Neutrinos can travel through dense matter such as the Earth without interacting with a single atom, leaving no trace of their passage. To observe even just a few of the extremely rare interactions of neutrinos with matter, physicists build detectors with massive amounts of target material and operate them for many years. The detectors record the tracks of the particles that emerge from the rare collisions of neutrinos with atoms of the target material.
The unique and valuable data that DUNE will collect will be stored and curated according to guidelines from the contributing funding agencies, as outlined in the DUNE Digital Data Management Plan.
The DUNE Far Detector
The DUNE collaboration will use state-of-the-art Liquid Argon Time-Projection Chamber (LArTPC) technology for the massive neutrino detector planned at the Sanford Lab site. Active particle detector elements will be immersed in liquid argon (LAr). Argon, a gas at room temperature, condenses to a liquid when cooled below -186°C (-303°F).
The four cryostats of the far detector will hold combined a total of 68,000 tons of liquid argon as the target material. Neutrino interactions in the liquid argon will produce ionization electrons that drift to wire planes (the TPC elements) in the fluid due to the presence of a high-voltage electric field.
The wire planes collect the ionization electrons, and the detector sends these signals to the data acquisition system. The installation of three planes of wires allows the 3D reconstruction of the particle tracks.
The image below shows a beautiful charged-current muon neutrino interaction in the ArgoNeut detector, a small-scale LArTPC at Fermilab that ended its data run in 2010. The image shows four gamma-induced electromagnetic showers from the decay of two neutral pions, detached from the primary interaction vertex.
The DUNE far detectors will be installed 1,475 meters (4850 feet) underground to shield them from cosmic rays, which constantly bombard Earth’s surface. These particles would generate tracks in the detector that would complicate the data analysis. The large amount of rock above the far detector will ensure that almost all cosmic rays will get absorbed in rock before reaching the DUNE far detector.
The Near Detector
A design effort is underway for a fine-grained neutrino detector to be located at Fermilab, a few hundred meters downstream of the muon neutrino source powered by the accelerator complex at Fermilab.
The near neutrino detector’s principal role is to characterize the neutrino beam as it leaves the near site in order to better understand the signals collected at the far detector and thus maximize the neutrino oscillation physics potential of the experiment. In addition, the near detector will enable a rich program of physics measurements independent of the far detector and provide the data for many PhD theses.
A potential detector design includes a straw-tube tracking detector and electromagnetic calorimeter placed inside a 0.4-Tesla dipole magnet that enables particle tracking.
Prototype Detectors for DUNE
The DUNE far detector will be by far the largest liquid-argon neutrino detector ever built in the world. The two largest LArTPC neutrino detectors that have been built to date are the ICARUS detector (760 tons of liquid argon, originally operated at the INFN Gran Sasso laboratory in Italy, and recently refurbished at CERN for its next phase of operation in the Short Baseline Neutrino Program at Fermilab) and the MicroBooNE detector (170 ton; detector is currently taking data as part of the SBN program at Fermilab).
The DUNE collaboration is pursuing an aggressive program of building and testing detector components for the construction of the far detector. The next big step is the construction of two large prototype detectors at the CERN Neutrino Platform and have them operational by 2019.
The Single Phase ProtoDUNE detector will be built using the full-scale Single Phase LAr TPC detector components designed for the construction of the first of four DUNE far detectors. The SP ProtoDUNE will be tested with a low-intensity particle beam provided by the CERN accelerator complex. The SP ProtoDUNE builds on the SP LAr TPC technology developed for ICARUS and MicroBooNE. A smaller, 35-ton prototype SP LAr TPC detector for DUNE was tested at Fermilab in early 2016.
A 30-second animation of the single-phase liquid-argon TPC technology.
The Dual Phase LAr TPC ProtoDUNE detector (300 tons of liquid argon) will test an innovative modification of LAr TPC technology chosen for the second of the four DUNE detector modules for the far site. This detector features amplifiers that operate in a layer of gaseous argon above a large target volume of liquid argon. Compared to the SP ProtoDUNE, this Dual Phase detector technology promises a 20-fold increase in amplification of the faint signal produced by ionization electrons drifting through the liquid argon. Construction of a small, 25-ton DP Lar TPC prototype detector took place at CERN in 2016.
Insertion of the cryostat of the 25-ton Dual Phase Liquid-Argon TPC prototype detector at CERN in July 2016.