Seth Putterman is usually on the side of the sceptics when it comes to tabletop fusion. But now he has created a device that may convince researchers to change their minds about the ‘f-word’.

Tabletop fusion has been a touchy subject since Stanley Pons and Martin Fleischmann said in 1989 that they had achieved ‘cold fusion’ at room temperature. Putterman helped to discredit this claim, as well as more recent reports of ‘bubble fusion’.

Now Putterman, a physicist at the University of California, Los Angeles, has turned a tiny crystal into a particle accelerator. When its electric field is focused by a tungsten needle, it fires deuterium ions into a target so fast that the colliding nuclei fuse to create a stream of neutrons.

Putterman is not claiming to have created a source of virtually unlimited energy, because the reaction isn't self-sustaining. But until now, achieving any kind of fusion in the lab has required bulky accelerators with large electricity supplies. Replacing that with a small crystal is revolutionary. “The amazing thing is that the crystal can be used as an accelerator without plugging it in to a power station,” says Putterman.

Putterman got the idea when he delivered a lecture on sonoluminescence and energy focusing at the Georgia Institute of Technology, Atlanta. Physicist Ahmet Erbil suggested that Putterman should instead consider ferroelectricity.

“Here's someone telling me in front of 100 people that I'm working on the wrong thing,” recalls Putterman. But the comment got him started on his fusion reactor. The result is published in this week's Nature (see page 1115).

Will he be able to avoid the controversy that has dogged other fusion claims? “My first reaction when I saw the paper was ‘oh no, not another tabletop fusion paper’,” says Mike Saltmarsh, an acclaimed neutron hunter who was called in to resolve the dispute over bubble fusion. “But they've built a neat little accelerator. I'm pretty sure no one has been able to generate neutrons in this way before.”

Putterman himself isn't worried. “If people think this is a crackpot paper that's just fine,” he says. “We're right. Any scientist who says this is too wonderful to believe is welcome to reproduce the experiments.”