Transition from the C3-dominated discharge to the sooting plasma

TL;DR

This study investigates the transition from C(3)-dominated discharge to sooting plasma in a graphite hollow cathode source, highlighting how magnetic field, geometry, current, and pressure influence plasma composition and emission characteristics.

Contribution

It identifies specific parameters and emission features that mark the transition from C(3) discharge to sooting plasma, providing new insights into plasma behavior and soot formation mechanisms.

Findings

Transition depends on magnetic field shape and profile.

Four emission bands between 300-400 nm indicate sooting plasma.

Atomic and molecular emission lines transform during the transition.

Abstract

Mass spectrometry and photoemission spectroscopy of a graphite hollow cathode source identify the parameters of the transition from the C(3) dominated discharge to the sooting plasma. The transition is a function of the shape and profile of a special cusp magnetic field which is a function of radius and azimuth angle, the geometry of the source, the discharge current, and pressure. Characteristic atomic and molecular emission lines and bands in the C(3) discharge transform into broad bands emitted by the excited soot. We identify four prominent emission bands between 300 to 400 nm to be the hallmark of the sooting plasma.