The Pierre Auger Observatory will study ultrahigh-energy cosmic rays, reaching full sensitivity for primaries with energies above 10/sup 19/ eV. The southern hemisphere site observatory is currently ...under construction. The surface array at this site will contain 1600 water Cherenkov detector stations distributed over 3000 km/sup 2/. In this paper, the front-end electronics of the surface detector stations, which couple analog signal processing with digital triggering, are described. The environmental constraints, history of the development, and the final design being deployed in the field are discussed. Performance characteristics of the electronics are presented.
The paper describes an optimization of 16-point Discrete Cosine Transform (DCT)algorithm implemented into a FPGA. Widely used for long-term numerical calculation 8-point algorithm of ...Arai-Agui-Nakajima, which minimized an amount of multiplication, is not optimal for the FPGA implementation. For new FPGA chips with large amount of fast multipliers located in embedded digital signal processing (DSP)blocks the number of multiplication is not a critical parameter. The registered performance and a total speed can be significantly increased by a parallel signal processing in DSP blocks. A lack of proper routines in Altera 's Library of Parameterized Modules (LPM)and a necessity of using shift registers for processes synchronization in a pipeline data flow additionally impose a factorization focused on wider use of DSP blocks and a reduction of a length of pipeline chains. The DCT algorithm optimization was a result of work on new spectral trigger designs for the Pierre Auger surface detectors based on the 16-point DCT. 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 hadron and starting their development early in the atmosphere.
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 by standard Auger array, where the transition from ...galactic to extragalactic sources is expected. The Auger array is enlarged by a relatively small dedicated area of surface detectors with nearby buried underground muon counters at half or less the standard 1.5 km grid. Lowering the Auger energy threshold by more than one order of magnitude allows a precise measurement of the cosmic ray spectrum in the very interesting regions of the second knee and the ankle. The paper describes the working principle of the Master/Slave (standard Auger surface detector/the underground muon counters) synchronous data acquisition, general triggering and the extraction of data corresponding to the real events from underground storage buffers applied in two prototypes: A) with 12.5 ns resolution (80 MHz) built from 4 segments: standard Auger Front End Board (FEB) and Surface Single Board Computer (SSBC) (on the surface) and the Digital Board with the FPGA and the Microcontroller Board (underground), B) with 4-times higher: 3.125 ns resolution (320 MHz) built with two segments only: new surface Front End Board supported by the NIOS ® processor and CycloneIII™ Starter Kit board underground, working also with NIOS ® virtual processor, which replaces the external TI μC, which in meantime became obsolete. The system with the NIOS ® processors can remotely modify and update: the AHDL firmware creating the hardware FPGA net structure responsible for the fast DAQ, the internal structure of the NIOS ® (resources and peripherals) and the NIOS ® firmware (C code) responsible for software data management. With the standard μC, the μC firmware was fixed and could not be updated remotely. The 80 MHz prototype passed laboratory tests with real scintillators. The 320 MHz prototype (still being optimized) is considered as the ultimate AMIGA design.
We present the FPGA/NIOS ® implementation of an adaptive finite impulse response (FIR) filter based on linear prediction to suppress radio frequency interference (RFI). This technique will be used ...for experiments that observe coherent radio emission from extensive air showers induced by ultra-high-energy cosmic rays. These experiments are designed to make a detailed study of the development of the electromagnetic part of air showers. Therefore, these radio signals provide information that is complementary to that obtained by water-Cherenkov detectors which are predominantly sensitive to the particle content of an air shower at ground. 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. In this paper we discuss an adaptive filter, which is based on linear prediction. The coefficients for the linear predictor are dynamically refreshed and calculated in the virtual NIOS ® processor, which is implemented in the same FPGA chip. The Levinson recursion, used to obtain the filter coefficients, is also implemented in the NIOS ® and is partially supported by direct multiplication in the DSP blocks of the logic FPGA segment. Tests confirm that the linear predictor can be an alternative to other methods involving multiple time-to-frequency domain conversions using an FFT procedure. These multiple conversions draw heavily on the power consumption of the FPGA and are avoided by the linear prediction approach. The FIR filter has been successfully tested in the Altera ® development kits with the the EP4CE115F29C7 from the Altera ® Cyclone ® IV family and the EP3C120F780C7 from the Cyclone ® III family at a 170 MHz sampling rate, a 12-bit I/O resolution, and an internal 30-bit dynamic range. Most of the slow floating-point NIOS ® calculations have been moved to the FPGA logic segments as extended fixed-point operations, which significantly reduced the refreshing time of the coefficients used in the linear prediction.
For the observation of UHECRs by the detection of their coherent radio emission an FPGA based trigger and 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 30-80MHz are significantly contaminated by radio frequency interferences (RFI) and human made distortions. The digitized signals are converted from the time to frequency domain by a FFT procedure, then 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 effects 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 Altera ® Cyclone III FPGA chip EP3C80F780C6 and tested in a prototype board with an 180 MHz sampling rate, 16 bit dynamic range, and 12-bit resolution.
Design of the trigger system for the Auger fluorescence detector Gemmeke, H.; Grindler, A.; Keim, H. ...
1999 IEEE Conference on Real-Time Computer Applications in Nuclear Particle and Plasma Physics. 11th IEEE NPSS Real Time Conference. Conference Record (Cat. No.99EX295),
1999
Conference Proceeding
A description of the trigger system for the 13 200 channels of the Auger fluorescence detector is presented. The concept for the front-end electronics, the first and second level trigger, the data ...flow and the data processing rests upon the system requirements. The design uses FPGAs to obtain a cost-effective and flexible solution whenever possible. The large scale integration of the modern FPGA allowed a massive parallel solution for recognition of tracks and suppression of background. The supervision task and readout is carried out by low cost PCs under LINUX operating system.
The trigger system of the Surface Detector (SD) of the Pierre Auger
Observatory is described, from the identification of candidate showers ($E>1$
EeV) at the level of a single station, among a huge ...background (mainly single
muons), up to the selection of real events and the rejection of random
coincidences at a higher central trigger level (including the reconstruction
accuracy). Efficiency of a single station trigger is evaluated using real data
, and the high performance of event selection hierarchy will be demonstrated.
The trigger system of the Surface Detector (SD) of the Pierre Auger Observatory is described, from the identification of candidate showers (\(E>1\) EeV) at the level of a single station, among a huge ...background (mainly single muons), up to the selection of real events and the rejection of random coincidences at a higher central trigger level (including the reconstruction accuracy). Efficiency of a single station trigger is evaluated using real data , and the high performance of event selection hierarchy will be demonstrated.
Growth and Characterization of (Cd, Mn)Te Kochanowska, D.; Witkowska-Baran, M.; Mycielski, A. ...
IEEE transactions on nuclear science,
10/2013, Letnik:
60, Številka:
5
Journal Article
Recenzirano
The present article presents technology, required for repeatable manufacturing of the 1.5 and 2 inch crystal rods of (Cd, Mn)Te is discussed. In order to obtain semiinsultaing crystals, compensation ...and annealing in Cd-vapours was used. Vanadium was mainly used as the compensating dopant. The resistivity of the obtained monocrystalline plates was around 10 9 Ω cm, and the μτ-product was about 10 -3 cm 2 /V. Mapping of the resistivity was performed on both as-grown crystals and the crystals annealed in the saturated Cd vapour. As-grown (undoped) crystals were inhomogeneous and their resistivities were in the range 10 5 -10 6 Ω cm. After annealing resistivity increased up to 1 -2 ·10 9 Ω cm and better homogeneity could be seen. Annealing in saturated Cd-vapours had influence on tellurium inclusions/precipitates. It was studied by IR transmission microscopy. For as-grown samples the density of Te inclusions (> 1 μm) was ≈ 3 ·10 5 cm -3 but for annealed samples was ≈ 10 4 cm -3 . The concentrations (measured by SIMS) of the unintentional impurities Na, Ca, and Ga were in the region 10 15 - 10 16 cm -3 , corresponding well with the purity (6N) of the elements used for crystallization of our (Cd, Mn)Te. The low temperature photoluminescence (PL) measurements indicated significantly lowered concentrations of acceptors after annealing. Nearly ohmic contacts to the high resistivity (Cd, Mn)Te plates were obtained by deposition of the amorphous layers of heavily doped semiconductor (ZnTe:Sb). We undertook the present work to show that low vanadium doping level and proper annealing conditions are sufficient to obtain detector grade material.
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