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Does the movement of protons create a magnetic field?

  1. May 28, 2009 #1
    Stupid question (or maybe stupid asker), but I'm having a hard time finding an answer. Of course the movement of electrons (- charge particle) creates a magnetic field when moving steadily through a conductor but what about protons (+ charge particle)? Lets just imagine you have protons passing through an ionically conductive material, would it create a magnetic field the same as electrons would but opposite poles? My science-sense says no, but I'm often wrong.
  2. jcsd
  3. May 28, 2009 #2
    Protons circulating in a proton synchrotron produce both an electric field, and a magnetic field. Either or both of these fields can be used to determine the number and position of bunches of protons. Same for antiprotons.
  4. May 28, 2009 #3
    Really? I always thought the synchrotron produced electric and magnetic fields to circulate the protons? Back to the books for me...:rolleyes:
  5. May 28, 2009 #4
    You need a DC magnetic field (dipoles) with focusing magnets (quadrupoles) to keep the protons in the vacuum chamber, and they will coast around and around for hours. The Lorentz force bends the protons' direction, but because the Lorentz force is perpendicular to the protons' velocity, there is no increase or decrease in the protons' speed.
  6. May 28, 2009 #5


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    Fields ared used to contain the protons; but there are places where there are no coils and this is where the beam current can be measured using e.g a current comparator (this can be done using SQUIDs meaning the measurement is very sensitive).
  7. May 28, 2009 #6
    You know the hand rules to determine the direction of the magnetic field (vector B) produced by a current?

    If you have charged particles moving in a straight line, stick out your thumb like you're hitching a ride, point the thumb in the direction of the charge motion, and the curled fingers point will point in the direction of the circular magnetic field caused by the current. For positive charges use your right hand, and for negative charges use your left hand.

    For charged particles moving in a circular path, like a loop or coil, point the curled fingers in the direction of charge motion, and then the thumb will point in the direction of the magnetic field caused by the current. Just as in the first case, for positive charges use your right hand, and for negative charges use your left hand.
  8. May 29, 2009 #7
    For simultaneously counter-rotating 900-GeV beams of protons and antiprotons in the Fermilab Tevatron, it is not quite so simple. Directional couplers, which measure BOTH the radial electric field AND the azimuthal magnetic field, can distinguish between simultaneous clockwise and counterclockwise rotating beams. Recall that the Poynting vector P = E x H uniquely determines direction.
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