Influence of magnetic filter on plasma parameters of the prototype RF ion source at ASIPP

Abstract Radio frequency negative ion source is playing an increasingly important role in the field of neutral beam heating of thermonuclear fusion devices worldwide. In order to provide long-pulse, high-power, stable ion beams, there are many key technologies that need to be studied. Therefore, a prototype RF driven negative ion source was developed at the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP). The magnetic field filter (MFF) can reduce the loss of negative ions due to the collision of electron by cooling down the electron temperature. In addition, the influence of the MFF on the plasma is various, including the uniformity distribution of the plasma, the electron temperature and density, etc. In this paper, two main diagnostic systems (i.e. Langmuir probe system and optical emission spectroscopy system) are used to study the influence of MFF generated by permanent magnets on plasma, and the possible reasons for these influences are given. This paper can deepen the understanding of the current MFF, which provides ideas for the future upgrade of the magnetic field filter of the prototype RF ion source.