Use of FPGA embedded processors for fast cluster reconstruction in the NA62 liquid krypton electromagnetic calorimeter

The goal of the NA62 experiment at the CERN SPS is the measurement of the Branching Ratio of the very rare kaon decay K(+)→π(+) ν bar nu with a 10% accuracy by collecting 100 events in two years of data taking. An efficient photon veto system is needed to reject the K(+)→π(+) π(0) background and a liquid krypton electromagnetic calorimeter will be used for this purpose in the 1-10 mrad angular region. The L0 trigger system for the calorimeter consists of a peak reconstruction algorithm implemented on FPGA by using a mixed parallel architecture based on soft core Altera NIOS II embedded processors together with custom VHDL modules. This solution allows an efficient and flexible reconstruction of the energy-deposition peak. The system will be totally composed of 36 TEL62 boards, 108 mezzanine cards and 215 high-performance FPGAs. We describe the design, current status and the results of the first performance tests