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The design and development of the electron gun for vacuum electronic devices is a critical and challenging task having a profound impact on device performance. Current state-of-the-art electron gun simulation codes employ the concept of a virtual cathode for the simulation of space charge-limited electron guns, where the virtual cathode distance is to be provided as an input by the user. In this report, an approach to calculate the virtual cathode position through analytical formulation and simulation is presented. The effect of inaccurate virtual cathode on gun parameters is studied through simulation and its repercussions are explained. The approach has been applied in the simulation using three-dimensional tracking solver to design a 50 kV, 10 Amp electron gun, which is to be used in a C-band Klystron. Based on the design, a Gun-Collector-Test-Module (GCTM) has been developed and hot-tested for experimental validation. A good agreement between the simulated and measurement results validates the design approach of the electron gun. [ABSTRACT FROM AUTHOR]

Metal additive manufacturing technologies, such as electron beam powder bed fusion (PBF-EB), rely on layer heating to overcome the so-called "smoke" phenomenon. When scaled up for industrial manufacturing, PBF-EB becomes less productive due to the lengthy preheating process. Currently, only the electron beam (EB) is used for preheating in PBF-EB, resulting in increased manufacturing times, energy consumption, and in some cases limiting the applicability of the technology. In this study, a new preheating approach is suggested that incorporates a near-infrared radiation (NIR) emitter inside an PBF-EB system. The NIR unit eliminates the need for EB heating, reducing build time and powder charging. Successful builds using 316 L and Ti6Al4V precursor powders validate the feasibility of the proposed approach. The produced samples exhibit similar properties to those obtained by the standard PBF-EB process. The introduction of NIR technology also reduced build cost and increased the service intervals of the electron gun. [ABSTRACT FROM AUTHOR]

This study evaluates dosimetric data such as PDD, dose profile and tissue phantom rate (TPR20/10) after replacing the LINAC device's electron gun and ion chamber pump. These values obtained after the change were compared with the standard PDD protocol, British Journal of Radiology Supplement 25 (BJR 25) report, Beam Data (measured and recorded as reference values during the setup phase, BD) and simulation results. In additional, uncertainty results were obtained for absorbed doses to water using different calculation tools. The experimental setup was created in the GATE/Geant4 simulation program, and the experimentally obtained TPR20/10, beam profile and PDD values were compared with the simulation. The difference between TPR20/10 values for 6 and 18 MV photon energies was found to be below 1% for 6 MVs and 3% for 18 MV. When different calculation tools were used, uncertainties were found in the absorbed dose measurements ranging between 0.8% and 1.87%, which is compatible with the uncertainties (1.4-2.1%) specified in the IAEA report. Even though small uncertainties were observed in the results, the differences between the calculations in the measurements of absorbed doses were insignificant. Estimated uncertainties for GATE was a little smaller than those measured using experimental methods, BD and BJR 25. Although the values obtained are within the tolerance, after such significant materials are changed in the LINAC device, a water phantom should be set up, the measurements should be repeated, and the results should be confirmed to be within the limit values. [ABSTRACT FROM AUTHOR]

A new source of an electron beam with laser heating of the cathode is presented. The general description, the main parameters and the arrangement of the electron beam source are given. The cathode assembly and its operation features are described, which consist in controlling the emission current from the cathode by changing the cathode temperature by controlling the laser heating power. With this method, due to the heat capacity of the cathode and the parts nearby, the time to reach the set current level of the source from the moment the laser power is applied is several seconds. A method is proposed to reduce this time to fractions of a second by forcing the heating power at the beginning of turning on the heating and introducing preheating, and it is also proposed to stabilize the source current by introducing feedback of the heating power control signal with the current signal of the high-voltage source of the electron gun. The source current control range is discussed. [ABSTRACT FROM AUTHOR]

This paper presents a design investigation of the Electron Optical Gun (EOG) for a 42 GHz, 200 kW second harmonic gyrotron operating in the TE0, 3 mode. The initial design of MIG is done using established design equations and then optimized through numerical simulations. The different software, such as 2D-Numerical codes EGUN, TRAK and 3D-CST Particle Studio, are used to optimize the design and found good agreement in results obtained from these codes. The sensitivity analysis has also been carried out for the sake of complete design. Furthermore in brief, a design has been done for the un-depressed and Single-Stage Depressed Collector (SDC). In addition, the uneven or uniform beam distribution on collector wall is presented with result comparison of both the collectors. The optimized beam voltage and single-stage depressed collector voltage are 65 kV, 30 kV respectively. [ABSTRACT FROM AUTHOR]

Electron beam deposition is a process that involves the use of an electron beam as a source of energy and wire as a raw material for the fabrication of metal products with complex shape in a vacuum and is part of the promising additive technologies group. In this paper a methodology for determining the electron-beam deposition regimes of a wire by the example of corrosion-resistant austenitic steel ANSI 316L is proposed. The proposed calculation methodology connects the main parameters of the process: the electron beam current, the addition wire feed rate, the movement speed of the electron gun and the dimensions of the deposited rollers. The investigation results of the microstructure and properties of the deposited metal are presented. Examples of the obtained cylindrical and conical products are adduced. [ABSTRACT FROM AUTHOR]

A 352.2 MHz klystron with an output power of 100 kW CW is under development at CSIR-CEERI for charged particle accelerator application. The paper presents various design results achieved through simulation of the electron gun, radio frequency (RF) interaction structure and collector for the device. Based on the design results, a beam stick tube has been developed and hot tested for which the test results are given. A study for the design of RF interaction structure of this klystron has been carried out to get the optimized design parameters using 1-D code AJDISK and MAGIC (2D/3D). The intermediate RF cavities have been developed and characterized for their designed frequencies and the results of cold RF measurements are given. [ABSTRACT FROM AUTHOR]

Conventional klystrons using single beam of electrons have several limitations for increasing of beam voltage or current which can be overcome using multiple electron beams. The paper presents the design of a single beam electron gun for a practical 100 kW CW conventional klystron and then translation of the design into a fivebeam gun for reducing operating voltage and overall improvement in tube performance. The design parameters of multi beam electron gun have been derived from existing single beam parameters using some scaling laws, and are further optimized through CST Particle Studio. The simulation results of CST have been cross-validated using Opera-3D code. The electron gun is currently under development. [ABSTRACT FROM AUTHOR]

Investigations were carried out into the production of combined welded joints in 316L(N) austenitic steel and BrKh1Tsr (CuCrZr) and CuAl10Ni5Fe4 bronzes 30 mm thick by electron beam welding (EBW). The formation of the welded joints in dissimilar materials is investigated and the EBW conditions determined. The microstructure, mechanic properties and chemical composition of the welded joints are also determined. It is shown possible to obtain the mechanical properties of welded joints similar to the properties of the parent bronze by weldbrazing. It is therefore necessary to increase the accuracy and stability of the electron beam parameters as a technological tool. [ABSTRACT FROM AUTHOR]

The paper reports the theoretical approach and computer-aided design results for a 350 MHz, 100 kW (CW) inductive output tube. The design considerations and methodologies employed for electromagnetic simulation of individual electron gun and RF cavity assemblies and that of their combined assembly were presented. The electron gun parameters namely the beam radius, perveance and electrodes dimensions were optimized. The input cavity was designed and the parameters, namely the resonant frequency, radius and length of the cavity with respect to the desired propagating mode were characterized. The combined integrated model demonstrates the RF input cavity placed onto the gun structure. The interaction of electron beam (40 kV, 3.5 A) and applied input RF signal of 400 W produces an RF current of ~ 85 A in the interaction gap (i.e. cathode-grid spacing). The focusing structure of the device necessary for getting the efficient amplification has also been designed and optimized. The simulations presented in the paper are carried out using CST, MAGIC2D and TRAK codes. [ABSTRACT FROM PUBLISHER]

Energetic ion beams are proving to be versatile tools for modification and depth profiling of materials. The energy and ion species are the deciding factor in the ion-beam-induced materials modification. Among the various parameters such as electronic energy loss, fluence and heat of mixing, velocity of the ions used for irradiation plays an important role in mixing at the interface. The present study is carried out to find the effect of the velocity of swift heavy ions on interface mixing of a Ti/Bi bilayer system. Ti/Bi/C was deposited on Si substrate at room temperature by an electron gun in a high-vacuum deposition system. Carbon layer is deposited on top to avoid oxidation of the samples. Eighty mega electron volts Au ions and 100 MeV Ag ions with same value ofSefor Ti are used for the irradiation of samples at the fluences 1 × 1013–1 × 1014ions/cm2. Different techniques like Rutherford backscattering spectroscopy, atomic force microscopy and grazing incidence X-ray diffraction were used to characterize the pristine and irradiated samples. The mixing effect is explained in the framework of the thermal spike model. It has been found that the mixing rate is higher for low-velocity Au ions in comparison to high-velocity Ag ions. The result could be explained as due to less energy deposition in thermal spike by high-velocity ions. [ABSTRACT FROM PUBLISHER]

We propose the design of a dual-anode electron gun, so named due to the presence of an additional electrode, namely, the control anode in the vicinity of the cathode in addition to the ion-barrier anode and the ground anode. We found the potential of the control anode to play an important role in enhancing the life of a space traveling-wave tube. By a telemetric command, one could control the control anode potential with a view to enhancing the cathode current that would otherwise deteriorate with the progress of time. Further, due care was taken in the thermal design by providing a heat shielding of the cathode of the proposed dual-anode gun to ensure that the cathode, which is operated at a lower temperature for a longer cathode life, does not further suffer a decrease in temperatures due to heat dissipation. Furthermore, to compensate for the deterioration of the cathode current with the progress of time, we propose the application of a nominal change in the control anode potential by a telemetric command. The electrostatic and thermal simulations of the proposed dual-anode gun were carried out by the commercial simulation codes EGUN and ANSYS, respectively. The paper presents the effect of heat shield thickness and material property on the cathode temperature as well as the effect of the structural deformation caused by the axial and radial expansion of the cathode on electron beam optics, a demountable dual-anode gun was set up for validating the cathode temperature against simulation. [ABSTRACT FROM PUBLISHER]

This paper demonstrates the operating characteristics of an axis-encircling large-orbit electron gun and a corresponding permanent magnet system of a W-band peniotron. The practical novel large-orbit electron beam with axial velocity spread of 5.17%, transverse velocity spread of 1.28%, guiding center deviation ratio 10.7%, and high velocity ratio 2 is designed. The main advantages of such a peniotron in the large-orbit configuration with a permanent magnet system are its compact size, reduced operational gap, and lower cost. Critical characteristics, such as acceleration voltage and the relative axial position of the magnetic system and electrode system have also been well examined and it is shown that a careful control of them is important for the device performance. [ABSTRACT FROM AUTHOR]

The generation of axis-encircling large-orbit electron beam using magnetron type injection gun is studied theoretically and numerically. Since the cathode emission band is parallel not only to the system's axis but also to the magnetic field lines, it eliminates the initial angular momentum spread at the cathode and helps to reduce the velocity spread greatly. Through numerical simulation by EGUN, a large-orbit electron beam with axial velocity spread of 1.82%, guiding center deviation of 6.1%, and velocity ratio of 1.67 is obtained. By adjusting the voltages of the two anodes, the beam quality can be modulated easily to meet the specific requirements of different gyro-devices. The scheme provides a new electron gun candidate for the large-orbit devices. [ABSTRACT FROM AUTHOR]

Requirements and challenges for high-brightness electron injectors operating in a high-repetition-rate X-ray FEL are described. Schemes presently under development or study are reviewed, and their advantages and limitations are compared. Beam dynamics and engineering/technological aspects are addressed, with a particular emphasis placed on how the high-repetition-rate requirement impacts the choice of cathodes and of gun/accelerator technologies, and on how those choices consequently impact beam dynamics. [ABSTRACT FROM AUTHOR]

Design of an axis-encircling large-orbit electron gun for a terahertz harmonic gyrotron is presented. Based on a canonical momentum conservation theory, analytical calculations are carried out to determine critical electron gun parameters. This procedure provides a fast optimization process to determine electron gun parameters. The calculated results are compared with electron gun code. [ABSTRACT FROM AUTHOR]

Numerical studies were undertaken to elucidate the field ripple behavior on the magnetic axis, γ ax , and on the last closed magnetic surface, γ lc , as a function of the transverse magnetic field B z in helical magnetic system models with l = 2,3 polarity. The models are similar to some heliotrons/torsatrons now in operation such as LHD and U-3M that have no additional longitudinal magnetic field coils. In the investigated B z range, the existence of closed magnetic surface configuration in the regime B z = B zm with a minimal field ripple has been revealed. The main features of these configurations are the zero value of the minor radius of the magnetic axis (plane magnetic axis) in the l = 2 system and the minimal minor radius of the bifurcation line of inner separatrix of the maximum developed inner island structure in the l = 3 system. At B z range boundaries, the γ lc values begin to decrease and the γ ax values continue to increase. [ABSTRACT FROM AUTHOR]

Describes the design of diode electron gun. Restriction in the beam parameter space; Distribution of the cathode magnetic field; Average values of beam parameters.

Studies the change in oscillating characteristics of a tunable gyrotron with the change of cavity wall material, all other dimensions and operating parameters remaining constant. Basis of the gyrotron on a two-electrode electron gun consisting of a field-emission, field-immersed cold cathode; Impact of the change in cavity construction material on the production of the electron beam.

Describes the design, manufacture and testing of a 50 A electron gun with a beam power of 4.5 MW for a 1.5 MW, 140 GHz coaxial gyrotron. Measurement of the beam properties using scaled-down parameters; Experimental values of the velocity ratio.

The design and the experimental results of a 120 GHz, TE[sub 15, 2, 1] mode gyrotron are presented. The determination of an output mode and the designs of a cavity and an electron gun are described in some detail. In the initial pulse test on the tube, the oscillation mode map and the output mode pattern experimentally obtained showed that the designed TE[sub 15, 2, 1] cavity mode was successfully excited. The highest output power was 610kW, corresponding to an efficiency of 306%. This was achieved at a beam voltage of 831 kV and a beam current of 24A. The peak efficiency was 322%, achieved at 831 kV and 189 A, resulting in an output power of 506 kW. The purity of the output mode was also measured by a k-spectrometer. The output mode spectrum included several parasitic modes in addition to the main TE[sub 1 5, 2] mode. [ABSTRACT FROM AUTHOR]

The results of a numerical simulation and experimental study of magnetron-injection guns forming intense helical electron beams for powerful gyrotrons are compared. Beams of three types—laminar beams, beams with regularly intersecting trajectories and beams with irregularly intersecting (mixed) trajectories are studied. The numerical simulation is performed taking into account the influence of the space charge field. The experimental beam characteristics are measured by the retarding field method. The experimental data agree satisfactorily with the results of the theory if the temperature deformation of the electrode systems is taken into account. It is shown that the best velocity distribution characteristics are realized for guns forming laminar beams and boundary beams (intermediate topology between beams with regularly intersecting trajectories and laminar beams). [ABSTRACT FROM AUTHOR]

Results of a long-pulse, cyclotron autoresonance maser (CARM) oscillator experiment are reported. A Stanford accelerator (SLAC 5045) klystron gun produced a 1 µs electron beam at 250-300 kV and 10-25 A at a repetition rate of up to 4 Hz. A beam α ≡ β[sub ⊥/β[sub 1], variable from 0 to 1, was produced on this electron beam with a wiggler magnetic field near guide field resonance. The experiments were carried out with two different Bragg reflection resonators designed for the TE[sub 11] mode. Using the first resonator, many harmonic gyrotron modes were observed in the 28-40GHz frequency range in the TE[sub 21] and TE[sub 01] modes and, for the first time, a second harmonic upshifted (CARM) TE[sub 11] mode at 74.5 GHz. Using the second resonator, fundamental CARM operation was observed for many parameter settings, and for frequencies ranging from 29 to 32 GHz. Output powers ranged from ∼0.1 kW to 100 kW, resulting in efficiencies of 0.1% to 2%. Identification of CARM and gyrotron modes is made by comparison of measured frequencies with dispersion theory and measurement of the farfield radiation pattern. Comparison with theory indicates that the device efficiency is reduced by finite spread in the axial electron beam momentum. [ABSTRACT FROM AUTHOR]

Proposes a non-adiabatic electron gun for gyrotron application. Advantages over used electrons guns of the magnetron type; Reduction of influence of space charge and the roughness of the emitter surface on the beam properties; Generation of a hollow electron beam with a low velocity spread.

The operating characteristics of high power relativistic magnetron injection guns (MIGs) are studied theoretically. A set of analytic expressions based on adiabatic approximations for a coaxial diode is used to identify feasible design regions in parameter space. Particle simulations are then used to optimize particular designs. Results for a 1 μs, 100MW, 500kV MIG, designed for an X-band gyroklystron, are critically examined. [ABSTRACT FROM AUTHOR]

First-order magnetron injection gun (MIG) design trade-off equations are given for use in obtaining an adequate starting point for gun simulations on the computer. These equations are based on conservation of angular momentum and adiabatic electron flow and they contain relativistic corrections for high voltage design. The equations provide considerable insight into the basic physical processes by which gyro-cyclotron beams are formed and controlled. They have also proven very useful in design feasibility studies of high power MIGs. Two examples of MIG designs are given in which these equations were utilized. [ABSTRACT FROM AUTHOR]

The results of tests on a Varian 140GHz CW gyrotron are presented. In initial pulse tests on the tube, an output power of 100 kW was achieved at 28% efficiency in the desired TE[sup 0][sub 0][sub 31] cavity mode. Under CW operating conditions, the tube achieved an output power level of 75 kW at 31% efficiency. This is the highest CW power level ever obtained at a frequency above 100GHz in a microwave tube. During CW tests, measurements of the ohmic losses in the interaction circuit were made and the temperature of the output window was monitored. These measurements, as well as those of the output power and efficiency, are presented and compared with theoretical predictions. Future experimental 140GHz tubes will employ alternate electron gun and interaction cavity designs. The benefits of these design changes are discussed in the context of achieving higher output power levels and efficiencies. [ABSTRACT FROM AUTHOR]

A synthesis method is used in the design of the electron gun for a 35 GHz gyrotron to be built at the Institute for Space Research (INPE). The synthesized equipotentials are obtained by integrating a system of equations, whose boundary conditions are defined by the analytically extended self-consistent equations describing the laminar flow. For laminar beams, with no-intersecting electron paths, spacecharge effects cancel out and, when compared to beams with intersecting trajectories, the velocity spread is greatly reduced. A systematic procedure for the design of axisymmetric electro-optical systems is presented, which allows the derivation of the synthesis parameters from the required characteristics of the electron gun. In the present paper, the synthesized gun is able to deliver a 215 kW electron beam with a calculated velocity spread of ∼ 1%. [ABSTRACT FROM AUTHOR]

We report an application of the Harker electode synthesis technique to the design of a high power MIG-type gun with a laminar flow beam. The beam is represented by the temperature-limited flow equations of Manuilov and Tsimring. This technique enables the design of temperature-limited guns in the moderate to high space-charge regime. We find this regime is well-suited to the formation of high power, low velocity spread beams. The gun design reported here has been developed for the NRL 94 GHz Megawatt Gyrotron. The beam power is 4 MW and the estimated axial velocity spread is 6% for v[sub ⊥]/v??? = 1·5. Space-charge fields depress the cathode electric field by approximately 45%. This gun demonstrates the feasibility of obtaining multi-anode designs by the synthesis method. The design procedure makes use of an electron beam simulation code such as the Herrmannsfeldt code. [ABSTRACT FROM AUTHOR]

A variable-mesh finite-element electron gun design code has been developed to simulate hollow beams produced by magnetron injection guns. Very accurate solutions of the self-consistent space charge forces are obtained by using a computational mesh, distorted in a way which allows a high density of mesh points within the hollow beam. A generalized ‘hybrid model’ for cathode emission has been incorporated which combines temperature-limited and space-charge-limited emission in a way justified from empirical and physical arguments. Beam characteristics of a magnetron injection gun arc presented as the transition from temperature-limited to space-charge-limited operation is made. Limited comparisons with experimental results are presented. [ABSTRACT FROM AUTHOR]

The paper describes the design and testing of a new type of electron gun suitable for use in either a gyrotron oscillator or amplifier tube. The gun is space charge limited to reduce the noise produced by the usual temperature limited magnetron injection guns. It has been designed so that the cathode size is independent of the final beam diameter so the gun is as large as practical considerations dictate irrespective of the operating frequency and final beam size. It is controlled by a low voltage grid and produces a hollow beam having uniform longitudinal and transverse energies. [ABSTRACT FROM AUTHOR]

A new synthesis method is described to produce a first design for axially-symmteric electron guns of high-current density. Starting from a specification based on a desired beam cross section, a convergent gun can be synthesized by amalgamating segments of electron flow from conical cathodes. Focusing electrodes are then derived using Pierre's methods. Synthesis thus forms the basis for refinement of the design by subsequent analysis and modification. Analysis shows that the beam profile is largely independent of cathode shape, but changes in cathode shape have a large effect on beam-current distribution. [ABSTRACT FROM AUTHOR]

Integration of the equations of motion of an electron by various numerical techniques is discussed in the context of computer simulations of electron guns. Methods considered are of the Runge-Kutta, predictor-corrector and Taylor series type. All employ an automatically adjusted time step which is controlled by the truncation error of the process. Various degrees of approximation are tested for each method and their relative efficiencies are considered for different specified tolerances. It is concluded that a set of Runge-Kutta formulae proposed by Fehlberg exhibits distinct advantages over other methods both in the required number of steps and computer time. Results are obtained with reference to a typical electron flow problem.
A number of computer programmes have been written in the past to model electron guns as used in devices ranging from electron microscopes and cathode-ray tubes to travelling-wave tubes and welding guns. An important part of such programmes is devoted to electron ray tracing which in general involves the solution of six non-linear equations of motion. [ABSTRACT FROM AUTHOR]

A method of comparing the basic performance of electron guns is described. The method is applied to some recently computed results on two versions of an electron gun which has a hairpin-filament cathode.
In an interesting and useful paper by Worster (1979 a), hereafter referred to as JW, computed results are given relating to two electron guns. When the performance of the guns was compared it was concluded that one gun was better than the other in all respects. However, in making the comparison the electron beam divergence was not taken into account. Although the method of comparison used in JW may, of course, be satisfactory for some purposes, the computed results in JW are comprehensive enough to provide information for an alternative method of comparison which includes beam divergence. Such an alternative method, described in this note, leads to different conclusions. [ABSTRACT FROM AUTHOR]

A method of computing the electrostatic potential and electron trajectories in electron guns the electron microscope type is described. Potentials are computed digitally using the successive over-relaxation technique, using two different mesh sizes. Electron trajectories are computed by a predictor-corrector method, using a bivariate interpolation formula for the electrostatic fields. Gun parameters of interest are readily obtained from the slope and displacement of trajectories as they leave the gun. Two electron guns with different grid shapes are investigated, and the grid shape is shown to influence the gun performance considerably. A re-entrant cone on the grid is shown to be deleterious in all respects, giving a source position of -12.1 mm compared with -5.1 mm, a source size of 20m compared with 8m, and a spherical aberration of 2.5 mm compared with 0.7 mm. [ABSTRACT FROM AUTHOR]

The focal properties and spherical aberration of a simple model of a field emission electron gun are investigated theoretically. Results are presented graphically. For a fixed source position, spherical aberration decreases as the grid aperture increases, but for a fixed image position, spherical aberration decreases as the grid aperture decreases, down to 01S, where S is the grid-anode distance. The results are almost independent of the anode aperture. [ABSTRACT FROM AUTHOR]

The design, advantages and applications of automatic electron diffractometers are discussed with reference to an improved system.
The power to measure electron scattering profiles from which loss electrons are virtually eliminated is the fundamental difference between the new instruments and traditional photography of electron diffraction patterns.
The basic limitations of the diffractometers are discussed.
A new treatment of the electron gun is given, based on angular distributions of current which prove to be Gaussian. The treatment is necessary when maximum signal intensity is required.
A number of improvements in electronic circuitry are described which include servostabilization of the gun emission; automatic two-dimensional scanning, and control of CRT display brightness or of xy writing rate in accordance with the intensity of the peaks.
The fields of application where the new diffractometers have advantages are when accurate, that is filtered, intensities must be determined, and when growing or changing specimens are studied. The applications are illustrated by the performance of the improved system and the first measurements of two-dimensionally scanned growing films are presented. It is shown that the speed of the new instrument, both in producing growths and in recording them, is important for thin film studies. The speed is itself an aid to consistency, to effective improvement in vacuum conditions, and extensive tests for consistency become practicable while parameters of the specimen growth may be systematically varied. [ABSTRACT FROM AUTHOR]

This paper describes an investigation of the performance of a medium perveance, high convergence electron gun, when operated at low voltages, so that thermal velocities were important in determining the beam conditions. The gun was designed following the work of Danielson et al. (1956), together with the use of an automatic trajectory tracer, with facilities for injection of space-charge information. The trajectory tracer predicts a fairly uniform cathode loading with some spherical aberration in the beam.
The gun was studied in a demountable system using a pin-hole analyser. The results confirm the predictions of the trajectory tracer and show that the results of Danielson et al. predict the beam diameter with reasonable accuracy. Some initial experiments on fitting a confining magnetic field to the gun region and the resultant beam profiles are described. [ABSTRACT FROM AUTHOR]