GNAM: a low-level monitoring program for the ATLAS experiment

During the last years many test-beam sessions were carried out on each ATLAS subdetector in order to assess the performances in standalone mode. During these tests, different monitoring programs were developed to ease the setup of correct running conditions and the assessment of data quality. The experience has converged into a common effort to develop a monitoring program, which aims to be exploitable by various subdetector groups. The requirements which drove the design of the program as well as its architecture are discussed in this paper. Characteristic features of the application are a modular software based on a Finite State Machine core to implement the synchronization with the data acquisition system and exploiting the ROOT Tree as transient data store. The first version of this monitoring program was used for the 2004 ATLAS Combined Test Beam.