A next-generation nuclear detection system that could aid US national security efforts has logged its first operational measurements in Michigan. The Gamma-Ray Energy Tracking Array, known as GRETA, recently completed its initial characterization run at Michigan State University. Traditional gamma-ray spectrometers measure only the total energy an incoming photon deposits inside a single detector block. Holding clues about subatomic physics Researchers from around the world will use the facility to study short-lived isotopes generated by heavy-ion collisions. These exotic isotopes exist for only fractions of a second, yet they hold key clues about subatomic physics.