The surface detector (SD) array of the Pierre Auger Observatory needs an upgrade which allows space for more complex triggers with higher bandwidth and greater dynamic range. To this end this paper ...presents a front-end board (FEB) with the largest Cyclone V E FPGA 5CEFA9F31I7N. It supports eight channels sampled with max. 250 MSps@14-bit resolution. Considered sampling for the SD is 120 MSps; however, the FEB has been developed with external anti-aliasing filters to retain maximal flexibility. Six channels are targeted at the SD, two are reserved for other experiments like: Auger Engineering Radio Array and additional muon counters. The FEB is an intermediate design plugged into a unified board communicating with a micro-controller at 40 MHz; however, it provides 250 MSPs sampling with an 18-bit dynamic range, is equipped with a virtual NIOS processor and supports 256 MB of SDRAM as well as an implemented spectral trigger based on the discrete cosine transform for detection of very inclined "old" showers. The FEB can also support neural network development for detection of "young" showers, potentially generated by neutrinos. A single FEB was already tested in the Auger surface detector in Malargüe (Argentina) for 120 and 160 MSps. Preliminary tests showed perfect stability of data acquisition for sampling frequency three or four times greater. They allowed optimization of the design before deployment of seven or eight FEBs for several months of continuous tests in the engineering array.
Radio stations can observe radio signals caused by coherent emissions due to geomagnetic radiation and charge excess processes mainly in the frequency band from 30 to 80 MHz. This range is highly ...contaminated by human-made radio frequency interference (RFI). In order to improve the signal-to-noise ratio, RFI filters are used to suppress this contamination. Infinite impulse response (IIR)-notch filters operate with fixed parameters and suppress several narrow bands. IIR filters are generally potentially unstable due to feedbacks; however, they are much shorter and more power efficient than finite impulse response filters. We implemented an NIOS virtual processor calculating new set of IIR filter coefficients, which are reloaded dynamically on-the-fly. Spectrum analysis of the 30-80-MHz band can also be supported by the Altera IP Cores. The NIOS adjusts the new coefficients of the filter checking whether the poles are inside the unique complex radius (a condition of stability) as well as tuning the width of the notch filter. Practical implementation was tested in the laboratory with signal and pattern generators. Laboratory results are very promising. The IIR filter follows the drifting frequencies over very wide ranges (even 15 MHz for investigated range of 30-80 MHz), keeping a suppression factor on a very high level (≥10). The novelty of this paper is an introduction of the adaptive IIR-notch filter, which has not been used in any previous experiment.
At the Pierre Auger Observatory, the radio emission from cosmic-ray-induced air showers is measured. We will discuss the physics results from a setup consisting of three antennas triggered by an ...auxiliary particle detector. With this setup, a total of 494 events were registered in coincidence with the surface detector of the Pierre Auger Observatory. This data allows us to study the dependence of the radio signal on air shower parameters. From an analysis of the measured polarization of the radio signals, we conclude that the emission is dominated by the geomagnetic mechanism. However, the polarization study indicates that the pure geomagnetic description by itself is not sufficient to describe all features of the data set.
The Auger Engineering Radio Array Fuchs, Benjamin
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2012, Letnik:
692
Journal Article
Recenzirano
High and ultra-high energy cosmic rays hitting the Earth's atmosphere cause extensive air showers (EAS). In recent years, these cosmic rays have been extensively studied at the Pierre Auger ...Observatory in Argentina. The EAS mainly consist of charged particles, especially electrons and positrons, which cause electro-magnetic emission in the MHz range by interaction with the Earth's magnetic field. To measure this radio emission, AERA, the Auger Engineering Radio Array, was deployed in October 2010 and commenced regular data acquisition in April 2011. AERA was designed as an engineering array for technology and methodology development towards future large-scale radio arrays. It will allow studies on the radio emission mechanism and the physics capabilities of the detection technique. AERA's unique site within the surface detector array (SD) of the Pierre Auger Observatory provides the possibility of coincident hybrid and super-hybrid EAS detection especially in overlap with the fluorescence telescopes Coihueco and HEAT. Besides a description of the setup, we present an overview of analyses of commissioning data taken between November 2010 and April 2011. Also, we show the first hybrid and self-triggered events detected with AERA in April 2011.
The Pierre Auger Observatory is an Ultra-High Energy Cosmic Ray (UHECR) detector which has studied cosmic particles with energies above and around 10
18
eV for more than 15 years. It has proved to ...be the most competitive instrument at these energies and has produced a wealth of valuable results, improving our understanding of UHECRs. A complete understanding of these highest energy particles is crucial to understand the extreme astrophysical events in which they are produced and accelerated, as well as their propagation to Earth. In the same range of energies, UHE photons and neutrinos are of paramount importance as, being electrically neutral, they point back to their origin while charged particles are deflected in the galactic and extragalactic magnetic fields. The flux of extragalactic photons, neutrinos, and cosmic rays are believed to be highly linked, by their origin and their interactions. Each messenger provides different information about the potential sources, and having detection means for all four messengers, including gravitational waves, allows us to shed light on energetic sources of astroparticles. The Pierre Auger Observatory benefits from a large exposure and a good angular resolution, and is efficient in detecting UHE photons and neutrinos. These performances make possible follow-up searches for events detected by gravitational waves, such as the binary mergers observed by the LIGO/Virgo detectors, or any other energetic sources of particles.
The Pierre Auger Observatory in Argentina is the largest cosmic ray detector array ever built. Although the construction was completed in 2008, the Observatory has been taking data continuously since ...January 2004. Its main goal is to measure ultra high energy cosmic rays (UHECRs, energy above 1018eV) with unprecedented statistics and precision. Measurements of the energy spectrum, chemical composition (including neutrinos and photons) and arrival directions of UHECRs can provide hints for understanding their origin, propagation and interactions.
The fluorescence detector of the Pierre Auger Observatory measures the atmospheric depth, Xmax, where the longitudinal profile of a high energy air shower reaches its maximum. This is sensitive to the nuclear mass composition of the cosmic ray and to the characteristics of the hadronic interactions at very high energy. Due to its hybrid design, the Pierre Auger Observatory also provides independent experimental observables obtained from the surface detector for the study of the shower development.
A selection of the Pierre Auger Observatory results on the study of the UHECRs will be presented, focusing on composition results. In particular, the measurements and the different roles of the observables with respect to mass composition will be discussed.
We report a measurement of the cosmic ray energy spectrum based on a large amount of data collected by the Pierre Auger Observatory. This measurement combines data from the fluorescence (FD) and ...surface (SD) detectors of the Observatory and does not rely on detailed numerical simulation or any assumption about the chemical composition. The energy calibration of the observables, which exploits the correlation of surface detector data with fluorescence measurements in hybrid events, is presented in detail. Besides presenting statistical uncertainties, we address the impact of systematic uncertainties. We also summarize the combined energy spectrum obtained when hybrid data are used to extend the spectrum to lower energies.
The paper describes the prototype of a synchronous (Master/Slave) data acquisition system for underground muon counters triggered by surface detectors. A water Cherenkov surface detector (Master) ...when hit by extensive air showers generates and transmits the trigger to the underground system (Slave) to register the muon fraction of the showers which survived the propagation through 3 m layer of soil. The surface and underground segments are built on the Altera field-programmable gate array (FPGA) CycloneIII/CycloneIV platforms, respectively. Both FPGAs are equipped with NIOS processors, which makes previously used external microcontrollers unnecessary. They also generate necessary interfaces: SDRAM controller, UART, SPI, DMA; interfaces which were previously implemented by means of logic elements. Moving several time-consuming tasks from the logic block (coded in the Altera Hardware Description Language) to the NIOS (coded in "C") dramatically simplifies the system and increases its flexibility. The time margin for all processes managed by the soft-core NIOS for the 100 Hz T1 trigger rate remains sufficient. NIOS processors communicate with each other via UART protocol and by the RS485 standard. The underground CycloneIV FPGA is programmed remotely via additional MAXII CPLD with nonvolatile programmable memory. Tests have shown that a full string of data processing goes smoothly. The above-mentioned string involves the following processes: the transfer of the trigger with a time stamp from the surface detector into the underground segment via a dedicated line with a galvanic barrier, freezing data from 64 channels at 320 MHz sampling in internal DPRAMs, writing/reading data into/from external SDRAM, extracting physical data identified by GPS time stamps sent from Central Data Acquisition System (CDAS) and the data transfer from the underground NIOS via the surface NIOS to CDAS.
The surface detector array of the Pierre Auger Observatory contains 1600 water Cherenkov detectors spread over an area of 3000 km 2 . The Cherenkov light is detected by three 9-inch photomultiplier ...tubes from which the signals of the anode and last dynode are digitized by 10 bit ADCs. The currently used Front-End Boards equipped with the ACEX ® and Cyclone ® FPGA are sampled with 40 MHz. New requirements from the Auger North (100 MHz) and AMIGA (80 MHz) specification as well as the proposal of new spectral triggers based on the 16-point Discrete Cosine Transform (DCT) impose a new Front End Boards with more powerful FPGA chip with a sufficient amount of DSP blocks. The DCT trigger allows recognition of ADC traces with a very short rise time and fast exponential attenuation related to a narrow, flat muon component of very inclined extensive air showers generated by hadrons and starting their development early in the atmosphere. Ten prototype boards equipped with Altera ® Cyclone ® III FPGA have been fabricated and successively tested in the lab and in real pampas conditions in six test surface detectors within April 19 - July 26, 2009. Boards contain only a single FPGA chip, which implements also the slow channel, in previous three generations supported by the external Dual-Port RAM. Tests confirmed full stability and high reliability of the digital part. Both lab and field tests confirm a high efficiency of the recognition of expected patterns of ADC traces.
The paper describes a new spectral trigger based on the 16-point discrete cosine transform (DCT) algorithm that was implemented into an FPGA. The DCT trigger allows recognition of FADC traces with a ...very short rise time and fast exponential attenuation related to a narrow, flat muon component of very inclined extensive air showers generated by hadrons and starting their development early in the atmosphere. The discrete cosine transform, based on only real coefficients in the frequency domain, provides much more sensitive trigger conditions and a simpler interpretation in comparison to a discrete Fourier transform (DFT) that is based on complex coefficients or their absolute values. It also offers a scaling feature. The ratio of the DCT coefficients to the 1st harmonics depends only on the shape of signals, not on their amplitudes. However, an implementation of the DCT into an FPGA requires more resources than DFT even based on an FFT algorithm.
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