Comparison of Plastic Ablation Materials of Capillary Discharge

Abstract

Summary form only given. Fast capillary discharge is well known as a soft X-ray radiation source in the near vacuum environment. In addition, with a long discharge of ms duration in the open air it also has been used as a simple and efficient plasma source of electrothermal ignition of propellants. Since the plasma materials are mainly provided from the wall ablation inside capillary, electrical property changes with different liner materials depending on the ablation property. In order to achieve robust discharge operations capable of energy transfer over 100 kJ under a limited capillary geometry of 5 mm in diameter and 25-30 mm in length, various plastic liner materials were tested. The discharge experiments have been conducted around a few tens kA current and several ms duration in the open air. A Mach cone appearing at the capillary exit region was used for the estimation of plasma pressure. Direct pressure measurements also have been done. For the estimation of electrical properties, plasma resistivities were calculated using Saha equation of state, and compared with experimental results, where the model by Kurilenkov and Valuev (1984) was more appropriate for the circuit simulation of our result. Among various materials polyacetal showed best result for a high power and energy transfer. Though the model using a wall ablation through blackbody radiation explains well the discharge properties, the experimental result of different resistivity values corresponding to the same rising and falling current is not clearly understood. The possible reasons will be proposed and discussed.