Roles of metalions and plasma radiation in the interactions between a capillary discharge plasma and propellants

Summary form only given. Capillary discharge plasmas have been widely used as electrothermal chemical (ETC) launch devices, fusion reactor pellet injectors and high heat flux sources for material studies. In the electro thermal chemical launcher, the mechanisms of the plasma-propellant interaction are critical, with many factors being of potential importance. In particular, the role of plasma radiation is disputed. We will report the effect of three different metal ions and radiation in the capillary discharge plasma on the plasma-propellant interactions. Conventionally, a capillary initiated by a metal wire of about 2 mg and with an ablative liner material (e.g. polyethylene) is used as the plasma generator. The plasma is mainly composed of CO, H
⁺
, C, etc. The proportion of metal ions was negligible. We have designed a new capillary discharge plasma generator with different metal powders of higher weight as the initiators. The performance of the new generator is compared with the traditional one through an open-air test. A spectrometer and ICCD were used to measure the surface temperature of the propellants while a CCD was used to visualize the plasma jet. The combustion tests were conducted in a transparent closed vessel, making it possible to measure the plasma parameters at the propellant surface and observe the combustion process in the closed vessel. A fused silica window was placed between the plasma and propellants to ensure that the propellant could only be affected by plasma radiation. The burning rate and the p-t curve were obtained in the tests and the combustion products were analyzed by a mass spectrometer. Interrupted burning tests were also carried out to acquire information about the surface of the propellants at different burning stages. In order to perform accurate modeling of the plasma-propellant interaction, we have also developed a two-dimensional time-dependent capillary discharge model based on a modified ablation model. In our model, special attention is paid to the radial distribution of the capillary discharge plasma characteristics. To investigate the factors that influence the radial distribution, the radial transport of the ablation products is taken into consideration. Further, the competition between the ablation and deposition process with time in the capillary discharge is also studied. The aim of our study are to provide results that will assist the design of new propellants and new plasma generators for the ETC launcher.