Two small nuclei can merge into one nucleus {fusion, physics} {nuclear fusion}|. Fusion releases million times more energy per mass than burning.
products
Nuclear fusion makes all atoms up to and including iron.
efficiency
Nuclear hydrogen fusion to helium makes 0.007 of mass into energy, so efficiency is 0.007. Other fusions make 0.017 of mass into energy. If efficiency is less, universe has no or less helium and heavy atoms. If efficiency is more, universe has more helium and heavy atoms, but no hydrogen. Carbon production also depends on ratio, because it involves resonance energy.
Main fusion reaction {proton-proton cycle} unites two protons. In stars, hydrogen fusion to helium requires 10^6 K. Two protons change to deuterium and proton. These two nuclei combine to make helium 3. Two helium 3 make helium 4 and two protons.
The second-most-important fusion reaction {carbon-nitrogen cycle} makes helium starting from protons and carbon. Carbon acts like catalyst to make lithium, beryllium, and boron, which combine or decay to helium. Carbon-nitrogen cycle is not chain reaction.
Reactions {chain reaction, fusion}| that have proton reactants and make protons can be self-sustaining. Chain reaction continues until limiting reactant amount becomes zero or system disrupts physically.
Minimum mass {critical mass} starts chain reactions. Below minimum mass, too many proton initiators do not collide and escape to outside.
Absorbing protons {damping} slows fusion reactions. In nuclear reactors, metal rods absorb proton initiators to slow reaction.
5-Physics-Matter-Atom-Reactions
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Date Modified: 2022.0225