Single voxel approach for Lorentz force evaluation

Abstract

Purpose Lorentz force evaluation is a non-destructive evaluation method for conducting specimens. The movement of a specimen relative to a permanent magnet leads to Lorentz forces that are perturbed in the presence of a defect. This defect response signal (DRS) is used for defect reconstruction. To solve a linear inverse problem for defect reconstruction, an accurate and fast forward computation method is required. As existing forward methods are either too slow or too inaccurate, the purpose of this paper is to propose the single voxel approach (SVA) as a novel method. Design/methodology/approach In SVA, the DRS is computed as a superposition of DRSs from single defect voxels, which are calculated in advance, by applying the boundary element source method. This research uses a setup of an isotropic conducting specimen, a spherical permanent magnet and defects of different shapes at different depths. With the help of simulations, this study compares the SVA to the previously proposed approximate forward solution (AFS) and the extended area approach (EAA) using the normalized root mean square error (NRMSE). Simulated data using the finite element method serve as the reference solution. Findings SVA shows across all simulations NRMSE values <2.5 per cent compared to <8 per cent for EAA and <12 per cent for AFS. Originality/value The superposition principle of SVA allows for the application of linear inverse methods for defect reconstruction while providing sufficient accuracy of the forward method.

Larmor Precession: Observation and Utilization for Boosting the Signal Intensity of Radio Frequency Glow Discharge Mass Spectrometry

“…With the single-block magnet and 2 × 2, 3 × 2, and 3 × 4 magnet arrays (Figure b–e), the electron trajectories were curved and spun near the sample surface, which would cause inelastic collisions between primary electrons and sample to produce numerous secondary electrons (Dynamic simulation is illustrated in the Supporting Information S1). Investigations of different electron motions further suggest that the movements of the high-speed electrons perpendicular to the magnetic induction line were considered as the Larmor precession induced by Lorentz forces (Figure f). − …”

“…The investigations of different electron motions further suggest that the movements of highspeed electrons perpendicular to the magnetic induction line were considered as the Larmor precession induced by Lorentz forces (Figure 5f). [29][30][31] With Larmor precession, the spiral path of the electron and the path duration time could be extended in the discharge area. In addition, Larmor precession produced many secondary electrons resulting from inelastic collisions of primary electrons and samples, leading to more collisions between electrons and other particles and increases in the sputtering rate and the ionization efficiency.…”

“…This enhancement was evidently affected by the magnetic field strength and its spatial distribution. Under the action of the Lorentz force, the electron can change course and move in a direction perpendicular to the magnetic induction line and velocity, generating Larmor precession. − Moreover, the Larmor precession trajectory is related to the magnitude and direction of the Lorentz force. The larger the Lorentz force and the more complex the direction, the longer the precession trajectory will be.…”

Beam Shift Modulation Based on Larmor Resonance in Graphene–VO2 Photonic Crystal

“…[28] The surface plasmon resonance (SPR), created by SPs, can strengthen the localized electromagnetic field tremendously. [29] In 1897, Joseph Larmor [30][31][32] first deduced that the electrons in the atoms rotating around the nucleus under the action of a magnetic field produced an additional magnetic moment opposite to the direction of the external magnetic field. When the applied magnetic field reached a certain size, it will resonate with electrons.…”