Focused anode layer thruster for ion beam figuring

Ion beam figuring for final processing of ultra-precision optical elements was first conceived several decades ago. Ion beam sputtering has been considered as a tool for optical elements milling/trimming/polishing for the first time in mid 1960`s. At that time, ion beam figuring was carried out with high energy (20 keV and above), low current (fraction of a milliampere), and narrow beam diameter (usually less than one millimeter). Low etching rates, ion implantation, and radiation damage were among the key problems of that approach. During then, various ion beam figuring instruments based on ExB, ICP, CCP, ECR, and laser were developed and investigated. Thrusters with anode layer (TAL) are well-known for high current efficiency as well as being robust in design. With this approach, there are various applications ranging from space propulsion to microelectronics thin films trimming and even fusion material research. This work presents the design of the focused anode layer thruster for ion beam figuring. Main design concepts to prevent electrode erosion and to increase current density/efficiency are discussed. Basic current-voltage characteristics, discharge ignition curves as well as SiC etching profile with Argon ions are presented.

This work was supported by R&D program of Plasma Convergence & Fundamental Research through National Fusion Research Institute (NFRI) funded by the Ministry of Science and ICT of the Republic of Korea (No. NFRI-EN2021).