Development of a limiter-like Langmuir probe system for the Q-shu university experiment with steady-state spherical...

A limiter-like Langmuir probe system was developed to measure scrape-off layer (SOL) plasmas in the Q-shu University Experiment with a steady-state Spherical Tokamak (QUEST) all-metal device. The system is mainly made of metals such as tungsten to keep compatibility with the all-metal conditions under which retention of plasma fueling gases in first walls is controlled. The system also includes built-in water coolant systems to withstand high heat loads originating from high energy electrons excited by radio frequency plasma heating/current drive systems during the fully non-inductive operations. Development of the system enables us to measure scrape-off layer plasmas in the presence of high energy electrons during fully non-inductive steady-state tokamak operations in QUEST. Preliminary experimental results of plasma measurements in QUEST SOL plasmas where high energy particles exist are presented.