ALICE ITS: the Run 1 to Run 2 transition and recent operational experience

The characterisation of the Quark-Gluon Plasma produced in ultra-relativistic heavy-ion colli- sions is the main goal of the ALICE experiment at the CERN LHC. The ALICE Inner Tracking System (ITS) plays a key role in the study of short-living hadrons through the primary and sec- ondary vertex reconstruction. The system is composed of two innermost layers of pixel detectors, two middle layers of drift detectors and two outermost layers of strip detectors. The ITS covers the central pseudo-rapidity range of | h | < 0.9 and the distance from the beam line ranges from 3.9 cm for the innermost layer to 43 cm for the outermost layer. During the Run1 data taking period, the ITS contributed with tracking and charged particle identification capabilities, as well as a contribution to the definition of the Level 0 trigger signal. In particular at low p T the event reconstruction relies on the ITS performance as tracks do not reach the outer tracking detectors. In this contribution, after a brief description of the design of the three sub-detector systems and the respective performance during Run1, the consolidation activities carried out during the LHC long shutdown period (LS1) and the re-commissioning to prepare the detector for the data taking during Run2 will be presented.