Operation and performance of the NA62 Gigatracker

The GigaTracKer is a hybrid silicon pixel detector designed for the fixed-target experiment NA62 at the CERN SPS aiming to measure the branching ratio of the very rare kaon decay K⁺ → π⁺ν ν̄ with 10% precision. The detector has to provide measurements of momentum, direction and time of beam particles arriving at a rate of 750 MHz. The tracking system consists of four stations installed in vacuum (~10⁻⁶ mbar), 60.8 × 27\ mm² each, with a total material budget of less than 2X₀. Each station is cooled with a microchannel cooling plate used for the first time in a high energy physics experiment. The beam particles are tracked in 4 dimensions by means of time-stamping pixels (300×300\ μ m²) with the single hit time resolution reaching 115 ps. This performance has to be maintained despite the beam irradiation amounting to a yearly fluence of 4.5 × 10¹⁴\ 1MeV\ neq/200\ days. The detector has been fully operational since 2016. We describe the GigaTracKer design and performance in the 2016-2022 years of NA62 data taking.