1,721,046 research outputs found
A flexible printed-circuit coil for scanning transversal magnetic-fields errors in accelerator magnets
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Data-driven simulation of transient fields in air–coil magnets for accelerators
No full textTime-varying fields in fast-ramping magnets for accelerators are difficult to compute in the range of accuracy required for magnet operation. This is due to the complexity of the dynamic phenomena such as hysteresis and 3D eddy currents. On the other hand, magnetic measurements that intercept all these physical phenomena are often limited to a subset of excitation cycles and restricted spatial domains. The measurement results are therefore difficult to extrapolate without a validated physical model of the device. This paper proposes measurement-updated field simulations to characterize dynamic effects in accelerator magnets. The main idea is to construct a reduced-order model, whose variables are retrievable from measurements by means of a state estimator, and to update the model by minimizing the error between simulations and measurements. The proposed method is applied to a linear, time-transient electromagnetic-field problem of an air–coil corrector magnet with aluminium collars. The proposed method is a first step towards a hybrid twin of an accelerator magnet
A mechanical analysis of rotating-coil magnetometers
No full textRotating-coil magnetometers are among the most common and most accurate transducers for measuring the integral magnetic-field harmonics in accelerator magnets. The measurement uncertainty depends on the mechanical properties of the shafts, bearings, drive systems, and supports. In this paper we study the mechanical phenomena (static and dynamic) affecting rotating-coil measurements and propose analysis and diagnostic methods for improving the instrument in terms of material choice and geometrical design. The propagation of uncertainty is investigated on the measured quantities (induced voltages, integrated and developed into a Fourier series, the coefficients of which are know as field harmonics). This results in a consistent framework for the design of a measurement bench for rotating-coil magnetometers. The paper also presents the design of a complete system, including displacement stages, supports, rotating coils, and an angular position system
Performance of the stretched-and vibrating-wire techniques and correction of background fields in locating quadrupole magnetic axes
No full textA single conducting wire is used for localizing the magnetic axis of a quadrupole magnet. The localization is performed by both the stretched-wire and the vibratingwire method. The compatibility of the two measurements is demonstrated and the measurement repeatability is assessed for both the methods at varying the magnet gradient. Furthermore, the influence of the background magnetic field in the two approaches is studied at varying the magnetic field strength. Experimental results are given for a normalconducting quadrupole magnet
Data-driven modeling of nonlinear materials in normal-conducting magnets
No full textAccurate numerical modeling of normal-conducting accelerator magnets requires a reliable characterization of the iron saturation and hysteresis as well as a precise knowledge of the magnet geometry as built. Computations of the field quality are not easily achieving the accuracy required by the accelerator operation, particularly for eddy-current effects in fast-ramping magnets. This paper proposes a (measurement) data-driven model for the nonlinear magnetization of normal-conducting magnets. The model adopts a volume integral formulation compatible with eddy-current simulations. A two-step updating procedure is applied. The first step is the fitting of material parameters directly in the magnet model. The second step is the updating of the magnetization by measurements of the integral field harmonics. The result is a full-order updated model that can be employed in static or dynamic simulations. Finally, the procedure is validated on an iron-dominated, normal-conducting magnet
A magneto-mechanical model for rotating-coil magnetometers
Full text linkRotating-coil magnetometers are among the most common transducers for measuring local and integral magnetic fields of accelerator magnets. The measurement uncertainty strongly depends on the mechanical properties of the shafts, bearings, drive systems, and supports. This paper proposes an analytical mechanical model for rotating-coil magnetometers, which allows a sensitivity analysis of mechanical phenomena affecting magnetic measurements. Both static and dynamic effects are considered. The model is validated numerically with a finite element model, and experimentally on an operational device
Metrological characterisation of rotating-coil magnetometer systems
Full text linkRotating-coil magnetometers are among the most common and most accurate transducers for measuring the integral magnetic-field harmonics in accelerator magnets. The measurement uncertainty depends on the mechanical properties of the shafts, bearings, drive systems, and supports. Therefore, rotating coils require a careful analysis of the mechanical phenomena (static and dynamic) affecting the measurements, both in the design and in operation phases. The design phase involves the estimation of worst-case scenarios in terms of mechanical disturbances, while the operation phase reveals the actual mechanical characteristics of the system. In previous publications, we focused on modelling the rotating-coil mechanics for the design of novel devices. In this paper, we characterise a complete system in operation. First, the mechanical model is employed for estimating the forces arising during shaft rotation. Then, the effect of the estimated disturbances is evaluated in a simulated measurement. This measurement is then performed in the laboratory and the two results are compared. In order to characterise the robustness of the system against mechanical vibrations, different revolution speeds are evaluated. This work thus presents a complete procedure for characterising a rotating-coil magnetometer system
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