Electron Lenses Research Articles

Theoretical model of an electrically tunable liquid-crystal-based contact lens

Milton, et al. [Opt. Express 22, 8035 (2014)10.1364/OE.22.008035] have constructed a model electronic liquid crystal contact lens for the correction of presbyopia. This paper constructs a theoretical model for this lens. Good agreement between theory and experimental data is achieved, although the indications are that the precise parameters of the lens differ slightly from those prescribed by the designers of the lens. We discuss the temperature dependence of the optical power, the sensitivity of the device to manufacturing process and the properties of such lenses containing a number of different known liquid crystals. The model can be used for engineering optimization of the existing prototype.

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).

Tungsten Electron Emitter (TE2) with direct heated cathode by plasma stream

At Goethe-University, a novel concept of heating metallic cathodes is currently under investigation. In the scope of the ARIES collaboration WP16, an RF-modulated electron gun was developed and manufactured for application in electron lenses for space charge compensation. The goal of this project is to increase the intensity of primary beams, especially in low energy booster synchrotrons like the SIS18 and SIS100 at GSI/FAIR or the SPS at CERN. The gun was designed to produce electron currents of 10 A at extraction voltages of 30 kV. The tungsten electron emitter (TE2) and the grid electrode were designed and manufactured to be integrated in the extractor of the original volume type ion source. Significant effort was put into a robust and flexible design with highly reliable key components. The cathode is heated by a plasma stream generated in the plasma chamber of the source. Different heating options of the cathode are currently being studied. This contribution presents the working principles of the electron gun and first measurements results of cathode heating.

Status of the development of the electron lens for space charge compensation at GSI

At GSI a prototype electron lens for space charge (SC) compensation is currently being designed and main components as the RF-modulated electron gun are already under commissioning. The goal of this project is the (partial) compensation of SC forces within the ion beam by an overlapping electron beam. This may help to increase the intensity of primary beams, especially in the FAIR facility and potentially all large synchrotrons operated at the SC limit. For an effective SC compensation, the generated electron beam needs to follow the transverse and longitudinal beam profile of the ion bunch structure. The requirements are maximum currents of 10 A and grid modulation to cover a broad frequency range from 400 kHz to 1 MHz. The RF-modulated electron gun was designed and manufactured in the scope of the ARIES collaboration and is currently being tested at the E-Lens Lab of Goethe-University Frankfurt. A dedicated test bench was built for commissioning of the major e-lens components and diagnostics. In this contribution the overall set-up will be presented putting special emphasis on the beam dynamics and collector design as well as simulation results of the electron gun.

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.

Quench Protection of the HL-LHC Hollow Electron Lens Superconducting Solenoid Magnets

The High-Luminosity LHC (HL-LHC) project is an upgrade of the Large Hadron Collider (LHC) and comprises the installation of two Hollow Electron Lens (HEL) systems, each acting on one beam on both sides of LHC Point 4. The systems aim for a controlled depletion of hadron beam tails and an enhanced hadron beam halo collimation. Each HEL unit contains 22 circuits made up of solenoid, saddle coils and canted cosine theta corrector magnets. The largest magnet is a 1.6 m long solenoid, with a 180 mm bore diameter and central field of 5 T at 300 A and 4.5 K. This contribution focuses on the powering and protection strategy of the solenoid magnet circuits. The circuits are protected by active quench detection and a timely switch-off of the power converter. For the circuit with the largest stored energy, a study is performed on the efficiency of an energy extraction system. The quench simulations performed using the STEAM-LEDET code are combined with uncertainty quantification methods available in the DAKOTA software. Quench simulation input parameters related to the superconducting wire, magnet, circuit, and detection have been parametrized and randomly varied to calculate statistics of key output parameters. These are compared to the allowed limits, namely 500 V maximum peak voltage-to-ground and 120 K maximum coil temperature.

Conceptual Design of the HL-LHC Hollow Electron Lens Superconducting Magnet System

The Hollow Electron Lens (HEL) units are part of the upgrade baseline of the High-Luminosity LHC accelerator (HL-LHC) and will be installed in the machine ring at point P4 on each counter-rotating LHC proton beamline during a long shutdown in 2025-2027 at CERN. The main goal is to improve the collimation system performance by controlling beam energy loss in the beam halo. The magnet system consists of two 1.6 m long, 5 T superconducting solenoids operating at constant current equipped with steering dipole correctors and fringe field coils which compress the annular low energy e-beam (15 keV) generated from the e^− gun cathode and provide a stable interaction region with the high energy proton beam (7 TeV). Other sets of superconducting solenoids up to 4 T are used for fine-tuning and guiding the electron beam at the extremities of the interaction region on both the gun and the collector side. A standalone dipole compensator is part of the system to correct the net transverse field components up to 0.5 T.m. In this paper, the design progress of the HEL magnet system is presented and discussed.

Landau damping of transverse head-tail instabilities with a pulsed electron lens in hadron synchrotrons

A pulsed electron lens produces a betatron tune shift along a hadron bunch as a function of the longitudinal coordinates, which is a longitudinal detuning. An example of transverse detuning is the tune shifts due to octupole magnets. This paper considers a pulsed electron lens as a measure to mitigate the head-tail instabilities. Using a detailed analytical description within a Vlasov formalism, the coherent properties of the longitudinal and transverse detuning are presented. The analytical predictions are compared with the results of the particle tracking simulations. A pulsed electron lens is demonstrated to be a source of tune spread with two components: a static one, leading to Landau damping and a dynamic one, leading to an effective impedance modification, which we demonstrate analytically and in our particle tracking simulations. The effective impedance modification can be important for beam stability due to devices causing longitudinal detuning, especially for nonzero head-tail modes. The Vlasov formalism is extended to include the combination of longitudinal and transverse detuning. As a possible application at the SIS100 heavy-ion synchrotron [Facility for Antiproton and Ion Research (FAIR) at GSI Darmstadt, Germany], a combination of a pulsed electron lens with octupole magnets is considered.

Smart contact lenses and anterior chamber electronic implants: prospects of application in ophthalmology

Systemic and ophthalmological diseases are on the rise the world over, which is, to a large extent, caused by life expectancy growth. Therefore, early diagnosis, screening and monitoringpossibilities of human health parameters is becoming more and more important. Contact lenses, due to being fitted on the eye’s surface, are constantly wetted by tear fluid, and due to present-day microelectronics achievements may be used as a convenient technical means for locating a variety of sensors. The existing prototypes of electronic contact lenses (ECL) are able to monitor intraocular pressure (IOP), levels of glucose, hormones and other biomarkers that reflect the presence of ophthalmic and systemic diseases. The review discusses the publications focused on prototyping results and first laboratory tests. As of today, only one developed device is available for clinical practice (IOP monitoring), others are at different stages of research but have all potentials for being used widely.

A gas curtain beam profile monitor using beam induced fluorescence for high intensity charged particle beams

A minimally invasive transverse beam profile monitor based on supersonic gas curtain technology and beam-induced fluorescence has been developed and demonstrated. The concept presented can be used to measure both the profile of the proton beam in the Large Hadron Collider (LHC) and the concentricity of the electron and the proton beams in the LHC hollow electron lens. In this Letter, the performance of such a monitor for a low energy electron beam is discussed, which paves the way for its wider implementation.

Properties of electron lenses produced by ponderomotive potential with Bessel and Laguerre–Gaussian beams

The properties of electron round lenses produced by the ponderomotive potential are investigated in geometrical optics. The potential proportional to the intensity distribution of a focused first-order Bessel or Laguerre–Gaussian (LG) beam is exploited to produce an electron round lens and a third-order spherical aberration (SA) corrector. Several formulas for the focal length and SA coefficients in the thin-lens approximation are derived to set the lens properties and associated light beam parameters. When the mode field of the optical beam is small, the electron trajectory calculation results show properties similar to those obtained using the formulas. Alternatively, large higher-order aberrations are introduced because of the annular distribution of the potential. The second- and higher-order Bessel and LG beams produce no focusing power and no negative third-order SA; however, they can still be used as circularly symmetric higher-order aberration correctors. Results show that the ponderomotive potential–based electron lens or phase plate forms a refractive index medium with a shape that is considerably more flexible than that achieved in the case of conventional electrostatic and magnetic electron optics. The formulas presented herein can serve as guidelines for designing preferred light fields, thus promoting the advancement of a novel technology in electron optics that exploits the electron–light interaction.

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.

Three-dimensional chiral Veselago lensing

The effect by which light focuses upon entering a medium with a negative refractive index, known as Veselago lensing, may enable optical imaging below the diffraction limit. Similarly, focusing electrons across a $p\ensuremath{-}n$ junction could realize a technologically promising electronic Veselago lens. However, its scope remains limited by the lack of three-dimensional platforms and its insensitivity to computational degrees of freedom, such as spin or chirality. Here, we propose a single-material three-dimensional electronic Veselago lens that selectively focuses electrons of a given chirality. Using the chiral anomaly of topological semimetals it is possible to create a sharp $p\ensuremath{-}n$ junction for a single chirality, a chiral Veselago lens, and tune it with a magnetic field to an ideal lensing condition. We estimate that chiral Veselago lensing is observable in nonlocal transport and spectroscopy experiments. In particular, we show that the chiral Veselago lens leads to giant nonlocal magnetoresistance.

Periodic Nanoarray of Graphene pn‐Junctions on Silicon Carbide Obtained by Hydrogen Intercalation

AbstractGraphene pn‐junctions offer a rich portfolio of intriguing physical phenomena. They stand as the potential building blocks for a broad spectrum of future technologies, ranging from electronic lenses analogous to metamaterials in optics, to high‐performance photodetectors important for a variety of optoelectronic applications. The production of graphene pn‐junctions and their precise structuring at the nanoscale remains to be a challenge. In this work, a scalable method for fabricating periodic nanoarrays of graphene pn‐junctions on a technologically viable semiconducting SiC substrate is introduced. Via H‐intercalation, 1D confined armchair graphene nanoribbons are transformed into a single 2D graphene sheet rolling over 6H‐SiC mesa structures. Due to the different surface terminations of the basal and vicinal SiC planes constituting the mesa structures, different types of charge carriers are locally induced into the graphene layer. Using angle‐resolved photoelectron spectroscopy, the electronic band structure of the two graphene regions are selectively measured, finding two symmetrically doped phases with p‐type being located on the basal planes and n‐type on the facets. The results demonstrate that through a careful structuring of the substrate, combined with H‐intercalation, integrated networks of graphene pn‐junctions could be engineered at the nanoscale, paving the way for the realization of novel optoelectronic device concepts.

Near-infrared fundus imaging system with light illumination from an electronic contact lens

As for the diagnosis and treatment of eye diseases, an ideal fundus imaging system is expected to be portability, low cost, and high resolution. Here, we demonstrate a non-mydriatic near-infrared fundus imaging system with light illumination from an electronic contact lens (E-lens). The E-lens can illuminate the retinal and choroidal structures for capturing the fundus images when voltage is applied wirelessly to the lens. And we also reconstruct the images with a depth-dependent point-spread function to suppress the scattering effect that eventually visualizes the clear fundus images.

Electron lens Optimization for Beam Physics Research using the Integrated Optics Test Accelerator

This study proposed control system that has been presented to control the electron lens resistance in order to obtain a stabilized electron lens power. This study will layout the fundamental challenges, hypothetical plan arrangements and development condition for the Integrable Optics Test Accelerator (IOTA) in progress at Fermilab. Thus, an effective automatic gain control (AGC) unit has been introduced which prevents fluctuations in the internal resistance of the electronic lens caused by environmental influences to affect the system's current and power values ​​and keep them in stable amounts. Utilizing this unit has obtained level balanced out system un impacted with electronic lens surrounding natural varieties.

Ultrafast high energy electron lens radiography suitable for transient electromagnetic field diagnosis

Transient electromagnetic fields — during or after laser/particle beam-target interaction — are a significant and hardly explored parameter. This paper proposes a new method for measuring transient electromagnetic fields, based on ultrafast high-energy electron lens radiography, that has a high tolerance for matter in the diagnosed region. With this method, a continuous point strength diagnosis helps to obtain delicate. Furthermore, dual-band diagnosis can be used to determine the field direction. To verify its feasibility, a 50 MeV electron lens radiography beamline was designed and optimized and a preliminary simulation for diagnosing circular magnetic fields ranging from 170 T·μm to 680 T·μm was performed. For a number density of 2000/pixel and ±10% non-uniformity, ±15% diagnostic field strength accuracy has been obtained. The direction diagnosis also works well. Combined with the advantages of high-energy electron beams, ultrafast high-energy electron lens radiography is suitable for transient electromagnetic field diagnosis.

Nonlinear dynamics of proton beams with hollow electron lens in the CERN high-luminosity LHC

The design stored beam energy in the CERN high-luminosity large hadron collider (HL-LHC) upgrade is about 700 MJ, with about 36 MJ in the beam tails, according to estimates based on scaling considerations from measurements at the LHC. Such a large amount of stored energy in the beam tails poses serious challenges on its control and safe disposal. In particular, orbit jitters can cause significant losses on primary collimators, which can lead to accidental beam dumps, magnet quenches, or even permanent damage to collimators and other accelerator elements. Thus, active control of the diffusion speed of halo particles is necessary and the use of hollow electron lenses (HELs) represents the most promising approach to handle overpopulated tails at the HL-LHC. HEL is a very powerful and advanced tool that can be used for controlled depletion of beam tails, thus enhancing the performance of beam halo collimation. For these reasons, HELs have been recently included in the HL-LHC baseline. In this paper, we present detailed beam dynamics calculations performed with the goal of defining HEL specifications and operational scenarios for HL-LHC. The prospects for effective halo control in HL-LHC are presented.

Recent Advances in Bioinspired Hydrogels: Materials, Devices, and Biosignal Computing.

The remarkable ability of biological systems to sense and adapt to complex environmental conditions has inspired new materials and novel designs for next-generation wearable devices. Hydrogels are being intensively investigated for their versatile functions in wearable devices due to their superior softness, biocompatibility, and rapid stimulus response. This review focuses on recent strategies for developing bioinspired hydrogel wearable devices that can accommodate mechanical strain and integrate seamlessly with biological systems. We will provide an overview of different types of bioinspired hydrogels tailored for wearable devices. Next, we will discuss the recent progress of bioinspired hydrogel wearable devices such as electronic skin and smart contact lenses. Also, we will comprehensively summarize biosignal readout methods for hydrogel wearable devices as well as advances in powering and wireless data transmission technologies. Finally, current challenges facing these wearable devices are discussed, and future directions are proposed.

On the Design of an Efficient Inductive Wireless Power Transfer for Passive Neurostimulation Systems.

In this paper, a minimally invasive wireless powered electronic lens (e-lens) with passive electrodes is presented for an ocular electrical stimulation. Previous research has focused on the differentiation property of the induction phenomenon and half wave rectifiers. However, these approaches are generally application specific, non efficient, suitable for low current, and deliver monophasic current stimulation. Existing rectifier-based techniques can lead to safety concerns as the offset voltage could change unpredictably. A new wireless power transfer circuit is presented for the design of an efficient system to wirelessly deliver charge-balanced biphasic waveforms through passive electrodes for transcorneal electrical stimulation. The absence of active components allows the development of a flexible e-lens system for therapeutic electrical stimulation of the eye.