Particle Accelerators and Detectors World’s Largest ‘Microscopes’

Contents What is a Particle Accelerator? An Early Accelerator Modern Linear and Circular Accelerators Particle Detectors Examples of Accelerators and Detectors Accelerators and Detectors as Giant Microscopes

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

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

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

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

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

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

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

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

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)

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

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

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

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

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

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

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