The 8th International Conference on Micro Pattern Gaseous Detectors (MPGD24)

The Near Detector of the T2K experiment at J-PARC has recently being upgraded  in order to reduce the present systematic uncertainties affecting the oscillation parameters measurements and  to exploit the increased neutrino beam power of the J-PARC complex. 
One of the major improvement to the T2K ND280 detector consisted in the   the integration of two large size (~ 3m³  each)  new horizontal High -Angle  Time-Projection Chambers (HATPC).
The new  HATPCs  are based on a gaseous active volume contained in a Field Cage made of lightweight composite material, combining optimal mechanical and electrical properties with minimal radiation length and dead volume.
The readout is performed by innovative Resistive Micromegas modules featuring a resistive layer for charge spreading on top of the readout plane to enhance spatial resolution performance. The mentioned technologies have been studied in test beams and cosmic rays campaigns. After the installation at J-Parc in Fall 2023, a commissioning period of data taking with cosmics and then with a neutrino beam has been performed.
In this talk the  details about the detector concepts, the design and construction methods are presented  within the technological challenges and the solution adopted to cope with the challenging requirements of the upgrade. Furthermore the results  of the characterization and commissioning performance of the HA-TPCs at CERN and J-Parc, including also the first results using beam neutrinos interactions will be illustrated.
 

TPC, MPGD, Micromegas, DLC