scholarly journals MICROWAVE NOISE IN ACCELERATED ELECTRON STREAMS

1961 ◽  
Vol 39 (4) ◽  
pp. 579-587
Author(s):  
R. A. McFarlane
Keyword(s):  
Electron Beam ◽  
Space Charge ◽  
Theoretical Calculations ◽  
Electron Gun ◽  
Current Fluctuations ◽  
Beam Diameter ◽  
Poor Agreement ◽  
Potential Minimum ◽  
Noise Current ◽  
Microwave Noise

Measurements have been made of the noise current fluctuations on the electron beam from a space-charge limited diode electron gun, at 1,400 Mc/s, 4,250 Mc/s, and 9,520 Mc/s. Theories which do not consider the finite beam diameter and the multivelocity nature of the stream in the region of the potential minimum are in poor agreement with experiment. The measurements here reported and those of other workers are compared with the results of theoretical calculations in which these two effects are considered. Significant improvement in agreement with experiment is realized.

THE FINITE BEAM SPACE-CHARGE LIMITED DIODE AS A NOISE TRANSDUCER

1961 ◽  
Vol 39 (4) ◽  
pp. 568-578
Author(s):  
R. A. McFarlane
Keyword(s):  
Electron Beam ◽  
Space Charge ◽  
Shot Noise ◽  
Anode Voltage ◽  
Electron Gun ◽  
Beam Diameter ◽  
Noise Current ◽  
Space Charge Limited

A method is presented for calculating the noise properties of a cylindrical electron beam from a space-charge limited diode electron gun. The multivelocity character of the beam is considered and correction is made for finite beam diameter. The ratio of anode noise current to full shot noise is found to depend on ω1/2/V0a where ω is the frequency and V0a the anode voltage.

Study of Displacement Value of the Electron-Beam in the Electron Gun in Electron-Beam Furnace

2013 ◽  
Vol 652-654 ◽  
pp. 2391-2394
Author(s):  
Dong Hui Zhang ◽  
Chun Dong Liu ◽  
Jian Ming Liang ◽  
Chang Sheng Li
Keyword(s):  
Mathematical Model ◽  
Electron Beam ◽  
Space Charge ◽  
Molten Metal ◽  
Space Charge Effect ◽  
Electron Gun ◽  
Ideal Condition ◽  
Charge Effect ◽  
Beam Spot ◽  
The Ideal

The concept of maximal and minimal displacement value of the electron-beam was proposed considering the influence of space charge effect based on the displacement value of the electron-beam in the process of magnetic deflection scanning in the ideal condition. The deduction of mathematical model of the maximal and minimal displacement value was accomplished. The position of the beam spot can be more accurately controlled by the model, thus it is made sure that un-molten metal is bombarded by the beam spot accurately, which can increase the melt quality.

Examination of Solid Specimens in a High Resolution SEM Having a Condenser-Objective Lens

1974 ◽  
Vol 32 ◽  
pp. 314-315
Author(s):  
O. C. Wells ◽  
A. N. Broers
Keyword(s):  
Electron Beam ◽  
Conversion Efficiency ◽  
Signal To Noise Ratio ◽  
Beam Current ◽  
Electron Gun ◽  
Objective Lens ◽  
Beam Diameter ◽  
Signal To Noise ◽  
Signal Conversion ◽  
Incident Electron Beam

The theoretical resolution of the surface SEM is limited by four factors: A lower limit is imposed on the beam diameter by the aberrations of the focussing lens. The brightness of the electron gun determines, for a specified beam current, how closely this limit can be approached. The required beam current is determined by signal-to-noise ratio (SNR) considerations based on the required information content of the image and the signal conversion efficiency and the background conversion efficiency between the incident electron beam and the noise bottleneck of the system. With sone types of image contrast a limit is also imposed by the size of the region which is needed to contain the relevent electron/specimen interaction.

scholarly journals Study of the operating modes of the electrostatic lens of the welding electron gun

2021 ◽  
Vol 2077 (1) ◽  
pp. 012022
Author(s):  
E K Titarev ◽  
A L Goncharov ◽  
I A Kharitonov ◽  
A I Davletshin
Keyword(s):  
Mathematical Model ◽  
Electron Beam ◽  
Electron Beam Welding ◽  
Beam Current ◽  
Electron Gun ◽  
Beam Diameter ◽  
Operating Modes ◽  
Current Voltage ◽  
Different Temperatures ◽  
Current Voltage Characteristics

Abstract The paper presents the results of a study of the operating modes of a technological electron gun used in installations for electron beam welding. The design of an electron gun, which is part of the ELA-15I power complex, is considered, and the results of modeling the accelerating gap for a new design gun with an accelerating voltage of 120 kV are presented. The current-voltage characteristics of the gun operation were experimentally obtained at different temperatures of the main LaB6 cathode. For this, the beam current was recorded at different values of the control electrode potential. A mathematical model of the accelerating gap was implemented, which makes it possible to analyze the shape of the electron beam in the region of the first lens. Using a mathematical model, the shapes of the electron beam were calculated for various operating modes of the gun, and the characteristic transverse size of the beam in the crossover was determined. The beam diameter and the angle of convergence in the area of focusing the beam on the product were determined experimentally. Conclusions were made about the equality of the crossover diameters of the full-scale and mathematical models, as well as about the sufficient coincidence of the experimental and calculated volt-ampere characteristics. The design of the accelerating gap of the ELA-15 gun was optimized with an increase in the accelerating voltage from 60 kV to 120 kV. The optimization results are shown for the original and modified design in the form of a comparison of the patterns of the distribution of the electrostatic field strength and a comparison of the current-voltage characteristics.

Experimental Research on Flight Trajectory of Edge Electron of the Electron-Beam in the Electron Gun of Furnace

2013 ◽  
Vol 652-654 ◽  
pp. 2388-2390
Author(s):  
Dong Hui Zhang ◽  
Chun Dong Liu ◽  
Landi Zhang ◽  
Zhan Ying Wang
Keyword(s):  
Experimental Data ◽  
Electron Beam ◽  
Experimental Research ◽  
Copper Foil ◽  
Pore Diameter ◽  
Measuring Method ◽  
Electron Gun ◽  
Beam Diameter ◽  
Flight Trajectory ◽  
Theoretical Results

An experimental measuring method of flight trajectory of edge electron of the electron-beam in the electron gun of furnace was designed. Intermediate perforated copper foil plate is placed in parallel at a key position within the electron gun. The theoretical beam diameter of the electron beam which is reaching the position can be obtained through measuring pore diameter in copper foil plate left after being broke down by the electron-beam, so experimental data got can be verified the theoretical results.

Application of Improved Voltage Compensation in the SEM to Imaging of Organic Materials

1973 ◽  
Vol 31 ◽  
pp. 444-445
Author(s):  
P.J. Killingworth ◽  
M. Warren
Keyword(s):  
Electron Beam ◽  
Organic Materials ◽  
Operating Parameters ◽  
Low Density ◽  
Beam Diameter ◽  
Incident Electron Beam ◽  
Specimen Material ◽  
Voltage Compensation ◽  
Selection Of ◽  
Scanning Electron

Ultimate resolution in the scanning electron microscope is determined not only by the diameter of the incident electron beam, but by interaction of that beam with the specimen material. Generally, while minimum beam diameter diminishes with increasing voltage, due to the reduced effect of aberration component and magnetic interference, the excited volume within the sample increases with electron energy. Thus, for any given material and imaging signal, there is an optimum volt age to achieve best resolution.In the case of organic materials, which are in general of low density and electric ally non-conducting; and may in addition be susceptible to radiation and heat damage, the selection of correct operating parameters is extremely critical and is achiev ed by interative adjustment.

Reduction of Specimen Contamination in Electron-Beam Instruments

1976 ◽  
Vol 34 ◽  
pp. 576-577
Author(s):  
G. Lehmpfuhl ◽  
P. J. Smith
Keyword(s):  
Electron Beam ◽  
Cold Trap ◽  
Beam Diameter ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Hydrocarbon Molecules ◽  
Electron Microscopes ◽  
Combination Of Methods ◽  
Convergent Beam ◽  
Very High

Specimens being observed with electron-beam instruments are subject to contamination, which is due to polymerization of hydrocarbon molecules by the beam. This effect becomes more important as the size of the beam is reduced. In convergent-beam studies with a beam diameter of 100 Å, contamination was observed to grow on samples at very high rates. Within a few seconds needles began forming under the beam on both the top and the underside of the sample, at growth rates of 400-500 Å/s, severely limiting the time available for observation. Such contamination could cause serious difficulty in examining a sample with the new scanning transmission electron microscopes, in which the beam is focused to a few angstroms.We have been able to reduce the rate of contamination buildup by a combination of methods: placing an anticontamination cold trap in the sample region, preheating the sample before observation, and irradiating the sample with a large beam before observing it with a small beam.

New type electron gun with electrostatic and electromagnetic lenses

1978 ◽  
Vol 36 (1) ◽  
pp. 62-63
Author(s):  
T. Ichinokawa ◽  
H. Maeda
Keyword(s):  
Electron Microscopy ◽  
Electron Beam ◽  
Optimum Condition ◽  
Bias Voltage ◽  
Electron Gun ◽  
Charge Effect ◽  
Micro Fabrication ◽  
Maximum Brightness ◽  
New Type ◽  
The Ideal

I. IntroductionThermionic electron gun with the Wehnelt grid is popularly used in the electron microscopy and electron beam micro-fabrication. It is well known that this gun could get the ideal brightness caluculated from the Lengumier and Richardson equations under the optimum condition. However, the design and ajustment to the optimum condition is not so easy. The gun has following properties with respect to the Wehnelt bias; (1) The maximum brightness is got only in the optimum bias. (2) In the larger bias than the optimum, the brightness decreases with increasing the bias voltage on account of the space charge effect. (3) In the smaller bias than the optimum, the brightness decreases with bias voltage on account of spreading of the cross over spot due to the aberrations of the electrostatic immersion lens.In the present experiment, a new type electron gun with the electrostatic and electromagnetic lens is designed, and its properties are examined experimentally.

Energy Distribution in Electron Beams

1972 ◽  
Vol 30 ◽  
pp. 568-569
Author(s):  
Tamotsu Ohno
Keyword(s):  
Electron Beam ◽  
Energy Distribution ◽  
Cross Section ◽  
Integral Curve ◽  
Electron Beams ◽  
Electron Gun ◽  
Angular Divergence ◽  
Apparent Increase ◽  
Integral Width ◽  
The Cross

The energy distribution in an electron; beam from an electron gun provided with a biased Wehnelt cylinder was measured by a retarding potential analyser. All the measurements were carried out with a beam of small angular divergence (<3xl0-4 rad) to eliminate the apparent increase of energy width as pointed out by Ichinokawa.The cross section of the beam from a gun with a tungsten hairpin cathode varies as shown in Fig.1a with the bias voltage Vg. The central part of the beam was analysed. An example of the integral curve as well as the energy spectrum is shown in Fig.2. The integral width of the spectrum ΔEi varies with Vg as shown in Fig.1b The width ΔEi is smaller than the Maxwellian width near the cut-off. As |Vg| is decreased, ΔEi increases beyond the Maxwellian width, reaches a maximum and then decreases. Note that the cross section of the beam enlarges with decreasing |Vg|.

A New High Intensity Grid Cap for RCA-EMU-3 Electron Microscopes

1968 ◽  
Vol 26 ◽  
pp. 316-317
Author(s):  
George Christov ◽  
Bolivar J. Lloyd
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
High Voltage ◽  
High Intensity ◽  
Electron Gun ◽  
Tungsten Filament ◽  
Fluorescent Screen ◽  
Electron Microscopes ◽  
Pass Through ◽  
Ground Potential

A new high intensity grid cap has been designed for the RCA-EMU-3 electron microscope. Various parameters of the new grid cap were investigated to determine its characteristics. The increase in illumination produced provides ease of focusing on the fluorescent screen at magnifications from 1500 to 50,000 times using an accelerating voltage of 50 KV.The EMU-3 type electron gun assembly consists of a V-shaped tungsten filament for a cathode with a thin metal threaded cathode shield and an anode with a central aperture to permit the beam to course the length of the column. The cathode shield is negatively biased at a potential of several hundred volts with respect to the filament. The electron beam is formed by electrons emitted from the tip of the filament which pass through an aperture of 0.1 inch diameter in the cap and then it is accelerated by the negative high voltage through a 0.625 inch diameter aperture in the anode which is at ground potential.

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