| 摘要 |
In a nuclear magnetic resonance apparatus with a permanent magnet (2) the permanent magnetic material consists of laterally magnetised bars (30,40) each of which is rotatable about is longitudinal axis in the magnet system. If the bars have a circular cross-section all the bars in the magnet system are made mutually identical and only the direction of each of the bars needs to be matched to the magnetisation direction required at the relevant position. If the direction of magnetisation in the system satisfies the condition alpha = 2 gamma at all times, where alpha is the magnetisation direction and gamma is the polar angular coordinate of the relevant bar, efficient use can be made of the magnetic material and, in contrast to other magnetisation directions, it is possible to work without a return yoke. |
