A conductor assembly and method of manufacture. The assembly includes a magnetic coil positioned about a curvilinear axis with one or more coil rows comprising conductive material having an arcuate shape. A generated field is characterized by a dipole component having a first magnitude, a quadrupole component having a second magnitude, a sextupole component having a third magnitude and a decupole component having a fourth magnitude. The third and fourth magnitudes are each 10−3 the first magnitude or less.