SMES coil configurations with reduced stray field

Legendre polynomials have been used in studying the stray field outside a solenoid. The stray field outside a thin solenoid coil can be expanded in a series of Legendre polynomials in cylindrical coordinate where an observation point is designated as R(sub p).Results indicate that the term of a stray field decreasing as r(sub p) raised to the negative third power can be cancelled out as long as the summation of magnetic moments from all coils is zero. The higher order of the stray field can vanish if the coil arrangement is optimized.