Matrix shim system with grouped coils

摘要

A matrix shim system for generating magnetic field components superimposed on a main static magnetic field, comprising a plurality of annular coils, is characterized in that it comprises g groups G₁ . . . 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 $B_z\left(G_i\right)=\sum _{n=0}^{\infty }{A}_{n0}\left(G_i\right).T_{n0}.$ For each group G_i, there are at least two values of n for which $\frac{A_{n0}\left(G_i\right).R^n}{\max \left\{A_{20}\left(G_i\right).R^2,\mathrm{...},A_{N0}\left(G_i\right).R^N\right\}}>=0.5\mathrm{and}N>=n>=2,$ 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. An individual, adjustable electrical current supply is provided for each group G_i of coils. The inventive matrix shim system is both simple in design and stable against current fluctuations.