The Deep Underground Neutrino Experiment seeks to measure neutrino CP violation (if it exists) and the neutrino mass ordering using a new intense beam to be built at the Long Baseline Neutrino Facility (LBNF).
The basic idea is shown in the figure below. Protons from the Fermilab Main Injector are directed towards a carbon target to produce pions. These pions (both plus and minus) are sign-separated and focussed using a pulsed magnetic field from a "horn" (so-called becuase of its shape). The pions are send into a long tunnel where they decay into muons and muon neutrinos. Due to the relativistic boost of the pions, the neutrinos mostly travel in the forward direction.
The neutrinos then travel 1,300 km to the Sanford Underground Research Facility (SURF) located in Lead, South Dakota where they are detected by a large liquid argon Time Projection Chamber (TPC).