1. Fusion Energy

2. Source of Energy Before 1940 the Sun’s energy was a mystery.  Chemical reactions:  Gravitational energy:  Nuclear forces: The Sun is 5 billion years old.  Can’t create enough energy  Produces enough, but Sun runs out in 100 million years  Einstein showed that there was enough energy in mass

3. Subatomic Particles Components of atoms:  Proton, positive electric charge, 1.0073 AMU  Neutron, no electric charge, 1.0087 AMU  Electron, negative electric charge, 0.0005 AMU 1 atomic mass unit (AMU) = 1.66  10 -27 kg electron nucleus protonneutron Helium atom with 2 protons, 2 neutrons, and 2 electrons

4. Nuclear Forces Strong Nuclear Force  Strongest of the forces  Holds together protons and neutrons, others not affected  Very short range – size of a proton (10 -15 m) Weak Nuclear Force  Weaker than electric force  Causes radioactivity and affects all particles  Same short range as the strong nuclear force

5. Energy in the Nucleus Einstein’s relativity relates mass and energy: E = mc 2. –Nuclear mass from the sum of its protons and neutrons –Altered by strong force binding energy Mass can be converted to energy. –Hydrogen-1 atom 1.0078 AMU –Helium-4 atom is 4.0030 AMU –4  (1.078) minus (4.030) equals available energy

6. Nuclear Fusion Electric charge causes positive nuclei to repel. At high temperatures nuclei get close enough for the strong force to pull them together. –Nuclear fusion –Extra particles to conserve charge and energy fusion starting nuclei heavier nucleus other particles

7. 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

8. 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

9. 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

10. Solar Neutrinos Neutrinos from fusion can be detected on Earth. –Deep mine detectors (Sudbury Neutrino Observatory) –Energy estimates from Sun’s core Single solar neutrino