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A general phenomenon that the edge localized modes (ELMs) can be effectively mitigated with the enhanced coherent modes (CMs) has been observed on EAST. For this phenomenon, the experimental statistical analysis and electromagnetic (EM) simulations have been performed. There is a threshold value of the CM intensity in the experiments, which plays a key role in ELMs mitigation. Through the ELITE and conventional BOUT++ analysis, we found that when the insignificant ELM and enhanced CM co-exist, the pedestal is located in unstable Pâ€"B region and the ELM is relatively large. The simulation results only using the experimental profiles without considering other factors cannot reproduce the no significant ELM experiment. The CM enhances the edge turbulence, which can control ELMs. Therefore, the effects of CM are considered to explain the ELM mitigation. Modifying the three-field reduced model in BOUT++, an imposed perturbation is added as the CM. The simulation results indicate that: without the CM, the ELM size belongs to the relative large ELM region; after considering the CM, the ELM is mitigated and the energy loss is reduced by about 44.5%. Analysis shows that the CM enhances the three-wave nonlinear interactions in the pedestal and reduces the phase coherence time (PCT) between the pressure and potential, which lead the perturbation to tend to be ‘multiple-mode’ coupling. The competition of free energy between the multiple modes leads to the lack of obvious filament structures and the decreased energy loss. The above reveals that there is a competitive relationship between turbulence and ELMs, and the CM-enhanced turbulence can effectively reduce ELM energy loss. In addition, through the parameter scanning, there is a threshold of the amplitude A, which is consistent with the statistical results in the experiments. [ABSTRACT FROM AUTHOR]

Purpose: Liquid water being the major constituent of the human body, is of fundamental importance in radiobiological research. Hence, the knowledge of electron‐water interaction physics and particularly the secondary electron yield is essential. However, to date, only very little is known experimentally on the low energy electron interaction with liquid water because of certain practical limitations. The purpose of this study was to gain some useful information about electron emission from water using a Monte Carlo (MC) simulation technique that can numerically model electron transport trajectories in water. Methods: In this study, we have performed MC simulations of electron emission from liquid water in the primary energy range of 50 eV–30 keV by using two different codes, i.e., a classical trajectory MC (CMC) code developed in our laboratory and the Geant4‐DNA (G4DNA) code. The calculated secondary electron yield and electron backscattering coefficient are compared with experimental results wherever applicable to verify the validity of physical models for the electron‐water interaction. Results: The secondary electron yield vs. primary energy curves calculated using the two codes present the same generic curve shape as that of metals but in rather different absolute values. G4DNA underestimates the secondary electron yield due to the application of one step thermalization model by setting a cutoff energy at 10 eV so that the low energy losses due to phonon excitations are omitted. Our CMC code, using a full energy loss spectrum to model electron inelastic scattering, allows the simulation of individual phonon scattering events for very low energy losses down to 10 meV, which then enables the calculated secondary electron yields much closer to the experimental data and also gives quite reasonable energy distribution curve of secondary electrons. Conclusions: It is concluded that full dielectric function data at low energy loss values below 10 eV are recommended for modeling of low energy electrons in liquid water. [ABSTRACT FROM AUTHOR]

A systematic calculation of the backscattering factor in quantitative analysis by Auger electron spectroscopy is performed for the primary electron beam of energy from the threshold energy of inner-shell ionization and principal Auger transition and Auger electrons emitted from over 28 pure elements by using a Monte Carlo simulation method. The backscattering factors have described the experimental dependence of Auger electron intensity on primary energy and on incident angle for Si, Cu, Ag and W.

The full Penn algorithm (FPA) is adopted to derive the energy loss function for the calculation of differential inelastic mean free paths (IMFPs). The results of the energy distributions and the secondary electron emission yields for Al and Cu have agreed well with the experimental results.

A Monte Carlo (MC) simulation method is developed for calculating scanning electron microscopy (SEM) images of rough surfaces. This MC simulation method is useful for critical dimension (CD) metrology of nanostructures by CD-SEM, especially, for the linewidth measurement in the integrated circuit industry.