Measuring the magnetic axis alignment during solenoids working

Abstract

A method for monitoring the misalignment of the magnetic axis in solenoids is proposed. This method requires only a few measurements of the magnetic field at fixed positions inside the magnet aperture, and thus overcomes the main drawback of sturdy moving mechanics of other Hall sensor-based methods. Conversely to state-of-the-art axis determination, the proposed method can be applied also during magnet operations, when the axis region and almost the whole remaining magnet aperture are not accessible. Moreover, only a few measurements of the magnetic field at fixed positions inside the magnet aperture are required: thus a slow process such as the mapping of the whole aperture of a magnet by means of moving stages is not necessary. The mathematical formulation of the method is explained, and a case study on a model of a multi–layer solenoid is presented. For this case study, the uncertainty is assessed and the optimal placement of the Hall transducers is derived.

On-field monitoring of the magnetic axis misalignment in multi-coils solenoids

“…For an actual multi-coil magnet, the same definition of magnetic axis is no longer trivial, and the equation of the magnetic axis in a proper reference frame cannot be found by applying the method proposed in [16]. In fact, even by assuming the magnetic field of each coil as axially symmetric, the actual misalignments of such fields make the overall magnetic field not axially symmetric.…”

“…Thus, by monitoring the magnetic axis we mean deriving the polygonal chain and thus approximating the overall magnetic axis in a given reference frame. To this aim, the method for a single coil proposed in [16] is to be extended by relying on the axisymmetry of each coil. The basic idea is that the field measured through Hall transducers traces back to the misalignment thanks to a local field model.…”

“…Most of the standard methods for the solenoid axis identification are useless for on-line monitoring, owing to their need of accessing a wide area of the solenoid's air gap (evidently, almost full of the beam-line and auxiliary accessories). In [16], a novel Hall transducers-based method was proposed for the on-line monitoring of the magnetic axis for single-coil solenoids, relying on measurements of the magnetic flux density at a few points and a simple Taylor expansion as local field model. However, in presence of overlapping magnetic fields generated by several coils, the definitions of the magnetic axis and of its misalignment, as well as the field model, are significantly more complicated.…”

A Novel Model of Unipolar Induction Phenomena Based on Direct Interaction Between Conductor Charges

“…For the calculation of the magnetic field B we are using a state-of-the-art model by Derby & Olbert [44] that has been incorporated into a MATLAB tool by D. Cébron [45]. The success of this model has been demonstrated by various scientists and has been applied to many topics in solenoid research [46][47][48][49][50][51][52].…”

A Charged Particle Model based on Weber Electrodynamics for Electron Beam Trajectories in Coil and Solenoid Elements

“…To this end, this paper tests three models for electron beam deflection -a direct-interaction model, a field based model, and predictions obtained with a commercially available software package. We present a direct-interaction model that considers the forces acting between the charge carriers of the electron beam and a coil to predict the deflection experienced by the beam due to the magnetic field, within the low velocity limit v ≪ c. The standard field model [25] is based on the derivations of Derby & Olbert [26] and Callaghan & Maslen [27], which has been further applied to solenoids with permeable cores, off-axis solenoids, parallel solenoids and axis alignment measurements [28][29][30][31][32][33]. These two models will be further compared to commercially available software CPO [34].…”