3D silicon pixel detectors for the High-Luminosity LHC

3D silicon pixel detectors have been investigated as radiation-hard candidates for the innermost layers of the HL-LHC upgrade of the ATLAS pixel detector. 3D detectors are already in use today in the ATLAS IBL and AFP experiments. These are based on 50 × 250 μm² large pixels connected to the FE-I4 readout chip. Detectors of this generation were irradiated to HL-LHC fluences and demonstrated excellent radiation hardness with operational voltages as low as 180 V and power dissipation of 12–15 mW/cm² at a fluence of about 10¹⁶  n _eq/cm², measured at -25°C. Moreover, to cope with the higher occupancies expected at the HL-LHC, a first run of a new generation of 3D detectors designed for the HL-LHC was produced at CNM with small pixel sizes of 50 × 50 and 25 × 100 μm², matched to the FE-I4 chip. They demonstrated a good performance in the laboratory and in beam tests with hit efficiencies of about 97% at already 1–2 V before irradiation.