Simulation of the ribbon-shaped electron beam of the diode electron-optical system of microwave devices
Complex numerical simulation of the ribbon-shaped electron beam, which is formed by the diode electron gun with magnetic field focusing was conducted. Analysis of the beam formation dynamics in longitudinal and cross-section as well as the results of calculation of the separate electron trajectories agree with experimental data, obtained previously by using of the method of electron beam diagnostics by means of transient radiation.
The problem of ribbon electron beam modeling
The three-dimensional model and algorithm of numeral calculation of electric field intensity is offered in a diode gun, and calculation of current density in the cross-sections of ribbon electron beam is carried out. The emission nonuniform, power and angular dispersion, electrons settling on electrodes are taken into account during calculations.
EFFECT OF SAMPLE PREPARATION ON WATER TREE RESISTANCE OF XLPE/SEBS BLENDS
The effects of an aromatic polymer, such as poly[styrene-b-(ethylene-co-butylene)b-styrene] (SEBS), and its preparation processes on water tree resistance, morphology, crystallinity, dielectric constant and dielectric loss tangent of crosslinked polyethylene (XLPE)/SEBS and XLPE/SEBS/ethylene vinyl acetate (EVA) blends were investigated. The XLPE/SEBS samples were characterized by means of differential scanning calorimetry, scanning electron microscopy, dielectric spectral analysis and the accelerated water treeing experiment. The results clearly showed that although SEBS was partially compatible with LDPE and it was dispersed evenly in XLPE matrix, the blends demonstrated excellent dielectric performances, such as dielectric constant and dissipation factor. The crystallinity of XLPE/SEBS blends was decreased with increase in SEBS content and it was further decreased with the addition of EVA. SEBS could effectively improve the water-tree resistance of XLPE and both SEBS and EVA were found to improve the water tree resistance of XLPE synergistically as expected. The differences in sample preparation processes could change the phase morphology and dielectric performance of the blends, and could also influence the dispersion of SEBS in XLPE matrix as well as the crystallinity of the blends. Different preparation processes led to different water tree resistance behaviours of the samples. The improvement of SEBS dispersion in XLPE matrix helped to improve the water tree resistance of XLPE.