High Frequency, Low Pressure, Plasma Generation using Extremely Small Diameter Tube

Electrodeless electric propulsion method has a very long life compared with conventional electric propulsion method, because electrode and plasma do not have a direct contact each other, leading to no wear of the electrode [1]. In addition, miniaturization of the plasma generation unit is desired as one of important propulsion objectives. The generation of electrodeless plasma in a quartz tube with an inner diameter down to only 3 mm has already been succeeded by changing rf frequency, but there remains a problem of a high pressure (Lower limit 100 Pa range) operation [2]. Therefore, plasma generation under lower pressure (Lower limit 2 Pa range) by improving the experimental setup external parameters were performed. Here, the plasma characteristics was investigated, using the SHD device [3]. Furthermore, rf plasma generation has been performed with a diameter of only 1 mm. [1] S. Shinohara et al., IEEE Trans. on Plasma Sci. 42 (2014) 1245. [2] T. Nakagawa et al., Plasma Fusion Res. 10 (2015) 3401037. [3] D. Kuwahara et al., Rev. Sci. Instrum. 84 (2013) 103502.