AugerAccess - Database

The quality of the physics results, derived from the analysis of the data collected at the Observatory, depends heavily on the calibration and monitoring of the sensitive components of the detectors.

The response of the photomultipliers and associated electronics to the amount of light produced by the shower particles in the detectors is the basic experimental information needed to determine the energy of the incoming cosmic ray. Errors on the absolute detector calibration affect directly the determination of the energy.
To ensure high quality physics results, it is crucial to maintain and update a database containing complete information on the absolute calibration factors of all photomultipliers and also on the time evolution of these parameters. In fact knowledge of the calibration parameters alone is not sufficient. At least as important is to follow and keep record of their behaviour with time.
The very low rate of the events of interest implies that the analysis will have to be made in an integral way over a lengthy period of operation of the Auger Observatory: 15 years is envisaged. This requirement imposes a very organized and reliable data storage architecture that will make calibration data and every working parameter of the detectors easily accessible together with the related information on the time evolution.
The database has to be dynamic in character and must contain diverse information to allow the determination of the working conditions of the detectors at any time in the past.

The total number of photomultipliers of the Fluorescence and of the Surface Detector are 10,560 and 4,800 respectively, for a total of about 15,000. This number does not create problems per se. The difficulty of designing and operating such a database is the consequence of requiring that the different elements are working together.

The detector chain (composed of the photomultipliers plus associated electronics of front-end and read-out) must be calibrated periodically.

For the photomultipliers of the Surface Detector (SD), the absolute calibration is obtained from the signal given by atmospheric muons traversing the water tanks. This means that the calibration is a continuous process, active every time the sub-detector is operating, and providing simultaneously calibration data and information on the stability and time-behaviour of the chain.
For the Fluorescence Detector (FD) a special absolute calibration system is used. This is based on a calibrated light source and a diffusing screen that illuminates all photomultipliers of the cameras uniformly. This absolute calibration of the cameras of the fluorescence telescopes is performed every few months, as its use is not compatible with the normal operation of the detector. To monitor the stability and the time-behavior of the chain, another light source system operates every night of data taking.

In addition to the calibration factors of the photomultipliers, the database (DB) will also contain information on other relevant parameters of each individual detector. For the FD the DB will contain the results of the analysis of the atmospheric data that are needed to apply the correction for atmospheric absorption of the fluorescence light. This parameter is crucial in order to derive the energy of the cosmic ray shower from the light observed by the telescopes.

The parameters to be collected in the database are either needed for the analysis or to monitor possible instabilities representing hints of malfunctioning. The ability to observe these in real time represents a powerful tool to plan preventive maintenance and increase the operational efficiency.
As the DB will contain the configuration and the operating parameters of the detectors at each instant, it will also improve the efficiency of the maintenance of the facility.

Aim of the present activity is to define a general Auger database system, based on MySQL,
identifying all the parameters which are necessary to fulfill the objectives that have been summarized above.