Earlier this year in South Dakota, crews carved out the future home of particle detectors for the international Deep Underground Neutrino Experiment. Installation of the four neutrino detectors is expected to begin soon to record the rare interaction of neutrinos with liquid argon. Building experiments deep underground is a bit like building a ship in a bottle — it’s both exciting and challenging at the same time.
Earlier this year in South Dakota, crews carved out the future home of particle detectors for the international Deep Underground Neutrino Experiment. Installation of the four neutrino detectors is expected to begin soon to record the rare interaction of neutrinos with liquid argon. Building experiments deep underground is a bit like building a ship in a bottle — it’s both exciting and challenging at the same time.
First detected by Los Alamos researchers in 1956, tiny particles called neutrinos are everywhere. They are the products of exotic phenomena such as solar fusion, and even ordinary occurrences such as the natural radioactivity of the potassium in bananas. Once produced, these ghostly particles almost never interact with other matter. Hold up your hand — as you watch, neutrinos are invisibly passing clean through it by the trillions.
Despite decades of study, the neutrino’s elusiveness means it is still little understood. This subatomic particle rarely interacts with matter, exhibits no electrical charge and is nearly weightless. In the physics community, we speculate that neutrinos may explain why the universe is made of matter — stars, galaxies, atoms and all life — and why most antimatter disappeared after the Big Bang. To put it simply, why is there something, instead of nothing?
To explore these kinds of questions, the physics community is embarking on one of the most ambitious science experiments in recent U.S. history. And Los Alamos National Laboratory is playing an important role.
Prototype detectors at the European Center for Nuclear Research (CERN) — the home of the Large Hadron Collider, the world’s largest particle accelerator and the place where the Higgs boson was discovered in 2012 — will pave the way for a U.S.-based experiment of unprecedented scale called the Deep Underground Neutrino Experiment (DUNE). With detectors in South Dakota and in Illinois, DUNE aims to launch the most intense neutrino beam in the world. Los Alamos is a key player with more than 1,400 international collaborators in this experiment.
Building enormous experiments deep underground is a bit like building a ship in a bottle — it’s both exciting and challenging at the same time. Each of the four neutrino detectors is about the size of a seven-story building and will be housed in a cavern big enough to hold a football stadium. Locating them underground ensures that background radiation from cosmic rays doesn’t interfere with the experiment.
Given the scale of the DUNE experiment, we need to make sure the technology works before deploying it. The two prototype detectors at CERN — we call them ProtoDUNEs — are testing the technologies under development. The first prototype detector took a year to assemble. Even the scaled-down detectors are massive: each detector cryostat can hold a total of 770 tons of liquid argon.
Liquid argon is a cryogenic liquid with a boiling point of minus-303 degrees Fahrenheit. It is a relatively new medium for this high-energy physics research, where neutrinos are observed indirectly as they hit the extremely cold liquid argon in the detector and produce charge and light that can be measured. The hope is that this experimental setup will enable more precise measurements of neutrinos.
Our team at Los Alamos, in collaboration with the Laboratory of Instrumentation and Experimental Particle Physics in Portugal, has designed and built the laser calibration instruments for the prototype detectors. We installed the laser calibration atop the detectors in January and are now busy validating their performance.
DUNE itself is currently under construction. This spring, excavation of the three caverns that will house the four detectors was completed. We will begin installing detectors in the fall. After several years, likely in the early 2030s, a neutrino beam will be sent from Fermi National Accelerator Laboratory in Illinois, traveling underground more than 800 miles to the Sanford Underground Research Facility in the Black Hills of South Dakota. Pointed down into the Earth, the beam will take advantage of the Earth’s curvature to meet these four immense liquid-argon detectors a mile underground at the site of the former Homestake gold mine. When it begins taking beam in the early 2030s, the facility will collect data for 20 years.
DUNE represents an enormous project for such a small particle. But neutrinos have the potential to resolve enormous science questions, including how the universe came into existence and its composition at an elemental level. These elusive, invisible particles have profound insights to offer us — and much more to reveal in the decades to come.
Sowjanya Gollapinni is a senior scientist in the Physics Division at Los Alamos National Laboratory.
