“The old joke is that nuclear fusion is 30 years away and always will be,” quips Greg De Temmerman, managing director of Paris-based energy think tank Zenon Research. In fact, the joke has become so hackneyed over the decades it has been banned by editors at the Economist. “But more seriously, many things are happening right now in the field,” De Temmerman adds. Jokes aside, they are. Earlier this month, China’s Experimental Advanced Superconducting Tokamak (EAST) reactor eclipsed previous records by sustaining a high plasma temperature for minutes (1,056 seconds). It reached two milestones: a one-million-ampere current and a 1,000-second...