The Level 0 trigger processor of the NA62 liquid krypton electromagnetic calorimeter

The NA62 experiment at the CERN SPS aims to measure the Branching Ratio of the ultra-rare decay K + → π + νν, collecting about 100 events in two years of data taking with a signal to background ratio of 10∶1. An hermetic photon veto system has been designed to efficiently reject the pi0 background, one of the main background sources, and the 20-ton liquid krypton calorimeter is a fundamental component of such system in the angular acceptance region 1–10 mrad. We present the design of the Level 0 trigger processor that identifies electromagnetic clusters in the calorimeter providing information on time, position and energy reconstruction for each cluster. It is composed of 36 readout boards (TEL62), organized in a three layer parallel system, 108 mezzanines and 215 high-performance FPGAs. It is designed to sustain an instantaneous hit rate of 30 MHz, to process data with a latency of about 100 µs, and to achieve a time resolution of 1.5 ns on the single cluster. Updated production and functionality test results of a trigger slice are presented.