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Pierre Auger Observatory
Digital electronics for the FD system
The Pierre Auger observatory intends to
measure the energy spectrum, the arrival direction,
and the isotope composition of primary
particles above 1019eV. The very
low integrated particle flux of only 1 event
per km2 and century for energies above
5 × 1019 eV demands a very large detector area.
The observatory is a hybrid system consisting
of 1600 surface detector (SD) stations and
an independent fluorescence detector (FD)
system. The SD measures the lateral distribution
of secondary particles using water
Cerenkov detectors equally spaced on a grid
over an area of more than 3000 km2.
The FD system observes the longitudinal development
of the shower profile through 4 optical
detectors - called "FD eye" station. During
clear dark nights each eye collects the fluorescence
light emitted isotropically along the
shower track as a time sequence of light.
The design provides a central FD eye station with
a 360 degree field of view and three perimeter eyes
with 180 degree field of view looking towards the
center of the SD array. IPE is responsable for
processing of the digital data, the detection
of fluorescence light in the image of a camera and
provides the software for readout of the
digital electronic.
Concept of the digital trigger system
All functions of the digital electronic are implemented
in reprogrammable FPGA logic in order to achieve high exibility,
cost-effectiveness and ease of maintenance. The
high data rate from the sampling of the PMT
signals is reduced through a multilevel trigger
system:
| Trigger level |
Reduction method |
Rate (Hz)/ Unit |
| Pure data |
none |
107 per pixel |
| First Level Trigger (FLT) |
Filtering and threshold |
100..200 per pixel |
Second Level Trigger (SLT) |
Pattern recognition |
0.1...1 per mirror |
Third Level Trigger |
further criteria |
<< 0.02 per eye |
Contact
Dr. Matthias Kleifges, matthias.kleifges@ipe.fzk.de,
Tel.: +49 7247 82-3540
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The first FD building at Los Leones
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The frontend electronic for the FD camera
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First level trigger electronic (left) and analog
electronic build by INFN, Turino (right)
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Screen shot of the diagnostic program showing
a cosmic event
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