| 摘要 |
A primary gradient coil and a screen coil for use with the primary coil are constructed to create a substantially null field adjacent to the screen coil and a substantially distortion free linear gradient field adjacent to the gradient coil. A method is disclosed for generating the coils by considering the screen coil to be of infinite length, deriving a Fourier transform of the axial and other components of the field in which the transform is the sum of the permissible harmonic modes on the coil surface in which a coefficient Cn is derived representing the nth harmonic. A perfect screen coil is created and the number of terms Cn selected using least squares optimization until there is no longer a significant change in the resulting field. Examples are given for creating unscreened, screened, linear, axial and transverse gradient field coils. |
