https://phys.org/news/2018-07-lhc-atoms.html

During normal operation, the LHC produces a steady stream of proton–proton collisions, then smashes together atomic nuclei for about four weeks just before the annual winter shutdown. But for a handful of days a year, accelerator physicists get to try something completely new during periods of machine development. Previously, they accelerated xenon nuclei in the LHC and tested other kinds of partially stripped lead ions in the SPS accelerator.

"This special LHC run was really the last step in a series of tests," says physicist Witold Krasny, who is coordinating a study group of about 50 scientists to develop new ways to produce high-energy gamma rays.