In this work, a Preisach-recurrent neural network model is proposed to predict the dynamic hysteresis in ARMCO pure iron, an important soft magnetic material in particle accelerator magnets. A recurrent neural network coupled with Preisach play operators is proposed, along with a novel validation method for the identification of the model’s parameters. The proposed model is found to predict the magnetic flux density of ARMCO pure iron with a Normalised Root Mean Square Error (NRMSE) better than 0.7%, when trained with just six different hysteresis loops. The model is evaluated using ramp-rates not used in the training procedure, which shows the ability of the model to predict data which has not been measured. The results demonstrate that the Preisach model based on a recurrent neural network can accurately describe ferromagnetic dynamic hysteresis when trained with a limited amount of data, showing the model’s potential in the field of materials science.

Due to its flexibility in generating advanced field harmonic corrections and potential for low cost compared to traditional designs, the Canted Cosine Theta (CCT) configuration is particularly interesting for compact particle accelerators and gantries for medical applications. This article presents the design of a curved demonstrator named Fusillo, a Canted Cosine Theta Nb-Ti dipole magnet that is being developed at CERN, featuring a large aperture of 236 mm, a small bending radius of 1 m, a bending angle of 90 $^{\circ }$ , and multi-harmonic field correction, with a 3.61 T conductor peak field. We detail the magnetic coil design, incorporating high-order magnetic field correction of the errors produced by the heavily curved coil, peak field reduction at the coil ends, the development of a new rope type cable, and the mechanical design and the development of the former that supports the coil and provides the curved shape. We also present the first results of a subscale model used to qualify the coil's former manufacturing process, the rope cable, the coil winding optimization, and the coil impregnation system.

Sensing coils are inductive sensors commonly used to measure magnetic fields, such as those generated by electromagnets used in many kinds of industrial and scientific applications. Inductive sensors rely on integrating the output voltage at the coil’s terminals in order to obtain flux linkage, which may suffer from the magnification of low-frequency noise resulting in a drifting integrated signal. This article presents a method for the cancellation of integrator drift. The method is based on a first-order linear Kalman filter combining the data from the coil and a second sensor. Two case studies are presented. In the first one, the second sensor is a Hall probe, which senses the magnetic field directly. In a second case study, the magnet’s excitation current was used instead to provide a first-order approximation of the field. Experimental tests show that both approaches can reduce the measured field drift by three orders of magnitude. The Hall probe option guarantees, in addition, one order of magnitude better absolute accuracy than by using the excitation current.

Rotating-coil measurement systems are widely used to measure the multipolar fields of particle accelerator magnets. This paper presents a rotating-coil measurement system that aims at providing a complete data set for the characterization of quadrupole magnets with small bore diameters (26 mm). The PCB magnetometer design represents a challenging goal for this type of transducer. It is characterized by an aspect ratio 30% higher than the state of the art, imposed by the reduced dimension of the external radius of the rotating shaft and the necessity of covering the entire magnet effective length (500 mm or higher). The system design required a novel design for the mechanical asset, also considering the innovation represented by the commercial carbon fiber tube, housing the PCB magnetometer. Moreover, the measurement system is based primarily on standard and commercially available components, with simplified control and post-processing software applications. The system and its components are cross-calibrated using a stretched-wire system and another rotating-coil system. The measurement precision is established in a measurement campaign performed on a quadrupole magnet characterized by an inner bore diameter of 45 mm.

A superconducting permeameter is proposed to characterize the magnetic properties of high-energy superconducting magnet yokes at their operating temperature and saturation level. The main problem of superconducting coils, an undesired quench, was faced by specific protection simulations, which has led to a self-protected system. The superconducting permeameter was used to perform the magnetic characterization of ARMCO Pure Iron, the material for the new High-Luminosity Large Hadron Collider (HL-LHC) superconducting magnet yokes, which was performed at the cryogenic temperature of 4.2 K and a saturation level of nearly 3 T. Two case studies based on the new HL-LHC superconducting quadrupole and dipole magnets highlight the impact of the magnetic properties of the yoke on the performance of the superconducting magnets, showing that the common assumption that heavily saturated steels with similar chemical composition behave precisely the same way has been proven wrong.