Electron Beam Spot Research Articles

Monte Carlo modeling of cathodoluminescence generation using electron energy loss curves

AbstractThis work demonstrates the validity of approximating cathodoluminescence generation throughout the electron interaction volume by the total electron energy loss profile. The energy loss profiles in multilayer specimens were accurately calculated using the Monte Carlo simulation CASINO. Resolution of cathodoluminescence images can be estimated from the electron beam spot diameter, the electron penetration range, and the minority carrier diffusion length.

Effect of target-emitted ions on the focal spot of an intense electron beam

Intense electron beams are known to produce surface plasmas when they strike typical target materials. The beam space charge then draws an ion current that can substantially affect the beam dynamics. We consider these effects for two intense-beam sources: (1) a needle-tip cathode immersed in a strong magnetic field, and (2) an induction accelerator-produced beam that is focused onto a field-free target. For the first case, the dominant effect is an electrostatic dipole instability between the beam and the ions. A sufficiently large magnetic field can keep the oscillation amplitude to a low level. For the second case, the dominant effect is that the focal length changes in time. For the “worst case” of space-charge-limited proton emission, the predicted effect is severe. The actual abundance and charge state of the target-plasma ions will need to be measured or inferred from planned experiments. Mitigation schemes also are discussed briefly.

Calculation of aberration of electron gun in color picture tubes

In a color picture tube, aberration is an important factor influencing the electron beam spot on the screen. This paper discusses a new method which is used to calculate the aberration of an electron gun in a CPT. In this method, electron trajectories are simulated directly in the cathode and the pre-focus lens. In the main lens, the asymptotic aberration is calculated to decide the size of the image. Some results of the calculation are shown in this paper.

Behaviour of polarized ammonia in an intense electron beam

Polarized target experiments with intense particle beams suffer from the depolarization effects due to radiation damage and beam heating. The local depolarization of the target material 14NH 3 at the electron beam spot has been investigated by hitting it with 1.2 GeV electrons. This beam has been delivered from the electron stretcher accelerator ELSA of the Bonn University. The polarized target consists of a 4 T superconducting magnet with a Helmholtz configuration and a 4He evaporation cryostat which operates at a temperature around 1 K. The heating of the target chips by the electron beam has been measured up to an intensity of 70 nA using a specific set-up of the nuclear magnetic resonance apparatus for the polarization measurements.

Welding characteristics of thin aluminium and aluminium alloy sheets in electron beam and resistance spot welding

Welding characteristics of thin aluminium and aluminium alloy sheets in electron beam and resistance spot welding

Cathodoluminescence dependence on electron beam diameter

Abstract An interesting behaviour of the cathodoluminescence (CL) intensity as a function of electron beam spot size was found, i.e. the relative CL intensity of both edge and defect emissions in all semiconducting materials studied here depends strongly upon the electron beam diameter; while the defect emission increases, the edge emission always decreases with increasing spot size.

A Novel Probe Size Measurement Method for a Fine Electron Beam

A novel electron beam (EB) spot size measurement method is proposed. In this method, EB spot size is obtained from the relationship between the width of the trenches in the reference sample and the intensity profile of backscattered electrons. Selective chemical etching of a GaAlAs/GaAs superlattice produces an ideal structure for the reference sample. Such superlattice is fabricated by metalorganic chemical vapor deposition and trench widths are verified by transmission electron microscopy. Using 0.6 µm deep and 8.5-65 nm wide trenches, nanometer-level EB spot sizes can be accurately measured.

Monte Carlo analysis of electron scattering in microstructure processes in the 0.2 μm region

Theoretical understanding of electron scattering phenomena is essential to the implementation of X-ray lithography. In this paper we theoretically investigate electron scattering effects in X-ray mask-making, by means of a subtractive process, in the 0.2 μm region. The results of Monte Carlo simulation are utilized in order to calculate radial absorbed energy distributions and resist development profiles with respect to some cases of practical interest. Relevant process variables are considered, such as electron-beam energy (10 to 30 keV) and spot sizes. The results show how, by choosing appropriate working conditions, high-resolution patterns can be obtained. Favourable process conditions are found at the low electron energy limit. However, it is shown that suitable electron-beam spot sizes are required in order to take fully advantage of the favourable properties of the scattering.

2. マルチフォーマットカメラの MTF(3. 解像特性, ディジタルラジオグラフィの画像評価)

Multi-format camera or laser printer is important device of digital radiography. We have investigated the characteristics of the resolution for multi-format camera. It is said that the diameter and the luminance distribution of electron beam spot of the cathode ray tube (CRT) are the fluctuating factors which depend upon cathode current. In this study, we have taken a photograph of slit image which is one pixel, and after generating the luminance distribution curve of that photograph. We assessed the characteristics of the spatial resolution by using modulation transfer function (MTF). Results are as follows : 1) The brightness of CRT is controlled with cathode voltage and current. Deterioration of the resolution of CRT was caused by the expansion of the diameter of electron beam spot, which is induced by increment of the cathode current. 2) The contrast is adjusted with amplification of image signals. The maximum value of line spread function (LSF) is variable with ajustment of the contrast, however the diameter of electron beam spot is constant. The MTF was improved with increment of amplification of the image signals. But, this tendencies did not observed in CRT with low resolution. 3) The spatial resolution was inconstant on the locations of the CRT. Especially it was remarkably decreased in the peripheral area of the CRT.

Cathodoluminescence determination of the temperature rise in CdS under an electron beam spot

Abstract Different models for calculation of the temperature rise under an electron beam spot are reviewed. From a study of the cathodoluminescence (CL) shift as a function of temperature in CdS, a model for determining the temperature rise is proposed.

Mechanical effects of simulated plasma disruptions in Cr-Ni and Cr-Mn stainless steels

Plasma disruptions were simulated on three materials of interest for fusion purposes (a Cr-Mn low activation austenitic steel (AMCR 0033), an age-hardenable high-Mn stainless steel (VA 64) and the European 316 L fusion reference composition stainless steel) by single electron beam spots reaching a power of several KW on an area of few millimeters. The resulting damage on the resolidified region of AMCR-0033 and AISI 316 L samples was primarily constituted of solidification cracking, which however had little effect for the various combinations of process parameters, whereas in VA 64 samples extensive cracking occurred and an equiaxed dendrite structure formed with an embrittlement effect.

The advantages of a negative branch unstable resonator for use with free-electron lasers

The sensitivity to misalignment of an almost concentric stable resonator is compared to that of a negative branch confocal unstable resonator, with specific applications to free-electron lasers. The practicability of both resonators is examined for both grazing and normal incidence configurations within the constraints of maximum feasible length, finite angular stability of resonator mirrors, size (determined by cooling requirements) of laser beam on mirrors, and minimum electron beam spot size in the wiggler. For the examples presented, a numerical fast Fourier transform propagation code was used.

Some consequences of the shadow-mask CRT dot structure

The major CRT technology contender for multi-colour displays is the shadow-mask tube in one of its several variants. In each variant the phosphor screen structure is finely divided into a regular pattern of red, green and blue emitting phosphors with the expectation that this pattern of individual emission will visually fuse together to produce a clean image of the desired resultant colour. This paper discusses some of the consequences of the screen structure. This includes an analysis of the visual effects of the screen structure, including colour errors, symbol degradation and raster interference, leading to recommendations on the pitch of the screen structure in relation to the electron beam spot size. Recommendations are given on how to define and measure CRT ‘brightness’ and ‘line width’ parameters in the presence of the screen structure.

Measurement of the profile of finely focused electron beams in a scanning electron microscope

Electron beam spot diameters can be estimated either by resolution tests or by scanning the beam over a sharp edge and detecting the transmitted (or reflected) current. The sharp edge method can yield quantitative information about the beam profile, but the resolution is usually limited to tens of nanometres because of the difficulty of providing a suitably straight, opaque edge. A method is described whereby vertical etched silicon edges can be used to provide reliable and consistent measurements of beam diameters. The resolution limit depends on various factors described, but is usually better than 5 nm. The use of the method for manual or automatic astigmatism correction is also discussed.

Computer-Automated Linac Diagnostics and Data Acquisition

Computer interactive diagnostics have been developed and tested for measuring RF Linac electron beam position and emittance. Electron beam position is measured with ferrite-loaded stripline monitors. The measured signals are processed by an APPLE-II computer, displayed and updated (at the Linac repetition rate) on a monitor. Data to determine emittance is collected by measuring electron beam spot size (using the wire scanner technique) as the focal strength of a quadrupole triplet is adjusted around the focus at the scanner. The emittance is calculated by the APPLE-II making a hyperbolic curve fit to these data.

Influence of Bonding Wire on Electron Beam in Camera Tube with NEA Cold Cathode

When an NEA cathode is used in a camera tube, a disturbance of the electric field adjacent to the cathode, produced by the bonding wire needed to apply the bias voltage to the electron emitting layer, causes asymmetric aberrations and distortions in the electron beam spot focussed on the target. We have investigated the influence of the bonding wire on the focusing of the electron beam by computer simulation and have confirmed the results using an experimental camera tube. It was shown that a bonding wire positioned 0.2 mm from the center of the cathode caused aberration in the beam spot and gradual saturation of the landing curve; but when the wire was 1 mm from the cathode center, it had no influence on the beam spot and the landing curve.

A New 30 V" Beam-Index Color Cathode Ray Rube

The advantages of a beam-index color CRT over a conventional color CRT with a color selection mechanism have been discussed elsewhere.1-6 Despite these advantages, beam-index TV receivers have never been mass-produced, because of the complexity of the electronic circuits, difficulties with the index phosphor screening process and the stringent requirements for a narrow electron beam spot.

Correction of the distorted electron beam spot deflected by electrostatic crossed deflection fields

The aberration constants of a deflected electron beam passing through electrostatic crossed deflection fields due to four circular electrodes arranged round the optical axis are evaluated. The results show that the aberration of a distorted beam spot deflected by the crossed deflection fields is dominated by the second- and third-order astigmatisms, and aberration constants of their astigmatisms are much greater than those for a sequential deflection system with parallel plates. Various caustic patterns of the corrected deflection beam are graphically displayed by computer calculations.

A STUDY ON THE ELECTRON STIMULATED INTERACTIONS OF RESIDUAL OXYGEN CONTAINING GASES WITH Ni (001) SURFACE

When an electron beam bombards the residual oxygen-containing gases, such as H2O, CO2 and CO, these gaseous molecules will be dissociated as follows: H2O→Oad+H2,CO2→Oad+CO,CO→Oad+Cad, and the oxygen, and carbon atoms will coad-sorb on Ni(001) surface forming respectively many independent adsorption domains. The structure of them is either p(2×2) or c(2×2),depending upon the oxygen and carbon concentrations on the surface. The electron beam bombardment assists the nuclea-tion, growth, coalescence and ordering of these domains. When the oxygen and carbon atoms have occupied about one half of four-fold adsorption sites of the Ni(001) surface, the above- mentioned reactions will be in a state of equilibrium with following desorp-tion reactions: C*+Oad→CO,O*+Cad→CO, where * denotes the electron excited atoms, and the nickel oxide or carbide begins to nucleate. As the content of oxygen in the residual gases surpasses that of carbon, the nucleation of nickel oxide will be predominant. Once nickel oxide is growing, the desorp-tion reaction of carbon becomes effective and the already adsorbed carbon atoms will desorb or diffuse away and the oxygen concentration will increase quickly. As a consequence, the oxygen concentration inside the electron beam spots becomes much higher than that outside and the reverse is true for the carbon concentration. During the electron beam bombardment a change of carbon Auger peak shape, indicating diffrent bonding states between the carbon and substrate atoms, takes place. In the initial stage of adsorption the dissociative effect of an electron beam plays an important role, but during the growth of nickel oxide its thermal effect in enhancing diffusion becomes predominant.

Correction of the distorted electron beam spot deflected by electrostatic crossed deflection fields. (GB)

Correction of the distorted electron beam spot deflected by electrostatic crossed deflection fields. (GB)