Quadrupole Magnetic Lens Using Permanent Ceramic Magnets

A quadrupole lens pair is described utilizing permanent ceramic magnets. The field gradient is 470 Oe/cm, across a 7.94-cm aperture. Variation in lens strength is achieved by driving the lenses over a mild steel magnetic shunt welded to the inside of the beam tube. The lenses are of relatively low cost, light weight, and simple construction. Of the two units described, when used at full strength, the smallest lens pair brings a 10-MeV proton beam to a focus in a distance of 4 m from it.