Characterization and commissioning of two large volume gaseous Time Projection Chambers at CERN and JPARC laboratories

The T2K Experiment is a long baseline accelerator neutrino experiment devoted to the study of oscillation neutrino Physics. In the last decade, T2K was able to perform measurements of the θ13 neutrino mixing angle and of the δCP phase giving hints on CP-violation. To confirm or not the CP-violation and to perform precise measurements of the PMNS matrix parameters, the T2K experiment is upgrading the neutrino beam and the Near Detector ND280 respectively to increase statistics and to provide constrains for reducing systematics uncertainties at the far detector. The University of Padova and INFN are involved in the ND280 Upgrade project in the construction of the two new High-A Time Projection Chambers. Two large TPCs have been assembled in the summer 2023 to form the bottom HA-TPC. After been characterized and calibrated at CERN the HA-TPC has been shipped to the JPARC laboratory (Tokai, Japan) and integrated into the T2K ND280 Near Detector, followed by commissioning. In my thesis I verified whether straight ionization tracks can be produced by a Nd:YAG Q-switching Laser to study the presence of biases in space resolution of tracks and the effects of electric field non-uniformities. This kind of tracks, together with accurate monitoring of gas composition and density with a mass spectrometer, makes possible precise measurements of the drift velocity by photo-extracting from the cathode and the anode. During my thesis I joined the commissioning activities at CERN, finalizing the purging procedures of inner volumes, calibrating the detector using pulsed Laser-induced tracks and testing the HA-TPC with Cosmic Rays. After the shipment and the installation of the bottom HA-TPC, I participated in the T2K neutrino run for the final commissioning and integration in the global DAQ.