Development and Implementation of a Novel Particle Flux Probe for an RF Inductively Coupled Plasma Source*

Neutral Beam Injection (NBI) is a reliable plasma heating and current drive system used in magnetic confinement fusion experiments. The DIII-D NBI system utilizes eight ion sources, operating at up to 83 keV, delivering 20 MW of heating power. However, the current filament-driven Common Long Pulse Source (CLPS) design is facing challenges due to increasing performance requirements.

 

To address these issues, a transition from filament-driven CLPS to RF inductively coupled source (ICP) is desired for the DIII-D ion sources. A research program is underway, focusing on RF ICP plasmas. As part of this program, a novel particle flux probe has been developed and tested on an RF ICP system to study its properties.

 

The particle flux probe employs alternately biased conductors within a cavity to attract and collect ions and electrons. With a spacing smaller than the plasma's Debye length, this non-perturbing diagnostic placed at the plasma edge provides real-time information on particle flux to the wall, offering insights into plasma parameters.