A NOVEL COMPENSATED COIL SYSTEM WITH HIGH HOMOGENEITY AND LOW STRAYFIELDS

A novel coil system as a replacement for Helmholtz coil systems will be presented. It consists of three pairs of coils with one pair having opposite polarity. In comparison to Helmholtz coils the novel coil system has the following advantages: (a) The magnetic field amplitude on the coil axis (z-axis) outside the coil system declines with H similar to z(-5) significantly faster than in a Helmholtz coil (H similar to z(-3)). (b) It provides an homogeneity up to the sixth order of the magnetic field along the coil axis. Hence a larger homogeneous volume in comparison to a Helmholtz coil system with equipollent dimensions could be achieved. The novel coil system can be applied for the stray field insensitive measurement of magnetic moments and for the generation of magnetic fields especially inside of magnetic shielding chambers whose walls should not be magnetized in any circumstance. An excellent agreement between calculated field profiles and field measurements of prototypes has been found. The homogeneity of the field profile of a prototype could be further improved by connecting a resistor in parallel to three of the six coils. This way precision measurements by nuclear magnetic resonance could be accomplished.