| 摘要 |
Apparatus including a superconducting magnetic assembly for inducing nuclear magnetic resonance within a flowing medium. In order to make nuclear magnetic resonance measurements on a flowing medium it is preferred to have separate polarizing and resonating fields situated consecutively along the flow path, with the magnetic flux density in the resonating region being reduced from that in the previous polarizing region. The signal to noise ratio in such a system is improved by increasing the magnetic flux density in the polarizing region as much as possible. Using superconducting coils to provide the magnetic fields a lighter assembly with increased polarizing field strength over that of an equivalent iron-cored electromagnet is obtained. The geometry of the coil windings establishes the field differences, the lower field region being in consequence of any combination of an increased coil spacing, greater coil width or reduced number of turns on the portion of windings corresponding to the resonating field region. Homogeneity of the field regions is enhanced by the ends of each set of windings being upturned.
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