Scientists from the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have built and delivered a high-resolution X-ray spectrometer for the largest and most powerful laser facility in the world. The diagnostic, installed on the National Ignition Facility (NIF) at the DOE’s Lawrence Livermore National Laboratory, will analyze and record data from high-energy density experiments created by firing NIF’s 192 lasers at tiny pellets of fuel. Such experiments are relevant to projects that include the U.S. Stockpile Stewardship Program, which maintains the U.S. nuclear deterrent without full-scale testing, and to inertial confinement fusion, an alternative to the magnetic confinement fusion that PPPL studies.