1. Fusion

2. Light Nuclei  Light nuclei have relatively high rest masses. H-1: 1.008665 uH-1: 1.008665 u H-2: 2.014102 uH-2: 2.014102 u He-3: 3.016029 uHe-3: 3.016029 u He-4: 4.002603 uHe-4: 4.002603 u C-12: 12.000000 uC-12: 12.000000 u  Energy is available compared to heavy mass nuclei. Si-28: 27.976926Si-28: 27.976926 Fe-56: 55.934942Fe-56: 55.934942

3. The Sun  The energy output of the sun is inconsistent with chemical processes. Chemical bonds too weak  Gravitational contraction would have to be too fast. Sun would last 100 My  Nuclear fusion of light nuclei explains the energy output.

4. 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 starting nuclei heavier nucleus other particles

5. Proton-Proton Cycle  Fusion takes place two particles at a time.  Step 1: two protons form a deuterium nucleus with positron and a neutrino. hydrogen nuclei with one proton each neutron neutrino: related to electrons by the weak nuclear force photons electron positron: positive charged electron; annihilates to form photons

6. Proton Fusion 2  Step 2: A deuterium nucleus absorbs a proton and becomes helium-3.  The helium-3 is in an excited state and emits a photon when it goes to a ground state. neutron photon proton

7. Proton Fusion 3  Step 3: Two helium-3 nuclei collide.  They rearrange particles so that very stable helium-4 is formed with two extra protons spit out. helium-3 helium-4 proton next

8. Excess Energy  The fusion reaction in a star is exothermic. H-1: 1.0078 uH-1: 1.0078 u He-4: 4.0030 uHe-4: 4.0030 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 = 0.0282 u  Convert to MeV. Q = (0.0282 u)(931.5 MeV/u) Q = 26.27 MeV  This is per single fusion reaction.

9. Thermonuclear Blast next  Fusion of deuterium into helium is exothermic.  The high temperature of an uncontrolled fission reaction can overcome the nuclear charge. A fission bomb to ignite fusion device