"There is no chance of any kind of accident with fusion"

Mr Suppes, 32, is part of a growing community of “fusioneers” – amateur science junkies who are building homemade fusion reactors, for fun and with an eye to being part of the solution to that problem.

He is the 38th independent amateur physicist in the world to achieve nuclear fusion from a homemade reactor, according to community site Fusor.net. Others on the list include a 15-year-old from Michigan and a doctoral student in Ohio…

While they might un-nerve the neighbours, fusion reactors of this kind are perfectly legal in the US.

“As long as they [private citizens] obtain that material [the components of the reactor] legally, they could do whatever they want,” says Anne Stark, senior public information officer for California’s Lawrence Livermore National Laboratory.