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.

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.

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.

A novel self-injection relativistic backward wave oscillator

2021 ◽  
Author(s):  
Zhiqiang Fan ◽  
Jun Sun ◽  
Yibing Cao ◽  
Zhimin Song ◽  
Yanchao Shi ◽  
...  
Keyword(s):  
Electron Beam ◽  
Conversion Efficiency ◽  
Dominant Role ◽  
Wave Interaction ◽  
Operating Mode ◽  
Beam Current ◽  
Frequency Locking ◽  
Backward Wave Oscillator ◽  
Wave Oscillator ◽  
Backward Wave

Abstract A novel self-injection relativistic backward wave oscillator (RBWO) has been proposed. By introducing a self-injection path into the RBWO, a small portion of the energy in the reflector can be coupled to the upstream of the reflector, and then the formed electric field in the self-injection path region can pre-modulate the passing electron beam, to promote a frequency-locking oscillation of the electron beam. The pre-modulated electron beam can be expected to enhance the beam-wave interaction and suppress parasitic mode oscillation, which is beneficial for maintaining the dominant role of the operating mode. The proposed self-injection RBWO shows great potential for improving the conversion efficiency and pulse duration time. Through particle-in-cell simulation, a microwave with a power of 10.6 GW is obtained, when the beam voltage is 1.08 MeV, and the beam current is 18.6 kA. The conversion efficiency is 53%.

Annular Focused Electron/Ion Beams for Combining High Spatial Resolution with High Probe Current

2016 ◽  
Vol 22 (5) ◽  
pp. 948-954 ◽  
Author(s):  
Anjam Khursheed ◽  
Wei Kean Ang
Keyword(s):  
Electron Beam ◽  
Ion Beam ◽  
Current Mode ◽  
Spot Size ◽  
Beam Current ◽  
Ion Beams ◽  
Second Order ◽  
Primary Beam ◽  
Objective Lens ◽  
Probe Current

AbstractThis paper presents a proposal for reducing the final probe size of focused electron/ion beam columns that are operated in a high primary beam current mode where relatively large final apertures are used, typically required in applications such as electron beam lithography, focused ion beams, and electron beam spectroscopy. An annular aperture together with a lens corrector unit is used to replace the conventional final hole-aperture, creating an annular ring-shaped primary beam. The corrector unit is designed to eliminate the first- and second-order geometric aberrations of the objective lens, and for the same probe current, the final geometric aberration limited spot size is predicted to be around a factor of 50 times smaller than that of the corresponding conventional hole-aperture beam. Direct ray tracing simulation is used to illustrate how a three-stage core lens corrector can be used to eliminate the first- and second-order geometric aberrations of an electric Einzel objective lens.

Analytic Theory and PIC Simulation of Electron Beam Generation under High Voltage

2014 ◽  
Vol 960-961 ◽  
pp. 877-880
Author(s):  
Hai Zhang ◽  
Wei Guo Zhang ◽  
Yang Zhou Shao ◽  
Jian Guo Wang
Keyword(s):  
Electron Beam ◽  
Theoretical Models ◽  
Beam Current ◽  
Accurate Solution ◽  
Electron Gun ◽  
Beam Model ◽  
Pic Simulation ◽  
Electron Beam Generation ◽  
Beam Generation ◽  
Voltage Wave

The theoretical analysis and numerical simulation of electron beam generation in foil-less diode are presented. The theories of OAL, CL, and equilibrium beam model are briefly compared. All the theoretical models can give a relatively accurate solution of electron gun, and the equilibrium beam model is more appreciated. A PIC simulation tool UNIPIC is introduced and is used to analyze the behaviors of a foil-less diode. Under the conditions of 180 kV incident voltage wave and 2.5 T axial magnetic fields, we obtained the 250 kV, 1.5 kA output beam current which can be used in high power microwave generators.

scholarly journals Methodology for deriving the telescope focus function and its uncertainty for a heterodyne pulsed Doppler lidar

2020 ◽  
Author(s):  
Pyry Pentikäinen ◽  
Ewan James O'Connor ◽  
Antti Juhani Manninen ◽  
Pablo Ortiz-Amezcua
Keyword(s):  
Signal To Noise Ratio ◽  
Focal Length ◽  
Quantitative Information ◽  
Absolute Difference ◽  
Beam Diameter ◽  
Doppler Lidar ◽  
Signal To Noise ◽  
Uncertainty Estimates ◽  
Noise Ratio ◽  
Two Parameters

Abstract. Doppler lidars provide two measured parameters, radial velocity and signal-to-noise ratio, from which winds and turbulent properties are routinely derived. Attenuated backscatter, which gives quantitative information on aerosols, clouds, and precipitation in the atmosphere, can be used in conjunction with the winds and turbulent properties to create a sophisticated classification of the state of the atmospheric boundary layer. Calculating attenuated backscatter from the signal-to-noise ratio requires accurate knowledge of the telescope focus function, which is usually unavailable. Inaccurate assumptions of the telescope focus function can significantly deform attenuated backscatter profiles, even if the instrument is focused at infinity. Here, we present a methodology for deriving the telescope focus function using a co-located ceilometer for Halo Photonics Streamline and XR pulsed heterodyne Doppler lidars. The method derives two parameters of the telescope focus function, the effective beam diameter and the effective focal length of the telescope. Additionally, the method provides uncertainty estimates for the retrieved attenuated backscatter profile arising from uncertainties in deriving the telescope function, together with standard measurement uncertainties from the signal-to-noise ratio. The method is best suited for locations where the absolute difference in aerosol extinction at the ceilometer and Doppler lidar wavelengths is small.

Sign in / Sign up

Export Citation Format

Share Document