Nuclear Energy & Dectors


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Nuclear Energy & Dectors

  1. 1. Nuclear Energy & Detectors
  2. 2. The basics, mass <ul><li>A device called a Mass Spectrometer is used to measure mass of atoms. </li></ul><ul><li>We use a unit called Unified Atomic Unit (u) which ranks the atom in relationship to C-12. </li></ul><ul><li>u = mass of atom x 12 </li></ul><ul><li>mass of C-12 </li></ul><ul><li>1u = 1.661x10 -27 kg </li></ul>What is mass? What has happened? 4.001505 Alpha Particle 4.002603 Helium (He) 1.007825 Hydrogen Atom (H) 1.008665 Neutron (n) 1.007276 Proton (p) 0.000549 Electron (e) Mass (u) Particle
  3. 3. Missing energy <ul><li>The nucleons appear to be lighter ( mass defect  M ) inside an atom then outside. </li></ul><ul><li>In the beginning (BIG BANG) work had to be done in order bring the nucleons together. (same for electrons but this is significantly less). </li></ul><ul><li>This energy is a direct conversion from mass (Einstein). </li></ul><ul><li>In a nucleus the nucleons are in a lower energy state. </li></ul><ul><li>So to separate them an amount of energy is needed to be supplied, this is then converted into mass. </li></ul><ul><li>The binding energy (  E) is the energy released when the nucleus is assembled (same as energy needed to separate) </li></ul><ul><li> E =  Mc 2 </li></ul><ul><li>Worked example: </li></ul><ul><li>Since mass and energy are interchangable they can be expressed in the same units: </li></ul><ul><ul><li>1u = 931.3MeV </li></ul></ul>Mass of helium nuclei = 4.001505u Mass of parts = 4.031882u  M = 0.030377u = 0.030377 x (1.661x10 -27 ) = 5.046x10 -29 kg  E = 55.046x10 -29 x (3x10 8 ) 2 = 4.541 x 10 -12 J = 28.38MeV
  4. 4. Practise Questions <ul><li>Find mass defect of each. </li></ul><ul><li>Find binding energy of each. </li></ul><ul><li>Find binding energy per nucleon </li></ul><ul><li>Which is most stable and why? </li></ul>4.002603 Helium – 4 12.000000 Carbon – 12 3.016030 Helium – 3 Mass (u) Particle/ nuclide
  5. 5. Beta decay <ul><li>Remember what happens in Beta decay? </li></ul><ul><li>Neutron proton + electron + energy </li></ul><ul><li>Therefore how much energy is given out? </li></ul><ul><li>1.25x10 -13 J </li></ul>1.008665 Neutron (n) 1.007276 Proton (p) 0.000549 Electron (e) Mass (u) Particle
  6. 6. Binding energy <ul><li>All nuclei have binding energy. </li></ul><ul><li>More nucleons more binding energy. (Helium is a slight oddity – very stable) </li></ul><ul><li>Higher binding energy per nucleon more stable nucleus. </li></ul><ul><li>The difference in binding energy suggests a means of extracting energy! </li></ul><ul><li>If Heavy Nuclei can be split into lighter nuclei energy would be released (same as difference in binding energy). Nuclear Fission . </li></ul><ul><li>If lighter nuclei can be fused together energy would also be released. Nuclear Fusion . </li></ul>Hydrogen -1 Helium -4 Carbon Uranium What happens in nuclear fission & fusion Fission Fusion
  7. 7. Bubble Chamber <ul><li>Superheated Hydrogen at high pressure (stops it from boiling). </li></ul><ul><li>When pressure is reduced bubbles form (think of fizzy drink), but need a site to form on. </li></ul><ul><li>When particles move through liquid it causes ions, which will let bubbles form on. </li></ul><ul><li>A magnetic field in the machine allows mass, speed and charge of particles to be deduced (how?) </li></ul>http:// =jB2BTzez2g4&feature=related Can be used to work out mass, speed and charge. Takes about 1 second to set up again (increase pressure) a life time in modern times. Simple to use and take photo’s off Have to time particle entry with reduction of pressure Because medium is dense high energy particles can be slowed enough to be recorded. Disadvantages Advantages
  8. 8. Paths of a Bubble Chamber Magnetic Field into page Positive particle low speed, low mass Positive particles, higher speed/ mass Negative Particle, high speed/ mass 1 3 2 Maths window (Remember) F = Bqv F = mv 2 /r Therefore r = mv/Bq
  9. 9. Cloud Chamber & Spark/drift chanber <ul><li>Use the internet to find out how these work. </li></ul><ul><li>Then give a few advantages & disadvantages. </li></ul>
  10. 10. Cloud chamber tracks   short straight clear tracks…why?   high energy )  thin straight tracks…why?   low energy )  short thick , tortuous tracks…why?    Rays  why?