Rotating coil system for multipole magnets

We are preparing a rotating coil system for precise magnetic harmonic field measurement. A flexible print circuit sheet, where a pair of one turn coils are printed on, is glued on a quartz rod. The coil location can be well defined because of the one turn coil scheme and the small thermal expansion coefficient of quartz eliminates the ambient temperature effect. The two coils located on the quarts rod with the angle difference of 180 degree can separate the odd and even harmonics components by recording both the signals simultaneously to get their sum and difference. 24-bit ADC's are used for higher resolution and the signal are integrated digitally. The coil wire positions (radius and azimuthal angle) are evaluated by a small magnet that has a sharp magnetic field distribution. (author)