|M.Sc Thesis||Department of Physics|
|Supervisors:||Prof. Krasik Yakov|
|Prof. Emeritus Felsteiner Joshua|
This work is dedicated to the research of physical processes in ferroelectric cathodes, which could serve as a source for high current electron and ion beams under moderate electric fields (<105 V/cm). the processes of plasma generation and expansion were studied, by investigating the plasma parameters such as plasma electron and ion temperature, plasma density and electric fields inside the plasma.
The research is divided into two main subjects: the investigation of plasma parameters in a ferroelectric cathode with different methods of plasma generation (double pulse experiment), and the investigation of electric fields inside the plasma when a high frequency current-modulated electron beam is extracted from the plasma boundary (HF experiment). The main methods for plasma generation that were investigated in the first part were a sharp rise of the driving pulse, two successive driving pulses in a varying time delay between them and one driving pulse with varying duration (effectively it is two current pulses). Spatial and time resolved optical diagnostics and time resolved electrical diagnostics were used in both parts of the research to study the dynamics of the plasma parameters.
It was shown that the plasma density in a distance of up to 2mm from the cathode surface can reach the value of ne=1015 cm-3, depending on the plasma generation method, the ion temperature in all our experiments was approximately constant eV, and the electron temperature varied in time in the range of 1-10 eV. The plasma total charge was shown to be roughly equal to the surface charge of the ferroelectric cathode. In the second part, spatially varying fields of 0-1 kV/cm were found inside the plasma with spatial period of ~0.5mm.
Models were developed for both the double pulse experiment and the HF experiment, showing a satisfactory agreement with the experimental results.