Bunch-crossing identification for the ATLAS first-level calorimeter trigger

As part of the design studies for the ATLAS first-level calorimeter trigger, we have been investigating the process of bunch-crossing identification (BCID). Various digital BCID algorithms have been investigated using software simulation. Furthermore, a demonstrator system has been constructed which performs BCID on 36 channels of trigger data. The BCID algorithms are implemented in Field-Programmable Gate Arrays (FPGAs). The field-programmable nature of the system has allowed a number of BCID algorithms to be tested in a CERN test beam. The initial results show BCID being performed with good efficiency on signals corresponding to energies of a few GeV. An ASIC which performs BCID has been designed, built and tested in a CERN test beam.