Redukcja zakłóceń interferencyjnych w detektorach radiowych Obserwatorium Pierre Auger

W ciągu ostatnich lat dokonany został ogromny postęp w elektronice, który umożliwił rozwój technik detekcji pęków atmosferycznych, inicjowanych przez cząstki promieniowania kosmicznego. Postęp ten spowodował również, że możliwa stała się skuteczna detekcja emisji radiowej z pęków atmosferycznych. Działające w czasie rzeczywistym stacje radiowe umożliwiają zbadanie rozwoju pęków od dotychczas nieosiągalnej strony i są alternatywą dla detektorów fluorescencyjnych w detekcji hybrydowej. Pomiary dokonywane przez stacje radiowe są w znacznym stopniu skażone zakłóceniami interferencyjnymi, co skutkuje zniekształceniem zarejestrowanego sygnału i w konsekwencji zafałszowaniem danych, które można w ten sposób uzyskać. Z tego powodu, w detektorach radiowych używane są filtry cyfrowe, działające w czasie rzeczywistym. Skuteczne filtrowanie sygnałów radiowych emitowanych przez pęki atmosferyczne, może być jednak osiągnięte na wiele sposobów. Dzięki coraz wydajniejszym układom elektronicznym możliwa jest implementacja coraz bardziej skomplikowanych algorytmów filtrujących, które pozwalają na skuteczniejszą redukcję zakłóceń interferencyjnych. W eksperymencie AERA (Auger Engineering Radio Array), dodatkowymi uwarunkowaniami są również zużycie energii oraz zasobów układów FPGA. Wybór najlepszego filtra polega zatem na odpowiednim zoptymalizowaniu wymienionych czynników. Niniejsza praca skupia się na omówieniu nowej metody redukcji zakłóceń interferencyjnych, bazującej na liniowej predykcji sygnału. Szczegółowo omówione zostały techniczne aspekty jej implementacji w strukturę FPGA, a także uzasadniony został wybór używanych przez nią parametrów. Sprawdzone i przedyskutowane zostały różne warianty kodu, zarówno pod względem szybkości obliczeń, jak i poboru mocy oraz zużycia zasobów. Optymalizacja parametrów uwzględniała zagadnienie minimalizacji wpływu pomiarów na rejestrowane dane. Wybrany wariant został sprawdzony symulacyjnie i laboratoryjnie oraz porównany z aktualnie używanymi filtrami. Szybka adaptacja do zmieniających się warunków środowiskowych, niewielkie zniekształcenia sygnału oraz wysoka skuteczność filtrowania przy akceptowalnym poziomie zużycia energii powodują, że filtr ten ma szansę być zaimplementowany w nowych układach FPGA, planowanych do użytku w związku z wymianą sprzętu elektronicznego, nadchodzącą wraz z modernizacją AERA++

Artificial Neural Network as a FPGA Trigger for a Detection of Neutrino-Induced Air Showers

Neutrinos play a fundamental role in the understanding of the origin of ultrahigh-energy cosmic rays (UHECR). They interact through charged and neutral currents in the atmosphere generating extensive air showers. However, the very low rate of events potentially generated by neutrinos is a significant challenge for detection techniques and requires both sophisticated algorithms and high-resolution hardware. We developed the FPGA trigger which is generated by a neural network. The algorithm can recognize various waveform types. It has been developed and tested on ADC traces of the Pierre Auger surface detectors. We developed the algorithm of artificial neural network on a MATLAB platform. Trained network that we implemented into the largest Cyclone V E FPGA was used for the prototype of the front-end board for the AugerPrime. We tested several variants, and the Levenberg–Marquardt algorithm (trainlm) was the most efficient. The network was trained: (a) to recognize ‘old’ very inclined showers (real Auger data were used as patterns for both positive and negative markers: for reconstructed inclined showers and for triggered by time over threshold (ToT), respectively, (b) to recognize ‘neutrino-induced showers’. Here, we used simulated data for positive markers and vertical real showers for negative ones.This work is supported by the National Science Centre (Poland) under NCN Grant No. 2013/08/ M/ST9/00322. The authors would like to thank the Pierre Auger Collaboration for an opportunity of using the CORSIKA and offline simulation packages

Measurement of the cosmic ray spectrum above 4×10184{\times}10^{18} eV using inclined events detected with the Pierre Auger Observatory

A measurement of the cosmic-ray spectrum for energies exceeding $4{\times}10^{18}$ eV is presented, which is based on the analysis of showers with zenith angles greater than $60^{\circ}$ detected with the Pierre Auger Observatory between 1 January 2004 and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above $5.3{\times}10^{18}$ eV, the "ankle", the flux can be described by a power law $E^{-\gamma}$ with index $\gamma=2.70 \pm 0.02 \,\text{(stat)} \pm 0.1\,\text{(sys)}$ followed by a smooth suppression region. For the energy ($E_\text{s}$) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find $E_\text{s}=(5.12\pm0.25\,\text{(stat)}^{+1.0}_{-1.2}\,\text{(sys)}){\times}10^{19}$ eV.Comment: Replaced with published version. Added journal reference and DO

Energy Estimation of Cosmic Rays with the Engineering Radio Array of the Pierre Auger Observatory

The Auger Engineering Radio Array (AERA) is part of the Pierre Auger Observatory and is used to detect the radio emission of cosmic-ray air showers. These observations are compared to the data of the surface detector stations of the Observatory, which provide well-calibrated information on the cosmic-ray energies and arrival directions. The response of the radio stations in the 30 to 80 MHz regime has been thoroughly calibrated to enable the reconstruction of the incoming electric field. For the latter, the energy deposit per area is determined from the radio pulses at each observer position and is interpolated using a two-dimensional function that takes into account signal asymmetries due to interference between the geomagnetic and charge-excess emission components. The spatial integral over the signal distribution gives a direct measurement of the energy transferred from the primary cosmic ray into radio emission in the AERA frequency range. We measure 15.8 MeV of radiation energy for a 1 EeV air shower arriving perpendicularly to the geomagnetic field. This radiation energy -- corrected for geometrical effects -- is used as a cosmic-ray energy estimator. Performing an absolute energy calibration against the surface-detector information, we observe that this radio-energy estimator scales quadratically with the cosmic-ray energy as expected for coherent emission. We find an energy resolution of the radio reconstruction of 22% for the data set and 17% for a high-quality subset containing only events with at least five radio stations with signal.Comment: Replaced with published version. Added journal reference and DO

Measurement of the Radiation Energy in the Radio Signal of Extensive Air Showers as a Universal Estimator of Cosmic-Ray Energy

We measure the energy emitted by extensive air showers in the form of radio emission in the frequency range from 30 to 80 MHz. Exploiting the accurate energy scale of the Pierre Auger Observatory, we obtain a radiation energy of 15.8 \pm 0.7 (stat) \pm 6.7 (sys) MeV for cosmic rays with an energy of 1 EeV arriving perpendicularly to a geomagnetic field of 0.24 G, scaling quadratically with the cosmic-ray energy. A comparison with predictions from state-of-the-art first-principle calculations shows agreement with our measurement. The radiation energy provides direct access to the calorimetric energy in the electromagnetic cascade of extensive air showers. Comparison with our result thus allows the direct calibration of any cosmic-ray radio detector against the well-established energy scale of the Pierre Auger Observatory.Comment: Replaced with published version. Added journal reference and DOI. Supplemental material in the ancillary file

Multiple Scenario Generation of Subsurface Models:Consistent Integration of Information from Geophysical and Geological Data throuh Combination of Probabilistic Inverse Problem Theory and Geostatistics

Neutrinos with energies above 1017 eV are detectable with the Surface Detector Array of the Pierre Auger Observatory. The identification is efficiently performed for neutrinos of all flavors interacting in the atmosphere at large zenith angles, as well as for Earth-skimming \u3c4 neutrinos with nearly tangential trajectories relative to the Earth. No neutrino candidates were found in 3c 14.7 years of data taken up to 31 August 2018. This leads to restrictive upper bounds on their flux. The 90% C.L. single-flavor limit to the diffuse flux of ultra-high-energy neutrinos with an E\u3bd-2 spectrum in the energy range 1.0 7 1017 eV -2.5 7 1019 eV is E2 dN\u3bd/dE\u3bd < 4.4 7 10-9 GeV cm-2 s-1 sr-1, placing strong constraints on several models of neutrino production at EeV energies and on the properties of the sources of ultra-high-energy cosmic rays

Observation of inclined EeV air showers with the radio detector of the Pierre Auger Observatory

International audienceWith the Auger Engineering Radio Array (AERA) of the Pierre Auger Observatory, we have observed the radio emission from 561 extensive air showers with zenith angles between 60o and 84o. In contrast to air showers with more vertical incidence, these inclined air showers illuminate large ground areas of several km2 with radio signals detectable in the 30 to 80 MHz band. A comparison of the measured radio-signal amplitudes with Monte Carlo simulations of a subset of 50 events for which we reconstruct the energy using the Auger surface detector shows agreement within the uncertainties of the current analysis. As expected for forward-beamed radio emission undergoing no significant absorption or scattering in the atmosphere, the area illuminated by radio signals grows with the zenith angle of the air shower. Inclined air showers with EeV energies are thus measurable with sparse radio-antenna arrays with grid sizes of a km or more. This is particularly attractive as radio detection provides direct access to the energy in the electromagnetic cascade of an air shower, which in case of inclined air showers is not accessible by arrays of particle detectors on the ground

Erratum: Combined fit of spectrum and composition data as measured by the Pierre Auger Observatory

We present a combined fit of a simple astrophysical model of UHECR sources to both the energy spectrum and mass composition data measured by the Pierre Auger Observatory. The fit has been performed for energies above 5 ⋅ 10(18) eV, i.e. the region of the all-particle spectrum above the so-called ankle feature. The astrophysical model we adopted consists of identical sources uniformly distributed in a comoving volume, where nuclei are accelerated through a rigidity-dependent mechanism. The fit results suggest sources characterized by relatively low maximum injection energies, hard spectra and heavy chemical composition. We also show that uncertainties about physical quantities relevant to UHECR propagation and shower development have a non-negligible impact on the fit results