Towards the mass production of readout chambers for the upgrade of the ALICE TPC

The LHC will provide, during run 3 (2021 onwards) lead-lead collisions at interaction rates as high as 50 kHz. In order to cope with this luminosity the ALICE Time Projection Chamber (TPC) will be upgraded with new readout chambers and new readout electronics. The goal of this upgrade is to allow continuous readout of the TPC, while preserving its excellent momentum and dE/dx resolution. Therefore the ion back flow into the drift volume must be less than 1%, otherwise the field distortions due to space-charge build-up would decrease the performance significantly. Extensive R and D was performed to develop new readout chambers, meeting these goals. The resulting chambers employ a stack of four Gas Electron Multipliers (GEMs) with a special high voltage configuration. With the long shutdown 2 approaching at the end of 2018, the design parameters have been finalized and the mass-production of the GEM-based readout chambers has started. In this talk the status of the ALICE TPC upgrade is given. In particular the design of the chambers is presented. An overview of the recent R and D activities is shown as well. These include stability studies of the four GEM setup, tests to ensure the quality of the GEM foils during mass-production and the commissioning of the first front-end cards. In addition we report on the challenges of the mass production.