Preliminary measurement of ion drift velocity in T2K gas mixture

Abstract In recent years, the near detector of the T2K experiment underwent an important upgrade of part of its equipment, which involved the construction of a set of new detectors. As a part of the upgrade, two gaseous Time Projection Chambers (TPC), placed above and below the active target, enable the study of particles produced at large angles with respect to the beam axis by neutrino interactions. Each High Angle TPC includes a large active volume defined by rectangular cross-section field cages with lightweight composite material walls and two readout planes instrumented with eight Encapsulated Resistive Anode Micromegas (ERAM) each. A deep knowledge of this detector is crucial to achieve good performance. This communication reports the studies that are being carried out in order to get a deeper comprehension of the T2K mixture properties that have a relevant impact on the signal formation; in particular, the focus is on the determination of the ion drift velocity, which affect the spread of the electrons in the resistive layer of the ERAM and, consequently, the signal shape.