Construction of a gridded energy analyzer for measurements of ion energy distribution in the versatile toroidal facility

Abstract

The Versatile Toroidal Facility (VTF) at MIT's Plasma Science and Fusion Center provides a laboratory environment for studying ionospheric plasmas. Various plasma diagnostic devices have been created and used to study the VTF plasma since 1991. An accurate method for measuring VTF's ion characteristics has never been designed or installed in the laboratory facility. Gridded Energy Analyzers (GEA) are useful diagnostic tools for determining plasma ion energy distributions and ion temperature. Research was done on the theory behind Gridded Energy Analyzers and their applicability for use in the Versatile Toroidal Facility. A design and method for constructing a miniaturized GEA for VTF was developed and documented. The construction method covers material selection, machining, and assembly of VTF's miniature GEA. The miniature GEA is a non-perturbing probe used in VTF's plasma, which is approximately 3 cm in diameter. The GEA was constructed and preliminary experimental data was obtained. From this data VTF's ion temperature was found to be approximately 8eV and an ion distribution function was determined to be roughly Maxwellian in nature.