Rotating coil measurement system for the APT/LEDA CCDTL quadrupole magnets

A rotating coil measurement system has been developed to characterize the magnetic properties of the Coupled Cavity Drift Tube Linac (CCDTL) quadrupole magnets for the Accelerator Production of Tritium-Low Energy Demonstration Accelerator (APT/LEDA) at the Los Alamos Neutron Science Center (LANSCE). The setup is designed to measure the quadrupole gradient-length product with an absolute error of less than 0.25%, and to determine the relative multipole content of the quadrupole at a radius of 80% of the aperture. The bench for the system consists of a granite surface plate with a pair of rails attached on which the magnet and rotating coil supports rest. The signal is routed through a slipring to a digital voltage integrator triggered by an incremental encoder attached to one end of the coil. Two different rotating coils were designed and fabricated for the system. The first coil is a conventional radially-wound harmonic coil that provides a good measure of the relative quadrupole strength and harmonic content, while the second coil is a specially designed printed circuit coil that can accurately measure the quadrupole gradient-length product.