Fusion Energy

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

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

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

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 AMU –Helium-4 atom is AMU –4  (1.078) minus (4.030) equals available energy

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

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

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

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

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