Magnetic Prism Research Articles

Spin echo small-angle neutron scattering using superconducting magnetic Wollaston prisms.

We show the implementation of superconducting magnetic Wollaston prisms for spin echo small-angle neutron scattering. Two calibration methods for the spin echo length are presented: one utilizing spin echo modulated small-angle neutron scattering and the other based on the neutron refraction by quartz wedge crystals. Our experimental results with polystyrene nano-particle colloids showcase the system's efficacy in measuring both dilute and concentrated colloidal systems. Additionally, investigations into the pore diameter and pitch of a nano-porous alumina membrane demonstrate its capability in analyzing nano-porous materials. Furthermore, we discuss potential optimizations to further extend the accessible spin echo length.

Simulation of spin-echo SANS (SESANS) using McStas on monochromatic and time of flight instruments

We conduct simulations of Spin Echo Small Angle Neutron Scattering (SESANS) by employing Monte Carlo methods to a setup using four magnetic Wollaston prisms. Our primary focus involves the validation of these models, encompassing monochromatic scenarios across various neutron wavelengths to ascertain the reliability of the simulations. Subsequently, we extend this validation to encompass simulations in time-of-flight mode. Our model consistently and precisely predicts the scattering patterns emanating from dilute spheres in both monochromatic and time-of-flight modes. Notably, it also accurately reproduces the intricate encoding associated with scattering occurring between the third and fourth magnetic Wollaston prism, which provides us with another approach to increase the solid angle coverage of a SESANS instrument. This validation process conclusively demonstrates the efficacy of our simulation methods. Importantly, it paves the way for simulating more intricate and realistic instrumental configurations, broadening the horizons for future research endeavours.

Approximate calculation of static mass analyzers based on two-dimensional fields

The concurrent utilization of electric and magnetic fields in static mass analyzers proves highly effective in sparticle separation solely based on their masses, thereby ensuring remarkable analytical capabilities. High-resolution mass analyzers employ an achromatizing electrostatic system to precisely focus ion radiation by energy. Devices featuring zero energy dispersion are created through the collaborative action of electric achromatizing systems and the magnetic field within the analyzer, resulting in ion separation based solely on mass. Expanding the ion beam prior to its magnetic field exposure enhances the overall quality of static mass analyzers. This article delves into a static mass analyzer with dual ion beam focusing, elucidating the ion acceleration and deceleration processes at electrode boundaries, their focalization via a transaxial lens, and the impact of the electrostatic prism's refractive surface on the mass analyzer's "quality" parameter. Additionally, the transition from a sector homogeneous magnetic field to the fields generated by a two-dimensional magnetic prism and a three-electrode transaxial focusing lens is explored to augment the mass analyzer's linear dispersion. To refine ion beam focus pre-magnetic field entry, the proposed adoption of a two-dimensional electrostatic prism promises heightened linear dispersion in the mass analyzer while expanding the beam pre-magnetic field entry. This study also examines the impact of a two-dimensional electric prism on the charged particle beam, presenting an approximate expression for its angular energy dispersion. It is demonstrated that a prism-based mass analyzer integrating two-dimensional electric and magnetic prisms enables energy-focused operations alongside enhanced linear dispersion and reduced linear dimensions.

Spin-textured neutron beams with orbital angular momentum

We present a rigorous theoretical framework underpinning the technique of spin-echo modulated small-angle neutron scattering (SEMSANS), and show how the technique can be extended in order to generate spin-textured neutron beams with orbital angular momentum (OAM) via birefringent neutron spin-polarization devices known as magnetic Wollaston prisms. Neutron OAM beams are mathematically characterized by a ``cork-screw'' phase singularity ${e}^{i\ensuremath{\ell}\ensuremath{\phi}}$ about the propagation axis where $\ensuremath{\ell}$ is the OAM quantum number. To understand the precise relationship between the emergent OAM state and the variety of spin textures realized by various setups, we have developed a path-integral approach that in the interferometric limit makes a judicious use of magnetic Snell's law. We show that our proposed technique produces a complex two-dimensional pattern of spin-OAM entangled states which may be useful as a probe of quantum magnetic materials. We compare our path-integral approach to the well-known single-path Larmor precession model and present a pedagogical derivation of magnetic Snell's law of refraction for both massive and massless particles based on Maupertuis's action principle.

Simulations and concepts for a 2-D spin-echo modulated SANS (SEMSANS) instrument

The spin-echo small-angle neutron scattering (SESANS) technique utilises a series of inclined magnetic fields before and after the sample to encode the scattering angle into the polarisation to obtain a much higher resolution than in conventional SANS. The analogous technique (spin echo modulated SANS (SEMSANS)) implements spin manipulations before the sample only to encode the scattering into an intensity modulation. The technique can be combined with SANS to expand the length scale range probed from 1 nm to microns.Using McStas we show that using a series of four magnetic Wollaston prisms in two orthogonal pairs with a 90° rotation can be utilised to create SEMSANS modulations in 2-D. These modulations can also be of different periods in each encoding direction. This method can be applied to anisotropic scattering samples. Also this allows for the simultaneous measurement at two orthogonal independent spin-echo lengths. This technique yields directly information about the structure of oriented structures.

A Detailed Model of Magnetic Field Sources of the Earth’s Core Obtained by Solving the Inverse Problem of Magnetometry

Abstract —Magnetic field sources are sometimes approximated by magnetic dipoles or current loops. The usefulness of such approximations is not obvious at the initial stage of the study of objects. Investigating them in detail requires volumetric magnetic field sources. In this paper, they are represented by magnetized prisms. Such a model is valid due to the equivalence of current and magnetized objects. As there should be no real magnetization in the core, this property of a virtual prism to generate a magnetic field strength is referred to as virtual or effective magnetization (EM), which is determined for each prism by solving the inverse problem via the adaptive method. Initial data for solving the inverse problem are the Z vector components of the main magnetic field of the IGRF-2005 model in the geocentric coordinate system. Based on the effective magnetization and known formulas, the bulk current distribution, the bulk current density, and the magnetic moments of prisms of a two-layer core model are obtained. Their sum coincides with the magnetic moment of the virtual central dipole of the core, but, as many scientists assumed, the central dipole is not actually distinguished. At the same time, four significant inhomogeneities are identified in the core, which create the Canadian, Siberian-Asian, Australian, and negative South Atlantic global anomalies on the Earth’s surface. Based on the analysis of the results obtained, assumptions are made that the current generating the magnetic field is the motion of a positively weakly charged liquid of the core. Liquid motion is created by the rotation of the Earth and the decelerating gravitational forces of the Moon and the Sun. Arguments are given to support these assumptions. The results are illustrated in figures.

Practical realization and design of three-cascade prism mass analyzer for isotopic analysis of H-He mixtures using MS-platform technology

The paper presents the construction of a mass analyzer for the analysis of hydrogen-helium mixtures based on a magnetic prism using a three-stage circuit that includes two cylindrical capacitors. The choice of an ion-optical scheme that provides a high resolution of 3300, which is necessary for the separation of all nuclides formed during the analysis of hydrogen-helium mixtures, is justified. It is shown that the innovative «MS-Platform» technology makes it possible to ensure high assembly accuracy of the elements of the prism mass analyzer ion-optical circuit, which is necessary to realize all the advantages of a prism mass spectrometer compared to sector ones.

The linear phase correction of modulation of intensity emerging from zero effort (MIEZE) with magnetic Wollaston prisms

This study proposes the use of two magnetic Wollaston prisms (MWPs) to correct for the linear Larmor phase aberration of modulation of intensity emerging from zero effort (MIEZE), introduced by the transverse size of the sample. With this approach, the contrast of the intensity modulation can be maximized at any scattering angle of interest such that the same contrast as the direct transmission geometry can be fully recovered. The optimum magnetic fields required for the MWPs depend only on the scattering angle and the frequencies of the radio-frequency flippers, and they are independent of the neutron wavelength and beam divergence, which makes the approach suitable for both pulsed and continuous neutron sources.

Computer technology for interpreting vector measurements of the magnetic field

Computer technology is presented to solve the inverse problem of magnetic field vector measurements using software and algorithmic support for an automated system to interpret potential fields. The technology includes constructing a numerical model of the magnetic field of the studied area, forming an initial approximation model, assessing the depth of the sources and their magnetization. An approximation structure is used to describe the sources of anomalies (a set of uniformly magnetized polygonal prisms). To solve the problem, we used real vector measurements of the magnetic field by the components Xа, Ya, Zа, Та in the sections of Gruzsko South and Gruzsko Severnaya. Geologically, the area belongs to the central part of the Ukrainian Shield — the Kirovograd tectonic megablock. The area of work is confined to the Subotsko-Moshorin latitudinal fault zone. The possibility of comparing the results of the interpretation of anomalies on each profile by the components of the anomalous magnetic field increases the reliability of the geological interpretation of magnetic prospecting data compared to the interpretation of modular surveys. The presence of vector measurements greatly facilitates the ability to determine the parameters of anomalous objects, which makes it possible to obtain more reliable solutions to the inverse problem. The use of vector information makes it possible to localize geological sources more successfully, thereby reducing the amount of work.

Neutron-state entanglement with overlapping paths

The development of direct probes of entanglement is integral to the rapidly expanding field of complex quantum materials. Here we test the robustness of entangled neutrons as a quantum probe by measuring the Clauser-Horne-Shimony-Holt contextuality witness while varying the beam properties. Specifically, we prove that the entanglement of the spin and path subsystems of individual neutrons prepared in two different experiments using two different apparatuses persists even after varying the entanglement length, coherence length, and neutron energy difference of the paths. The two independent apparatuses acting as entangler-disentangler pairs are static-field magnetic Wollaston prisms and resonance-field radio frequency flippers. Our results show that the spatial and energy properties of the neutron beam may be significantly altered without reducing the contextuality witness value below the Tsirelson bound, meaning that maximum entanglement is preserved. We also show that two paths may be considered distinguishable even when separated by less than the neutron coherence length. This work is the key step in the realization of the new modular, robust technique of entangled neutron scattering.

Electromagnetic Approach to Cavity Spintronics

The fields of cavity quantum electrodynamics and magnetism have recently merged into cavity spintronics, investigating a quasiparticle that emerges from the strong coupling between standing electromagnetic waves confined in a microwave cavity resonator and the quanta of spin waves, magnons. This phenomenon is now expected to be employed in a variety of devices for applications ranging from quantum communication to dark matter detection. To be successful, most of these applications require a vast control of the coupling strength, resulting in intensive efforts to understanding coupling by a variety of different approaches. Here, the electromagnetic properties of both resonator and magnetic samples are investigated to provide a comprehensive understanding of the coupling between these two systems. Because the coupling is a consequence of the excitation vector fields, which directly interact with magnetization dynamics, a highly accurate electromagnetic perturbation theory is employed that predicts the resonant hybrid mode frequencies for any field configuration within the cavity resonator. The coupling is shown to be strongly dependent not only on the excitation vector fields and sample's magnetic properties but also on the sample's shape. These findings are illustrated by applying the theoretical framework to two distinct experiments: a magnetic sphere placed in a three-dimensional resonator and a rectangular, magnetic prism placed in a two-dimensional resonator. The theory provides comprehensive understanding of the overall behavior of strongly coupled systems and it can be easily modified for a variety of other systems.

An Ion-Optical Circuit of a Small-Sized Mass-Spectrometer for the Isotope Analysis of Hydrogen–Helium Mixtures

We discuss an ion-optical system (IOS) of a mass spectrometer designed for isotopic measurements of light gases, containing a magnetic prism with plane-parallel pole tips and two sector-wise, cylindrical-capacitor identical in geometry, symmetrically located relative to the prism. The relationships between the geometric parameters of the capacitors and the prism are given, which are necessary to ensure achromatic focusing of the ion beam in the plane of the detector receiving slit. We assessed numerically the effect of IOS aberrations on the mass resolution of the IOS and determined the optimal emittance of the ion beam at the source output, which enables achieving a resolution at the level of 3000–3500 with an output slit of the ion source of approximately 50 μm, high transmittance of the mass analyzer, small dimensions of the magnetic prism, and a moderate total length of the central ion trajectory (less than 1 m). The IOS is characterized by a high dispersion in masses, which is much larger than the dispersion of conventional sector magnetic mass spectrometers of the same dimensions. The IOS consists of simple geometry elements, which reduces the costs of its implementation and makes the mass spectrometer technologically advanced and convenient to set up and operate.

Can Euler deconvolution outline three‐dimensional magnetic sources?

ABSTRACTSevere limitations of the standard Euler deconvolution to outline source shapes have been pointed out. However, Euler deconvolution has been widely employed on field data to outline interfaces, as faults and thrust zones. We investigate the limitations of the 3D Euler deconvolution–derived estimates of source dip and volume with the use of reduced‐to‐the‐pole synthetic and field anomalies. The synthetic anomalies are generated by two types of source bodies: (1) uniformly magnetized prisms, presenting either smooth or rough interfaces, and (2) bodies presenting smooth delimiting interfaces but strong internal variation of magnetization intensity. The dip of the first type of body might be estimated from the Euler deconvolution solution cluster if the ratio between the depth to the top and vertical extent is relatively high (>1/4). For the second type of body, besides dip, the source volume can be approximately delimited from the solution cluster envelope, regardless of the referred ratio. We apply Euler deconvolution to two field anomalies which are caused by a curved‐shape thrust zone and by a banded iron formation. These anomalies are chosen because they share characteristics with the two types of synthetic bodies. For the thrust zone, the obtained Euler deconvolution solutions show spatial distribution allowing to estimate a source dip that is consistent with the surface geology data, even if the above‐mentioned ratio is much less than 1/4. Thus, there are other factors, such as a heterogeneous magnetization, which might be controlling the vertical spreading of the Euler deconvolution solutions in the thrust zone. On the other hand, for the iron‐ore formation, the solution cluster spreads out occupying a volume, in accordance with the results obtained with the synthetic sources having internal variation of magnetization intensity. As conclusion, although Euler deconvolution–derived solutions cannot offer accurate estimates of source shapes, they might provide a sufficient degree of reliability in the initial estimates of the source dip and volume, which may be useful in a later phase of more accurate modelling.

Standing spin waves in perpendicularly magnetized triangular dots

Standing spin waves in triangular dots (truncated pyramids) were investigated both experimentally and theoretically. Arrays of nickel triangular pyramids with the base side of 270 nm and height of 70 nm were deposited on Si (111) substrate. The spectra of ferromagnetic resonance were obtained at room temperature with an external saturating magnetic field directed perpendicular to the array plane. The theoretical approach, which allows to describe standing spin wave modes both in perpendicular magnetized regular prisms and in close to prisms truncated pyramids, was developed. Theoretically calculated resonance fields for the observed modes are in a good correlation with the experiment.

A New High‐Resolution Magnetic Scanner for Sedimentary Sections

AbstractWe developed a fully automated magnetic field scanner dedicated to uniaxial magnetic field measurements to determine remanent magnetization intensities and their variations in sedimentary U‐channels. A fluxgate magnetometer located as close as possible to the sedimentary section is used to perform uniaxial measurements of magnetic fields generated by the isothermal remanent magnetization of the sediment. This artificial magnetization, which is known to be a powerful proxy in environmental magnetism, is produced perpendicular to the U‐channel long axis, and parallel to the fluxgate axis, using a Halbach cylinder prior to the measurement. The present magnetic scanner offers a maximal spatial resolution of 5.8 mm for point sources. A spatial resolution of 14 mm is obtained for U‐channel samples. The magnetic scanner presents a reliable magnetic field range over about 3 orders of magnitude allowing measurement of magnetizations that saturate the Superconducting Rock Magnetometer in its classical configuration. The estimation of remanent magnetization intensities along the U‐channel is based on a modeling approach that uses successive uniformly magnetized prisms. In lacustrine laminated sections, comparison between modeling results based on prisms of a constant thickness, on prisms determined from sedimentary facies, and on prisms determined from X‐ray fluorescence data helps to understand the detrital versus diagenetic history of the sedimentary succession.

High-resolution phonon energy shift measurements with the inelastic neutron spin echo technique

The energy resolution of the conventional way of measuring a small change in a phonon dispersion curve using neutron scattering is restricted by the relatively coarse intrinsic resolution ellipsoid of the neutron triple-axis spectrometer (TAS). By implementing inelastic neutron spin echo on the host TAS using the Larmor precession of the neutron spin, the energy resolution of such measurements can be further improved without reducing the resolution ellipsoid. Measurements of the temperature-dependent phonon energy change are demonstrated using superconducting magnetic Wollaston prisms at the HB-1 instrument of the High-Flux Isotope Reactor at Oak Ridge National Laboratory, and the achievable resolution is <10 µeV.

Magnetic domain wall contrast under zero domain contrast conditions in spin polarized low energy electron microscopy

Important applications of spin polarized low energy electron microscopy (SPLEEM) employ this technique's vector imaging capability to resolve domain wall (DW) spin textures. Studying several thin film systems including Co/W(110), Co/Cu(001) and (Co/Ni)n/W(110), we show that an additional contrast can appear at magnetic DWs. By imaging the magnetization as a function of electron landing energy, electron energies are selected at which the magnetic domain contrast vanishes. Surprisingly, under such conditions of zero contrast between magnetic domains, we observe the appearance of magnetic contrast outlining the DWs. This DW contrast does not depend on the DW spin texture. Instead, our measurements show that this DW contrast results from a combination of the energy-dependence of the spin reflectivity asymmetry of the magnetic film, the finite energy width of the spin polarized electron source, and the dispersion of the magnetic prism array that separates the illumination and imaging columns of the instrument. Awareness of this DW contrast mechanism is useful to aid correct interpretation of SPLEEM images.

A Prism Mass-Spectrometer for Isotope Analysis of Hydrogen–Helium Mixtures

An original scheme of a special magnetic mass-spectrometer for isotope measurements in a mass range of hydrogen–helium mixtures and their main impurities is proposed. The ion optics system contains a two-dimensional magnetic prism supplemented with two identical cylindrical electrostatic capacitors matched so that the system operates in the regime of complete triple focusing of the ion beam in two orthogonal directions and with respect to ion energies. The system ensures high dispersion and allows the mass resolution (no less than 3500) required for analysis at high brightness and a central ion trajectory length on the order of 1 m.

New capabilities in high-resolution neutron Larmor diffraction at ORNL

Using superconducting magnetic Wollaston prisms, high-resolution neutron Larmor diffraction has been implemented at the High-Flux Isotope Reactor of Oak Ridge National Laboratory (ORNL), Tennesse, USA. This technique allows the inverse relationship between the achievable diffraction resolution and the usable neutron flux to be overcome. Instead of employing physically tilted radio-frequency spin flippers, the method uses magnetic Wollaston prisms which are electromagnetically tuned by changing the field configurations in the device. As implemented, this method can be used to measure lattice-spacing changes induced, for example, by thermal expansion or strain with a resolution of Δd/d ≃ 10−6, and the splitting of sharp Bragg peaks with a resolution of Δd/d = 3 × 10−4. The resolution for discerning a change in the profile of a Bragg peak is Δd/d < 10−5. This is a remarkable degree of precision for a neutron diffractometer as compact as the one used in this implementation. Higher precision could be obtained by implementing this technique in an instrument with a larger footprint. The availability of this technique will provide an alternative when standard neutron diffraction methods fail and will greatly benefit the scientific communities that require high-resolution diffraction measurements.

Призменный масс-спектрометр для изотопного анализа водородно-гелиевых смесей

AbstractAn original scheme of a special magnetic mass-spectrometer for isotope measurements in a mass range of hydrogen–helium mixtures and their main impurities is proposed. The ion optics system contains a two-dimensional magnetic prism supplemented with two identical cylindrical electrostatic capacitors matched so that the system operates in the regime of complete triple focusing of the ion beam in two orthogonal directions and with respect to ion energies. The system ensures high dispersion and allows the mass resolution (no less than 3500) required for analysis at high brightness and a central ion trajectory length on the order of 1 m.