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Cyclotron Magnet: NdFeB

  1. Jun 28, 2010 #1
    I want to make a 6" Cyclotron for low power applications accelerating protons and deuterons to 1.5-2.5 MeV. It seems that heart of the cyclotron is the magnet. The more powerful the magnet the higher the energy. I am interested in using NdFeB magnets and it looks like I can get some pretty good ones at N48 which have an average surface measurement of 6500 gauss for a single magnet but they claim the material is 13,900 gauss. The shape of the magnet I'm considering is a 6" x 2" disk. If I place two of these magnets one above the other (in a structurally sound jig) with a 2.5" gap would the gauss measurement be expected to increase above 6500 in the gap?

    I'm also thinking about attaching two ferrous plates 6" in diameter that are beveled:

    | mag |
    \ plate /

    "air gap"
    / plate \
    | mag |

    Excuse the bad ascii drawing, but this would be the side view and the ferrous plates would be about 1/2" thick. The beveling of the disk shaped steel plates is for shaping the field around the edge of the air gap so that a bulge occurs and the magnetic field bulges out looking like a wheel of cheese. This, to constrain the beam to the center in a horizontal plane. The air gap in the drawing above is where the dees will be situated.

    Does this look like I'm on the right track? I'm hoping that the homogeneity of the magnets' composition will provide a uniform field and I can get by without worrying about shimming and such.

    Obviously I can't adjust the power of the magnets. So I'll have to be able to make any adjustments by varying the RF frequency. Is that going to create problems? Or could I engineer some sort of screw adjustment mechanism in the jig that would enable me to increase the air gap?

    As far as magnet safety goes, I'm aware that they are dangerous and will see if I can get some in-person assistance from someone who's had experience with such high-powered permanent magnets.

    At 0.65 tesla, and 6" I come up with .0495 c, which for deuterons is just under 2.3 MeV (I think)

    Any input will be appreciated. Thanks,

  2. jcsd
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