Meet AAS Keynote Speakers: Professor Francis Halzen

In this series of posts, you’ll sit with some of the plenary speakers at the 240th AAS Conference to learn more about them and their research.You can see the full schedule of their story hereAnd read other interviews here!!

Professor Francis Halzen. Image courtesy of Professor Halzen, © Bernardo Pérez.

Dr. Francis Halsen is a lot. He is a professor at Hilldale and Gregory Breit at the University of Wisconsin-Madison. IceCube Neutrino Astronomy In Antarctica and the winner of the American Astronomical Society 2021 Bruno Rossi Prize “For the discovery of high-energy neutrino fluxes of astrophysical origin,” he is honored to share with the international group of scientists that make up the IceCube collaboration.

With such a shimmering resume, it may be permissible to focus solely on his many achievements. But just as interesting is everything he doesn’t.

Not an astronomer

“I need to understand that I’m not an astronomer, though I’m pretending to be an astronomer,” was one of the first things Professor Halzen told me. Instead, Halzen describes himself as a particle physicist. Neutrino.. Neutrinos are some of the most abundant particles in the universe, Electronic But with a much smaller mass. Neutrinos are particularly interesting because their mass (lack) is slightly tense with neutrinos. Standard model It hints at a new and interesting physics of particle physics.

Despite not being an astronomer, Halzen has been thinking about neutrino astronomy since at least the mid-1980s. Dr. Enrique Zas I have experienced all the possibilities of how to make a neutrino detector. “This is a matter of particle physics. Instead of making a telescope, we make a neutrino detector. And we have experienced all the possibilities, and in fact, at the end of this, we. Decided that this is what we want to do. This means the current IceCube. “This is how Halzen was interested in space physics, the astronomical source of neutrinos, and later. .. Multi-messenger astronomy..

Not an engineer

He finished his undergraduate career as a student in mathematics and physics, a natural segue in theoretical physics, but Halzen started something else. “In fact, my first semester was engineering. That’s what I was aiming for because my dad had a construction company,” he said. Still, he eventually needed to be involved in the construction of IceCube and its predecessors. AmandaFrom about From 1996 to 2011.. So, in the end, he got entangled in his father’s field and completed a perfect circle.

What is the key to designing a neutrino detector? Submerge the photomultiplier tube in water. Occasionally, neutrinos interact with water molecules to produce light. There are neutrino showers that constantly flow through the Earth, but they interact so weakly that this interaction is still rare and there is little radiation. Photomultiplier tube Is a device that can detect such radiation — several photons at a time! They are easy to manufacture and cheap, leaving only the technical question of how to sink them. Previous experiments were attempted in seawater, but the fight against water proved to be too logistically difficult. Later, at a conference in Poland, Halzen talked about another approach. And he was surprised that he wouldn’t be laughed at from the room. “The original idea was that it’s actually easier to put a photomultiplier tube in ice at a depth of a few kilometers than to put it in water or seawater, which is counterintuitive. And it turned out to be correct. And the important thing about IceCube is that once you understand how to do it, [it] It’s relatively easy to build, and once built it’s completely stable. “

Not an experimenter

“I haven’t experimented in my life. I’m still a theorist,” continued Halzen, Principal Investigator (PI) for the IceCube experiment. “I always thought it was a bad idea to hire a theorist as a PI. But the experiment actually started with three people, the other two were graduate students at UC Berkeley, and then. By the time I was in my 40s, I knew how to write a proposal, but they didn’t, so I wrote a proposal.

Despite Halzen’s anxieties, IceCube and its predecessors have had great success and are now 300 people in 14 countries.. Halzen says this is the real key to success. “The reason it worked is because, like science, I’ve always found great collaborators. When I launched the project in Madison, we found all the right people. As such, this was a group of incredibly talented people who designed a hot water drill and actually made it work. I found the right people and great project directors and engineers, so that’s part of it. I was lucky, but some thought I wouldn’t do it because I worked on it. “So another thing that Halzen doesn’t have is the lack of great collaborators. ..

Advice for [Not] Astrophysicist

Halzen was ready when asked if up-and-coming astrophysicists had any advice at the beginning of his career. “Yes, my advice is always the same. […] The most important thing is to do what you are interested in. Don’t chase money, chase your personality, or chase your own interests. He elaborated that the first two may be ways to build a career, but they won’t help build a happy life. He also recalled that about 90% of physicists read that they were only working on the topic of his dissertation. This is the number that confused him. “How can I do that? There must be other interesting things in my life? That’s another piece of advice. Don’t hesitate to switch topics. In your field, or even outside.”

For more information on how IceCube looks for astrophysical neutrinos, see Professor Halzen’s award lecture at # AAS240 at 8:10 AM PST on Wednesday, June 15.


Editor: Sumeet Kulkarni

Featured Image Credits: AAS

About Luna Zagorak

I have a PhD in Physics from Yale University. The focus of my research is ultra-lightweight (or fuzzy) dark matter in simulations and observations. I am also a Franke Fellow in the Natural Sciences and Humanities at Yale University and is working on a project on Egyptian astronomical archeology, my other passion. When I’m not writing code or decoding glyphs, I usually read, scribble, and drink coffee.

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