| 摘要 |
<p>A matrix shim system for generating magnetic field components superimposed to a main static magnetic field, comprising a plurality of annular coils, is characterized in that it comprises g groups G 1 ... G g of coils, with g being a natural number ‰¥ 1, wherein each group G i consists of at least two single annular coils connected in series, wherein each group G i is designed to generate, in use, a magnetic field B z G i = £ n = 0 ˆž A n �¢ 0 G i ‹ T n �¢ 0 , that for each group G i , there are at least two values of n for which A n �¢ 0 G i ‹ R n max | A 20 G i ‹ R 2 | , €¦ , | A N �¢ 0 G i ‹ R N | ‰¥ 0.5 and N ‰¥ n ‰¥ 2, with N: the total number of current supplies of the matrix shim system, and R: smallest inside radius of any of the annular coils of the matrix shim system, and that for each group G i of coils, an individual, adjustable electrical current supply (12) is provided. The inventive matrix shim system is both simple in design and stable against current fluctuations.</p> |
