High-power Microwave Source Pulse Shortening Phenomenon Of Particle Simulation Mechanism

In recently several years , in order to satisfy some practical demands for the HPM technology , which is to make HPM sources export high energy microwave efficiently , the researchers change the investigation keystone from pursuing merely the high output peak power to lengthening the output microwave pulse width . However , by studying we find that the means faces the pulse shortening phenomenon . To resolve this problem , we must discuss deeply the phenomenon universally existing in the HPM sources , and find out the origin of the phenomenon . The research on the phenomenon was done in 1980's . Up to the present time , some achievements have been obtained , but the deep meaning of the physical mechanism hasn't been understood , and has been still groped after ; The research on the problem is still in blank phase, at home .The main production and innovation of the dissertation are listed as follows:1. Various factors resulting in the pulse shortening phenomenon and the development of the research on the phenomenon are summarized . The material research object is selected and the research project is carried out.2. The pulse shortening mechanism in RBWOs is studied .We comparatively roundly summarize and analyze the various mechanisms causing the pulse shortening in RBWOs . With these mechanisms , some factors causing the phenomenon are separately simulated by the MAGIC code for the first time . According to the simulated results , we discuss the influence of some macroscopical parameters on the output microwave pulse width , quest for the means of lengthening the pulse width , and provide a optimization basis for the design of the devices with long pulse and high energy microwave output .The contents of the simulations include : the influence of the ionization of neutral gas in the tube by the relativistic electron beam , the explosive emission in the inner surface of RBWOs , the changes of the electron beam emission radii resulting from the cathode plasma expansion and the fluctuation of the relativistic electron beam on the pulse width and output power .According to the discussion about the mechanisms and the simulation results , we find the main causes limiting the RBWO output pulse width and energy , bring forward the practical methods of weakening the influence of the phenomenon , lengthening pulse width and enhancing output energy .We offer the reference to study the phenomenon more deeply in theory , and provide a common way to study the phenomena in other HPM sources by means of the particle-in-cell method .