SD Mines Researcher Leads CASPAR At Sanford Underground Lab

This is a photo of CASPAR (Compact Accelerator System for Performing Astrophysical Research) now in operation at the Sanford Underground Research Facility.

Nuclear astrophysicists, led by principal investigator and SD Mines professor Frank Strieder, have successfully created the first low-energy particle accelerator beam deep underground in the United States, bringing them one step closer to understanding how the elements of our universe are built.
The project is called CASPAR (Compact Accelerator System for Performing Astrophysical Research).  The team of scientists working on CASPAR will recreate the nuclear fusion processes inside stars. The project’s principal investigator is South Dakota School of Mines & Technology associate professor Frank Strieder. “CASPAR can help us answer some basic questions like: How do stars run? How do they produce energy? How elements are made?” says Strieder. “Where are we from? What is our cosmic heritage? I think it’s exciting to know all of the heavier elements inside our bodies were once produced inside stars,” he adds.     

CASPAR is one of only two underground accelerators in the world. The other is in the Laboratory for Underground Nuclear Astrophysics (LUNA) located near Gran Sasso mountain in Italy, where Strieder worked prior to coming to Mines.

“Installing and operating accelerators underground is a considerable challenge,” says Michael Wiescher, Freimann Professor of Nuclear Physics at the University of Notre Dame.  “CASPAR is unique since it covers a broader energy range than the LUNA accelerator. It allows us, for the first time, to explore reactions of stellar helium burning, which take place in stars like Betelgeuse, at laboratory conditions. Through these studies, we will learn about the origin of oxygen and carbon as the most important ingredients of biological life in the universe, and we will learn about the mechanisms stars have developed to produce gradually heavier elements through neutron fusion processes.”

Wiescher and research assistant professor Dan Robertson are with the team from Notre Dame, working in collaboration with researchers from the South Dakota School of Mines & Technology and the Colorado School of Mines.

“The complexity of moving an accelerator facility deep underground is greatly outweighed by the potential benefits when recreating nuclear reactions of astrophysical interest,” says Robertson. “Currently, a significant amount of the information we have about reactions that take place in the exact conditions inside a star can only be extrapolated from data in other energy ranges. This is mostly because the probability of that reaction is so small, and without a star’s worth of material to play with, it is difficult to measure when competing with cosmic background. We hope to measure key reactions in elemental production scenarios directly, providing insights into their behavior and helping to understand how and where the material in our everyday lives was produced.”

The 50-foot low-energy particle accelerator was assembled 4,850 feet underground in August 2015 at the Sanford Underground Research Facility (SURF) in Lead, S.D., formerly the Homestake Gold Mine. The accelerator had to be transported in pieces from its original home at Notre Dame to SURF and then lowered in a cage elevator and moved via mine trolley to the experimental space.

Taking the project underground shields it from the cosmic radiation the Earth is exposed to on a constant basis, which can interfere with highly sensitive physics experiments. “These kinds of studies need an environment free of cosmic rays as only provided at places like SURF,” says Wiescher.

The nuclear fusion that takes place inside a star is what creates the elements that are necessary for life. Older stars, born around the time of the Big Bang, consist of very few elements, while younger stars include a buildup of heavier elements such as lead and gold. Understanding that buildup of elements is just one of the many questions researchers hope to help answer through a series of CASPAR experiments.

With operations underway, the team plans to begin data collection in the fall. CASPAR received funding from the National Science Foundation, the South Dakota Science and Technology Authority and the University of Notre Dame. For more on the history of the project, visit nd.features/caspar. For a video showing SD Mines involvement in the project, click here.

Last edited 7/14/2017 2:02:20 PM

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