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The first parts of the international Deep Underground Neutrino Experiment have arrived at the Sanford Underground Research Facility in Lead, South Dakota, after traveling via rail, ship, highways, and shafts. One day, DUNE’s Far Detector will use the anode plane assemblies, or APAs, to collect data from neutrino collisions. According to Mike Headley, executive director of SURF, “this APA arrival and test lift signals the commencement of DUNE onsite activity at SURF.” I’d want to express my gratitude to the collaborative team from CERN, Fermilab, the University of Manchester, and SURF for making this first experiment lift a huge success.
By examining neutrinos, odd subatomic particles that infrequently interact with matter, DUNE will provide a fuller understanding of the creation of matter and the cosmos. From the United States, a beam of neutrinos will travel 800 miles through the planet. DUNE’s enormous subsurface detectors at SURF to the Fermi National Accelerator Laboratory in the Chicago area. The experiment, which is being run by Fermilab, involves more than 1,400 scientists and engineers from more than 30 different nations. “This was a test of the entire logistical chain,” said Joe Pygott, deputy director of the Fermilab South Dakota Services Division. “From the UK through Switzerland to Illinois and eventually to South Dakota.” “It was great to see the international effort come together after a year of preparing.”
Making things awkward
The APAs are the largest and one of the most vulnerable parts of DUNE, measuring a remarkable 19.7 feet tall and 7.5 feet wide (6.0 meters tall and 2.3 meters wide). Numerous electronic read-out boards are installed in the huge steel frames of the APAs by researchers. The frame is then covered with 15 miles of hair-thin copper-beryllium wire, giving it a delicate, mesh-like look. 150 APAs in total, 136 from the UK and 14 from the US, will be constructed for DUNE. Olga Beltramello, a mechanical engineer at CERN, stated that the APAs are categorized as an “essential transport” because to their size, fragility, and expense. The project established the Awkward Material Shipping Team, which has the perfect name, to handle the logistics and transport of strange components like the APAs.
Beltramello, an AMTT participant, was in charge of designing the frames that would support the APAs during transportation. She anticipated the characteristics of the journey during the design phase, including the jostle of the rail car, the lurch of the waves, and the sway of an overhead crane. According to Beltramello, “We do analysis to determine how the APA will endure the dynamics of the shipment.” The calculations are difficult because the vibrations caused by track transport in Europe differ from those caused by tire transit in the United States, which differ from those caused by sea shipping. The delivery of two prototype APAs to SURF allowed the team to stress-test their transportation strategy since mass production of APAs was already under way. Researchers were able to determine how much stress the components actually underwent during the travel thanks to acceleration sensors and vibration detectors that tracked every tremble along the way.
By land and sea
The APAs were built at the Daresbury Laboratory of the UK’s Science and Technology Facilities Council before being transported to CERN, the particle physics research facility in Europe. In ProtoDUNE, the APAs were set up and tested. ProtoDUNE is a prototype of the DUNE detectors that will be constructed at SURF, and it is a huge detector in and of itself. Researchers tested the APAs’ resistance to the freezing temperatures of liquid argon (minus 200 degrees Celsius) and their ability to provide noise-free data transmissions. According to Justin Evans, physics professor at the University of Manchester and academic director of the UK project for APA creation, “In ProtoDUNE, we saw gorgeous, crisp visuals.”
The APAs then traveled 1,600 miles across the United States on a semitruck after traveling by rail to the coast and over the Atlantic in a cargo ship. To reach the level where workers are digging the huge caves that will house the DUNE Far Detector, the final step of the voyage was down the mile-deep Ross Shaft. The APAs are too big to fit on the device that moves people and materials through the shaft, which resembles an elevator. Instead, to drop them underground, the APAs were suspended below the cage. Assuring themselves of the APA performance in ProtoDUNE and the successful test transfer, researchers have begun mass fabricating APAs for DUNE. SURF’s rigging supervisor Jeff Barthel, who oversaw the move, said the test lift of the almost 6,400-pound load “couldn’t have gone smoother.” “The good teamwork across groups is, for me, even more crucial than achieving this technological goal,” Beltramello added. “This was our first time working with these groups together, and it was a huge success. It’s beneficial for the future.
A neutrino trap
The caves will house detector modules that are each filled with 70,000 tons of liquid argon after the excavation is finished. The APAs will be immersed side by side in the chilly liquid argon to create a series of net-like walls that span the detector’s width. A cascade of charged particles is produced when neutrinos strike an argon nucleus. These particles then dislodge electrons from argon atoms’ outer shells. The free-floating electrons will be pushed towards the direction of an APA wall by an electric field. The APA wires will trap the stray electrons like a spider’s web, sending data shivers up the lines to the electrical read-out boards. Particle tracks are one way that researchers might visualize this data. According to Evans, “the electrons are striking these miles and miles of wires, and we gain information from that little pulse of electrical current on the cable.” “The pattern of electrons colliding with the APAs is mirrored in the pattern of particles that traveled through the detector.” Researchers can learn details about neutrinos and their antimatter counterparts from these particle trails. The outcomes will clarify the part neutrinos played in the universe’s evolution.