The NA62 GigaTracker

The GigaTracker is a hybrid silicon pixel detector built for the NA62 experiment aiming at measuring the branching fraction of the ultra-rare kaon decay K⁺→π⁺νν¯ at the CERN SPS. The detector has to track particles in a beam with a flux reaching 1.3 MHz/mm² and provide single-hit timing with 200 ps RMS resolution for a total material budget of less than 0.5% X₀ per station. The tracker comprises three 60.8 mm×27 mm stations installed in vacuum (∼10⁻⁶mbar) and cooled with liquid C₆F₁₄ circulating through micro-channels etched inside a few hundred micron thick silicon plates. Each station is composed of a 200 μm thick silicon sensor read out by 2×5 custom 100 μm thick ASICs, called TDCPix. Each chip contains 40×45 asynchronous pixels, 300 μm×300 μm each and is instrumented with 100 ps bin time-to-digital converters. In order to cope with the high rate, the TDCPix is equipped with four 3.2 Gb/s serialisers sending out the data. We will describe the detector and the results from the 2014 and 2015 NA62 runs.