Central Data Acquisition System

Auger Central Data Acquisition System (CDAS) is a custom built set of applications running under Unix based OS. Its purpose is to operate the Surface Detector with minimal need of human intervention, provide interface with the Fluorescence Detector acquisition system for hybrid triggered events, and recollect, store, and prepare for transfer the auger data set.

The internal CDAS system is based on the following applications:

• Ik, the Information Kernel, which allows CDAS applications to communicate to one another
• Pm, the PostMaster, which makes the interface between the CDAS and the wireless communication system of the individual surface detectors
• Ct, the Central Trigger, which receives second level trigger information in real time from the detectors and determines the third level trigger
• Eb, the Event Builder, which receives the event data whenever a third level trigger is issued by Ct
• Fd, the Fluorescence Detector interface, which receives third level trigger from the fluorescence detector and forwards it to the array.
• Mr, the Monitor Recorder, which stores monitoring and calibration information from the detectors
• Rc, the Run Controller, which configures new stations upon installation

A complete set of modules to reconstruct and visualize the events has been written by the CDAS group, initially to monitor the proper behaving of the acquisition. It is now very complete and is widely used in the collaboration to perform SD analysis and reconstruction.

The CDAS Reconstruction package

The CDAS reconstruction package is composed of various modules:

• RootW, doing the interface with Root
• STCoordonates, doing basic coordinates conversions
• IoSd, doing the I/O part of the SD data files
• IoFd, based on FdEventLib, doing the I/O part of the FD data files
• IoAuger, to access both SD and FD data
• Ec, to calibrate surface detectors in SD events
• Es, to select physical events (fourth and fifth level offline trigger), and reject casual coincidences
• Er, to do the SD reconstruction
• ED, an event display

Latest CDAS version

The current CDAS version is v4r2, based on Ec v0r6, Es v0r6 and Er v3r2. Some features:

• Calibrates stations with a VEM extracted from high statistics muon histograms
• Recover saturated stations by extrapolating their signal
• Selects events and removes casual stations in events
• Takes into account signal and time of arrival fluctuations based on real data analysis
• Showers asymmetries at ground are corrected
• Silent stations (stations with no signal) are used in the fit
• Reconstruction behavior can be driven using an ensemble of global variable to select geometrical fit options, ldf fit options, global fit options...

The complete package is available at the CDAS web page, with restricted access to the members of the collaboration.

For more informations, feel free to contact the CDAS task leader, Antoine.Letessier-Selvon@in2p3.fr.