Image Processing Reference
In-Depth Information
19
An Optimization of 16-Point Discrete Cosine
Transform Implemented into a FPGA as a Design
for a Spectral First Level Surface Detector Trigger
in Extensive Air Shower Experiments
Zbigniew Szadkowski
University of Łódz
Department of Physics and Applied Informatics,
Faculty of High Energy Astrophysics, Łódz
Poland
1. Introduction
The Pierre Auger Observatory is a ground based detector located in Malargue (Argentina)
(Auger South) at 1400 m above the sea level and dedicated to the detection of ultra
high-energy cosmic rays with energies above 10
18
eV with unprecedented statistical and
systematical accuracy. The main goal of cosmic rays investigation in this energy range is to
determine the origin and nature of particles produced at these enormous energies as well as
their energy spectrum. These cosmic particles carry information complementary to neutrinos
and photons and even gravitational waves. They also provide an extremely energetic stream
for the study of particle interactions at energies orders of magnitude above energies reached
at terrestrial accelerators (Abraham J. et al., 2004).
The flux of cosmic rays above 10
19
eV is extraordinarily low: on the order of one
event per square-kilometer per century. Only detectors of exceptional size, thousands of
square-kilometers, may acquire a significant number of events. The nature of the primary
particles must be inferred from properties of the associated extensive air showers (EAS).
The Pierre Auger Observatory consists of a surface detectors (SD) array spread over 3000
km
2
for measuring the charged particles of EAS and their lateral density profile of muon
and electromagnetic components in the shower front at ground, and of 24 wide-angle
Schmidt telescopes installed at 4 locations at the boundary of the ground array measuring
the fluorescence light associated with the evolution of air showers: the growth and
subsequent deterioration during a development. Such a "hybrid" measurements allow
cross-calibrations between different experimental techniques, controlling and reducing the
systematic uncertainties.
Very inclined showers are different from the ordinary vertical ones. At large zenith angles
the slant atmospheric depth to ground level is enough to absorb the part of the shower that
follows from the standard cascading interactions, both of electromagnetic and hadronic type.
Only penetrating particles such as muons and neutrinos can traverse the atmosphere at large
zenith angles to reach the ground or to induce secondary showers deep in the atmosphere and
close to an air shower detector.
