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Fusion

Light

Nuclei

Light nuclei have relatively high rest masses.

H ‐ 1:

u - H ‐ 2: 2. u - He ‐ 3: 3. u - He ‐ 4: 4. u - C ‐ 12: 12. u Energy is available compared to heavy mass nuclei. - Si ‐ 28: 27. - Fe ‐ 56: 55.

Nuclear

Fusion

Electric charge causes positive nuclei to repel. At high temperatures nuclei get close enough for the nuclear force to pull them together. fusion startingnuclei heaviernucleus otherparticles

Proton

Proton

Cycle

Fusion takes place two particles at a time.

Step

two protons form a deuterium nucleus with positron and a neutrino. hydrogennuclei withone protoneach neutron neutrino: related toelectrons by theweak nuclear force photons electron positron: positivecharged electron;annihilates to formphotons

Proton

Fusion

Step

Two helium

nuclei collide. They rearrange particles so that very stable helium

is formed with two extra protons spit out.^ helium- helium- proton next

Excess

Energy

The fusion reaction in a star is exothermic.

H ‐1:

u - He ‐4: 4. u This is less than 4 hydrogen masses so there is energy released.

Find the mass energy difference.

Q

4(1.0078) ‐ (4.0030)

Q

u

Convert to MeV.

Q

(0. u)(931. MeV/u)

Q

MeV

This is per single fusion reaction.