Magnetic Lens Research Articles

Radially Periodic Metasurface Lenses for Magnetic Field Collimation in Resonant Wireless Power Transfer Applications

In this paper, a new procedure and topology of magnetic metasurface lens are proposed for improving the performance of Resonant Wireless Power Transfer systems. Firstly, three subwave-length unit cells are optimized in order to get negative magnetic permeability in the same frequency, each one with a different refractive index, and they are experimentally characterized. Then, the Transformation Optics technique is applied in order to find the unit cell arrangements which lead to the magnetic field focusing in a given direction. For this purpose, two coordinate transformations are proposed, and the effective electric permittivity and permeability that generate these profiles are calculated. It is shown from simulations and measurements that the refractive index gradient produced by the radial disposition of the unit cells can lead to a magnetic field manipulation similar to the optical converging and diverging lenses. Both metamaterials lenses are built, and the calculation of the magnetic flux density as a function of the measured induced voltage in a probe coil verifies their effects on the magnetic field. Finally, their performance in a resonant wireless power transfer system is tested, and improvements in terms of efficiency and range are presented. The proposed design method and the lenses that were developed demonstrate that metasurface lenses can improve efficiency without reducing the range, once these lenses are positioned close to the transmitter coil. Besides that, this method can reduce the losses due to misalignment between coils once the field can be collimated in a specific direction.

Recent Development-1 of CADTEL Software: The Resolution and Focusing Parameters Affecting at the Properties of Electron Magnetic Lenses

Computer Aided Designing Tools of Electron Lenses (CADTEL) is a software packages cares about design, compute and plot simultaneously of the objective and projector properties of electron magnetic lenses. The developments in CADTEL software leads to contain a large fields and methods, adding to previous publish in 2013. The current improvement is inserting of some important parameters which are the resolution and focusing parameters. These parameters are angular semi-angle (α), focusing power (β), resolution limit (δ), image rotation (θ), spherical aberration (Cs), defocus (ΔZ), wave aberration (Χwab), depth of field (Dfld), and depth of focus (Dfoc) at certain magnification conditions. Thus, user can easily compute and plot, according to relations and forms, the effect of these parameters at the lens properties of four magnification conditions; zero, infinite and finite (low and high) magnification modes. This work introduces a new development for CADTEL software which is an interactive visual interface in electromagnetic lenses.Whereas, it reflects a substantial reduction of time and resources desired for training new users and researchers in electron optics field. The results and curves representations appear with visual interfaces which are coded in visual basic programing language. In addition, the computations and figures which were plotted appeared that complete identification between these results which are obtained from CADTEL and that from other software’s and direct computations methods.

Boosting the performance of magneto-mechano-electric energy generator using magnetic lens

Herein, we introduce a concept of the magnetic lens, which were composed of high permeability ceramic ferrites, to enhance the output performance of Magneto-Mechano-Electric (MME) energy generator. The magnetic lens was found to enhance the output voltage of MME generator by concentrating the weak magnetic flux originating from the magnetic field sources onto magnetic constituents in MME structure. The feasibility of the use of the magnetic lens as a magnetic flux concentrator was first evaluated by using Finite Elemental Analysis. The simulation results are then experimentally verified by harvesting the weak fields originating from the Helmholtz coil. Depending on the configuration of magnetic lens, the output of MME was different. The MME generator with a magnetic lens composed of four ferrites exhibited enhancement of 288% and 125% over that of MME generator without a lens and with a lens composed of one ferrite, respectively.

A generalized framework for the image formation model and disentanglement of CTF parameters in cryo-electron microscopy

In cryo-electron microscopy (cryo-EM), the microscope has a point spread function, whose Fourier transform, known as the Contrast Transfer Function (CTF), is determined by various parameters with a physical meaning (including height of the sample, magnetic lens aberrations, operating voltage, amplitude contrast, etc.). Some of the parameters are under experimental control, but they can also contain some experimental uncertainty and fluctuate over the course of data collection. While it is routine to use point estimates for the CTF parameters in a simplified forward model of image formation, we characterize here the uncertainty of the CTF by (1) framing the forward model of image formation as a probabilistic graphical model, (2) deriving conditional probabilities that leverage analytical linking functions, and (3) compare these results with existing approaches that model noise in frequency space, such as the “B-factor envelope” and the “white/coloured noise model”.

Recent Development-2 of CADTEL Software: The Optimum Conditions of Scherzer Imaging in the Electron Magnetic Lenses

CADTEL software was developed to provide the simplest and most versatile computing resource that a wide range of skilled researchers and designers can use. In this paper, a development on this program, relying on sixteen mathematical models, produced a new version of CADTEL software package which focuses on the optimum conditions of Scherzer imaging for round electron magnetic lenses.. These models depend on synthesis procedure which is mainly designed to work with the inverse design problem, and represent the axial magnetic flux density of desirable electron magnetic lens which can be proposed or selected , using the four (zero, low, high, infinite) magnification states. The program provides the freedom of selecting multiple models and changing its variables (which appear on the home page), in addition to providing facilities for numerous proposed magnetic lens. The objective properties calculated in the program were used to compute and plot the optimum conditions for Scherzer imaging
 The CADTEL software was written in Visual Basic – 6, in an easy-to-use mode, even for a beginner computer user. The results of the analysis clearly show that there is an excellent equivalent calculation which could be obtained for the same lens from CADTEL software when evaluated with other counterpart software.

Control of the Longitudinal Compression and Transverse Focus of Ultrafast Electron Beam for Detecting the Transient Evolution of Materials.

Ultrafast detection is an effective method to reveal the transient evolution mechanism of materials. Compared with ultra-fast X-ray diffraction (XRD), the ultra-fast electron beam is increasingly adopted because the larger scattering cross-section is less harmful to the sample. The keV single-shot ultra-fast electron imaging system has been widely used with its compact structure and easy integration. To achieve both the single pulse imaging and the ultra-high temporal resolution, magnetic lenses are typically used for transverse focus to increase signal strength, while radio frequency (RF) cavities are generally utilized for longitudinal compression to improve temporal resolution. However, the detection signal is relatively weak due to the Coulomb force between electrons. Moreover, the effect of RF compression on the transverse focus is usually ignored. We established a particle tracking model to simulate the electron pulse propagation based on the 1-D fluid equation and the 2-D mean-field equation. Under considering the relativity effect and Coulomb force, the impact of RF compression on the transverse focus was studied by solving the fifth-order Rung–Kutta equation. The results show that the RF cavity is not only a key component of longitudinal compression but also affects the transverse focusing. While the effect of transverse focus on longitudinal duration is negligible. By adjusting the position and compression strength of the RF cavity, the beam spot radius can be reduced from 100 m to 30 m under the simulation conditions in this paper. When the number of single pulse electrons remains constant, the electrons density incident on the sample could be increased from to , which is 11 times the original. The larger the electron density incident on the sample, the greater the signal intensity, which is more conducive to detecting the transient evolution of the material.

Ion beam source upgrade of the neutron source at IAP RAS

The results of the ion source of the neutron generator upgrade, which makes it possible to operate in a CW mode, are presented. A magnetic trap consisting of permanent magnets (NdFeB) was developed. A 3-electrode extraction system equipped with a magnetic lens was used to extract the deuterium ion beam. Calculations are made for the formation of a deuterium ion beam with a current over 500 mA and an energy of 100 keV with practically no losses in the extraction system. Keywords: extraction system, magnetic trap, neutron generator, ion beam.

Design of a Lens System Reduces Chromatic Aberration for Proton Radiography

Multi-GeV proton radiography is an important tool for diagnosing density distribution of thick objects. The magnetic lens system called Zumbro lens is widely employed because it compensates for the image distortion induced by small angle multiple Coulomb scattering (MCS) that occurs when the charged protons passing through the object. However, radiography is still suffering from chromatic aberration induced blurring, if the momentum of transmitted proton is different from the reference value of Zumbro lens. In this paper, two methods are employed to reduce chromatic aberration. The first is based on magnetic lens optimization. In addition, a new lens system is first proposed locating the downstream of Zumbro. It is named “auxiliary” lens, which can correct the chromatic aberration for certain protons with momentum far away from the reference of Zumbro lens. Monte Carlo simulation shows that this proposed lens can decrease chromatic aberration and improve the radiography image evidently.

Design of Miniaturized High Gain Bow-Tie Antenna

A high gain low-frequency bow-tie antenna with artificial magnetic conductor (AMC) and metamaterial lens for ground penetrating radar (GPR) is proposed. First, a bow-tie antenna working in 348–772 MHz frequency band is designed. The substrate is a square with side length of 420 mm. A periodic AMC reflector is designed. The in-phase reflection region of the unit is 481 MHz–1.44 GHz. The results show that the gain of antenna loaded with reflector is increased by 5 dB. A metamaterial lens based on the zero-index metamaterial element is also proposed to improve the gain. The zero refractive index frequency point is 810 MHz, the unit size of the metamaterial is 60 mm, and the lens size is consistent with the antenna substrate size. The gain of the antenna loaded with AMC reflector and the metamaterial lens is increased by 6.5 dB and the front-to-back ratio is 23 dB. The directivity of the antenna is further optimized. The measured results are in good agreement with the simulations.

Development of Beam Optics Code LEADS-v5

To calculate nonlinear transport of space charge dominated beam in 6D phase spaces, a computer code package LEADS-v5 (Linear and Electrostatic Accelerator Dynamics Simulations) has been developed. The codes calculate particle motions in the beam transport systems consisting of electrostatic and magnetic focusing lenses, ion analyzers, multipoles and RF accelerating structures. The nonlinear forces of external electric/magnetic fields are analyzed by the Lie algebraic method, and the space charge forces are obtained by the particle in cell (PIC) scheme. In the codes, Uniform and Gaussian particle distributions can be chosen to generate randomly the particle initial coordinates. The optimization procedures are provided to make the beam optics designs reasonable and fast. Graphically displays of calculated results are provided.

Effect of magnetic lens on the electrospinning whipping instability, fiber diameter and its distribution

Electrospinning is an efficient and straightforward method for producing thin fibers from various materials. Although such thin fibers have diverse potential applications, the remaining problems with electrospinning are the whipping instability (also known as bending instability) of electrically charged liquid jets of polymer nanofibers and uneven fiber diameter distribution. In this study, we report a novel magnetic lens electrospinning system and discuss the principle of reducing the fiber diameter and width of the whipping circle in this electrospinning process. The effects of three types of electrospinning devices, needle-to-plate, needle-exciting coil-to-plate, and needle-magnetic lens-to-plate types, were studied through numerical simulation to analyze the electrospinning fiber collection state. For the 12 wt% polyacrylonitrile solution, when the applied voltage was 14–20 kV, the feed rate was 0.4–0.7 ml/h, and the current applied to the excitation coil or magnetic lens was 1 A, the experimental results demonstrated that, compared with needle-to-plate-type and needle-exciting coil-to-plate-type electrospinning, needle-magnetic lens-to-plate-type electrospinning produced smaller whipping circles with thinner and more uniform fibers.

Моделювання електродних систем газорозрядних гармат з фокусуванням електронного пучка в магнітному полі короткої лінзи

In the article, based on the analysis of the basic provisions of the theory of high - voltage glow discharge (HVGD), a method of modeling electrode systems of gas discharge guns with focusing of the electron beam in the field of a short magnetic lens is proposed. To calculate the electric field in the electrode system the finite-difference Poisson equation has been used, which, to simplify its using in the software, is written in the form of an arithmetic-logical expression. Analysis of the guiding of the electron beam in the free drift region was performed with using a system of equations of discrete mathematics based on the Rutherford scattering model. A numerical algorithm for calculating the focus position of the electron beam and its focal diameter is also proposed. To estimate the position of the plasma boundary, a simulation method based on the conversion of the anode plasma volume from a one-dimensional system to the actual spatial geometry of the electrodes was used. In this case, the calculation of the height of the anode plasma in a real electrode system is reduced to the analytical solution of the cubic equation. The calculation of the magnetic field of a short lens was performed using the Yavor model. To implement the proposed methods of modeling HVGD guns, it is proposed to use arithmetic and logical expressions and methods of matrix programming. The obtained results of calculations on the distribution of the electric field in the electrode system, the boundary trajectories of the electron beam in the field of magnetic lense, as well as the distribution of the current density in the focal plane of the hollow electron beam with the ring focus are presented.

Methods and algorithm for calculating the focal parameters of a hollow conical electron beam in high-voltage glow discharge electron guns with a focusing magnetic lens

The algorithm is considered for calculating the focal distance of a hollow conical electron beam generated by high-voltage glow discharge electron guns with magnetic focusing of the beam in the drift region, as well as a method for calculating the diameter of the focal ring and its thickness for such a beam. The proposed algorithm is based on the theory of electron drift in the field of a focusing magnetic lens and is designed using the methods of discrete mathematics and the minimax analysis. The obtained simulation results made it possible to establish the influence of the magnetic lens current on the focal diameter of a hollow conical electron beam and on its focal ring thickness. It is shown that the change in the focal parameters of a hollow conical electron beam can be effectively provided through the regulation of the magnetic lens current.

Upgrade of the external beamline at the microanalytical center of the Jožef Stefan Institute

The existing external beamline at the Microanalytical Centre of the Jožef Stefan Institute (JSI) in Ljubljana has been upgraded in order to extend the capabilities towards in-air PIXE imaging across relatively large sample surface area (∼1 cm2) with lateral resolution of sub 100 µm. For that purpose, a doublet of magnetic quadrupole lenses was installed on the beamline together with the newly designed exit nozzle with a 200 nm Si3N4 exit window resulting finally in ∼ 50 × 50 μm2 lateral resolution. Additionally, an in-vacuum beam chopper was installed before the exit nozzle to measure the proton dose deposited on the sample. The beam characterization results are presented together with the first application from the field of biology, namely quantitative concentration maps of a longitudinal section of a whole thick wheat grain.

Nonlinear Metamaterial Lenses for Inductive Power Transmission Systems Using Duffing-Resonator Based Unit Cells

Metamaterials (MTMs) based on a periodic array of resonant coils have been shown to behave as μ-negative (MNG), enabling the focusing of magnetic flux. The phenomenon has been deployed by designers to boost the efficiency of many inductively coupled systems, such as magnetic resonance imaging, underwater and underground communications, and charging base stations (CBS) for consumer electronics and implanted devices. However, due to their dependency on high-Q unit cells, linear MNG-like MTMs have limited bandwidth, restricting their use in many applications, notably in near-field simultaneous wireless information and power transmission (NF-SWIPT) systems. To improve the tight constraints of the amplitude-bandwidth trade-off of artificial magnetic lenses, this paper presents a theoretical analysis of nonlinear MTMs based on a lattice of Duffing resonators (DRs). Additionally, it introduces a criterium for the quantification and evaluation of the amplitude-bandwidth enhancement. The analytical results are based on a circuit model and further verified by numerical simulations using commercial software. The preliminary findings in this paper open up possibilities for nonlinear MTM lenses and can be applied to enhance the linear amplitude-bandwidth limit.

Demonstration of high energy electron radiography with sub-micron spatial resolution

As a new scheme, High Energy Electron Radiography (HEER) was considered as an effective diagnostic tool in the mesoscale sciences due to its high spatial temporal resolution and large area density diagnostic range. Some improvements were implemented to achieve high spatial resolution using a 50 MeV electron beam in Lanzhou, China. These included improving the uniformity of the beam transverse distribution, optimizing the energy spread and increasing the magnet lens magnification. Then the HEER image was collected by a CCD camera with image processing program and in-situ spatial resolution optimization adjustment program. To the best of our knowledge, the achieved spatial resolution of 0.8 μm constitutes a world record. The details of this experiment are described in this publication.

Design of self-triggering parallel Marx generator with thyristor

We use a thyristor with a charging direct current (DC) power of 600 V as the circuit switching element and a Marx generator structure combined in series and parallel to design a high current pulse generator for long magnetic lens. According to the current driving characteristic of thyristors, the gate electrode is grounded through the current stabilizing inductance and current limiting resistance to form a self-triggering structure. The circuit output and the self-triggering waveform of thyristors at all levels are simulated. Under the load resistance of 500 mΩ and load inductance of 1.14 mH, a pulse current with amplitude of -1.1 kA and pulse width of 2.68 ms is obtained. The current pulse is used to excite a long magnetic lens, and a magnetic field with a duration of 1.2 ms and an intensity higher than 0.6 T is obtained. The influence of parameters such as charging voltage, energy storage capacitor, and the number of parallel stages of the circuit on the amplitude and width of the pulse current is studied. When the charging voltage increases, the pulse current becomes larger and the width remains unchanged. When the value of the energy storage capacitor and the number of parallel stages increase, the amplitude of the pulse current becomes larger and the pulse width becomes wider.

Collective-Mode Enhanced Matter-Wave Optics.

In contrast to light, matter-wave optics of quantum gases deals with interactions even in free space and for ensembles comprising millions of atoms. We exploit these interactions in a quantum degenerate gas as an adjustable lens for coherent atom optics. By combining an interaction-driven quadrupole-mode excitation of a Bose-Einstein condensate (BEC) with a magnetic lens, we form a time-domain matter-wave lens system. The focus is tuned by the strength of the lensing potential and the oscillatory phase of the quadrupole mode. By placing the focus at infinity, we lower the total internal kinetic energy of a BEC comprising 101(37) thousand atoms in three dimensions to 3/2 k_{B}·38_{-7}^{+6} pK. Our method paves the way for free-fall experiments lasting ten or more seconds as envisioned for tests of fundamental physics and high-precision BEC interferometry, as well as opens up a new kinetic energy regime.

Design and investigate the optical characteristics of single polepiece magnetics lenses

Computational analysis has been presented in this paper to discuss one of the approaches of optimum synthesis for the design of magnetics lenses (analytical method). This investigation concentrates on finding the optimum design for single-pole piece magnetics lenses magnetically unsaturated to use in construction magnetics optical systems for transmission electron microscopes (TEM). In this investigation, the same computer program (EOD) program is the geometry of the magnetic lens and the axial magnetic field generated and drawing lines of magnetic flux through the lens. The electron beam's trajectory and objective optical characteristics have been calculated, taking the values of axial magnetics field as input data to calculate the objective length of focal and coefficient of aberrations (spherical and chromatic). In present work has been studied the impact of geometrical parameters for magnetics lenses (axial bore diameter). This investigation's importance is the possibility of determining suitable geometry of the magnetics lenses for benefiting from it in making transmission electron microscopes.

Magnetically focused 70MeV proton minibeams for preclinical experiments combining a tandem accelerator and a 3GHz linear post-accelerator.

Radiotherapy plays an important role for the treatment of tumor diseases in two-thirds of all cases, but it is limited by side effects in the surrounding healthy tissue. Proton minibeam radiotherapy (pMBRT) is a promising option to widen the therapeutic window for tumor control at reduced side effects. An accelerator concept based on an existing tandem Van de Graaff accelerator and a linac enables the focusing of 70MeV protons to form minibeams with a size of only 0.1mm for a preclinical small animal irradiation facility, while avoiding the cost of an RFQ injector. The tandem accelerator provides a 16MeV proton beam with a beam brightness of as averaged from 5µs long pulses with a flat top current of 17µA at 200Hz repetition rate. Subsequently, the protons are accelerated to 70MeV by a 3GHz linear post-accelerator consisting of two Side Coupled Drift Tube Linac (SCDTL) structures and four Coupled Cavity Linac (CCL) structures [design: AVO-ADAM S.A (Geneva, Switzerland)]. A 3GHz buncher and four magnetic quadrupole lenses are placed between the tandem and the post-accelerator to maximize the transmission through the linac. A quadrupole triplet situated downstream of the linac structure focuses the protons into an area of (0.1×0.1)mm2 . The beam dynamics of the facility is optimized using the particle optics code TRACE three-dimensional (3D). Proton transmission through the facility is elaborated using the particle tracking code TRAVEL. A study about buncher amplitude and phase shift between buncher and linac is showing that 49% of all protons available from the tandem can be transported through the post-accelerator. A mean beam current up to 19nA is expected within an area of (0.1×0.1)mm2 at the beam focus. An extension of existing tandem accelerators by commercially available 3GHz structures is able to deliver a proton minibeam that serves all requirements to obtain proton minibeams to perform preclinical minibeam irradiations as it would be the case for a complete commercial 3GHz injector-RFQ-linac combination. Due to the modularity of the linac structure, the irradiation facility can be extended to clinically relevant proton energies up to or above 200MeV.