Development of AMAROK: A prototype RF ICP source for the DIII-D NBI System*

The Advanced Multi-turn Adaptive Radio-frequency source on Kinetic Neutrals (AMAROK) is currently under development at NC State University to help inform the design of an improved DIII-D Neutral Beam Injection (NBI) system. AMAROK is an RF-Inductively Coupled Plasma (ICP) source featuring a racetrack-shaped dielectric window measuring 40 cm in length, with a turn diameter of 28 cm at the curved ends, and a height of 20 cm. AMAROK will operate with hydrogen, deuterium, and helium at a flow rate of 15 Torr-L/s to match the conditions in the DIII- D NBI injector, with an operating pressure ranging from 1 to 10 Pa. This configuration aims to create a homogeneous plasma source across a potential extraction area of 48 cm by 12 cm. The system also includes a racetrack-shaped, water-cooled Faraday shield designed to minimize the erosion of the dielectric window. The setup incorporates commercially available solid-state RF generators capable of providing at least 150 kW of power. The optimal frequency for efficient power coupling is currently being explored, with the goal of achieving an ion density of approximately 1018 m−3 that is needed to sustain the required ion density for extraction of an 85 A positive ion beam. AMAROK is expected to explore innovations in RF generator technology to help deliver a design for upgrading the NBI ion sources of the DIII-D tokamak.