Tile Calorimeter Upgrade Program for the Luminosity Increasing at the LHC

The Tile Calorimeter (TileCal) is the central hadronic calorimeter of the ATLAS experiment at the Large Hadron Collider (LHC). The LHC is scheduled to undergo a major upgrade, in 2022, for the High Luminosity LHC (HL-LHC). The ATLAS upgrade program for high luminosity is split into three phases: Phase-0 occurred during $2013-2014$ and prepared the LHC for Run 2; Phase-I, foreseen for 2019, will prepare the LHC for Run 3, whereafter the peak luminosity reaches $2-3 \times 10^{34}$ cm$^{2}s^{-1}$; finally, Phase-II, which is foreseen for 2024, will prepare the collider for the HL-LHC operation ($5-7 \times 10^{34}$ cm$^{2}s^{-1}$). The TileCal main activities for Phase-0 were the installation of the new low voltage power supplies and the activation of the TileCal third layer signal for assisting the muon trigger at $1.0<|\eta|<1.3$ (TileMuon Project). In Phase-II, a major upgrade in the TileCal readout electronics is planned. Except for the photomultipliers tubes (PMTs), most of the on- and off-detector electronics will be replaced, with the aim of digitizing all PMT pulses at the front-end level. This work describes the TileCal upgrade activities, focusing on the TileMuon Project and the new on-detector electronics.