Ph.D Thesis


Ph.D StudentKonstantin Chirko
SubjectHigh Power Electron Beam Generation from Ferroelectric
Plasma Sources
DepartmentDepartment of Physics
Supervisors Full Professors Krasik Yakov
Professor Emeritus Felsteiner Joshua


Abstract

This research is aimed at the investigation of time and space dependent behavior of the plasma produced in ferroelectric plasma sources (FPS). These FPSs serve as sources of intense electron beams. The main diagnostic method is time- and space- resolved emission spectroscopy.

Two modes of plasma formation were investigated. The first mode was the plasma    formation on the surface of ferroelectric resulting from application of high-voltage driving   pulse. The parameters of the plasma layer were investigated in details. A method allowing significant increase in the density and uniformity of the plasma was suggested and investigated. The density of the plasma reaches up to 1015 cm-3 that corresponds to electron current density emitted from the plasma boundary up to 103 A/cm2. A mechanism controlling the density of the surface plasma was studied. This mechanism relates to the surface density of bound polarization charges, which in turn depends on the driving electric field amplitude and ferroelectric sample properties.

The second mode of the FPS operation was dense surface plasma generation during self-sustaining high-frequency current oscillations. These oscillations are due to the coupling of the plasma with the external circuit. The plasma has a spatially periodic quasi-stable structure providing emission of the electron beam with duration of 10-5 - 10-4 ms. By polarization spectroscopy, an anisotropic electric field and a directed electron flow in the plasma were found. A model was suggested which considers fast periodic appearance of anomalous resistivity in the FPS plasma which controls the current amplitude during the high-frequency oscillations.