| 摘要 |
COMPENSATION COIL FOR TEMPORAL DRIFT OF A SUPERCONDUCTING MAGNET A superconducting coil assembly for a nuclear magnetic resonance imaging system has a main coil for producing a static magnetic field within a cylindrical volume. A conventional set of active correction coils are provided to spatially homogenize the magnetic field. A pair of passive compensation coils are electrically connected in series and shorted together. The compensation coils are inductively coupled to the main coil so that the temporal decay of the current in the main coil induces current in the compensation coils. The magnetic field harmonics produced by this induced current is opposed to the magnetic field harmonics produced in the correction coils by main coil decay. The compensation coil thereby counteracts the inhomogeneity effects from the main coil current decay. |
