Research of High Quality Electron Beam and THz-FEL Based on Numerical Simulation for Electromagnetic Fields Employing a 3-D FDTD Method

点击翻译按钮获取中文摘要

In this research work, we have investigated concerning high-brilliant electron beam and free electron laser (FEL) oscillation by means of numerical simulation employing Finite Difference Time Domain (FDTD) method as a Maxwell's equations solver. As a first step, beam characteristics produced by a thernionic RF gun was studied by the FDTD simulation. Results of the work have improved design work of the actual RF gun. In the 2nd year, the beam optics for the bunch compression has been optimized by using results of the FDTD simulation, then it was found that there would be a possibility of producing very short electron bunch length around 70 femto-second. In addition, properties of coherent synchrotron radiation in Terahertz region were studied theoretically and a basic layout of light source accelerator has been designed. As the simulation code has been progressed, the beam dynamics in a bunch compressor was precisely evaluated by taking the effect of space charge into account. As the result the possibility of producing 100 femto-second beam bunch and its application for a new accelerator based coherent light source were pointed out.Meanwhile lasing of Smith-Purcell backward wave oscillator (BWO) FEL using a low energy DC beam was successfully simulated by using the FDTD code. It was found that the dc beam having the normalized emittance less than 1 mm mrad and the kinetic energy of less than 50 keV is required for Smith-Purcell BWO FEL. This source is concluded to be very promising and unique for future narrowband intense sub-Terahertz radiation.