The latest round values the company at $3 billion. Helion said $1.7 billion in follow on investments were committed if it can prove its technology works, which would be a major step toward making fusion technology a practical solution for generating power while emitting no carbon.

Fusion is the process that fires the sun as the nuclei of two atoms fuse under extreme heat. It creates enormous amounts of energy.

Helion's newest prototype named Polaris will add a so-called regenerative energy technology to its fusion technology already developed to generate electricity, said Helion founder and CEO David Kirtley. The target date for demonstration is 2024.