AMADEUS on-line trigger and filtering methods

Abstract

AMADEUS is a system designed to investigate the method of acoustic particle detection for high energy neutrinos and the acoustic environment in the deep sea as part of the ANTARES neutrino telescope. In this context, six local clusters of six acoustic sensors each were integrated into the ANTARES infrastructure. The first three clusters have been taking data since December 2007 and the second three since the completion of ANTARES in May 2008. In the paper, the methods used for the on-line triggering and filtering of the data acquired with the AMADEUS set-up are described. On-shore, a dedicated computer-cluster is used to control the off-shore DAQ hardware, to process and store the acoustic data arriving from the sensors. On this cluster different data filtering schemes and triggers are implemented. Transient signals are selected by a variable threshold, which is self-adjusting to the changing conditions of the deep sea. For bipolar pulses—the characteristic acoustic signature of a neutrino—a pattern recognition is used based on cross-correlating the output of the sensors with a pre-defined bipolar pulse. To study the characteristics of the ambient noise in the deep sea an amount of unfiltered data is stored in regular intervals.