Speaker
Description
The off-axis near detector ND280 of the T2K experiment has recently undergone a major upgrade. As part of this upgrade, two new gaseous High-Angle Time Projection Chambers (HA-TPCs) were installed above and below the SuperFGD, a highly segmented scintillator target. This configuration allows precise reconstruction of particles produced at large angles with respect to the neutrino beam. The upgraded detector also incorporates six new time-of-flight scintillator panels, providing improved timing capabilities. Each HA-TPC is equipped with an innovative, lightweight field cage constructed from low-density, low-Z materials, resulting in a total wall thickness of less than 4% of a radiation length. The readout system consists of 16 ERAM modules per chamber, based on a novel resistive Micromegas technology that was extensively tested and characterized before installation. However, field studies showed that shifting the first field strip by 8mm toward the anode introduced localized distortions, most pronounced near the cathode. To further investigate electric field non uniformities and deepen our understanding of ERAM performance, a dedicated laser based setup for a half volume TPC is currently being commissioned at CERN. A 266 nm Nd:YAG laser enters the chamber through a quartz window on the anode plane and is redirected by a movable mirror near the cathode to steer the beam along controlled trajectories. This contribution will present the development of this setup and the first results from the characterization campaign.