  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.
