1. Particle Accelerators
Nguyen Hong Quang
Materials Science and Metallurgy Department
Student Number:
Oct 18th 2004

2. Outlines How physicists observe and study fundamental particles
What is a particle accelerator
Principle machine components of accelerators
Types of accelerators
References

3. How physicists observe and study fundamental particles
Since fundamental particles are extremely tiny, in order to see and study them physicists need very special tools:
- Particle accelerators: Speed up particles to very high energies before smashing them into other particles.
- Particle detectors: allow physicists to observe and study the collisions.
By accelerating and smashing particles, physicists can identify their components or create new particles, revealing the nature of the interactions between them.

4. What is a particle accelerator?
An accelerator can be used as a super-microscope to "see" tiny particles (quarks, leptons, etc)
Accelerators can be used to transform energy into mass and vice versa.

5. Accelerator as super-microscope
Tiny particles (smaller than a micron) can be examined by using electrons, provided their energy large enough. This is the principle of the electron microscope (SEM, TEM, HRTEM…)
The electron microscope is actually a small accelerator. It conveys energy to charged particles (electrons) to make wavelength small enough to view such details.
The smaller the details you want to see, the larger the accelerator you will have to build.
The larger the energy the smaller is the wavelength.

6. Accelerator as energy transformer
In accelerators, charged particles are accelerated to high energy (high speed) by electric fields.
In particle collisions, more or all the available energy can be transformed into other particles or into X-rays:
The more powerful accelerators and higher energies, the more massive and sometimes new particles can be discovered
E = mc2
Energy  Mass

7. Principle machine components of an accelerator
Injection: Let original particle come to the vacuum chamber
Vacuum chamber: Avoid the accelerated particles collide with normal matter (like air molecules)
Radio-Frequency Cavities: Provide electric fields to speed up charged particles
Bending Magnets (dipole magnets): Curve the particles in the vacuum chamber
Focusing Magnets(quadrupole magnets) Concentrate the particles into a thick beam.

8. Type of accelerators Linear accelerator (LINAC)
Circular accelerator (synchrotron)
Fixed Target
Colliders
(Source:

9. A LINAC: SLAC’S ACCELERATOR CHAIN
Accelerator Components
Electron Gun
Damping Rings
Beam Switch Yard
Klystrons
(SLAC = Stanford Linear Accelerator Center)

10. SLAC: Electron Gun

11. SLAC: Beam Switch Yard

12. SLAC: Damping Ring

13. SLAC: Klystron The electron gun produces a flow of electrons
The bunching cavities regulate the speed of the electrons so that they arrive in bunches at the output cavity.
The bunches of electrons excite microwaves in the output cavity of the klystron.
The microwaves flow into the waveguide , which transports them to the accelerator .
The electrons are absorbed in the beam stop.

14. A synchrotron: Fermilab’s accelerators
Source:

15. FERMILAB’S ACCELERATOR CHAIN

16. FNAL: Cockroft-Walton accelerator
- Developed by John D. Cockroft and Earnest T. S. Walton at the Cavendish Laboratory (England)
- This type of accelerator consists of a multi-step voltage divider which accelerates ions linearly through constant voltage steps
The major accelerator facilities make use of several types of devices to build up the energy of the particles.
The Cockroft-Walton accelerator is used as the first stage of acceleration at Fermilab

17. FNAL: The LINAC at FermiLab
The Fermilab Linac is a negative hydrogen ion, 400 MeV accelerator. It includes a 25 keV H-minus ion source, a 750 keV electrostatic accelerating column, a 116 MeV drift-tube (Alverez) linac operating at MHz, and a 401 MeV side-coupled cavity linac operating at 805 MHz

18. FNAL: The booster
The Booster is a circular accelerator (synchrotron) that uses magnets to bend the beam of protons in a circular path. The protons travel around the Booster about 20,000 times so that they repeatedly experience electric fields. With each revolution the protons pick up more energy, leaving the Booster with 8 billion electron volts (8 GeV).

19. FNAL: The Main Injector Tunnel
- Main Injector, completed in 1999, accelerates particles and transfers beams.
- The functions of Main Injector Tunnel:
1) Accelerates protons from 8 GeV to 150 GeV.
2) Produces 120 GeV protons, which are used for antiproton production.
3) Receives antiprotons from the Antiproton Source and increases their energy to 150 GeV.
4) Injects protons and antiprotons into the Tevatron.

20. FNAL: The Tevatron
The Tevatron receives 150 GeV protons and antiprotons from the Main Injector and accelerates them to almost 1000 GeV, or one tera electron volt (1 TeV).
Traveling only 200 miles per hour slower than the speed of light, the protons and antiprotons circle the Tevatron in opposite directions.
The beams cross each other at the centers of the 5000-ton CDF and DZero detectors located inside the Tevatron tunnel, creating bursts of new particles

21. FNAL: The Tevatron Works

24. References
[1] Introduction to High Energy Physics, 4th Edition, Donald H. Perkin, University of Oxford, 2000
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… and many different websites