Helion Energy, a fusion energy tech startup, on Friday said it raised US$500 million to build a net positive electrical generator, one that creates more power than it uses. The latest round values the company at US$3 billion. Helion said US$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.