4th dimensional tracking: the GigaTracker of NA62 experiment

The GigaTracker is a lightweight hybrid silicon pixel detector built for the NA62 experiment at CERN, which aims at measuring the branching fraction of the ultra-rare kaon decay K+ -> pi+ nu nubar at the CERN SPS. The detector tracks charged particles in a 75 GeV/c hadron beam with a flux reaching 1.3 MHz/mm2. It consists of three stations, 61x27 mm2 each, which provide single hit timing with 130 ps resolution. Each station is composed of a 200 um thick planar silicon sensor, segmented in 300x300 um2 pixels, bump-bonded to 2x5 custom 100 um thick ASIC, called TDCPix. Each TDCPix contains 40x45 asynchronous pixels, and is instrumented with 360 pairs of time-to-digital converter channels with 100 ps bin. The three stations are installed in vacuum (about 10^-6 mbar) and cooled with liquid C6F14 circulating through micro-channels etched inside silicon plates a few hundred microns thick. The total material budget is less than 0.5% X0 per station. Detector description, operational experience and performance from the NA62 experimental run in 2016, at about 30% the nominal beam intensity, are presented.