Influence Of Electrode Structure On Plasma Characteristics Of Coaxial Gun Discharge

Due to the characteristics of high speed,high electron density and high energy density of coaxial gun discharge plasma,it has been widely concerned in many fields such as inertial confinement fusion,astrophysics and aerospace.With the further development of research,the applications in different fields put forward new requirements for the characteristics of plasma,which promotes the improvement of pulse power source,electrode structure,air apply mode and other aspects.In previous experiments,it is excessively concerned about how to improve the speed and density of plasma and how to improve the efficiency of energy utilization of coaxial gun discharge.However,the research on improving the plasma collimation is lack of attention.In this paper,by observing the evolution of plasma with time and measuring the optical signals and magnetic signals,the effects of different lengths and materials of external electrode on plasma characteristics of coaxial gun discharge and the collimation of plasma are studied.The main contents of this thesis are as follows:1.Through the magnetic signal measured by the magnetic probe and the discharge image taken by the high-speed camera,the influence of different lengths of external electrode on the plasma characteristics of coaxial gun is studied and the existence and effect of the virtual center electrode is confirmed in the experiment.The existence of the virtual central electrode prolongs the acceleration time of the plasma in the electrode and thus increases the velocity of the plasma.Meanwhile,due to the increased moving time of the plasma in the external electrode,the collision and recombination time between the plasma and the inner wall of electrode is increased.And thus the density of plasma decreases.The geometric constraint of external electrode is enhanced after prolonging the external electrode,which results in higher plasma collimation and longer transport distance.2.By measuring the photoelectric signals and capturing the discharge images,the effects of different permeability of external electrode materials on the characteristics of coaxial gun discharge plasma are studied.It is found that when carbon steel material with higher permeability is used,the magnetic line of force is mainly concentrated on the inner wall of carbon steel cylinder.The radial constraint of the magnetic field on the plasma increases the density and velocity of plasma.According to the experimental results of the above two aspects,the following conclusion is obtained.The velocity and density of plasma can be enhanced by using long external electrode made of high permeability material.