Thread: Some questions about Fusion

I've been reading about fusion lately and I had some questions.

What happens to the helium atoms in the grand scheme of things? Shouldn't they continue to fuse until they reach the heavy atom state where fusion is no longer possible?

Other than the released neutron, other nucleons are released as a result of the fusion yes? What are they?

What can be done to interrupt a self-sustained chain reaction? And how does a reaction 'run out of fuel?'

Is the heating of the plasma itself the ignition for the reaction? Are the atoms always in motion then?

yes if you look at stars the elements continue to fuse until..i think it's iron is fused at which point it stops.

in nucleur reactors they use neutron acceptors. i think its somekind of boron to absorb neutrons which controls the chain reaction.

Interesting, so then the released nucleons end up clashing together themselves to fuse smaller atoms which keep the reaction going?

Originally Posted by Sheep Extreme

I've been reading about fusion lately and I had some questions.

What happens to the helium atoms in the grand scheme of things? Shouldn't they continue to fuse until they reach the heavy atom state where fusion is no longer possible?

It is harder to fuse helium than hydrogen, and it becomes successively harder as the nuclei get heavier.

For example, in our Sun the primary fusion is hydrogen fusion. The pressure and temp is not enough to support large scale helium fusion. It isn't until the hydrogen at the core is used up that the core collapses enough to create the pressures needed for Helium burning.

How much further this process continues depends on the mass of the star. Small red dwarfs won't even reach helium burning, once the Hydrogen is used up, they quit fusing, as they aren't massive enough to produce the pressure needed to fuse Helium. Stars the size of or Sun will get as far as having a carbon core before fusion dies out.

Only stars much more massive than our Sun will ever reach the point where they fuse up to Iron. (and if the Iron core grows large enough, it will collapse under it own weight. The upper layers will rush in to fill the void and upon collision at the center ignite into a giant fusion explosion called a supernova.)

I see. So as the heavier elements are created, they are dragged in by gravity and compose the core? (Thinking of a star here)

or rather,
>the higher energies present in the core
(due to the pressure of the outer material, caused by gravity)

>allow the fusing of heavier elements

as the energy output of the core drops (due to the decline in fuel and lack of energy to fuse energy because of this lack of fuel)
the star contracts, heightening the energy in the core and allowing a heavier element to be fused.
This is how layers of heavy elements occur in stars.