Fusion in the sun

The sun's main energy source is via the following set of fusion reactions, in which lighter elements join to form heavier elements with the release of energy.

¹₁p + ¹₁p ®  ²₁D + ⁰₁e⁺ +  ⁰₀n + energy (carried off mostly as KE  by the Deuterium nucleus)

²₁D + ¹₁p ®  ³₂He + energy (carried off mostly as KE  by the Helium-3 nucleus)

³₂He + ³₂He ®  ⁴₂He + 2 ¹₁p  + energy (carried off mostly as KE  by the Helium-4 nucleus)

The first reaction happens twice, thereby producing two deuterium nuclei. Each deuterium takes place in a reaction like the second, so there are two of those as well to produce the two helium-3 nuclei needed for the final reaction. Thus six protons are needed altogether - but the final reaction gives us two of them back again. So we have only actually used the four protons in the the two 'first' reactions. Thus two positrons are kicking around, and so are the four electrons that used to 'belong' to the four protons. Two of these electrons annihilate with the positrons:

⁰₁e⁺ + ⁰_-1e^- ®  g (gamma rays, which carry off lots of energy)

leaving two electrons to be partnered eventually with the newly created helium nucleus.

Fusion in a reactor

Fusion in a bomb