Is nuclear fusion worth the research?

In my opinion, the chance of nuclear fusion "working" is so low that it's not worth what is currently being spent on it. To the extent that it is a worthwhile area of research, it should more resemble basic research in plasma physics, not targeted development at a limited number (or one) large scale concepts that are going to be dead ends.

Nuclear fusion is a necessity in assuring diversity among energy sources in the long term. It's probably much more fruitful an endeavour with eventual returns than macroscale particle accelerators.

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