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Mike's Blog: Capturing neutrinos at the South Pole

Jan. 29, 2019

On Jan. 15, my wife and I attended “National Geographic Live: View From Above”, which featured former NASA Astronaut and Air Force Colonel Terry Virts sharing his experiences as pilot of Space Shuttle Endeavor and what life was like aboard the International Space Station. It was a late Christmas gift from my wife, who knows I’m a space geek. Astronomy/astrophysics involved too much math for me to want to pursue academically, but I’ve remained a layperson fan of anything space-related nonetheless, and I relish the opportunity to learn from those who work in the field. It was a great night. Virts’ stories and perspectives he shared were fascinating. But surprisingly, there was something else at the venue that I found equally interesting before we even took our seats in the auditorium.

We arrived early at the Overture Center here in Madison, WI because we saw that there would be educational displays to check out before Virts took the stage. We eventually wandered up a couple of floors to a large room dedicated to learning about the IceCube Neutrino Observatory—a research station designed to search for and observe neutrinos from deep within the South Pole ice. Unbeknownst to me, the University of Wisconsin-Madison operates IceCube, which hosts 300 international scientists dedicated to studying neutrinos—tiny subatomic particles produced by the decay of radioactive elements. They are produced in high-energy collisions, travel at nearly the speed of light, and the majority are said to have been born soon after the birth of the universe.

The exhibit taught us that construction finished on IceCube in December of 2010, nearly 25 years after the idea of detecting neutrinos in ice was first proposed. The IceCube detector is made up of more than 5,000 sensors on 86 cables that run 2,450 meters below the ice surface down to the bedrock. Affixed to the cables between depths of 1,450 and 2,450 meters, the sensors collect light given off by particles and then digitize and time stamp the information. A more densely-instrumented region near the center of IceCube—DeepCore—enables the detection of lower-energy neutrinos, enhancing the detector for dark-matter searches and neutrino-oscillation studies. The surface component of IceCube—IceTop—detects cosmic-ray showers.

The exhibit had a model of the station that displayed what it looks like when a neutrino is detected. Also on display was one of the digital optical modules (DOMs)—the sensors that make up the detector. They were carefully tested before they were deployed on the cables beneath the ice. Once they are frozen down there, they can no longer be physically accessed. The IceCube Collaboration of nearly 50 organizations and UW-Madison can, however, troubleshoot electronic problems and update software remotely, because all DOMs are wired to the IceCube Lab that sits centrally atop the surface.

Constructed 800 meters away from the Amundsen-Scott South Pole Station and covering one cubic kilometer, IceCube was the first detector of its kind, designed to observe neutrinos from the most violent astrophysical sources in our universe. The station detects more than one hundred thousand neutrinos per year, but so far only slightly more than one hundred are in the energy range to be of interest to astronomy. While finding those qualifying neutrinos is a challenge, IceCube has already revealed the highest-energy neutrinos ever observed. These will allow the team there and the overall astronomy field to explore the origin and nature of cosmic rays.

It was mind-blowing to learn that not only did this station exist at the South Pole, but that it’s run by the university 6 miles from my house and that I’ve lived near most of my life, and that I had no idea until that date Jan. 15 date night. I already knew about the Super-Kamiokande neutrino observatory near Hida, Japan, and I recently watched a documentary about what life is like at Antarctica’s McMurdo Station. I consider myself decently-well-versed in science engineering marvels, but IceCube somehow wasn’t on my radar. It is a great achievement in concept engineering, test engineering, and cosmic exploration. I’ll certainly pay close attention to what they find down there.

Learn much more about IceCube at their website, and in this 6-minute informative video:

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