FOR IMMEDIATE RELEASE
Summer: Ice, Radiation, and Dark Matter?
One student’s research internship contributes to the building of dark matter detector in South
Pole.
06/25/13 – Urbana, Ill. – For many students, summer means relaxing and taking a break from learning, but for Alyssa Bowes of Glen Ellyn, IL, it means much more. Since she was young,
Alyssa Bowes had always taken an interest in astrophysics and especially dark matter. This summer, when Bowes was given the opportunity to be part of a project at the University of
Illinois at Urbana-Champaign that would help scientists search for dark matter two kilometers under the ice of the South Pole, it was too good for her to pass up.
As strange as it may seem, underground research is the most beneficial for direct dark matter detection. This is because Earth acts as a shield, blocking out most radiation coming from space.
Dark matter, however, is known as a weakly interacting matter particle, or WIMP.
“As ‘WIMP’ implies, dark matter rarely reacts with anything at all, so it can go through the Earth without trouble,” said Bowes.
One method for dark matter research is by observation of a dark matter halo, which is theorized to surround the galaxy, providing it with its mass and keeping it together in rotation. As the Sun rotates around the galaxy center and Earth rotates around the Sun, the observed dark matter halo’s magnitude and direction should fluctuate. The fluctuation should always be greatest when the Earth travels in the same direction as the Sun with respect to the galactic center, regardless of the location of the detector.

An experiment in Italy that took measurements beginning in 2003 observed a total of six fluctuations in one year. The results from this experiment could be profound, but need to be confirmed or rejected. In response, Dark Matter in Ice, abbreviated DM-Ice, went underway.
DM-Ice is a detector system much like the previous experiment, but it is at the South Pole, which is in the southern hemisphere and has opposite seasonal variations of Italy. If the final results match, it will provide strong evidence that dark matter interacted with the detector, and the dark matter halo’s fluctuation is not due to seasonal variation of Earth.
Bowes and her group were given the responsibility of testing a sodium iodide crystal for radioactive impurities, such as uranium and thorium contamination by setting up a system and using a source of gamma radiation to calibrate the detector.
“Although achieving our goals has been no trivial task, this has certainly been an exciting project,” said Alan Selewa, lab partner to Bowes.
The DM-Ice experiment employs the use of sodium iodide crystals. The sodium iodide composition was chosen because of its low background and great reactivity with radiation to create light. Bowes’ work is part of the detector R&D program, aimed at producing the world’s cleanest sodium iodide detector, with mass up to 250 kg (about 550 pounds!).
“I never imagined I would be involved with something so interesting and so important,” said
Alyssa Bowes. “Through this experience, I have learned what it means to be a scientist and part of something bigger than myself.”

Alyssa Bowes’ summer research was funded by National Science Foundation Grant No.
1062690. The opinions, results, and conclusions presented are those of the researchers and not necessarily those of the National Science Foundation.
About the “Research Experiences for Undergraduates” Program: The Research Experiences for Undergraduates (REU) program of the National Science Foundation supports active research participation by undergraduate students in science, technology, engineering, and mathematics.
The Department of Physics at the University of Illinois at Urbana-Champaign has hosted annual summer REU student participants since 1993.
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Contact: Siv Schwink, Communications Coordinator, Department of Physics, University of
Illinois; sschwink@illinois.edu; 217.300.2201
Contact: Liang Yang, Assistant Professor of Physics, Department of Physics, University of
Illinois; liangyg@illinois.edu; 217.244.2792
For more information about the Yang Group, see http://www.npl.illinois.edu/.
For more information about the Department of Physics at the University of Illinois at Urbana-
Champaign, see http://physics.illinois.edu/.