Arc Motion and Electrode Erosion in High-Current Rail Spark Gaps

Large capacitive energy storage systems are being implemented for powerful laser systems, electromagnetic launchers, and other pulsed power systems. Such megajoule-class modularized capacitor banks individually require precise reliable cost-effective robust closing switches for synchronous operation. The closing switch, under intense mechanical and thermal shocks imposed by a high peak current, must tolerate high charge transfer and provide long service life. The most popular closing switches up to date are spark gaps due to its relatively simple design, robustness, easy field maintenance, and repair. Spark gaps cover an impressive range of voltages, currents, Coulomb transfer, and repetition rates and an extremely wide range of applications. The main drawback of spark gaps is limited lifetime, which is related directly or indirectly to the erosion of the electrodes. The various types of switches have been introduced which utilize the principle of arc motion in a magnetic field thus effectively decreasing the current density on the switch electrodes. This paper presents the numerical calculations of arc motion and electrode erosion in a rail spark gap. The results of the numerical calculations are compared with the experimental results in this paper. The conditions for reduced electrode erosion are defined.