Discovering the highest energy particles from the top of the Greenland Ice Sheet

October 27, 2022
Maureen McMahon

Abigail Vieregg and her students build antennae arrays in valleys and on ice sheets
Prof. Abigail Vieregg and her students build instruments to detect the highest energy neutrinos.

Professor Abigail Vieregg received a Moore Foundation Experimental Physics Investigators Initiative Award for instrumentation development to advance the detection of the highest energy neutrinos.

Over the last decade, innovations in neutrino astronomy have probed the elusive interactions of neutrinos—tiny ghostly particles that can tell us about faraway astrophysical phenomena.

When neutrinos arrive from deep space, they penetrate Earth and sometimes enter ice sheets. In Greenland and at the South Pole, home to vast amounts of transparent glacial ice, the conditions are perfect for detecting traces of their behavior.

Abigail Vieregg
Abigail Vieregg

“When neutrinos interact in ice, they make a shower of particles that makes very fast blips of radio waves in the ice,” said Abigail Vieregg, a professor in the Departments of Physics and Astronomy and Astrophysics, the Enrico Fermi Institute, and the new David N. Schramm director of the Kavli Institute for Cosmological Physics. 

By placing radio antennas in an array into the ice of Greenland, her experiment assembles what is called a neutrino telescope, which enables them to measure radio waves and make detailed reconstructions of how neutrinos interact.

“Neutrinos are the perfect messenger particle, meaning that if you want to look at high energy things that are far away, all the other particles those high energy things make get absorbed on their way here,” she said. “Neutrinos persist, making it all the way here, and can tell the story of what happened.”

Many particle physicists aren’t looking for clues to high energy physics in astronomy and cosmology, but Vieregg pointed out that ultra high-energy neutrinos are one million times more energetic than what you can make at the Large Hadron Collider (LHC), the biggest particle accelerator on Earth.

With high sensitivity measurements, scientists can ask questions about the properties of neutrinos themselves, as well as measure how high energy sources evolve as a function of time, a central question in cosmology.

Vieregg is the founding primary investigator for the Radio Neutrino Observatory (RNO-G), which is currently under construction at Summit Station in Greenland. Building a neutrino telescope in Greenland has been in her plans since 2013. As a postdoctoral researcher, she led a field team to make measurements of the ice at Summit Station to make sure it was transparent enough. 

Her group at UChicago began testing hardware in 2015 to prove that a phased together group of antennas can make the world’s most sensitive detector for high energy neutrinos. They arrived at a design that uses interferometry to trigger when there is an event and measure it. It became a prototype for instrumentation used at the South Pole, which Vieregg’s group led the development and deployment of in 2018 as part of the Askaryan Radio Array (ARA).

It was not until 2019, when a collaboration of scientists from the U.S. and Europe came together, that deployment of a large detector in Greenland became a reality. The installation of central computing and communication infrastructure at Summit Station is done, as well as the installation of seven out of the planned 35 antenna stations. The experiment is set to be one of the world’s largest neutrino detectors. 

“We now have the highest sensitivity detector at the highest energies,” Vieregg said, “and that has helped RNO-G attract 16 partner institutions. Instrumentation is being built at several universities.” 

“To really scale up to make it a much bigger experiment—could we make it 500 antennas?—we have to solve an important problem: how to draw the least power from our wind turbines and solar panels and how to make the instrumentation easier to scale up.”

On October 27, the Gordon and Betty Moore Foundation Experimental Physics Investigators Initiative announced it has awarded Prof. Vieregg $1.25 million to support forward looking instrumentation that will be first tested on RNO-G, and ultimately could be used to develop multiple future detectors on the ground or in space.

“We are grateful the Moore Foundation has funded this next phase so we can work on delivering a more flexible design that can be used in many different applications,” she said.

She hopes their new system can be used for particle physics applications as well as paired down and used on cubesats, which are miniaturized satellites put into orbit at the International Space Station or put into payloads from launch vehicles.

The Gordon and Betty Moore Foundation fosters path-breaking scientific discovery, environmental conservation, patient care improvements and preservation of the special character of the Bay Area. 

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