Nuclear fusion will be the only energy source soon. On its development depends the future of our children. Will they live in world of wars for oil or in world of surplus of cheap energy?

Cold (bubble) fusion

Cold fusion is hypothetical sort of fusion reaction, which don't need large amount of incredible hot plasma to start. It can be initiated by large pressure, when atoms are so close to each other that attraction caused by strong nuclear force exceed repelling electric force thereby nuclei fuse. Some theories predict and explain cold fusion of two heavy nuclei or light and heavy nuclei, but I would like to tell you more about a special sort of cold fusion usually called bubble fusion or sonofusion. It is not good understood yet, but is interesting.

Sonoluminescence at the beginning

Researchers studied sonoluminiscence -- the effect, which occurs when little bubbles in liquid implode and emit visible light. Bubbles are created by high amplitude ultrasound. Top of wave causes high pressure in liquid and forthcoming low of wave causes so low pressure that liquid evaporates.

Cold bubble fusion - expanding of deuderated acetone vapours
First stage of cold bubble fusion

Next top forces vapour to implode (shrink) quickly, thus very high pressure occurs in centre of imploding bubble.

Cold bubble fusion - imploding of deuderated acetone vapours
Second stage of cold bubble fusion

Visible effect is emitted light. As initiation for creation of bubbles serves a beam of neutrons; used liquid is deuterated acetone (acetone where common hydrogen is substituted by heavy hydrogen -- deuterium). After experiment finished, scientists found traces of nuclear fusion. Of course, there are still many questions.

Infirmed experiment

In 2002 Rusi Taleyarkhan published his first paper about bubble fusion. He tried to prove fusion by measuring presence of neutrons with "right" energy and production of tritium during experiment. Opponents of bubble fusion admitted he measured rather neutrons from neutron source or space radiation than that from nuclear fusion. Really problem is the laboratory was not shielded from external radiation. Taleyarkhan repeated his experiment and said he had measured neutrons at the same time as light from bubbles. In order to confute doubts he repeated experiment once more and that time didn't use neutron beam, but uranium salt dissolved in deuterated acetone. Opponents are still persistent, so Taleyarkhan invited them to his laboratory to see bubble fusion by own eyeball.

Low production of energy

Nevertheless, bubble fusion is energy insufficient. Produced amount of energy is much lower than consumed. Researchers hope, they could improve bubble fusion to produce more energy and maybe in future will power some machinery. This sort of fusion has many advantages over tokamaks. It doesn't need expensive equipment, is really small and can be realized in common laboratory. But it is still far from practical use.

For more information see references