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Fusion

Explore the concept of nuclear fusion in light nuclei, such as H-1, H-2, He-3, and He-4, to comprehend the energy output and processes involved in the Sun's fusion reactions. Learn about the Proton-Proton Cycle and steps in proton fusion, understanding the mass-energy difference and excess energy released in these reactions.

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Fusion

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  1. Fusion

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

  3. 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. The Sun

  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. heavier nucleus starting nuclei fusion 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. neutrino: related to electrons by the weak nuclear force neutron hydrogen nuclei with one proton each positron: positive charged electron; annihilates to form photons electron 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. proton helium-3 helium-4 next

  8. The fusion reaction in a star is exothermic. H-1: 1.0078 u He-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. Excess Energy

  9. 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 Thermonuclear Blast next

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