Yifan Sun

Light in a fiber-optic ring usually dies out within hundreds of microseconds. Each lap, some energy is lost, and the pulse weakens. But physicists figured out how to give light a boost on every turn: they added gain along the entire ring, acting like a tailwind for a runner. Now light can circulate in the ring thousands of times longer. This gain is called Raman.

Inside the destroyed Fukushima reactors lie hundreds of tons of melted fuel — a mixture of uranium, zirconium, iron, and fission products. This debris is called fuel debris. It must be extracted, transported, and securely packaged for decades. But how will this volatile mixture behave under heat, compression, or accidental impact?