Magnetic Lens Research Articles

Geobody estimation by Bhattacharyya method utilizing nonlinear inverse modeling of magnetic data in Baba-Ali iron deposit, NW Iran

One of the essential geophysical concerns is the estimation of the physical and geometrical parameters of the reserve (geobody), which is done by exploiting the nonlinear inverse modeling of magnetic data. The present study includes preparing and modeling magnetic data to suggest the Baba Ali Iron ore deposit's drilling locations in NW Iran. The area is covered with 1000 points of geomagnetic reading with an almost 5 × 10 m2 regularly spaces grid trending WE. The areal and depth extent of the iron ore geobody was unknown. The Bhattacharyya method by MATLAB software coding was employed to underestimate the misfit function and re-construct potential field data, providing the most suitable fitting with measured magnetic data. In this order, the residual calculated anomaly exhibited an excellent two-dimensional conformation with forward modeling. Furthermore, 3D modeling correctly reconstructs the anomalies' productive resources' properties. After preparing full magnetic maps, the magnetic lenses distinguished in four anomalies of surface depths, 20, 50, and deeper than 50 m for this zone. This magnetite lens for the first zone was estimated based on analytical signal filters applied on the entire magnetic map so that the lens's depth is trivial and almost zero. Due to specific gravity calculated as 4.77 t/m3, initial storage capacity is suggested to be about 95,400 tons of magnetite, pyrite, and hematite minerals at most in an area about 6 Km2. Finally, to complete the preliminary explorations of the specified area, exploratory drilling is suggested for three points by inverse modeling. Regarding this study as the first try in magnetic reconnaissance step of Iron mineral exploration in the study area, there is no geological constraints available based on drilling evidences. However, the model is well satisfies the surface anomalies considering residual magnetic property.

Design of Electrostatic Aberration Correctors for Scanning Transmission Electron Microscopy.

In a scanning transmission electron microscope (STEM), producing a high-resolution image generally requires an electron beam focused to the smallest point possible. However, the magnetic lenses used to focus the beam are unavoidably imperfect, introducing aberrations that limit resolution. Modern STEMs overcome this by using hardware aberration correctors comprised of many multipole elements, but these devices are complex, expensive, and can be difficult to tune. We demonstrate a design for an electrostatic phase plate that can act as an aberration corrector. The corrector is comprised of annular segments, each of which is an independent two-terminal device that can apply a constant or ramped phase shift to a portion of the electron beam. We show the improvement in image resolution using an electrostatic corrector. Engineering criteria impose that much of the beam within the probe-forming aperture be blocked by support bars, leading to large probe tails for the corrected probe that sample the specimen beyond the central lobe. We also show how this device can be used to create other STEM beam profiles such as vortex beams and probes with a high degree of phase diversity, which improve information transfer in ptychographic reconstructions.

Reinforcement of the Magnetic Lens Effect in the Dipole Magnet for a Neutral Beam Injector

Reinforcement of the Magnetic Lens Effect in the Dipole Magnet for a Neutral Beam Injector

Effect of pole piece structure on magnetic lens electrospinning system: Experimental and simulation study

Magnetic lenses can effectively reduce the fiber diameter and whipping-circle width to control the random behavior of electrospinning. Although the axisymmetric magnetic lens for electrostatic spinning have several potential applications, the effect of its pole-piece structure on the electrostatic spinning process has not been adequately discussed. In this study, we explored the influence of changing the pole piece structure of the magnetic lens on the electrospinning process using experimental and numerical simulation methods. The results showed that for a 12 wt% polyacrylonitrile (PAN) solution, when the applied voltage was 15 kV, the feed rate was 1 mL/h, and current of the magnetic lens was 1 A, the gap width of the magnetic lens had a notable effect on the fiber deposition efficiency of the electrostatic spinning range of the magnetic lens. Appropriately reducing the gap width in the range of 1–10 mm can effectively reduce the deposition range of the fibers and improve fiber film thickness. Furthermore, when the angle of α is 45°, it exerts the most significant effect on the electrostatic spinning spray range and deposition efficiency, and the fiber film thickness and average fiber diameter attain their highest values. When the angle of α increases or decreases from 45°, the fiber film thickness and fiber diameter both show a decreasing trend. A change in the magnetic lens structure can effectively change the ejection range and fiber diameter during electrostatic spinning, which shows great potential in the field of nanofiber production.

New developments for theranostic radioisotope production with solid targets at the Bern medical cyclotron

The concept of theranostics in nuclear medicine is based on the use of a pair of radioisotopes to label radiopharmaceuticals for both diagnosis and therapy and is essential for nuclear medicine developments. The production of novel medical radioisotopes using solid target stations is challenging and new instruments and methods are needed. A research program is ongoing at the 18 MeV Bern medical cyclotron, equipped with a Solid Target Station and a 6.5 m Beam Transfer Line ending in a separate bunker. To irradiate isotope-enriched materials in form of compressed powder pellets, a novel target coin was conceived and realized together with methods to assess the beam energy and the production cross sections. To optimize the irradiation procedure, a novel ultra-compact active irradiation system based on a specific magnetic lens and a two-dimensional beam detector was conceived, constructed and tested. The system allows to control on-line the size and position of the beam and to correct its characteristics by steering and focusing it in order to keep it on target. The first results on the production of several radionuclides (43Sc, 44Sc, 47Sc, 61Cu, 64Cu, 67Cu, 68Ga, 165Er, 165Tm, 167Tm and 155Tb) are presented.

High demagnification probe-forming systems with spherical aberration correction for a nuclear microprobe

Probe-forming systems with high demagnification (up to 900) based on a separated orthomorphic quadruplet of magnetic quadrupole lenses are considered. Spherical aberrations are corrected using an octupole lens system. Three, two, and one lens correctors are used. The calculation of the octupoles parameters was carried out using the Matrizant method. The focusing properties of the systems are determined by optimizing the process of probe formation based on the value of the maximum reduced collimated acceptance in the range of beam spot sizes on the target from 10 to 100 nm. The possibility of implementing the considered systems in experimental setups for various applications is demonstrated by the results of the numerical analysis performed.

Effect of receiver plate temperature and magnetic lens on the performance of electrospun PAN

The homebuilt traditional electrostatic spinning apparatus was equipped with a silicone rubber heating plate and a magnetic lens to produce polyacrylonitrile (PAN) nanofiber films. The PAN nanofibers used in this experiment were examined using a scanning electron microscope (FE-SEM) as well as other characterization tools to determine their morphology, diameter, crystallinity, thickness, and mechanical characteristics. The experimental results showed that the combined effect of two parameters, the temperature of the receiver plate and the magnetic field generated by the magnetic lens let to the production of fibers with a smaller diameter (308 nm). The magnetic field generated by the magnetic lens increased the thickness of the nanofiber membrane, whereas the temperature decreased the diameter of the nanofibers. The combined effect of the temperature and magnetic fields increased the thickness of the nanofiber membrane. The combined effect of the aforementioned parameters led to a nanofiber crystallinity of 70.72%, which was higher than the average crystallinity generated by the individual impact of the said parameters. The mechanical characteristics also improved significantly with an increase in receiver plate temperature. In conclusion, the combined effect of the temperature of the receiver plate and the magnetic field generated by the magnetic lens improved the performance of the PAN nanofibers and was more significant than their independent impact. A foundation for the preparation of high-performance filtration membranes was laid and the results paved the way for industrializing the process.

Proton Injector for Compact Neutron Source DARIA Systems Optimization

This paper is devoted to magnetic trap and extraction system upgrade of ECR ion source GISMO to utilize it as a proton injector for linear accelerator of compact neutron source DARIA. An open permanent magnet (Nd–Fe–B) trap was designed. It was adjusted to place the extraction system inside a part of magnet with larger inner diameter. Then, the three-electrode extractor optimization was made. It was shown that the use of additional magnetic lens allows to produce the proton beam with a low divergence angle. The use of the magnetic trap and the extraction system as a part of the proton injector for DARIA project possibility was shown using computer modeling. The following steps of the proton injector creation are discussed.

HIGH RESOLUTION PROBE-FORMING SYSTEM WITH SPHERICAL ABERRATION CORRECTION FOR NUCLEAR MICROPROBE

A probe-forming system based on a separate orthomorphic quadruplet of magnetic quadrupole lenses with a short working distance is considered, allowing the system demagnification to be significantly increased. Three magnetic octupole lenses are used to correct spherical aberrations. The parameters of the octupole corrector are calculated using the matricant method. The focusing properties of the system are determined by means of a probe formation optimization process based on the value of the maximum reduced collimated acceptance. The calculations performed showed the feasibility of such a probe forming system for microanalysis and proton beam writing technique.

Experimental verification of magnetic near-field channeling using a helical-shaped wire medium lens

We experimentally verify that a magnetic uniaxial wire medium lens consisting of a racemic array of helical-shaped metallic wires may enable channeling the normal component of the magnetic field of near-field sources with resolution well below the diffraction limit over a broad bandwidth. It is experimentally demonstrated that the helical-shaped wire medium lens can be regarded as the magnetic counterpart of the usual wire medium lenses formed by straight metallic wires. The experimental results are validated with full-wave numerical simulations. We envision that the proposed metamaterial lens may have potential applications in magnetic resonance imaging, near-field wireless power transfer, and sensing.

The Buncher and the Magnetic Lens for the LINAC Based Low Energy Positron Beams at AIST

A buncher and a magnetic lens were introduced to improve the beam flux density of a pulsed positron beam extracted from the low energy positron accumulator at National Institute of Advanced Industrial Science and Technology (AIST). The buncher made the pulse width ~ 1/4 and the magnetic lens reduced the beam cross section ~ 1/9, which resulted in about 36 times increase in the beam flux density. Possible applications for electron-positron plasma experiments are also discussed.

TEMGYM Advanced: Software for electron lens aberrations and parallelised electron ray tracing

Characterisation of the electron beams trajectory in an electron microscope is possible in a few select commercial software packages, but these tools and their source code are not available in a free and accessible manner. This paper introduces the free and open-source software TEMGYM Advanced, which implements ray tracing methods that calculate the path of electrons through a magnetic or electrostatic lens and allow evaluation of the first-order properties and third-order geometric aberrations. Validation of the aberration coefficient calculations is performed by implementing two independent methods – the aberration integral and differential algebra (DA) methods and by comparing the results of each. This paper also demonstrates parallelised electron ray tracing through a series of magnetic components, which enables near real-time generation of a physically accurate beam-spot including aberrations and brings closer the realisation of a digital twin of an electron microscope. TEMGYM Advanced represents a valuable resource for the electron microscopy community, providing an accessible and open source means of characterising electron lenses. This software utilises the Python programming language to complement the growing ecosystem of free and open-source software within the electron microscopy community, and to facilitate the application of machine learning to an electron microscope digital twin for instrument automation. The software is available under GNU Public License number Three (GPL 3).

The effect of the shape of the outer electrode arm on the bipolar lens and the study of its properties

In this paper, several innovative designs of magnetic lenses were designed, a bipolar lens with different geometries, where the outer pole arm denoted by the symbol (L) was changed. With a current density (6 A / m²) and after its design, the geometric parameters were studied in terms of magnetic properties, then the optical properties were studied in terms of aberrations, i.e. the coefficient of spherical aberration and the coefficient of chromatic aberration. Which led to minor changes in some of them, while others did not make any changes

The Influence of Bores Diameter on the SEM's Objective Lens Properties

In a previous study, a new design of a magnetic objective lens had been chosen among five new designs as the preferred one. Both of the iron shroud and polepiece bore diameters of the preselected lens have been changed and studied in this work to improve its magnetic and optical properties. An extensive investigation has been done to analyze the magnetic field distribution, magnetic flux density, and optical properties for each model using the finite element method (FEM) with the computer-aided programs. All the analyses have been carried out at the same coil excitation (NI = 10 kA.t). The new improved design yield here will be prepared to fabrication to be used as an objective lens for the SEM.

The Influence of Narrowing Grivet-Lenz Model on the Projector Properties of Magnetic Lenses

present work consist of a computational investigation aims at reveal the influence of narrowing or extending Grivet-Lenz model on its own projector properties. For this reason the well known formula of Grivet-Lenz model is raised to a power named in this work by “shape factor”. Projector properties and their related variables were determined for several values of the shape factor. Results have shown that as the shape factor value increases the magnetic field become more narrowing and its projector properties efficiency get worse. Accordingly to enhance the projector properties of Grivet model it should be extended over a wide axial interval.

透射电子显微镜空间分辨率综述

Transmission electron microscope (TEM) is one of the most important research tools in a wide range of research fields such as chemistry, materials science, physics, and biological science. There are many factors affect the spatial resolution of TEM, including not only the construction of electron microscope and imaging mechanism, but also the nature of the sample and other reasons. In order to systematically and comprehensively understand the meaning, principle and application of TEM spatial resolution, this paper firstly briefly describes the history of TEM spatial resolution advancement, and then theoretically clarifies the concept, physical meaning, influencing factors and application scope of TEM spatial resolution, then outlines the influence of TEM electron gun, magnetic lens, image detector and internal and external environment on the resolution, the development of monochromator, aberration corrector and new image detector from the perspective of electron microscope device. Finally, from the perspective of practical applications, the mechanism of resolution degradation due to thickness, electron beam sensitivity, carbon accumulation and atomic vibrations and the corresponding solutions are highlighted.

The parameters of radio frequency quadrupole linear accelerator for DARIA project

The new proton linear accelerator (linac) with output energy 13 MeV and 100 mA current is under development at NRC “Kurchatov Institute” - ITEP for DARIA project. The linac consists of Radio-Frequency Quadrupole (RFQ) and Drift Tube Linac (DTL) with operating frequency 162.5 MHz. The RFQ is based on 4-vanes structure with shifted coupling windows. DTL has a modular structure and consists of separated individually phased cavities with focusing magnetic quadrupoles located between the cavities. The DTL is based on interdigital H-mode (IHDTL) 5-gaps cavities. The 6D beam matching between RFQ and DTL is provided by magnetic quadrupole lenses and RF-bunchers. The paper presents results of the radio-frequency (RF) design, thermal analyses and RF tuning of RFQ linac accelerating structure.

The Effect of the Iron Arm's Relative Position to the Pole piece Tip Position on the Objective Snorkel Lens Type

The bipolar region is one of the most important factors in determining the effectiveness of a magnetic lens. Regarding the focus and optical qualities of the display devices, the optimal position of the polepiece and the most significant aspect of the magnetic electron lenses were the iron shrouds, where the magnetic field increases smoothly and uniformly with the highest possible value and has just one peak. The goal of this study is to determine the position of the shroud tip relative to the axial axis (Z), where the tip of the polepiece is located at (Z = 0 mm). In practice, it has been seen that the optical properties of electron lenses have improved when the position of the polepiece iron shroud tip is separated by a distance of 180 mm. By extending the distance between the iron shroud and the polepiece face in the opposite direction of the coil, by removing or reducing magnetic flux leakage, it is possible to increase its performance. The axial magnetic field will then rise within the lens in a direction that prevents it from being lost. In this work, the FEMM and MELOP programs were used to investigate the lens' performance, axial magnetic field, and focal optical characteristics.

The Effect of Operation Modes on the Electron Beam Diameter in Condenser Magnetic Lenses System

The effect of operation modes of condensing magnetic lenses has been investigated to determining the total demagnification and the diameter of the electron beam coming out of it. The cross-over point inside the electron gun is considered as the object (do) with a diameters ranges of (10 – 100 µm) to find out the optical efficiency of the double lens condensing system and its ability to forming a high précising image of the 1st real image formed inside electron gun of thermal emission that acts as an actual source of electron beam. The following modes; (weak- weak), (weak- strong), (strong- strong), and (strong- weak); denoted as (#1, #2, #3, #4 respectively); have been studied. The best value for the total demagnification and the diameter of the electron beam has been obtained in the mode of (strong- strong; #3); where the parameters were: (dMt = 1014.199), (d2 = 49.3 nm), while the worst value has been achieved in the mode (weak- weak; #1) (dMt = 31.56267), (d2 = 1584.15 nm). It is found that by increasing the demagnification of the first condenser lens, the demagnification of the final real image produced by the double lens system has been positively affected. It is found that the relationships that obtained between the demagnification and the current density can be used as a calibration curve to obtain the required total demagnification for the electronic beam diameter for any mode according to the purpose of the desired application.

Magnetic Semiconductors as Materials for Spintronics

From the various aspects of spintronics the review highlights the area devoted to the creation of new functional materials based on magnetic semiconductors and demonstrates both the main physical phenomena involved and the technical possibilities of creating various devices: maser, p-n diode with colossal magnetoresistance, spin valve, magnetic lens, optical modulators, spin wave amplifier, etc. Particular attention is paid to promising research directions such as ultrafast spin transport and THz spectroscopy of magnetic semiconductors. Special care has been taken to include a brief theoretical background and experimental results for the new spintronics approach employing magnetostrictive semiconductors—strain-magnetooptics. Finally, it presents top-down approaches for magnetic semiconductors. The mechano-physical methods of obtaining and features of the physical properties of high-density nanoceramics based on complex magnetic oxides are considered. The potential possibility of using these nanoceramics as an absorber of solar energy, as well as in modulators of electromagnetic radiation, is shown.