Global Trigger and Readout System for the AGATA Experiment

Abstract

AGATA is a 4-pi array of high purity Ge detectors for in-beam gamma-ray spectroscopy based on the novel concepts of pulse shape analysis (PSA) and gamma-ray tracking. Tracking and PSA require the concurrent digitization-at a sampling rate of 100 Msamples/s-of preamplifier signals of the 36-fold segmented Ge crystals composing the array. Locally digitized data are optically transferred to remote pre-processing nodes for pulse energy computation. The design of the front-end readout and level-1 (L1) trigger in AGATA follows a synchronous pipeline model: the detector data are stored in pipeline buffers at the global AGATA frequency, waiting the global L1 decision. A global timing system provides a reference clock and time tag to the digitizers and the pre-processing units by means of a tree of optically connected timing units. Pre-processing nodes are integrated in advanced TCA-based carrier cards with full mesh connectivity in the backplane and read-out through pci-express based optical links. The front-end data readout and its integration in the global trigger and synchronization system will be described.