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Ring Accelerator

  1. Mar 14, 2006 #1
    Is a ring accelerator the same as a cyclotron? If not can someone please tell me somthing about ring accelerator, or send me links where I can find some information about ring accelerators.
  2. jcsd
  3. Mar 14, 2006 #2


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    A cyclotron (properly speaking) is an early type of ring accelerator, that does not attempt to compensate for relativistic effects as the particles move faster and faster. Therefore it's limited to rather low energies.

    A better term to search for (in Google, e.g.) is "synchrocyclotron" which does incorporate relativistic corrections.

    The biggest modern examples of synchrocyclotrons are at Fermilab in the USA and at CERN in Switzerland.
  4. Mar 14, 2006 #3
    I've usually heard the Tevatron and similar accelerators referred to as just "synchrotrons", but it must mean the same thing.

    One important difference is that a cyclotron (at least the first ones) were solid disks rather than rings. A constant magnetic field is used to create the circular motion, and the particles spiral out as they accelerate. In the modern synchrotrons the magnetic field can be adjusted so the particles always travel in the same path. This means the accelerator can be just the ring, instead of having to fill in the middle. When the machine is many kilometers across it's obviously better to use the second option :)
  5. Mar 14, 2006 #4
    Ok thanks a bunch
  6. Mar 14, 2006 #5


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    Staff: Mentor

    Yes, "synchrotron" is a shortened version of "synchrocyclotron". It's probably the more common version now.
  7. Mar 14, 2006 #6


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    The betatron probably qualifies as a true ring accelerator -

    The original cyclotrons consisted of "D"-shaped hollow electrodes with an alternating potential across the gap between the D's. The flat parts of the D faced each other. The D's were placed between the poles of large magnets, and the magnetic field, oriented perpendicular to the plane of the D's, caused the ions to move in circular orbits, starting in the center and moving outward as the energy increased. The polarity of the electrodes was changed with radiofrequency alternating voltage source.
    See also - http://en.wikipedia.org/wiki/Cyclotron

    A synchrocyclotron is simply a cyclotron with the accelerating supply frequency decreasing as the particles become relativistic and begin to lag behind. Although in principle they can be scaled up to any energy they are not built any more as the synchrotron is a more versatile machine at high energies. [CERN]
    Also - http://en.wikipedia.org/wiki/Synchrocyclotron

    The synchrotrons are the largest machines which incorporate magnets oriented in a ring or loop, now several km/miles in circumference.

    See this for Fermilabs accelerators - http://www.fnal.gov/pub/inquiring/physics/accelerators/

    As for Wikipedia - no endorsement of the accuracy is expressed or implied, but the pictures are OK.
  8. Mar 14, 2006 #7


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    But take note that cyclotrons and synchrotrons typically are not "accelerators" in the technical sense. The electrons are simply "coasting" in the ring after they come out of the injector. There are no accelerating mechanism.

    This is different than what we have at, let's say, the Tevatron, where in the booster ring, you do have accelerating structures that give the particles a kick every time they pass through.

  9. Mar 14, 2006 #8


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    As I recall, the classic cyclotron (Lawrence's original design) had the particle orbits enclosed in a pair of facing hollow "dees", with a gap between them, with the whole assembly between the magnet pole faces. An alternating potential difference between the dees gave the particles (which must have had to travel in bunches) a kick every time they passed through the gap.

    The big insight that led to the cyclotron was the realization that the orbital period doesn't depend on the energy, in the non-relativistic regime, so a simple alternating voltage with a suitable frequency would accelerate the particles, at least until relativistic effects become significant.
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