This is an old topic that I am not sure has been adequately explained.
As described in "Einstein’s Lost Hypothesis" -
http://nautil.us/issue/7/waste/einsteins-lost-hypothesis
- In 1951, Ernest Sternglass, conjectured he had found a way to produce neutrons, as described in this excerpt"
[In a letter to Einstein dated Aug. 26, 1951, Sternglass wrote, “You may be interested to learn that in the course of the past two months, I have been able to obtain experimental evidence for the formation of neutrons from protons and electrons in high-voltage hydrogen discharge.”
Sternglass’ neutron experiment consisted of an evacuated glass tube less than a foot long filled with hydrogen gas. He fired an electron gun, not unlike the type found in old tube TV sets, through the gas and at thin foils of silver and indium at the end of the tube. There was no known way that an electron beam of the energies he was studying (about 35,000 electron Volts) could have induced any radioactivity in the foils. Nevertheless, time and again, that is what he observed. When he ran a control experiment with the beam passing through regular air, the foils did not become radioactive.
The radioactive signature suggested that the two stable isotopes that make up silver (silver-107 with 60 neutrons and silver-109 with 62 neutrons) were undergoing transmutation. Adding a neutron to each would produce silver-108 and silver-110 isotopes, which are unstable. ]
I assume fairly similar experiments have been conducted, so I wonder whether Sternglass was correct, or some other cause was found.
Conventional fusion has been proposed, but is that persuasive?