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.
The paper describes the new design of the first level trigger for the surface array in the Pierre Auger Observatory. The previous design was tested in a small test segment called Engineering Array ...(EA). It confirmed full functionality and reliability of the PLD approach. However, because of the high price of the chips available at that time, a new cost-effective design was developed.
Altera
®
offered cost-effective family, which allows reducing the total budget of the electronics without compromise in the functionality. The here described concept of a splitting of data processing into two sub-channels implemented into the parallel working chips, the chips synchronization and the automatization of internal processing management, together with the fully pipelined AHDL code became the framework for the further implementation in the environmental condition of the Argentinian pampa.
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.
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 Pierre Auger Observatory studies ultra-high energy cosmic rays in the range of
10
18
eV
up to the highest energies. The apparatus reaches full sensitivity above
10
19
ev
. The southern hemisphere ...site is currently under construction. When completed, the surface array at this site will contain 1600 water Cherenkov detector stations distributed over
3000
km
2
. Prior to proceeding with full-scale construction, a prototype “Engineering Array”, consisting of 40 detector stations was tested. This paper describes the implementation of the first level surface detector trigger used in the engineering array.
The aim of the AMIGA project (Auger Muons and Infill for the Ground Array) is an investigation of Extensive Air Showers at energies lower than those accesible with the standard Auger array, where the ...transition from galactic to extragalactic sources is expected. The paper describes the working principle of the Master/Slave (standard Auger surface detector/the underground muon counters) synchronous data acquisition and general triggering applied in two prototypes: with 12.5 ns resolution built from 4 segments (2 FPGAs and 2 standard micro-controllers) and 3.125 ns resolution built from two segments only (2 FPGAs with implemented NIOS ® processors).
Extremely rare flux of UHERC requires sophisticated detection techniques. Standard methods oriented on the typical events may not be sensitive enough to capture rare events, crucial to fix a ...discrepancy in the current data or to confirm/reject some new hypothesis. Currently used triggers in water Cherenkov tanks in the Pierre Auger surface detector, which select events above some amplitude thresholds or investigate a length of traces are not optimized to the horizontal and very inclined showers, interesting as potentially generated by neutrinos. Those showers could be triggered using their signatures: i.e. a curvature of the shower front, transformed on the rise time of traces or muon component giving early peak for “old” showers. Currently available powerful and cost-effective FPGAs provide sufficient resources to implement new triggers not available in the past. The paper describes the implementation proposal of 16-point discrete Fourier transform based on the Radix-2 FFT algorithm into Altera Cyclone FPGA, used in the 3rd generation of the surface detector trigger. All complex coefficients are calculated online in heavy pipelined routines. The register performance
∼
200
MHz
and relatively low resources occupancy
∼
2000
logic elements/channel for 10-bit resolution provide a powerful tool to trigger the events on the traces characteristic in the frequency domain. The FFT code has been successively merged to the code of the 1st surface selector level trigger of the Pierre Auger Observatory and is planned to be tested in real pampas environment.
For the observation of ultra high-energy cosmic rays (UHECRs) by the detection of their coherent radio emission an FPGA based trigger and radio frequency interference (RFI) filter was developed. ...Using radio detection, the electromagnetic part of an air shower in the atmosphere may be studied in detail, thus providing information complementary to that obtained by water Cherenkov detectors which are predominantly sensitive to the muonic content of an air shower at ground. For an extensive radio detector array, due to the limited communication data rate, a sophisticated self trigger is necessary. However, radio signals in the frequency range of 30-80 MHz are significantly contaminated by RFI and human made distortions. The digitized signals are converted from the time to frequency domain by a FFT procedure, then a deconvolution and RFI-filters are applied to correct the frequency response and to suppress the RFI. Finally the filtered data is transformed back into the time domain by an iFFT, also generating an envelope as a base for the final self-trigger. To avoid leakage effect and to create an overlap of successive data blocks, trapezoidal windowing is applied with internal overclocking. The algorithms for two polarization channels have been successfully implemented in a single FPGA and tested in a prototype board with 180 MHz sampling rate, 16-bit dynamic range, and 12-bit resolution.
The trigger system for the AUGER fluorescence detector is presented. The main goals of the design were low price, high flexibility of the trigger, high reliability and good testability even at remote ...operation. The simulation of all boards using VHDL tools resulted in a design which is optimal with respect to these goals and highly independent of existing commercial solutions. The large-scale integration of modern FPGAs yielded a massive parallel system for recognition of tracks and suppression of background. The readout and control is carried out by low cost PCs under the LINUX operating system.
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