The Evolution of Discharge Mode Transition in Helicon Plasma Through ICCD Images

We employed integrated capacitively coupled detector (ICCD) as a novel diagnostic technology to distinguish the mode transitions in helicon plasma by taking evolution discharge images. Prior to characterizing the helicon plasma with Boswell type antenna, the Langmuir electrostatic probe diagnostic was performed, which affirmed the discharge mode transition by the jumped plasma density. The optical emission spectroscopy (OES) measurement in the same Ar plasma also confirmed these results. In the ICCD evolution images, it was observed that when the first mode transition appeared, the glow area moved from two sides of the tube to one side; subsequently, it moved to the center of the discharge tube when the second mode transition appeared, which was consistent with the results by Langmuir probe and OES. We also noted that with ICCD, the influence from endplates and process parameters, such as gas pressure, magnetic field, and RF power, on the helical discharge mode transition can be recognized.