Electron Gun Research Articles

The design of high-brightness ERL-FEL injector based on VHF electron gun

In the past decade, the fourth-generation light source based on the combination of Energy Recovery Linac (ERL) and Free-Electron Laser (FEL) using superconducting linear accelerators has garnered significant attention. It holds immense potential, particularly in generating high-power Extreme Ultraviolet (EUV) light sources. This article primarily focuses on the physical design of an injector for ERL-FEL, based on a Very High Frequency (VHF) electron gun with a charge of 100 pC. The beam energy is accelerated to 10 MeV using 3-cell superconducting cryomodule. The optimization of beam parameters is conducted through employment of BMad and ASTRA simulations, incorporating the concept of Merger optimization. The beam emittance is less than 0.6 mm mrad, and the peak current at the injector exit exceeds 18 A. We present a new method to evaluate the Longitudinal Space Charge (LSC) effects in merger sections, which can be readily applied in design work. Furthermore, we introduce a novel type of merger. The performance of this new merger is comparable to the previously known optimum, the zigzag merger, offering a potential alternative solution for injectors in ERLs.

High-resolution anionic velocity map imaging apparatus for dissociative electron attachment dynamics study.

Dissociative electron attachment (DEA) of a molecular target XY, e- + XY → XY- → X + Y-, is an important process in plasma, atmosphere, interstellar space, and ionizing radiation. DEA dynamics, i.e., the formation and fragmentation of an electron-molecule resonant complex, can be unveiled by measuring the product Y- with the velocity map imaging (VMI) technique. However, it is still challenging to achieve a high-resolution VMI measurement. Recently, we developed a high-resolution DEA apparatus that combined the VMI technique with a trochoidal electron monochromator. The energy spread (around 500meV) of thermally emitted incident electrons can be reduced remarkably, but the monochromatized electrons become diffuse again in energy when being pulsed with an electric pulse applied on the grid electrode because the electron beam must be pulsed in the VMI measurement. Now this long-standing technical contradiction is settled by introducing a parallel resistance-capacitor circuit to the electrode of an electron gun. A delay-line detector is used for the VMI measurement, which allows the three-dimensional velocity or momentum images of multiple anionic yields to be recorded efficiently. Our high-resolution VMI apparatus works at a pulse frequency of 5kHz and an energy spread of about 120-150meV, and its credible performances are exhibited by the measurements of the DEA processes of CO(a3Π) and NO2.

Silver Oxide Nanoparticle Decorated Carbon Nanotube as Efficient Electron Gun

AbstractAlthough there have been numerous great field emission reports of pure and hybrid carbon nanotubes (CNTs) with ultra‐low turn‐on field and ultra‐high emission stability, practically all of the reports indicate concern about CNT manufacture on a large scale. This is due to the fact that CNT experiments require high pressure, temperature, metal catalysis, and an inert environment, and even after meeting all of these perfect conditions, the yield is quite low. Furthermore, as CNT is relatively inert in nature, it is nearly hard to make it reactive with any other metal without adequate functionalization. Keeping this in mind, this work reports the synthesis of CNT in amorphous form by a simple low‐temperature solid‐state reaction between ammonium chloride and ferrocene. The as‐synthesized CNT is further functionalized by silver oxide nanoparticle without additional functionalization. X‐ray diffraction (XRD) confirms the proper phase formation as well as the successful functionalization of the pure and hybrid sample, electron microscopic images confirm the successful functionalization of the as‐prepared CNT whereas Fourier transformed infrared (FTIR) spectroscopic analysis gives the ideas about different bonding present in all the samples. It has been found that the hybrid sample gives much better field emission performance compare to the pure CNT with betterment in both turn‐on field and enhancement factor more than 100%. The betterment is believed to be due to the favorable band bending, larger number of emission sites, and sharp curvature of the silver particles.

High power target for the High Brilliance Neutron Source

The High Brilliance Neutron Source (HBS) is a High-Current Accelerator-driven Neutron Source (HiCANS) under development at Jülich Centre for Neutron Science - Forschungszentrum Jülich. The unique specifications of the HBS require a neutron target with a high neutron emission able to operate in vacuum with a 70MeV proton beam with 90mA peak current and 1.6% duty cycle leading to an average thermal load of 100kW. A tantalum target of 100cm2 irradiated area with an internal cooling structure which removes the heat quite homogeneously, provides a good compromise between low pressure and high heat transfer and ensures an homogeneous protons energy loss was designed and optimized by means of MCNP, CFD and FEM simulations. Such a target was successfully manufactured and its operational capability was demonstrated by operating it under a heat load of 1kWcm−2 from an electron gun.

Electron gun with an auto-emission cathode based on carbon nanotubes for a powerful millimeter-range extended interaction klystron

The possibilities of using auto-emission cathode-grided module in an electron-optical system of extended interaction klystron of the millimeter wavelength range are investigated. The results of a theoretical analysis of the developed design of an electron gun with high compression ratio are presented. The limits of the angular spread of electrons on the grid, which ensures the complete electron beam transmission through the interaction system of the device, are determined.

Open LEARN: Open access linear accelerator education and augmented reality Navigator

PurposeTo create an open-access Linear Accelerator Education and Augmented Reality Navigator (Open LEARN) via 3D printable objects and interactive augmented reality assets. MethodsThis study describes an augmented reality linear accelerator (linac) model accessible through a QR code and a smartphone to address the challenges of medical physics and radiation oncology trainees in low-to-middle-income countries. ResultsMajor components of a generic linear accelerator are modeled as individual objects. These objects can be 3D printed for hands-on learning and used as interactive 3D assets within the augmented reality app. In the AR app, descriptions are displayed to navigate the components spatially and textually. Items modeled include the treatment couch, klystron, circulator, RF waveguides, electron gun, waveguide, beam steering assemblies, target, collimators, multi-leaf collimators, and imaging systems. The linear accelerator is rendered at nearly 100% of its actual size, allowing users to change magnification and view objects from different angles. ConclusionsThe augmented reality linear accelerators and 3D-printed objects make these complex machines easily accessible with smartphones and 3D-printing technologies, facilitating education and training through physical and virtual interaction.

In Situ Transmission Electron Microscope Observation of Ruthenium Silicadation and Diffusion Behavior at Atomic Scale

Ruthenium (Ru) has the excellent characteristics of oxidation resistance and good chemical stability; therefore, it has been widely used in semiconductor manufacturing, specifically in application as capping layers of extreme ultraviolet lithography (EUV) masks. The main purpose of capping layers is to protect Mo/Si multilayers from EUV radiation, preventing oxidation, damages, and contamination of the multilayers. However, with prolonged use, the EUV mask accumulates heat, resulting in diffusion between Ru and Si. When diffusion reactions occurred, leading to a reduction in the EUV mask's lifetime. In order to study the reaction mechanism, we use in-situ transmission electron microscopy (TEM) to observe the reactions between Ru and Si. In this study, Ru thin film was deposited on silicon substrate by electron gun (E-gun) evaporation. The dynamic formation process of ruthenium silicide has been observed via in-situ TEM. During the heating process, Si atoms diffused into ruthenium thin film at 300 °C, at the same time, Ru atoms will also diffuse into silicon substrate. At 350 °C, due to the interdiffusion effect, Ru2Si is formed in the Ru thin film, and it is observed that Ru2Si3 is embedded in the Si substrate. As the temperature rises to 450 °C, Ru2Si was transformed into RuSi. Finally, at 600 °C, the Ru thin film completely transformed into Ru2Si3. We provide direct evidence of diffusion behaviors and formation mechanism of Ru-Si system for better investigation of EUV masks degradation processes in semiconductor manufacturing and design. Keywords: Ruthenium silicide, in situ TEM, diffusion mechanism, atomic-scale, EUV mask Figure 1. Structural identification of Ru thin film and in-situ heating process of ruthenium silicide formation. (a) Initial EDS mapping of as-deposited Ru thin film on silicon substrate, showing homogenous distribution of each elements. (b) HRTEM image of in-situ heating process during 350oC. (c) Magnified HRTEM image of Ru2Si indicated in blue frame in (b). (d) Corresponding fast Fourier transform (FFT) along [110] zone axis. (e) HRTEM image of in-situ heating process during 600oC. (f) Magnified HRTEM image of Ru2Si3 indicated in yellow frame in (e). (g) Corresponding FFT along [010] zone axis. Figure 1

Design and study of the shape parameters for the electrode plates of the electron gun in the four-dimensional transmission electron microscope.

The accelerating electrode of a four-dimensional transmission electron microscope electron gun is modeled. The general expression of the electric-field distribution is derived for any point on the axis in a cylindrical coordinate system, and equations for the shape parameters of the electrode plate are obtained. The accuracy of the field expression is determined for different electrode plate parameters, and the shape parameters of the electron gun electrode are further investigated. This work can provide a theoretical basis for the initial design of a transmission electron microscope electron gun and the retrofit design of a four-dimensional electron gun.

Characteristics of Carbon Nanotube Cold Cathode Triode Electron Gun Driven by MOSFET Working at Subthreshold Region.

The carbon nanotube cold cathode has important applications in the X-ray source, microwave tube, neutralizer, etc. In this study, the characteristics of carbon nanotube (CNT) electron gun in series with metal-oxide-semiconductor field-effect transistor (MOSFET) were studied. CNTs were prepared on a stainless steel substrate by chemical vapor deposition and assembled with a mesh gate to form an electron gun. The anode current of the electron gun can be accurately regulated by precisely controlling the MOSFET gate voltage in the subthreshold region from 1 to 40 µA. The current stability measurements show the cathode current fluctuation was 0.87% under 10 h continuous operation, and the corresponding anode current fluctuation was 2.3%. The result has demonstrated that the MOSFET can be applied for the precise control of the CNT electron gun and greatly improve current stability.

Practical design of the focusing system for transmission and reflection targets in X-ray sources

The incident beam quality at the target determines the resolution and intensity of micro-focus X-ray sources, which depends greatly on the focusing system and the target. To meet different spatial layouts of the focusing system with transmission and reflection targets, three-dimension (3-D) modelling of the focusing system was built with Monte Carlo simulation and coordinate transforming method in this paper. In the proposed approach, the focusing system was first optimized by a 2-D model to achieve a fine beam spot with high effective current at the optimum working distance for the transmission and reflection targets. Then, 3-D practical model of the focusing system was achieved by tracing N electrons from the electron gun in three directions using the 5-order Runge-Kutta method. Finally, examples of the focusing system for 90 keV and 30 keV X-ray sources were given to get the energy distributions at transmission and reflection targets. Results show that resolutions of 4 μm and 500 nm have been achieved for 90 keV X-ray source with the transmission target and 30 keV X-ray source with the reflection target respectively. Compared with the experimental results, 2-D modelling of the focusing system is also applicable for X-ray source with the transmission target while 3-D modelling of the focusing system is essential for X-ray source with the reflection target. In addition, the 3-D electron beam model will simplify the design of the real apertures, liner tubes, beam blankers etc.

Simultaneous Real and Momentum Space Electron Diffraction from a Fullerene Molecule.

Plane-wave electrons undergo momentum transfer as they scatter off a target in overlapping spherical waves. The transferred momentum leads to target structural information to be encoded in angle and energy differential scattering. For symmetric, periodic, or structured targets this can engender diffraction in the electron intensity both in real and momentum space. With the example of elastic scattering from a C_{60} molecule we show these simultaneous diffraction signatures. Simulated angle-momentum diffractograms can be imaged in experiments with a two-dimensional detector and an energy-tunable electron gun. The result may inspire the invention of technology to extend scopes of electron diffraction studies, open a track of electron crystallography using the momentum-differential diffraction, and motivate research about controlling the time delay between the pump laser pulse and probe electron pulse by tuning the electron impact speed in ultrafast electron diffraction experiments.

Design and performance of a low-emittance electron gun for electron beam probe

An Electron Beam Probe (EBP) is preferable to provide a non-interceptive measurement of the transverse distribution of a dense bunched ion beam. During EBP operation, it was observed that the electron beam spot subjects to expansion when scanned across the ion beam due to the strong space charge field of the ion bunch, leading to significant degradation of spatial resolution. To mitigate this effect, a small electron beam spot is beneficial as demonstrated in previous research. This paper presents design details of a low-emittance, small-spot, and long-work-distance electron gun. Geometry optimization of the gun and focus lens is conducted using a multiobjective genetic algorithm (MOGA) interfaced with space charge simulation codes to maintain normalized thermal emittance within an acceptable increase and achieve a small spot at a long work distance. The emittance is measured using a slit-screen technique, resulting in a norm. rms emittance of 0.046(+-0.005) um*rad under low beam current conditions (50 nA). In high-resolution mode, a beam spot size of 0.6 mm (rms) is achieved at a work distance of 1.2 m with the combination of Einzel lens and solenoid. The gun has been successfully operated as part of EBP experiments for accurate and high-resolution measurement of ion beam width, demonstrating excellent agreement with wire scanner measurements with relative deviation not exceeding 1%.

1D drift-kinetic numerical model based on semi-implicit particle-in-cell method

The paper presents a new one-dimensional drift-kinetic electrostatic model based on the particle-in-cell method and capable of simulating the processes of plasma heating and confinement in mirror traps. The most of particle and energy losses in these traps occur along the magnetic field lines. The key role in limiting these losses is played by the ambipolar electric potential which creates a potential barrier for electrons and significantly reduces the heat flux that, without this barrier, would go to wall due to the classical electron thermal conductivity. However, modeling the formation of such a potential on real spatial and temporal scales of experiments is a challenging problem, since it requires a detailed description of not only ion, but also electron kinetics. In this work, we propose to solve the problem of taking into account electron kinetic effects on the time scale of plasma confinement in a mirror trap using the particle-in-cell method adapted to the approximate drift-kinetic equations of plasma motion. Unlike other electrostatic particle-in-cell models, which use fully implicit schemes to solve the nonlinear system of Vlasov-Poisson and Vlasov-Ampere equations, we propose a semi-implicit approach. By analogy with the Energy Conserving Semi-Implicit Method (ECSIM), it allows for precise conservation of energy and reduces the procedure for finding the electric field to inverting a tridiagonal matrix without multiple nonlinear iterations. Such a model will be useful for simulating not only collisional losses of hot plasma in fusion experiments, but also for studying the features of creating cold starting plasma in mirror traps using plasma or electron guns.

Influence of the external magnetic field on structural characteristics of granular Co-Cu thin film alloys

We present the results of experimental studies of the influence of an external magnetic field on the structural characteristics (surface roughness and structural entropy) of nanogranular thin-film system based on Co and Cu. The samples CoxCu100-x in a wide range of compositions (17 at. % ≤ x ≤ 69 at. %) with the thickness of d = 35 nm were obtained by electron-beam co-evaporation using two independent electron guns. After obtaining, the films were annealed in a vacuum at a temperature of 800 K for 30 min. The studies of magnetoresistive properties have shown that the maximum giant magnetoresistance (GMR) amplitude (1.7 % in the transverse and 1.6 % in the longitudinal measurement geometries) in a magnetic field of H = 4.5 kOe at room temperature was observed in the Co21Cu79 film alloy. Transmission electron microscopy showed that this sample contains hcp-Co granules with a size of L = 5 ÷ 12 nm in a matrix of metastable fcc-Cu(Co) solid solution. The influence of the external magnetic field on the structural characteristics and surface morphology of the Co21Cu79 thin-film alloy was investigated using atomic force microscopy (AFM). It was found that a first impact of application of external magnetic field with H = 0.5 kOe causes a decrease in the values of the arithmetic mean Ra, and quadratic mean Rq, of the film roughness and structural entropy S. A decreases in Ra by 8.5 %, Rq by 6.5 %, and structural entropy S by 6.5 % were observed. After application of a larger magnetic field with H = 1.0 kOe and during the subsequent relaxation of the structure within 15 h after the field is turned off, the values of the structural parameters of the film surface did not change significantly.

Three-Dimensional Guidance Laws for Spacecraft Propelled by a SWIFT Propulsion System

This paper discusses the optimal control law, in a three-dimensional (3D) heliocentric orbit transfer, of a spacecraft whose primary propulsion system is a Solar Wind Ion Focusing Thruster (SWIFT). A SWIFT is an interesting concept of a propellantless thruster, proposed ten years ago by Gemmer and Mazzoleni, which deflects, collects, and accelerates the charged particles of solar wind to generate thrust in the interplanetary space. To this end, the SWIFT uses a large conical structure made of thin metallic wires, which is positively charged with the aid of an electron gun. In this sense, a SWIFT can be considered as a sort of evolution of the Janhunen’s E-Sail, which also uses a (nominally flat) mesh of electrically charged tethers to deflect the solar wind stream. In the recent literature, the optimal performance of a SWIFT-based vehicle has been studied by assuming a coplanar orbit transfer and a two-dimensional scenario. The mathematical model proposed in this paper extends that result by discussing the optimal guidance laws in the general context of a 3D heliocentric transfer. In this regard, a number of different forms of the spacecraft state vectors are considered. The validity of the obtained optimal control law is tested in a simplified Earth–Venus and Earth–Mars transfer by comparing the simulation results with the literature data in terms of minimum flight time.

The study of interaction of the high energetic plasma and electron pulses with multicomponent alloy surface

This paper investigates the impact of high-energy sources, namely, high-energy plasma pulses and high-energy electron beam pulses, on materials in the form of layer through separate and combined exposures. Experimental setups utilizing a Rod Plasma Injector (RPI) and an electron gun were employed for irradiation tests. The studies involved pre- and post-treatment analysis of morphology, chemical, and phase composition using scanning electron microscopy and x-ray diffraction measurements. Surface modifications under different exposure conditions were characterized, revealing that both sources induced significant alterations in surface composition and crystal structure. These interactions result in a more uniform chemical composition, reduced surface roughness, and a shift from an amorphous phase to a nanocrystalline or amorphous-nanocrystalline state. The results underscore the potential of high-energy sources for efficient surface engineering, offering opportunities for customized material surface modifications through meticulous adjustment of these generation parameters.

Bright terahertz electron gun opens new opportunities

Bright terahertz electron gun opens new opportunities

FENNECS: A novel particle-in-cell code for simulating the formation of magnetized non-neutral plasmas trapped by electrodes of complex geometries

This paper presents the new 2D electrostatic particle-in-cell code FENNECS developed to study the formation of magnetized non-neutral plasmas in geometries with azimuthal symmetry. This code has been developed in the domain of gyrotron electron gun design, but solves general equations and can be applied in other domains of plasma physics. FENNECS is capable of simulating electron-neutral collisions using a Monte Carlo approach and considers both elastic and inelastic (ionization) processes. It is also capable of solving the Poisson equation on domains with arbitrary geometries with either Dirichlet or natural boundary conditions. The Poisson solver is based on a meshless Finite Element Method, called web-splines, based on b-splines of any order, and used for the first time in the domain of plasma physics. In addition, the effect of fast ions colliding with the electrodes and causing ion induced electron emission at the electrode surfaces has been implemented in the code. In this paper, the governing equations solved by FENNECS and the numerical methods used to solve them are presented. A number of verification cases are then reported. Finally, the parallelization scheme used in FENNECS and its parallel scalability are presented.

A thermionic electron gun to characterize silicon drift detectors with electrons

The TRISTAN detector is a new detector for electron spectroscopy at the Karlsruhe Tritium Neutrino (KATRIN) experiment. The semiconductor detector utilizes the silicon drift detector technology and will enable the precise measurement of the entire tritium β-decay electron spectrum. Thus, a significant fraction of the parameter space of potential neutrino mass eigenstates in the keV-mass regime can be probed. We developed a custom electron gun based on the effect of thermionic emission to characterize the TRISTAN detector modules with mono-energetic electrons before installation into the KATRIN beamline. The electron gun provides an electron beam with up to 25 keV kinetic energy and an electron rate in the order of 105 electrons per second. This manuscript gives an overview of the design and commissioning of the electron gun. In addition, we will shortly discuss a first measurement with the electron gun to characterize the electron response of the TRISTAN detector.

A low-energy MHz repetition rate short-pulse electron gun

An electron gun that can produce MHz repetition rates and nanosecond pulses is described. The gun uses a Pierce grid in combination with an anode to extract electrons from a tungsten filament cathode. The electrons emerging from the anode are accelerated and focused using two triple-aperture lenses to form a beam. By applying a high slew rate grid pulse that transitions through the extraction voltage region of the grid/anode combination, pulses of electrons are produced from the gun that have temporal widths less than 5 ns. The pulsed beams are produced at both the rising and falling edges of the driving pulse. The characteristics of the emerging electron beams have been determined using an (e, 2e) coincidence spectrometer, and examples where they are used for time of flight decay measurements are presented.