  ALICE, one of the experiments at the Large Hadron Collider (CERN), is
undergoing ambitious upgrades during the ongoing second long shutdown (LS2).
The main goal of this project is to access rare events and previously
inaccessible physics observables. The increased Pb-Pb and pp collision rates
need a correspondingly higher TPC operation rate in the next Run 3 of the LHC.
The operational gated MWPC readout used so far cannot be used at such fast
rates. Therefore a new readout chamber is needed with a novel technology and
without any compromise on the momentum and energy resolution. As a solution the
Gas Electron Multiplier (GEM) technology is applied. This new readout chamber
consists of inner-(IROC) and outer (OROC) readout chambers with a 4 stage GEM
cascade in order to reduce back-drifting ion space charges. These quadruple
stacks have proven to provide sufficient ion blocking capabilities. This
structure also preserves the intrinsic energy resolution and keeps the
space-charge distortions at a tolerable level. The GEMs cannot be repaired
during operation, therefore to minimize the unsuitable foils, the Quality
Assurance system is developed. These cleanroom measurements investigate the
hole size uniformity, the gain uniformity and the electrical stability. Due to
the continuous readout, higher readout rate is possible. The new ASIC-SAMPA has
been developed for this purpose. After the ROC assembly some of chambers were
tested in the ALICE cavern, and a test campaign started for the further testing
of the ROC bodies at GIF at CERN.
