The Gigatracker, the silicon beam tracker for the NA62 experiment at CERN

The Gigatracker is the NA62 beam tracker. It is made of three 63.1mm x 29.3mm stations of 300μm x 300μm hybrid silicon pixel detectors installed in vacuum ( ∼10$^{-6} mbar$ ). The beam particles, flowing at 750 $M H z$ , are traced in 4-dimensions by mean of time-stamping pixels with a design resolution of 200ps . This performance has to be maintained despite the beam irradiation amounting to a yearly fluence of 2×10$^{14}$ 1MeV n$_{eq}$∕cm$^2$ . The detector material minimization is paramount, as the detector faces the full beam. The station material budget is reduced to 0.5% X$_0$ by using (HEP world first) micro-channels cooling. We will describe the detector design and performances during the NA62 runs.