Instrumentation for Magnetic Measurements of the Superconducting Magnets

A harmonic-coil measurement system is presented. The main task of the system is to determine the harmonic coefficients of the magnetic field in the aperture of the superconducting (SC) magnet such as dipoles, quadrupoles, sextupoles, and octupoles. The hardware includes a rotating shaft with a harmonic coil array, a motor controller linked to a personal computer (PC) via the CAN bus and a data acquisition controller linked to a PC by the USB bus. The system operation is based on a synchronization of a step motor rotating the shaft and a delta-sigma ADC, measuring a voltage induced during the coil´s rotation. Such a mode provides an integral number of samplings per one step allows storing the row measurement data to a local disk for an off-line analysis and permits to change an interval of integration. Inspection of linearity of dependence between the positions of the shaft and a number of steps of the step motor was done. All subsystems, except the power supply (PS) are programmed using the Lab View software.