After completing her PhD, Merminga held a
postdoctoral position at
SLAC National Accelerator Laboratory in the accelerator theory group. In 1992, she joined
Thomas Jefferson National Accelerator Facility as a member of the Center for Advanced Studies of Accelerators (CASA). In 2002, she became director of CASA's beam physics group, her first managerial position. There, she oversaw the design and construction of an accelerator that produced rare
isotopes for use in medicine and
nuclear physics. Merminga returned to Fermilab in 2018 as director of the lab's Proton Improvement Plan II (PIP-II) project, On 5 April 2022, it was announced that Merminga had been appointed as the next director of Fermilab. In addition to her role at Fermilab, as of February 10, 2023, Merminga serves as a member of the Board of Trustees at
Illinois State University. On 13 January 2025 it was announced that Merminga stepped down as director of Fermilab, effective immediately.
Young-Kee Kim was named as interim director. == Awards and honors ==