NSTX-U tokamak fusion device. The National Spherical Torus Experiment Upgrade (NSTX-U) was an upgrade of the existing fusion device that operated from 1999 to 2012. The upgrade took place from 2012 to 2015, at Princeton Plasma Physics Laboratory (PPPL), New Jersey, USA. The upgrade made it the most powerful experimental fusion facility or tokamak, of its type in the world. The upgrade spherical facility maintains a high-performance plasma under conditions of extreme heat and power. The research carried out here could influence the design of future nuclear fusion reactors. Photographed on 4 May 2012.