Keppel has been with the Thomas Jefferson National Accelerator Facility in various capacities since 1995. Keppel performed electron scattering experiments to investigate the structure of protons and neutrons. In 2001 she founded the Hampton University Center for Advanced Medical Instrumentation, where scientists at Hampton and Jefferson Lab collaborated to bring technology developed for nuclear and particle physics to nuclear medicine applications. She was pivotal in launching the world's largest independent proton therapy facility, the Hampton University Proton Therapy Institute. She was awarded numerous grants, including a $1.3 million grant to improve breast cancer imaging and therapy. Shielded accelerated partial breast irradiation, a technology developed by Keppel and colleagues, makes post-surgical radiation more feasible for patients. Another of her patents was used in the OARtrac system, a machine which helps radiation oncologists monitor dose in therapy for cancer patients, which was awarded a Medical Device Breakthrough Award in 2018. In 2012 Keppel was named Leader of Experimental Hall A at the Thomas Jefferson National Accelerator Facility., and soon after Leader of both Halls A and C. Keppel is Co-Spokesperson of the Coordinated Theoretical-Experimental Project on Quantum Chromodynamics. She has served on the National Nuclear Science Advisory Committee. Keppel was elected a Fellow of the American Physical Society in 2018, "For leadership on novel experimental techniques to study strong interactions, her contributions to CTEQ from the perspective of Nuclear Physics, and her instrumental role in founding the Hampton University Proton Therapy Center and other work applying Nuclear Physics to Medicine." Keppel delivered the 2019 American Physical Society Distinguished Lectureship on the Applications of Physics. She was awarded the honour for "pioneering work in proton therapy and for the promotion of the applications of physics to both experts and non-experts". Alongside her academic work, Keppel has mentored high school teachers about Nuclear physics, and campaigned to bring recognition to African-American and Hispanic physicists. In 2019 Keppel is giving a TEDx talk in Charlottesville, Virginia.
Awards and honours
Her awards and honours include;
2000 VA Outstanding Faculty Award
2010 Innovate Hampton Roads High Tech Leadership Award
2011 Virginia Outstanding Scientist Award
2016 American Physical Society Francis G. Slack Award
2019 American Physical Society Forum on Industrial and Applied Physics Distinguished Lectureship Award
2019 Alumni Association Award of Merit St. John's College