More About Magnets
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The figure at left shows the magnetic field lines for a quadrupole magnet and the corresponding forces on a negative particle traveling into the picture. |
Note:
- A particle moving directly through the middle feels no force. The force felt by a particle gets bigger the further out the particle is from the center
- Forces on a bunch of particles will squeeze the bunch
in the vertical direction, but spread the bunch in the horizontal
plane.
- This is the reason it takes two dipole magnets to achieve a focusing effect on the bunch.
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Angle View |
This figure shows a pair of quadrupole magnets --note that the second has the north and south poles reversed compared to the first. This magnet will squeeze in the horizontal plane and spread in the vertical. |
Side and top views (below) of a electron bunch traveling through a pair of quadrupole magnets, showing how net shrinking of the bunch size is achieved.
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Side View (in plane) |
Top view (perpendicular plane) |
