Long Baseline Neutrino Facility neutrino beam The beamline for DUNE is called the "Long Baseline Neutrino Facility" (LBNF). The final design calls for a 2.4 MW proton beam from the
Main Injector accelerator to be targeted in the LBNF beamline to produce
pions and
kaons that are magnetically focused into a decay pipe via a
magnetic horn where they decay to
neutrinos. The neutrinos will travel in a straight line through the Earth, reaching about underground near the mid-point, to arrive at the underground laboratory in Lead, South Dakota. To point the neutrinos toward the underground laboratory, the beam must be directed into the earth at a steep angle. LBNF construction will include a hill made of compacted soil, connecting to a tunnel that will contain a particle decay pipe. The hill is integral to the "improved tritium management [that is] a major focus on the design of this new, higher beam power facility." Tritium produced by beamlines can enter the surface ground water, however rates at Fermilab are maintained at a level well below that allowed by regulations.
Dependence of LBNF on the PIP II project In order to provide 1.2 MW of protons to LBNF, the second phase of the
Proton Improvement Project ("PIP II"), which will increase proton delivery from the Fermilab accelerator chain by 60%, must be completed. The cost of this Fermilab upgrade as of 2022 is $1.28B. Thus, the PIP II and DUNE Phase I combined costs exceed $4B. The PIP II project received approval to begin construction in April 2022 and is expected to be completed by 2028. The current design divides the liquid argon between four LArTPC modules with a "fiducial volume" (the volume usable for physics analysis, which is smaller than the total volume to avoid interactions near detector edges) of 10 kilotons each. About 800,000 tons of rock will be excavated to create the caverns for the far detectors. Since LArTPCs are relatively new technology, extensive R&D and prototyping have been required. Prototype detectors are being constructed and tested at
CERN. The first of the two prototypes, the single-phase
ProtoDUNE (CERN experiment NP04), recorded its first particle tracks in September 2018. CERN's participation in DUNE marked a new direction in CERN's neutrino's research and the experiments are referred to as part of the Neutrino Platform in the laboratory's research programme. The
MicroBooNE experiment and
ICARUS experiment detectors are a pair of 100-ton-scale LArTPCs in the Fermilab program that also act as R&D platforms for DUNE detector development. These experiments have provided important input, but are more than 20 times smaller than the DUNE modules.
MicroBooNE is the longest continuously running LArTPC detector, having taken data from 2015 to 2021—considerably shorter than the time-period of 20 years expected for DUNE.
DUNE near detector The DUNE near detector will be located on the Fermilab site, downstream of LBNF, about from where the neutrinos are produced. The DUNE near detector comprises several subdetectors that will sit side by side. One of these (SAND) will be installed along the neutrino beam axis. The others (NDLAr and NDGar) are movable and can be shifted in the direction perpendicular to the beam to detect neutrinos at different production angles. The primary purpose is to monitor and characterize the beam as the neutrinos are created in the LBNF line, so as to make accurate predictions for interaction rates at the DUNE far detector. ==History leading to the international collaboration==