Efficient negative ion production in rf plasmas using a mesh grid bias method

Area of Science:

• Plasma Physics
• Atomic and Molecular Physics
• Materials Science

Background:

• Volume production of hydrogen negative ions (H-) is crucial for applications like fusion energy.
• Radio-frequency (RF) plasmas are widely used for material processing and ion source development.
• Controlling plasma parameters is essential for optimizing negative ion generation.

Purpose of the Study:

• To investigate the effect of a grid bias method on the volume production of H- ions in pure hydrogen RF plasmas.
• To understand the relationship between extracted H- ion currents and key plasma parameters.
• To determine the optimal grid potential for maximizing H- ion production.

Main Methods:

• Utilizing a grid bias method for plasma parameter control in a hydrogen RF plasma device.
• Systematically varying the grid potential (Vg) to influence plasma characteristics.
• Measuring extracted H- ion currents and characterizing plasma parameters, including electron temperature (Te) and electron density (ne).

Main Results:

• Negative grid bias successfully produced plasmas with distinct high and low electron temperature regions.
• Increasing grid potential (Vg) led to an increase in electron density (ne) while decreasing electron temperature (Te).
• The extracted H- ion current showed a strong dependence on the grid potential and associated plasma conditions.

Conclusions:

• The grid bias method is an effective technique for controlling plasma parameters in hydrogen RF plasmas.
• Optimizing grid potential is critical for enhancing the volume production of hydrogen negative ions.
• The findings provide valuable insights for designing and operating H- ion sources for various applications.