Inside the tokamak at the DIII-D National Fusion Facility at General Atomics in San Diego. — TNS The main criticism about nuclear fusion has been that its vast potential as a commercial source of energy has always been just out of reach. But a group of the nation’s top fusion scientists and researchers just issued a report to the Department of Energy that calls for the United States to build a fusion pilot plant by the 2040s. The 80-page report, written by the Fusion Energy Sciences Advisory Committee, was two years in the making. “What really emerged strongly from this is a real sense that the fusion energy science portfolio should really pivot towards an energy mission and the realisation of that mission is the development and operation of a fusion pilot plant in the 2040s,” said Wayne Solomon, who served as a committee co-chair.