Commissioning of CMS Forward Hadron calorimeters with upgraded multi-anode PMTs and ?TCA readout

The high flux of charged particles interacting with the CMS Forward Hadron Calorimeter PMT windows introduced a significant background for the trigger and offline data analysis. During Long Shutdown 1, all of the original PMTs were replaced with multi-anode, thin window photomultiplier tubes. At the same time, the back-end electronic readout system was upgraded to ?TCA readout. The experience with commissioning and calibration of the Forward Hadron Calorimeter is described as well as the ?TCA system. The upgrade was successful and provided quality data for Run 2 data-analysis at 13 TeV. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0).