, from which the Levenberg-Marquardt one (trainlm) seems to be the most efficient. The network was taught: a) to recognize "old" showers learning from real Auger very inclined showers (positive markers) and real standard showers especially triggered by Time over Threshold (negative marker), b) to recognize "young" showers from simulated "young" events (positive markers) and standard Auger events as a negative reference. A three-layer neural network being taught by real very inclined Auger showers shows a good efficiency in pattern recognition of 16-point traces with profiles characteristic for "old" showers. Nevertheless, preliminary simulations of showers with CORSIKA and the response of the water Cherenkov tanks with OffLine suggest that for neutrino showers starting a development deeply in the atmosphere and with relatively small initial energy ~ 10 18 eV, signal waveforms are not to long and a 16-point analysis should be sufficient for recognition of "young" showers. The neural network algorithm can significantly support detection at small energies, where a denser neutrino stream is expected. For higher energies traces are longer, however, the detector response is strong enough for the showers to be detected by standard amplitude-based triggers.
Extensive Air Showers (EAS), initiated by Ultra-High-Energy Cosmic Rays (UHECRs), generate geo-synchrotron and geo-magnetic radiations and they are, also, the source of excess charge processes. In ...the frequency range of 10 to 100 MHz, coherent radiation is formed. Many experiments use the radio detection technique for studying EAS features. The Auger Engineering Radio Array (AERA), part of the Pierre Auger Observatory, uses hundreds of radio antennas working in the frequency range of 30 to 80 MHz to support the investigation of UHECRs together with the standard surface and fluorescence detectors. The AERA radio frequency range is significantly contaminated by the human-made and usually narrow-band Radio Frequency Interference (RFI), e.g., shortwave radio transmitters. The presence of RFIs in the detected signals increases the ratio of spurious triggers; in consequence, empty data inflate the databases. This study proposes replacing the currently used IIR-notch nonadaptive filter by the delayed version of the wellknown Least Mean Squares (LMS) algorithm, which offers crucial advantage adjustment. The current study implemented 32/64-stage Delay Least Mean Squares (DLMS) filters on cost-effective Cyclone® IV and Cyclone® V as non-canonical Finite Input Response (FIR) with a sufficient safety margin for a global clock being at least 20% higher than 200 MHz, which equals the ADC sampling frequency.
We present a detailed statistical treatment of the energy calibration of hybrid air-shower detectors, which combine a surface detector array and a fluorescence detector, to obtain an unbiased ...estimate of the calibration curve. The special features of calibration data from air showers prevent unbiased results, if a standard least-squares fit is applied to the problem. We develop a general maximum-likelihood approach, based on the detailed statistical model, to solve the problem. Our approach was developed for the Pierre Auger Observatory, but the applied principles are general and can be transferred to other air-shower experiments, even to the cross-calibration of other observables. Since our general likelihood function is expensive to compute, we derive two approximations with significantly smaller computational cost. In the recent years both have been used to calibrate data of the Pierre Auger Observatory. We demonstrate that these approximations introduce negligible bias when they are applied to simulated toy experiments, which mimic realistic experimental conditions.
The paper presents first results from the Front-End Board (FEB) with the biggest Cyclone ® V E FPGA 5CEFA9F31I7N, supporting 8 channels sampled up to 250 MSps @ 14-bit resolution. Considered sampling ...for the planned upgrade of the Pierre Auger surface detector array is 120 MSps, however, the FEB has been developed with external anti-aliasing filters to keep a maximal flexibility. Six channels are targeted to the SD, two the rest for other experiments like: Auger Engineering Radio Array and additional muon counters. More channels and higher sampling generate larger size of registered events. We used the standard radio channel for a radio transmission from the detectors to the Central Data Acquisition Station (CDAS) to avoid at present a significant modification of a software in both sides: the detector and the CDAS (planned in a future for a final design). Several variants of the FPGA code were tested for 120, 160, 200 and even 240 MSps DAQ. Tests confirmed a stability and reliability of the FEB design in real pampas conditions with more than 40°C daily temperature variation and a strong sun exposition with a limited power budget only from a single solar panel. Seven FEBs have been deployed in a hexagon of test detectors on a dedicated Engineering Array.
AERA—the Auger Engineering Radio Array—is currently being set up at the southern site of the Pierre Auger Observatory. AERA will explore the potential of the radio-detection technique to cosmic ray ...induced air showers with respect to the next generation of large-scale surface detectors. As AERA is co-located with the low-energy enhancements of the Pierre Auger Observatory, the observation of air showers in coincidence with the Auger surface and fluorescence detector will allow to study the radio emission processes in detail and to calibrate the radio signal. Finally, the combined reconstruction of shower parameters with three independent techniques promises new insights into the nature of cosmic rays in the transition region from 10
17 to 10
19
eV.
Besides the detection of coherent radiation in the MHz frequency range, the setups AMBER—Air-shower Microwave Bremsstrahlung Experimental Radiometer—and MIDAS—MIcrowave Detection of Air Showers—prepare to check the possibility to detect air showers due the emission of molecular bremsstrahlung in the GHz range at the Auger site.
This article presents the status of the radio-detection setups and discusses their physics potential as well as experimental challenges. Special focus is laid on the first stage of AERA which is the startup to the construction of a 20
km
2 radio array.
The Pierre Auger Observatory, which is the largest air-shower experiment in the world, offers unprecedented exposure to neutral particles at the highest energies. Since the start of data collection ...more than 18 years ago, various searches for ultra-high-energy (UHE, E≳1017eV) photons have been performed, either for a diffuse flux of UHE photons, for point sources of UHE photons or for UHE photons associated with transient events such as gravitational wave events. In the present paper, we summarize these searches and review the current results obtained using the wealth of data collected by the Pierre Auger Observatory.
To understand the origin and nature of Ultra High Energy Cosmic Rays their mass composition must be known. The Pierre Auger Observatory is an instrument which provides valuable information for the ...determination of the primary mass. Different parameters that describe various characteristics of the shower development and at the same time are sensitive to the primary mass are discussed. Their energy dependence and a comparison with predictions from different models are also presented.
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