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). TileCal is a sampling calorimeter with approximately 10,000 channels and is operating successfully (data quality efficiency above 99%) in ATLAS, since the start of the LHC collisions. The LHC is scheduled to undergo a major upgrade, in 2022, for the High Luminosity LHC (HL-LHC), where the luminosity will be increased by a factor of 10 above the original design value. The ATLAS upgrade program for high luminosity is split into three phases: Phase 0 occurred during 2013-2014 (Long Shutdown 1), and prepared the LHC for run 2; Phase 1, foreseen for 2019 (Long Shutdown 2), will prepare the LHC for run 3, whereafter the peak luminosity reaches 2-3 x 10^{34} cm^{2}s^{-1}; finally, Phase 2, which is foreseen for 2024 (Long Shutdown 3), will prepare the collider for the HL-LHC operation (5-7 x 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). During Phase 1, it is foreseen the replacement of the gap scintillators. In Phase 2, 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 and sending them with 10 Gb/s optical links to the back-end electronics. This work describes the TileCal upgrade activities, focusing on the TileMuon Project and the new on- and off-detector electronics. The TileMuon project aims at reducing the muon trigger rates due to the slow charged particles, which interact with the muon detector, by using the TileCal third layer signal. With the increase of the luminosity, the reduction of the muon trigger rates due to such slow charged particles is very important, since it improves the muon trigger efficiency. In order to receive the TileCal third layer signals, perform signal detection and provide communication with the muon trigger logic, a new electronic system was developed, tested, produced and is currently being installed in ATLAS. Concerning the on-detector electronics, three options are presently being investigated for the front-end electronic upgrade. The first option is an improved version of the present system built using commercial components, the second alternative is based on the development of an ASIC and the third is the development of a new version of the QIE (Charge Integrator and Encoder) based on the one developed at Fermilab. All three options will use the same readout and control system using high-speed (10 Gb/s) links for communication and clock synchronization. For the off-detector electronics, a new back-end architecture is being developed. Additionally, a Demonstrator program has been established, which combines the current and future architectures, as a proof of principle. The insertion of the first demonstrator is planned for the end of 2016.