The main purpose of the Deep Underground Neutrino Experiment is to measure the CP-violation phase in long-baseline neutrino oscillations, proton decay and super nova neutrinos with a liquid-argon detector of unprecedented size.
In order to constrain the systematics including the flux, neutrino interaction cross section, energy scale and so on, a near detector is needed to measure the un-oscillated neutrino spectra. In the near detector complex, a three dimensional scintillator tracker also called 3DST located downstream of the liquid-argon detector is proposed and being studied. The 3DST detector technology will consist of a large amount of 1 cm x 1 cm x 1cm scintillator cubes. We expect this tracker to have full angle coverage for charge particles, as well as precise energy and angular measurements, which, doing a neutrino-electron scattering study will lead to a strong flux constraint. Besides, 3DST gives an unique opportunity to connect carbon target cross sections and flux measurements in DUNE with other experiments, such as T2K and Minerva. In this poster, the simulation and test beam performances of the 3DST will be shown.