April 26, 2018
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Neutrino work breaks new ground

By Meg Adams, Special to the BDN

Just across the runway from me sits a cluster of red buildings. Their forms are a bright series of dots against the stark white background of the Polar Plateau. These buildings are the Ice Cube drill camp — an under-ice neutrino-detecting project, one of the most important science projects going on at South Pole Station today.

“OK, explain this one to me again,” I ask one of the Ice Cube scientists as we wait in line for dinner in the galley. “What exactly is a neutrino?”

He laughs, takes a deep breath, and explains. “A neutrino is a stable particle, but it’s not part of the atom. It has very little mass and doesn’t interact that much. There are lots of them around.”

He picks up his eating utensils and a plate as he talks. “Most people are familiar with protons, electrons and neutrons because our world is made up of these particles, and they interact with us. But there are lots of neutrinos out there, too — billions of them go through us every second.”

“Thanks,” I say, taking the plate he hands me. “So why are we interested in detecting neutrinos?”

“That’s a bit of explanation. What’s the soup today? Potato cheddar? Sounds good to me — anything warm is good.” Our noses are still red from working outside, and I gladly ladle steaming soup into a bowl. “Let’s sit over there and I’ll explain,” he says.

The opportunity to have cutting-edge science experiments explained over lunch is just one more of the pleasant curiosities of living at a science research station. I happily sit down.

“So, why do we want to detect these neutrinos? Well, light telescopes only go so far into space. Light is absorbed and scattered by dust and gases. And charged particles don’t follow a straight line — they interact with other matter, and are bent by magnetic fields. But neutrinos have very little interaction with other matter, and they go very far and straight. Neutrinos can look [at] places you cannot see with light or charged particles.”

“So what sorts of things are we looking for?”

“Other neutrino detectors have seen evidence of very high-energy particles out there … and the source is totally unknown to us. There are no known phenomena to explain energy levels as high as have been seen. One idea is that these particles are made in cosmic accelerators.”

He spoons some of the soup into his mouth and then continues. “Many observations suggest that there is a lot of matter in the universe that does not produce light, so we can’t see it. Other measurements suggest that this matter, ‘dark matter’, is not made up of protons and neutrons, either. A possible component for this dark matter could be producing the neutrinos we detect.”

“So by looking at neutrinos, we’re learning more about the unknown, ‘dark’ areas of the universe?”

“That’s correct.”

“What do you hope to find?”

“Well, as Jeff Cherwinka said in his Ice Cube lecture last week, ‘the most interesting things we see will likely be unexpected. Every time we look at the universe in a new way we are surprised.’”

Ice Cube is a federally funded project administered through the National Science Foundation. Now in its seventh year, South Pole has seen the project grow steadily. Ice Cube essentially has built a neutrino-detecting telescope by drilling deep holes into the ice and lowering orb-shaped sensors into them. These holes are drilled with very hot water. The team is always a buzzing hive of activity during drilling time, jubilant afterward with the success of more sensors placed into the ice.

“Why is the Ice Cube project here at the South Pole — why not elsewhere? You mentioned other neutrino detectors.”

“The South Pole is a great place to detect neutrinos because of the quality of the ice. Neutrinos are hard to detect, but not impossible. We see them indirectly, when they interact and create a charged particle. Well, here at the South Pole, the ice is very, very deep … and as a result, it’s very clear. The kind of ‘light’ we look for travels farther in it without scattering. This means that we can lay sensors in the ice farther apart and cover much more ground.”

“You’re up to 21 different holes now, yes?”

“Yep — right on schedule. Right now there’s about a cubed kilometer of ice out there covered with neutrino sensors.”

“That’s awesome.” I scrape the bottom of my soup bowl with my bread, savoring the last of it; working outside here always makes me hungry. “After lunch I have some cargo to deliver to your camp … I’m pretty sure it’s more of your sensors.”

“Wonderful! I’ll tell Jim to expect you. Don’t drop those,” he says with a grin. “They’re important.”

“I wouldn’t dream of it.”

Meg Adams, who grew up in Holden and graduated from John Bapst Memorial High School in Bangor and Vassar College in New York, shares her experiences with readers each Friday. For more about her adventures, go to the BDN Web site: bangordailynews.com or e-mail her at madams@bangordailynews.net.

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