Time-varying emission of electrons and its relevant EM phenomenon

• Main Author: Liu, Yangjie
• Other Authors: Ang Lay Kee, Ricky
• Format: Theses and Dissertations
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering::Mathematics and analysis
• Online Access: https://hdl.handle.net/10356/60623
• Institution: Nanyang Technological University

The main-body of this thesis or dissertation attempts to consider two aspects of electron emission scenario: one on increasing electron emission counts by injecting time-varying electron flow under short-pulse condition and the other on induced electromagnetic fields by electron flow within space. (1). Time-varying profile of injection electron flow from cathode side offers possibilities to transcend conventional time-uniform space-charge limit under short-pulse condition, as pointed out by \'A. Valfells {\itshape et al.} in {\itshape Phys. Plasmas} \textbf{9}, 2377(2002) and monotonously increasing functions of time-profile could be such a case. A laser-excited emission mechanism is computationally introduced here, illustrating that for ultrahigh laser field space charge effect becomes notable and DC electric field can be an efficient parameter to tune the space-charge limit. Particle-In-Cell(PIC) simulation is also performed to demonstrate agreement with theoretical analysis. (2). Another phenomenon related to electron flow is that evanescent wave produced by mechanical motion of an electron bunch can be accumulated under certain artificial circumstances, inhomogeneous or anisotropic space (realizable via metamaterial) such as Maxwell's fisheye structure. Other than the former electrostatics problem, electrodynamics has to be formulated to derive solution in frequency domain from vector Helmholtz equation. Dyadic Green's function and method of scattering superposition are chosen to give analytic electromagnetic field solution for transition radiation from Maxwell's fisheye. This calculation may pave the way to investigate novel scheme of brand band light source, transferring from electron's kinetics to radiation.