Stakeholders around the world are vying to realize nuclear fusion—a fossil fuel alternative that promises maximum energy generation with minimal environmental risk. Behind the efforts to build the world’s largest fusion reactor is an equally gigantic global collaboration: ITER, which has just announced a major advance in its quest to prove fusion’s viability. In a paper published September 11 in Superconductor Science and Technology, the ITER Collaboration reported completing a key test to validate the quality of more than 5,500 superconducting wire samples intended to power the final reactor’s core. These wires—stretching thousands of kilometers—form the backbone of ITER’s central magnet, a critical component that confines superhot plasma to induce fusion reactions. When in doubt, go big ITER is an ambitious plan that aims to hold five times more plasma than the largest machine operating today, according to the collaboration. Its extra-large size gives it the potential to revolutionize fusion research, but it also means that the reactor has many operating parts, each demanding careful maintenance. Indeed, once operational, the plasma in ITER’s experiments will reach temperatures in excess of 200 million degrees Fahrenheit. The plasma itself is confined, but the components surrounding it will still have to endure extreme heat and electromagnetic forces. The wires can carry huge electrical currents with no resistance but must endure brutal conditions, the researchers said in a statement. “Fusion energy could be transformative, but its success depends on getting the details right,” they said. For the new results, researchers with ITER at Durham University in the United Kingdom conducted around 13,000 measurements to ensure the wires could repeatedly withstand the extreme conditions of a reactor. They essentially baked the wires in a furnace heated up to about 1,200 degrees Fahrenheit (650 degrees Celsius) and checked how the strands responded under different conditions. In addition to collecting data on the wires’ behavior, the team devised a more cost-efficient, practical method to continuously check wire quality. They also found a way to better control the purity of hot gases used to treat the wires. Racing to the finish Constructions for ITER, located in southern France, began in 2010. If things go as planned, the reactor will commence operations in 2034 and start deuterium-tritium fusion experiments as early as 2039. So far, things seem to be going well; ITER has been publishing a steady stream of news signaling its progress toward completion. For example, on the same day as this result, a different team associated with ITER announced the completion of a key diagnostic system for the reactor.