Advances in Electron Plasma Diagnostics in a Tight-Aspect-Ratio Toroidal Trap for Transport Studies

Building on the unprecedented confinement of electron plasma in the “C” section of the small aspect ratio toroidal trap SMARTEX-C, this work presents key experimental and theoretical advances in toroidal non-neutral plasma research. The primary goal is to diagnose fundamental plasma parameters such as density, temperature, potential, and particle flux and to investigate confinement scaling laws that reveal the underlying transport mechanisms. To enable extended experiments, SMARTEX-C has been upgraded for long-duration operation at 200 Gauss under ultra-high vacuum (~1.0 × 10⁻¹⁰ mbar). Diagnostic advancements include an upgraded charge collector capable of measuring total confined charge over 30 s, a single-stage evaporative dump for temperature measurement, and a novel gas-puff method for indirect estimation of temperature diagnostics. Furthermore, controlled excitation of m = 1 and m = 2 diocotron modes has been used to estimate plasma density and radius, supported by a numerical model to infer equilibrium position and charge cloud trajectories. Together, these developments mark a significant step toward precise diagnostics and a deeper understanding of confinement in toroidal non-neutral plasmas.