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Particle Accelerators

Particle Accelerators

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Particle Accelerators

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  1. Particle Accelerators

  2. Contents • What is a Particle Accelerator? • An Early Accelerator • Modern Linear and Circular Accelerators • Particle Detectors • Examples of Accelerators

  3. What is a Particle Accelerator? • Any device that accelerates charged particles to very high speeds using electric and/or magnetic fields The picture to the right shows an early particle accelerator from 1937. This accelerator was used in the development of the first atomic bomb. http://en.wikipedia.org/wiki/Image:P3280014.JPG

  4. An Early Accelerator • In 1929, Ernest Lawrence developed the first circular accelerator • This cyclotron was only 4 inches in diameter, and contained two D-shaped magnets separated by a small gap • An oscillating voltage created an electric field across the small gap, which accelerated the particles as they went around the accelerator

  5. An Early Accelerator, cont. • Here is picture of Lawrence’s cyclotron: http://www.facstaff.bucknell.edu/mvigeant/univ_270_03/Jaime/History.html

  6. Today’s Accelerators • Modern accelerators fall into two basic categories: • Linear Accelerators • Circular Accelerators

  7. Linear Accelerators • In linear accelerators, particles are accelerated in a straight line, often with a target at one to create a collision • The size of linear accelerators varies greatly • A cathode ray tube is small enough to fit inside of a television • Stanford’s linear accelerator is two miles long http://www.exploratorium.edu/origins/cern/tools/linac.html

  8. Linear Accelerator – Example 1(Cathode Ray Tube) • The cathode ray tube is a linear accelerator found in many TVs, computer monitors, etc. http://science.howstuffworks.com/atom-smasher2.htm

  9. The tubes must have a progressive length • The time needed for a particle to cover the length L of a tube = T/2 or ½ the periodic time. • Since the velocity increases progressively then the length of tube number n must be longer than tube number n-1

  10. At tube number s the energy Es of the particle is given by • Since the particle starts from rest N = the total number of tubes V0=the potential difference m = the mass of the particle

  11. The length of the linear accelerator

  12. The length of the linear accelerator

  13. Numerical exmple The maximum energy of accelerated is Hydrogen 20MeV The applied voltage = 105 Volts The HF = 10 6 Hz Of course e=1.6 10-19 C U = 1.68 10-27 kg Find the number of tubes and The average velocity and The elapsed time to cover the last and first tubes

  14. In practices it is impossible to construct such machine because the wave length The accelerator length = 4000 meters i.e. there is no phase With such parameters on can achieve protons with only one MeV

  15. Linear Accelerator - Example 2(Stanford Linear Accelerator) http://en.wikipedia.org/wiki/Image:LINAC.jpg

  16. Electron linear accelerator • Linear electron accelerators are similar to the positive ion accelerators except that the drift tubes are replaced by a wave guide in which a high power electromagnetic wave travels at velocity slightly less than the velocity of light. • Electron being ejected from another generator , move along the wave continuously. These electrons travel at very nearly constant velocity. With no radiation losses

  17. Circular Accelerators • Circular accelerators propel particles along a circular path using electromagnets until the particles reach desired speeds/energies • Particles are accelerated in one direction around the accelerator, while anti-particles are accelerated in the opposite direction www.fnal.gov

  18. Circular Accelerators, cont. • Circular accelerators are able to bring particles up to very high speeds (energies) by allowing each particle to be accelerated for a longer period of time—around the accelerator. • The distance around a circular accelerator can be quite large • Fermilab’s Tevatron (Near Chicago, USA) - 4 miles (6.44 km) • CERN’s LHC (Near Geneva, Switzerland) –16.8 miles (27 km)

  19. Fermilab Accelerators • The protons and anti-protons at Fermilab go through a series of accelerators in order to accelerate them to 1 TeV (just 200 miles per hour slower than the speed of light) • At Fermilab, protons are accelerated in one direction around the ring; anti-protons are accelerated in the opposite direction • The series of accelerators at Fermilab is illustrated by an animation located at this website (be sure to press “play”):http://www-bd.fnal.gov/public/index.html

  20. Collisions • The particle and anti-particle beams are focused and directed at particular sites around the ring in order to collide with one another • These collisions are designed to occur within detectors, which are able to analyze the many events (particles created, etc.) that result from the collisions of the particles and anti-particles

  21. Particle Detectors • The large detectors are able to trace and characterize the particles that result from the collisions • The picture to the right shows the 5,000-ton CDF Collider Detector at Fermilab • 400,000 proton-antiproton collisions occur each second in this detector http://www.fnal.gov/pub/about/tour/index.html

  22. Particle Detectors, cont. • By analyzing the nature and type of particles resulting from the collisions, scientists are able to learn much about matter at a more fundamental level http://www.fnal.gov/pub/now/live_events/index.html

  23. CERN Accelerators and Detectors • The diagram to the right shows the accelerators and detectors at CERN near Geneva, Switzerland • The LHC is the largest circular accelerator at CERN and is to begin operation in 2007 • CMS and ATLAS are two of the five examples of detectors approved at CERN for the LHC

  24. Fermilab Accelerators and Detectors • The most powerful accelerator (the Tevatron) in the US is at Fermilab • The diagram to the right shows the series of accelerators (including the Main Injector and Tevatron) and detectors (including CDF and DZERO) at Fermilab http://www.fnal.gov/pub/about/whatis/picturebook/descriptions/00_635.html

  25. Accelerators and Detectors as Giant Microscopes • Together, particle accelerators and detectors have helped scientists discover very small building blocks of matter • For instance, scientists now think that protons within atoms are made up of even smaller particles known as quarks • Check out www.particleadventure.org for more information http://www2.slac.stanford.edu/vvc/theory/fundamental.html