A polyvalent harmonic coil testing method for small-aperture magnets

Abstract

A method to characterize permanent and fast-pulsed iron-dominated magnets with small apertures is presented. The harmonic coil measurement technique is enhanced specifically for small-aperture magnets by (1) in situ calibration, for facing search-coil production inaccuracy, (2) rotating the magnet around its axis, for correcting systematic effects, and (3) measuring magnetic fluxes by stationary coils at different angular positions for measuring fast pulsed magnets. This method allows a quadrupole magnet for particle accelerators to be characterized completely, by assessing multipole field components, magnetic axis position, and field direction. In this paper, initially the metrological problems arising from testing small-aperture magnets are highlighted. Then, the basic ideas of the proposed method and the architecture of the corresponding measurement system are illustrated. Finally, experimental validation results are shown for small-aperture permanent and fast-ramped quadrupole magnets for the new linear accelerator Linac4 at CERN (European Organization for Nuclear Research).

Precision Analysis and Design of Rotating Coil Magnetic Measurements System

“…The signal, received by the coil when the rotation cuts through the magnetic field, looks like a harmonic wave with the same wavelength as the number of poles of the electromagnet and amplitude. The position of 0-360 degrees around the magnetic cavity depends on the torsional angle of the coil that crosses a magnetic field whose direction is perpendicular to the motion [19][20][21][22]. Lastly, (3), analyzing the impacts on the accuracy of the electromagnetic field measurement based on the error value of the controlled speed and the orbit movement of the shaft with the coil as well as signal analysis using fast Fourier transform [23][24][25] for indicating the feature of orbits used for measuring the magnetic fields of each axis.…”

Rotating-coil calibration in a reference quadrupole, considering roll-angle misalignment and higher-order harmonics

“…Coils can be manufactured by traditional winding methods or printed-circuit board (PCB) [8] technology. The latter is especially suited for small-aperture magnets [9].…”