Helium-3
Helium-3 is a non-radioactive and light isotope of helium. It has two protons but only one neutron in contrast to two neutrons in ordinary helium. Helium-3 is rare on Earth and sought-after for use in fusion. More abundant helium-3 is thought to exist on the Moon (embedded in the upper layer of regolith from solar wind over billions of years) and the gas giants (left over from the original solar nebula) in our solar system.
Helium-3 undergoes the following reaction, among others, although this is the one most promising to fusion engineers:
- D + 3He → 4He (3.7 MeV) + p (14.7 MeV)
The production of a proton and helium-4 atom is much more containable than the neutrons produced in most fusion reactions, since protons can be much easier to contain using magnetic and electrostatic fields.
Helium-3 is used in cryogenics to achieve temperatures as low as a few thousandths of a kelvin; it was discovered by the Australian nuclear physisist Mark Oliphant while based at Cambridge University's Cavendish Laboratory.
