Readout Electronics of the Na62 Gigatracker System

A crucial detector of the NA62 experiment is the beam spectrometer named Gigatracker. It consists of three stations of hybrid silicon pixels sensors with 150 ps (rms) of time resolution and 100 μm (rms) of space resolution. In addition the system operates under a high radiation environment and a high density of particles (up to 1.5 MHz/mm in the centre and 0.8 1 GHz in total). To meet these requirements the readout electronics must compensate the discriminators time-walk and the dead time should be below 1%. In order to evaluate the best solution, two readout chips have been developed. One is based on the constant-fraction discriminator technique and the other one is based on the use of a time-over-threshold circuit. The global architectures of both the front-end ASIC will be discussed.