Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The radius of the synchrotron

  1. Nov 13, 2011 #1
    Hi, there. I have a question:
    If I want to build a facility for synchrotron RADIATION (not for particle physics experiment),
    how to chose the radius of the storage ring?
    (Why the radii of current facilities are so large?)
    Thank you.
  2. jcsd
  3. Nov 13, 2011 #2


    User Avatar

    I don't understand the question's direction/inference. Are you simply asking;

  4. Nov 13, 2011 #3
    well, I mean, how the researched decided the radius of the storage ring in the first place. If I want to use the radiation, I will think about the wavelength range and the radiation intensity. Are there anything else I should consider? And how to choose a radius based on these considerations?
    That's what I want to ask.

    About the last question, why current radii are so large, I feel it is strange because radiation intensity is inversely proportional to the radius: the smaller the radius, the larger the intensity -- so, why they made the radius so large?
  5. Nov 13, 2011 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2018 Award

    1. It depends on how high of an energy the electron beam will have. The high the energy, the more difficult it is to bend its path. So you tend to make a ring with a smaller curvature.

    2. Unless you have sophisticated electronics that can time the kick to each electron bunch just right, you will not have a "synchrotron".

    3. The "radiation" typically coming out of a typical synchrotron is a dangerous level of x-rays! Even the bremstrallung radiation coming from 1 MeV electron bunch will emit unsafe radiation if it is not shielded.

    4. Most synchrotron radiation centers often do not make use of the synchrotron radiation. Rather, they use radiation coming from various insertion devices along the path of the beam. These are inserted along the straight sections of the ring. So in essence, the ring is simply to recirculate the beam, rather than actually to produce the synchrotron radiation.

  6. Nov 13, 2011 #5
    Thank you ZapperZ!
  7. Nov 13, 2011 #6

    Andrew Mason

    User Avatar
    Science Advisor
    Homework Helper

    The strength of the dipole magnets used to bend the beam would also be an important factor. The smaller the radius of the circle of the beam for a given particle speed, the greater the bending force that is required from these bending magnets. Improvements in magnet technology have allowed synchrotrons to become smaller and more powerful.

    Each bend produces synchrotron radiation. As Zapperz points out, the synchrotron radiation produced at each bending magnet is normally wasted energy. So there is a trade off: the smaller you make the circle the greater the amount of power that is lost. The lost energy has to be replaced to keep the electrons moving at constant speed. So energy cost also a factor in how small you want to make the radius of the ring.

    Last edited: Nov 13, 2011
  8. Nov 14, 2011 #7
    Thank you Andrew! I can get what you and ZapperZ said. Maybe most synchrotrons are not built for radiation, that's why they made the storage ring so large. If for radiation, bending the relativistic electrons at a small radius is not impossible: at least, they have already developed free electron lasers using wigglers.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook