The Computation of the Skirt in VP-SEM OR ESEM With Monte Carlo Simulations

1999 ◽  
Vol 5 (S2) ◽  
pp. 296-297
Author(s):  
Raynald Gauvin
Keyword(s):  
Monte Carlo ◽  
Electron Beam ◽  
Beam Energy ◽  
Single Scattering ◽  
Gas Composition ◽  
Monte Carlo Program ◽  
Elastic Collisions ◽  
Electron Trajectories ◽  
Two Factors ◽  
Working Distance

It is well known that the interaction of the electron beam with the gas in the VP-SEM or ESEM generate the so-called skirt as a result of the elastic collisions between the electrons and the molecules. Since the electrons in the skirt hit the specimen far away from the electron beam, they degrade the resolution of the analyses performed in the VPSEM or ESEM. However, the magnitude and the shape of the skirt are still a matter of controversy despite the fundamental importance of knowing these two factors. In this context, a Monte Carlo program has been developed to simulate the interaction of the electron beam with a gas as a function of the gas composition, gas pressure, electron beam energy and working distance (in reality, we should talk of the total distance traveled by the electron beam in the gas). This Monte Carlo program used a single scattering approach considering elastic collisions only since energy loss is negligible owing to the low density of the gas. 10 millions electron trajectories have been simulated for each conditions.

A Universal Equation for the Emission Range of X Rays from Bulk Specimens

2007 ◽  
Vol 13 (5) ◽  
pp. 354-357 ◽  
Author(s):  
Raynald Gauvin
Keyword(s):  
Electron Beam ◽  
Free Path ◽  
Beam Energy ◽  
Mean Free Path ◽  
Electron Beam Energy ◽  
X Rays ◽  
Bulk Materials ◽  
Universal Equation ◽  
Electron Trajectories ◽  
X Ray

The derivation of a universal equation to compute the range of emitted X rays is presented for homogeneous bulk materials. This equation is based on two fundamental assumptions: the φ(ρz) curve of X-ray generation is constant and the ratio of the emitted to the generated X-ray range is equal to the ratio of the emitted to the generated X-ray intensity. An excellent agreement is observed with data obtained from Monte Carlo simulations of 200,000 electron trajectories in C, Al, Cu, Ag, Au, and an Fe–B alloy with boron weight fractions equal to 0.01, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 0.99, performed with the electron beam energy varied from 1 to 30 keV in 1-keV steps. When the ratio of the generated X-ray range to the photon mean free path is much smaller than one, the emission X-ray range is equal to the generated X-ray range, but when this ratio is much greater than one, the emission X-ray range is constant and is given by the product of the effective photon mean free path multiplied by the sine of the take-off angle.

Parametrization of The Range of Electron At Low Energy (Eo < 10 Kev) Using The Casino Monte Carlo Program

1997 ◽  
Vol 3 (S2) ◽  
pp. 885-886 ◽  
Author(s):  
Pierre Hovington ◽  
Dominique Drouin ◽  
Raynald Gauvin ◽  
David C. Joy
Keyword(s):  
Monte Carlo ◽  
Atomic Number ◽  
Beam Energy ◽  
Energy Analysis ◽  
High Energy ◽  
Low Energy ◽  
Qualitative And Quantitative Analysis ◽  
Monte Carlo Program ◽  
Qualitative And Quantitative ◽  
Heterogeneous Samples

The range of electrons for a given beam energy and atomic number is one of the most valuable piece of information a microscopist must know before carrying out qualitative and quantitative analysis of heterogeneous samples in a scanning electron microscope (SEM). The frequently used parametrization of Kanaya & Okayama is only « valid » at high energy (EO > 10 keV). However, with the advent of Field Emission Gun SEM (FEGSEM) most of the effort has been toward low energy analysis where no parametrization is available yet. In this paper, the parametrization of the range of electrons at low energy as a function of atomic number and beam energy will be presented for both the backscattered and the internal electrons.The distribution of the maximum depth reached by 250 k electrons generated by the CASINO Monte Carlo program2 was used to compute the range for 10 elements at 20 energies.

scholarly journals Study of the Peak to Background (P/B) Method Behavior as a Function of Take-Off Angle, Tilt Angle, Particle Size, and Beam Energy

Scanning ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Seyed Mahmoud Bayazid ◽  
Yu Yuan ◽  
Raynald Gauvin
Keyword(s):  
Particle Size ◽  
Monte Carlo ◽  
Electron Beam ◽  
Monte Carlo Simulations ◽  
Tilt Angle ◽  
Beam Energy ◽  
Spherical Particles ◽  
Beam Position ◽  
Size Of Particles ◽  
Higher Sensitivity

Monte Carlo simulations were performed to investigate the behavior of the peak to background ratio (P/B) of particles on a substrate as a function of different variables such as take-off angle, tilt angle, particle size, and beam energy. The results showed that the P/B highly depends on the beam energy, the size of particles, and the composition of the substrates. Results showed that the rate of intensity reduction of the peak is less than the background for a high tilt angle (60 degrees), and thereby, the P/B increases at a high tilt angle. It was shown that by increasing the take-off angle, the P/B initially reduces and then reaches a plateau. Results showed that the P/B highly depends on the size of particles. Analyses showed that by moving the electron beam from the center to the side of the particle, the P/B increases. Finally, the spherical particles have higher sensitivity of the P/B to the beam position than the cubical particles.

scholarly journals Траекторный анализ в коллекторе с многоступенчатой рекуперацией энергии для прототипа гиротрона DEMO. Часть II. Тороидальное магнитное поле

2021 ◽  
Vol 91 (7) ◽  
pp. 1182
Author(s):  
О.И. Лукша ◽  
П.А. Трофимов ◽  
В.Н. Мануилов ◽  
М.Ю. Глявин
Keyword(s):  
Electron Beam ◽  
Beam Energy ◽  
Trajectory Analysis ◽  
Spatial Separation ◽  
Electron Velocity ◽  
Maximum Efficiency ◽  
Recovery Efficiency ◽  
Optimal Parameters ◽  
Electron Trajectories ◽  
Overall Efficiency

The results of modeling of a collector with four-stage recovery of the residual beam energy for the prototype gyrotron designed for the DEMO project are presented. For spatial separation of electrons with different energies, the azimuthal magnetic formed by a toroidal solenoid is used. An increase of the recovery efficiency and a decrease of the flow of electrons reflected from the collector are achieved by reducing the spread of radial position of the leading centers of electron trajectories at the optimal parameters of the toroidal solenoid, as well as by using a sectioned electron beam. Trajectory analysis of the spent beam with electron velocity and coordinate distributions close to those obtained in experiments with high-power gyrotrons showed the possibility of achieving an overall efficiency of the gyrotron higher than 80 %, which is close to the maximum efficiency at ideal separation of electron beam fractions with different energies.

Monte-Carlo Simulation of the Charge-Deposition Distribution for Electron-Beam Energy Determinations

2008 ◽  
Vol 53 (9(6)) ◽  
pp. 3754-3757 ◽  
Author(s):  
Youngmi Gil ◽  
Youngdo Oh ◽  
Sanghoon Kim ◽  
Sungik Moon ◽  
Moohyun Cho ◽  
...  
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Electron Beam ◽  
Beam Energy ◽  
Electron Beam Energy ◽  
Charge Deposition

Monte Carlo study on effective source to surface distance for electron beams from a mobile dedicated IORT accelerator

2016 ◽  
Vol 16 (1) ◽  
pp. 29-37 ◽  
Author(s):  
Mir Rashid Hosseini Aghdam ◽  
Hamid Reza Baghani ◽  
Seyed Rabi Mahdavi ◽  
Seyed Mahmoud Reza Aghamiri ◽  
Mohammad Esmail Akbari
Keyword(s):  
Monte Carlo ◽  
Electron Beam ◽  
Beam Energy ◽  
Intraoperative Radiotherapy ◽  
Monte Carlo Study ◽  
Electron Beam Energy ◽  
Surface Distance ◽  
Mc Simulation ◽  
Mean Differences ◽  
Effective Source

AbstractPurposeThe effective source to surface distance (SSDeff) for different combinations of energy/applicator size of the electron beam produced by the light intraoperative accelerator, a mobile dedicated intraoperative radiotherapy accelerator, has been calculated in this study.MethodsBoth ionometric dosimetry and Monte Carlo (MC) simulation were followed to obtain the SSDeff for different combinations of electron energy/applicator size. Simulations were performed using Monte Carlo Nuclear Particles (MCNP) MC code. Measurements were performed by Advance Markus chamber and inside a polymethyl methacrylate slab phantom. Inverse square law method was employed to determine the SSDeff from acquired dosimetry data.ResultWith increasing the applicator diameter at a given energy, SSDeff is also increased. The same result is obtained with increasing the electron beam energy for a given applicator size. The results of MC-based SSDeff for 10 cm diameter reference applicator at different energies were in a good accordance with those obtained by ionometric dosimetry. The maximum and mean differences between the results were 1·1 and 0·6%, respectively.ConclusionsThe results of this study showed that SSDeff of intraoperative electron beam is highly dependent on the applicator size and is a mild function of electron beam energy. These facts are in accordance with those reported for conventional electron beam. The good agreement between the results of MC simulation and ionometric dosimetry confirms the application of MCNP code in modelling of intraoperative electron beam and obtaining the intended parameters.

Monte Carlo Modelling of Secondary Electron Yield from Rough Surfaces

1990 ◽  
Vol 48 (1) ◽  
pp. 422-423
Author(s):  
John C. Russ
Keyword(s):  
Monte Carlo ◽  
Energy Loss ◽  
Secondary Electron ◽  
Secondary Electron Emission ◽  
Analytical Calculation ◽  
Mean Free Path ◽  
Single Scattering ◽  
High Energy ◽  
Secondary Electron Yield ◽  
Electron Yield

Monte-Carlo programs are well recognized for their ability to model electron beam interactions with samples, and to incorporate boundary conditions such as compositional or surface variations which are difficult to handle analytically. This success has been especially powerful for modelling X-ray emission and the backscattering of high energy electrons. Secondary electron emission has proven to be somewhat more difficult, since the diffusion of the generated secondaries to the surface is strongly geometry dependent, and requires analytical calculations as well as material parameters. Modelling of secondary electron yield within a Monte-Carlo framework has been done using multiple scattering programs, but is not readily adapted to the moderately complex geometries associated with samples such as microelectronic devices, etc.This paper reports results using a different approach in which simplifying assumptions are made to permit direct and easy estimation of the secondary electron signal from samples of arbitrary complexity. The single-scattering program which performs the basic Monte-Carlo simulation (and is also used for backscattered electron and EBIC simulation) allows multiple regions to be defined within the sample, each with boundaries formed by a polygon of any number of sides. Each region may be given any elemental composition in atomic percent. In addition to the regions comprising the primary structure of the sample, a series of thin regions are defined along the surface(s) in which the total energy loss of the primary electrons is summed. This energy loss is assumed to be proportional to the generated secondary electron signal which would be emitted from the sample. The only adjustable variable is the thickness of the region, which plays the same role as the mean free path of the secondary electrons in an analytical calculation. This is treated as an empirical factor, similar in many respects to the λ and ε parameters in the Joy model.

Sign in / Sign up

Export Citation Format

Share Document