Speaker
Description
The ALICE Inner Tracking System detector is undergoing a major upgrade in order to cope
with the increased data rates and to meet the requirements as set out by the physics goals of
the experiment after Long Shutdown 2. The new ITS will be completely made up of ALPIDE
monolithic active pixel sensors based on a CMOS 180nm process. A single sensor measures
15mm x 30mm and contains half a million pixels distributed over 512 rows and 1024
columns. These 50um thick sensors, with 27um x 29um pixel pitch, are mounted on ultra-
lightweight carbon composite support structures with an embedded cooling system. This
results in a considerable reduction of the material budget (down to 0.35% X_0 for the inner
layers and ∼1% X_0 for the outer layers) and a significant improvement of the impact
parameter resolution and tracking efficiency. The innermost ITS layer will be moved as close
as 23mm to the interaction point. The integration of the ITS detector assembly, made of the
three innermost and four outermost layers, has been almost completed and the
commissioning, first in the laboratory, is ongoing. The detector will be installed in ALICE in
2020. This talk will give a brief overview of the motivation for the upgrade and will present
the first results of the detector performance obtained during the commissioning.
