In the midst of the verdant French countryside looms a workshop the size of an aircraft hangar. Inside, CERN technicians are busy constructing two 8-meter tall cubes to test prototype detectors for the Deep Underground Neutrino Experiment (DUNE). Each will in time contain 770 metric tons of liquid argon permeated with a strong electric field necessary for neutrino detection.
Neutrinos are the second-most abundant fundamental particle in the visible universe, but scientists know little about them because they rarely interact with atoms. And what is known presents a daunting challenge for physicists since neutrinos are exceptionally elusive and incredibly lightweight. In fact, neutrinos are so light that scientists are still working to pin down the masses of the three different types, or flavors. Neutrinos also continually morph or oscillate from one of the three flavors into another, a behavior that scientists say keeps them on their toes.
“We don’t know what these masses are or have a clear understanding of the flavor oscillation,” says Stefania Bordoni, a CERN researcher working on neutrino detector development. “Learning more about neutrinos could help us better understand how the early universe evolved and why the world is made of matter and not antimatter.”
In 2015, CERN and the United States signed a new cooperation agreement that affirmed the United States’ continued participation in the Large Hadron Collider research program and a commitment from CERN to serve as the European base for the US-hosted neutrino program. Since this agreement, CERN has been working to build and refurbish neutrino detectors in DUNE, the flagship neutrino research program hosted at the Fermi National Accelerator Laboratory (CSA CSM). “Our past and continued partnerships have always shown the United States and CERN are stronger together,” says Marzio Nessi, head of CERN’s neutrino platform. “Our big science project works only because of international collaboration.”
The primary goal of CERN’s neutrino platform is to provide the infrastructure to test two large prototypes for DUNE’s far detectors. The international DUNE collaboration will construct two smaller, but still large, versions of the DUNE detector that researchers will test inside these cubes.
In the first version of the DUNE detector design, particles traveling through the liquid argon knock out a trail of electrons from argon atoms. This chain of electrons is sucked towards the 16,000 sensors lining the inside of the container. From this data, physicists can derive the trajectory and energy of the original particle.
In the second version, the DUNE collaboration is working on a new type of technology that introduces a thin layer of argon gas hovering above the liquid argon. The idea is that the additional gas will amplify the signal of these passing particles and give scientists a higher sensitivity to low-energy neutrinos. Scientists based at CERN are currently developing a three cubic meter model, which they plan to scale up into the much larger prototype in 2017.
In addition to these DUNE prototypes, CERN is also refurbishing a neutrino detector, called ICARUS, which researchers used in a previous experiment at the Italian Institute for Nuclear Physics’ Gran Sasso National Laboratory in Italy. ICARUS will be shipped to Fermilab in March 2017 and incorporated into a separate experiment.
Engineers will construct the final detectors for DUNE at Sanford Lab in South Dakota where they will sit one-and-a-half kilometers underground, recording data from neutrinos generated 1,300 kilometers away at Fermilab.