Kiersten Ruisard
Beam halo — particles ejected far outside a particle accelerator’s core beam — limits the performance of high-intensity accelerators.
“As we accelerate protons to high energy, the beam carries a significant amount of power. Even one proton hitting the beam pipe is depositing power, which is causing radiation and is limiting the accessibility of our tunnels and the longevity of our accelerator hardware,” said Kiersten Ruisard, an accelerator physicist in the Research Accelerator Division.
Ruisard’s Early Career Research Program award project aims to improve the performance of high-power accelerators and support significant increases in beam power by developing more accurate models of beam distribution and halo.
Using the Spallation Neutron Source Beam Test Facility, Ruisard seeks to develop predictive capabilities that incorporate full and direct measurement of the beam distribution in six dimensions.
In the injector test stand, a replica of the first few meters of the SNS, the research team will map negative hydrogen ions in the first acceleration stage where complex physics are happening, which Ruisard said is challenging to model accurately.
“It sort of boils down to getting your initial conditions right to make the best possible predictions,” she said.
“The particles live in a six-dimensional space. They can be three spatial dimensions that also have a momentum vector that’s pointing in three dimensions,” she said. “No one measures that directly. It’s exciting to look at the beam that’s been in front of our eyes all along, but going deeper into it and really looking at it in this high-dimensional view.”
Ruisard rediscovered her interest in physics when trying out science courses during her first year at Rutgers University.
“I enrolled in Biology 101, and I think I dropped it in the first week. The vocabulary lists were so intimidating,” she said. “I had a good physics background from high school, and I’d had an inspiring AP Physics teacher, but somehow I never thought physics was for me.”
But, with the AP credit, she was able to jump into the second-year courses.
“It was a much smaller class, and no vocabulary, which sort of set the direction,” she said smiling, “but it was also compelling because of the flexibility. You can learn about how things work on so many different scales — astrophysics to quantum physics and everything in between.”
