Astrophysics, IceCube, and Building a Muon Detector

by Maddy Boettner, Century College Graduate, and UWRF undergrad in Physics.

The summer has flown by and we now only have two weeks left of the internship! The last eight weeks I have learned so much about particle physics and astrophysics.

I am from Stillwater, MN, which is only about twenty five minutes away from River Falls. Most of the students are from all around the United States. I have been going to school at Century College which is a two year community college. I have decided that I will be attending the University of Wisconsin River Falls this upcoming fall for physics. Growing up I always wanted to understand how the Universe works and I have also always loved astronomy, but I didn’t know that I had any interest in physics at all. When I started college I kept changing my mind and switching my major because I had no idea what I wanted to do, until I accidentally discovered physics. I discovered physics much later than most who go into the field. It wasn’t until after high school and well into college that I started becoming interested in physics and taking classes.

I am very excited to be apart of the REU group this summer. One of my favorite parts was going to Madison for the IceCube bootcamp. It was a great opportunity where we got to learn a lot of physics and computer programming from IceCube professors from all over. Then in the evenings we would all explore Madison together. We ate delicious food and listened to music on the lake.

I believe that I was the only one who started the internship this summer with no computer programming experience. At first this intimidated me but it has been a wonderful experience for me to learn some programming skills this summer and to work with other students who do have previous programming experience. They have helped me out and taught me so much!

My project this summer has been to build a prototype muon particle detector for IceCube Gen2, which would be an expansion of the existing IceCube Neutrino Observatory in the South Pole. Last year a student made a prototype of the detector using optical fibers in a PVC pipe and this year I am using a 55 gallon drum. Inside the drum it is full of water and it has 8 wavelength shifting optical fibers spread out in it.

Here I am feeding optical fibers into a holder, which will be set near a SiPM, a silicon photomultiplier. The black drum contains water, our Cherenkov medium, and the fibers are spread out inside the drum.

When a muon passes through the water it is moving faster than the speed of light in the water which creates an effect known as Cherenkov Radiation. Cherenkov radiation is bluish light emitted in a cone. It is equivalent to a sonic boom but with light instead of sound. When the radiation occurs my fibers absorb the light. The light then travels to the ends of the fibers which are pushed up against a silicon photomultiplier. The Silicon photomultiplier detects the light and then sends a signal to an oscilloscope where we can read the signal. From there I use code in python to sort the the data.

I have been working to build and test a detector that is more cost efficient and potentially easier to move than the current design that IceCube uses. Eventually the rigid drum will be replaced by a flexible container, like a sack that is easy to transport and deploy.

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