Design Of Electron Gun Research Articles

High power, high uniformity strip electron gun design, simulation and performance

This article discusses the simulation, design and performance of an 80 kW strip electron gun. Electrons from an electrically heated, multisegmented tantalum filament are electrostatically focused to provide a sheet of electrons in the postanode region, that when bent through 270° along a circle of radius 120 mm by a uniform magnetic field, focuses on the target. This gun has been tested up to 80 kW (45 kV×1.8 A), and delivers power densities on the target in the range of 20 kW cm−2. The linear current density is uniform up to 20%, over a focal spot of dimension 80×5 mm2. Good correspondence between filament geometry and focal spot image of the electron beam on the target has been obtained, which is desirable in applications involving metal vapor coatings. This design is scaleable along the length of the focal spot without sacrificing uniformity, which is not possible in scanning or multiple pencil-type of electron guns. Experimental measurement of gun parameters such as position of filament in relation to the cathode opening, distribution of current along the length of the beam, focal spot size, extraction efficiency, etc., along with data concerning electron beam quality as a function of various parameters, are presented. The performance of this gun under different experimental conditions, as well as the simulation and modeling using an in-house three-dimensional beam dynamics code, is discussed.

A High Performance Low Aberration Projection Electron Gun Design

A High Performance Low Aberration Projection Electron Gun Design

Study of the electron beam diagnostics and beam waist

In this work a study is made of the factors affecting the electron gun design and the diagnostics of the beam extracted from the gun. The use of both Pierce and shaping electrodes is necessary in order to produce thin intense beams. A theoretical study is made to find the beam envelope equation and the factors affecting the radius at the beam waist and its distance from the gun exit in a field free space region. The variations of the beam current, the beam perveance, the beam profile and transverse beam emittance with the extracting voltage are studied. The increase of the anode voltage is found to decrease the beam perveance, the beam waist and the beam emittance. The position and radius of the beam waist is found to depend on the beam perveance and beam slope at the gun exit aperture. It was found that to produce beams with minimum beam emittance and beam waist would necessitate working with higher extracting voltage.

Influence of electron injection on electron cyclotron resonance plasma properties and reflected mode electrons (abstract)

The injection of an additional strong focused electron beam from a special designed electron gun into a magnetic electron cyclotron resonance (ECR) confinement field is studied. The electron gun uses a cathode with a long lifetime and resistiveness providing high emission current densities with electron currents up to 50 mA and voltages up to 4 keV. A sequence of aluminum foils is used to investigate the trajectories of the electrons in the magnetic field without plasma. The high density electron beam passes through the foils, welds them, and prints its image into the foils. Details of this technique are described in Ref. 1. Using this technique we see that before the electrons enter the sextupole region the beam moves along the magnetic straight lines preserving its structure. Only a central beam passes through the sextupole region, thereby changing its form due to the interaction with radial components of the magnetic field. A new operation method at our 14.5 GHz ECR ion source is based on so-called reflection mode electrons (RMEs) analogous to a known electron beam ion source operation regime.2 The basic idea is that electrons, which traveling from the cathode in a strong axial field, meet an anticathode potential, are reflected from it, move back to the cathode, and will be reflected again and so on. It can be supposed that the electrons will make reflections up to the moment when the anode aperture of the gun is fulfilled and the electrons will be collected on the anode electrode. Investigations are performed extracting nitrogen ions using the RME beam. As a result we got a clear increase in the beam current of the extracted ions (e.g., at 10 mA electron injection an increase of the current of N5+ ions up to 400%) and a shift of the measured ion charge state distribution to higher mean ionization stages. Measured x-ray spectra from a neon loaded plasma show for the case of RME operation increasing energy shifts to the high energy side of the spectra, i.e., the mean ionization degree of the ions in the plasma increases. They also increase the intensity of the neon K x rays (more than 100% increase for RME injection of Ee=4 keV and Ie=10 mA) indicating that for the same operation parameters the mean density of energetic electrons rises at RME injection, i.e., there are more electrons with energies high enough to ionize K-shell electrons in neon.

Computer-aided design of electron guns and deflection yokes: A review (Part 2)

— Computer-aided-design (CAD) is now used in many engineering disciplines. CAD in electron optics applied to the design of electron guns and yokes eases and enables new designs. It makes old designs better. The general performance of a design can be anticipated with confidence. Modern CAD techniques allow the designer to predict performance, carry out engineering tradeoffs, and evaluate the sensitivity of different designs to manufacturing tolerances, avoiding lengthy and costly prototypes. Advantages, examples, tools, and an illustration of CAD were presented in Part 1 in 1997 (see Vol. 5, No. 3). The fundamental concepts were also reviewed and the essential physical and mathematical relationships presented. In this Part 2, numerical calculation methods and important algorithms are summarized. These allow beam simulations, which yield spot profiles and raster patterns more easily and more accurately than engineering prototypes, thereby expediting design. Data analysis and display techniques are described together with hardware and software considerations.

Improved Computer Program for Magnetron Injection Gun Design

Gyrotron has received extensive attention owing to its high-power capability, especially when the wavelength shrinks below the millimeter-wave range. The electron beam of a gyrotron is typically generated by a magnetron injection gun (MIG). For high cathode current density, the MIG may operate in a region that combines temperature limited and space-charge limited emissions. An improved computer program for electron gun design is appropriate for MIGs that operate between space-charge limited and temperature limited emission. Moreover, the initial input formation of the program resembles that of the EGUN code. Analysis of a Pierce electron gun and MIGs reveals that the stimulated beam current appears consistent with the measured results. However, EGUN simulation results in which the cathode emitters of MIGs are chosen for the temperature limited emission differ from those of our simulation results. This difference is most likely owing to that the initial emitting energy can not be completely described in the EGUN simulation. Finally, the improved computer program is used to design a MIG for a Ka-band, TE01 mode gyro-TWT.

Emission optics of the Steigerwald-type electron gun

The emission properties of a Steigerwald-type electron gun are reexamined. Several optical parameters were experimentally determined, and they indicate that the original telefocus mechanism proposed by Steigerwald in 1949 needs to be revised. “Remote focusing” is found to be nonexistent in most of the telefocus electron guns deployed in high-energy electron scattering experiments. Instead, almost parallel beams with variable beam diameters were found. The physical mechanism responsible for producing a very narrow, monochromatic, and highly collimated beam without limiting apertures is explained in this article with supporting evidences from measurements. We think the new emission model proposed here can help new types of electron or ion gun designs and applications using electron gun in electron optical systems.

Design and Development of Coaxial Convergent Electron Gun for Gain and Phase Matched Miniature Helix TWT

A Pierce type convergent electron gun with coaxial compact geometry has been designed and developed for a broadband gain and phase matched miniature helix Travelling Wave Tube. For the design of above gun, synthesis approach particularly for the estimation of anode hole aperture has been modified and used, which resulted in closer agreement with experimental value of the same parameter. A theoretical and experimental study regarding the effects of beam forming electrode (BFE) negative bias on beam optics has been discussed. Criticalities Involved in the development of such a compact miniature electron gun meeting the requirement of tube to tube gain and phase matching have been discussed along with the techniques to overcome the same.

An Iron-Free Magnetron-Injection-Gun for a 28GHz, 200kW Gyroklystron Amplifier

A design study of a double-anode magnetron-injection-gun is performed to incorporate the electron gun into a high power 28GHz gyroklystron amplifier operating at 70kV and 8.2A. The electron gun is designed to be used in a tapered magnetic field in the cathode region produced from an iron-free superconducting magnet. An electron trajectory code predicts a beam axial velocity spread of 5.9% at α = 1.5, 70kV, 8.2A and 10.4kG, which is a high quality electron beam suitable for the high gain, high efficiency, five-cavity gyroklystron amplifier. The successful design of the high quality electron gun is attributed to a longer gap between the modulating anode and the grounded anode compared with the case of the first 28GHz electron gun built with an iron enclosed electromagnet.

Electron gun and collector design for 94-GHz gyro-amplifiers

This paper presents the electrical design of a magnetron injection gun and collector for high peak and average power TE/sub 01/ W-band gyro-amplifiers. The magnetron injection gun design employs an optimized double-anode geometry and a cathode angle of 500 to achieve superior beam optics that are relatively insensitive to electrode misalignments and field errors. A transverse relative velocity spread of 1.6% at a velocity ratio of 1.5 is obtained in simulations for a 6-A 65-kV beam. Cathode edge emission was modeled, found to produce a major effect on velocity spread, and will be eliminated by nonemissive cylinders affixed to the cathode. The collector, which also serves as the output waveguide, is designed to minimize the required collector length while avoiding excessive power loading on the collector surface. An average power density of less than 640 W/cm/sup 2/ on a 3.25-cm-diameter collector is achieved for 91-kW average beam power. Both the gun and collector are currently under construction.

Electron and ion optical design software for integrated circuit manufacturing equipment

This article describes methods for the computer aided design of electron and ion beam columns for the integrated circuit (IC) manufacturing industry. The techniques described include computation of field distributions in electron lenses and deflectors, electron trajectories and aberrations, dynamic corrections, effects of discrete Coulomb interactions, design of electron guns, treatment of diffraction effects, optimization, and tolerancing of complete columns. These techniques are illustrated with examples relevant to the IC manufacturing industry, including systems for high-throughput electron beam lithography, nanolithography systems, and electron beam systems for inspection, metrology, and voltage testing.

Computer‐aided design of electron guns and deflection yokes: A review (Part 1)

Abstract— Computer‐aided‐design (CAD) is now used in many engineering disciplines. CAD in electron optics applied to the design of electron guns and yokes eases and enables new designs. It makes old designs better. The general performance of a design can be anticipated with confidence. Modern CAD techniques allow the designer to predict performance, carry out engineering tradeoffs, and evaluate the sensitivity of different designs to manufacturing tolerances, avoiding time‐consuming and costly prototypes. Advantages, examples, tools, and an illustration of CAD begin Part 1 of this review. The fundamental concepts are also reviewed and the essential physical and mathematical relationships presented. In Part 2, numerical calculation methods and important algorithms are summarized. These allow beam simulations, which yield spot profiles and raster patterns more easily and more accurately than engineering prototypes, thereby expediting design. Data analysis and display techniques are described together with hardware and software considerations.

Conceptual design of a novel instrument far producing intense pulses of 10 ps X-rays for ultra-fast fluorescence measurements

We report a conceptual design of a novel bench-top device for producing intense, fast pulses of X-rays with 10 ps fwhm (full-width at half-maximum) X-ray pulse width, 120 keV maximum energy, 100 kHz repetition rate, and 1 A peak current onto the X-ray anode. The device includes three sections: (1) an electron gun that generates 5 ns wide pulses of electrons; (2) solenoidal magnetic lenses and rectangular deflection plates that focus the electrons onto an aperture plate and sweep the pulsed beam past the slit aperture, respectively; and (3) a tungsten anode onto which the post-aperture electrons are focused, producing X-ray pulses. Solenoidal magnetic lenses with a current density of 150 A/spl middot/turns/cm/sup 2/ focus the 120 keV electron beam to a spot diameter of 0.32 mm such that a deflection plate dV/dt of 10/sup 13/ V/s (achieved with power triode circuitry) will yield X-ray pulse widths of about 10 ps. We used EGUN, an electron optics and gun design program, to simulate the electron trajectories throughout the instrument.

High-power operation of a 170 GHz megawatt gyrotron

Recent gyrotron oscillator experiments have achieved record powers at 170 GHz. Single mode emission with a peak output power of 1.5 MW and an efficiency of 35% has been measured. The experiment is based on a resonant TE28,8,1 cylindrical cavity situated in a 6.7 T magnetic field. Microwaves are generated in the cavity by an 83 kV annular electron beam produced by a triode-type magnetron injection gun that is capable of currents up to 50 A. Megawatt power levels with efficiencies between 30%–36% have been measured over a wide range of operating parameters for the TE28,8,1 mode. Similar results were also achieved in the neighboring TE27,8,1 mode at 166.6 GHz, and the TE29,8,1 mode at 173.5 GHz. The high output power is the result of a carefully designed electron gun with low perpendicular velocity spread (6%–10%) and a novel cavity with an output iris that is less prone to mode competition. These results are in good agreement with nonlinear multimode simulations.

Experimental study of matrix carbon field-emission cathodes and computer aided design of electron guns for microwave power devices, exploring these cathodes

The experimental study of matrix carbon field-emission cathodes (MCFECs), which has led to the stable operation of the cathodes with current emission values up to 100 mA, is described. A method of computer aided design of TWT electron guns (EGs) with MCFEC, based on the results of the MCFEC emission experimental study, is presented. The experimental MCFEC emission characteristics are used to define the field gain coefficient K and the cathode effective emission area Seff. The EG program computes the electric field upon the MCFEC surface, multiplies it by the K value and uses the Fowler–Nordheim law and the Seff value to calculate the MCFEC current; the electron trajectories are computed as well.

Ferroelectric electron emission: Principles and technology

The spontaneous electrical polarization of ferroelectric materials can be changed either by reversal or by phase transition from a ferroelectric into a non-ferroelectric state or vice versa. If spontaneous polarization changes are induced with fast heat, mechanical pressure, laser or electric field pulses on a submicrosecond time scale, strong uncompensated surface charge densities and related polarization fields are generated, which may lead to the intense self-emission of electrons from the negatively charged free surface areas of the ferroelectric sample. Hence, electron guns can be built with extraction-field-free ferroelectric cathodes, which may be easily separated from the high-field regions of post-accelerating gap structures. The intensity, the energy, the temporal and spatial distribution, and the repetitition rate of the emitted electron beams can be controlled within wide limits via the excitation pulses and external focusing and accelerating electromagnetic fields. The technological advantages and difficulties of ferroelectric cathodes during production and in practical operation are identified and discussed. A new design of electron guns with ferroelectric cathodes is described. Experience with a few applications of ferroelectric electron emission is reported and suggestions for further applications are made.

The synthesis method for design of electron flow sources

The synthesis method to design a relativistic magnetically - focused beam source is described in this paper. It allows to find a shape of electrodes necessary to produce laminar space charge flows. Electron guns with shielded cathodes designed with this method were analyzed using the EGUN code. The obtained results have shown the coincidence of the synthesis and analysis calculations [1].This method of electron gun calculation may be applied for immersed electron flows - of interest for the EBIS electron gun design.

Modelling and simulation of beam formation in electron guns

This paper describes a new PC version of the software package GUN-EBT for computer simulation of beam formation in rotationally symmetric electron guns with thermionic cathodes. It is based on a self-consistent physical model which takes into account the beam space charge and the initial velocities effects. The theoretical framework used for both the formulation of the model and for the interpretation of the results of numerical experiments is the formalism of the charged particle dynamics in phase space. This enables not only a trajectory analysis (ray tracing) but also a phase-space analysis of beams to be performed. The package can be used as an effective tool for computer aided design and optimization of electron guns in various electron-optical systems. The operation of the package is illustrated with a typical example.

Experimental design of high energy electron gun by means of scaling rules

The possibility of the design of a new family of electron guns by means of scaling theory of electron-optical devices (EOD) is presented. According to the theory, EOD with a relatively big space charge, as in high energy Pierce type electron guns used in technological equipment, generally cannot be scaled, because of their nonlinear space charge nature. Therefore, the scaling rules are applied here only to the anode zone of the gun, where the electron beam perveance is small, and the cathode lens of gun with considerable space charge remains unchanged. The procedure for scaling a 25 kV and 150 mA gun with cylindrical electron beam into a high voltage 75 kV and 150 mA electron system is given. An experimental investigation proved the high technological quality of a high voltage gun constructed according to the above conception.

A long-pulse 300 keV electron gun with a plasma cathode for high-pressure gas lasers

The design and main features of a plasma cathode electron gun for high-pressure gas lasers are discussed. The mesh plasma cathode in combination with a low-pressure gas discharge was used for the formation of a large cross-section (55×4 cm2) electron beam with emission current densities up to 1.7 A/cm2, accelerating voltages up to 300 kV, and a pulse length of 20 μs (full width at half maximum).