Mechanical Engineering Professor Nicholas Pohlman and his students of recent years can take more than a little pride in their contributions to the latest landmark finding at the U.S. Department of Energy’s Fermi National Accelerator Laboratory in Batavia.
For the past five decades, the Standard Model of particle physics, the top scientific theory explaining the nature of matter, has been amazingly accurate in predicting the behavior of the subatomic building blocks of our universe. But Fermilab’s long-awaited first results from its “Muon g-2 experiment” show muons behave in a way that is not predicted by the theory.
The strong evidence that muons deviate from the Standard Model hints at exciting new physics. Many scientists suspect muons must be interacting with an undiscovered particle or hidden force of nature.
Dating back to 2012, Pohlman and NIU physicists and their students were involved in preparations for the experiment. Pohlman led extraordinary involvement from NIU engineering from ideation, evaluation and eventual operations.
Three engineering graduate students and 28 engineering undergrads, many of them working in Senior Design teams, contributed to development of the “tracker system,” which detects particles known as positrons that result from the decay of muons (which exist for only 2.2 millionths of a second).
The tracker system work included
spacing the thin-walled mylar straws for maximum precisions while still maintaining structural integrity in the system’s vacuum. The NIU team also verified that the flammable gas inside the system would not damage the vacuum as a result of straw rupture. CEET’s machine shop was critical in fabricating the 32-channel prototype tracker that eventually became the basis for University of Liverpool’s 128-channel module.
“Physicists do a great job of drawing up conceptual ideas, and engineers turn those sketches into real-world devices,” Pohlman says. “For our students, this has been a great real-world experience.”
The experiment’s requirements for the tracker system were especially challenging.
“The system needed to be extremely precise to get the measurements physicists were seeking,” Pohlman says. “Every time you increase precision or detector density, you have to compensate in the system, managing and engineering your way out of new challenges that arise. So each problem solved led to a new problem—that’s why so many engineering students were involved.
“Seeing the tracker system, from starting concept through fabrication and operations, was a great opportunity for students to get a feel for how complex challenges can be solved while working in large collaborations,” Pohlman adds.
Now that the experiment is up and running, Pohlman’s g-2 work is done. But he and his students will continue to be involved in cool projects at the suburban laboratory, about a 40-minute drive from NIU.
“While g-2 is done for us, it’s still opening many doors at Fermilab for continued collaboration between physics and engineering,” Pohlman says.