The company said its reactors could be operating at a commercial scale by the end of the decade, thanks to its newfound ability to produce stable plasma at temperatures over 50 million degrees (nearly twice as hot as the sun).

While this is good news for TAE Technologies, it comes too late for Norman Rostoker. Rostoker was one of the company's co-founders who devoted his life to fusion energy research but died before he could see the company he helped create reach its latest milestone.

TAE's current chief executive officer, Michl Binderbauer, said that reaching this milestone was an apt tribute to his late mentor, Norman Rostoker's vision.

"Norman and I wrote a paper in the 1990s theorising that a certain plasma dominated by highly energetic particles should become increasingly better confined and stable as temperatures increase. We have now been able to demonstrate this plasma behaviour with overwhelming evidence. It is a powerful validation of our work over the last three decades and a very critical milestone for TAE that proves the laws of physics are on our side."

The company's technology platform is called "Norman", and in the last 18 months, it has demonstrated consistent performance, reaching over 50 million degrees in several hundred test cycles.

Six years ago, the company had proved that its reactor design could sustain plasma indefinitely -- meaning that once the switch is flipped on a reaction, that fusion reaction can continue indefinitely.

Now, the company said, it has achieved the necessary temperatures to make its reactors commercially viable. With these milestones behind it, TAE raised an additional $280 million in financing, bringing its total up to $880 million and making it one of the best-financed private nuclear fusion endeavours in the world.