High-magnetic-confinement mode in partially magnetized E×B plasmas

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Applied Electromagnetics

Background:

• Gradient-drift driven instability is a key factor limiting plasma confinement in E×B devices.
• Achieving high-magnetic-confinement modes is crucial for efficient plasma control and fusion energy applications.
• Nonambipolar plasma flow often leads to instabilities that degrade confinement.

Purpose of the Study:

• To experimentally investigate the suppression of gradient-drift instability in a cylindrical partially magnetized E×B plasma.
• To explore the transition to a high-magnetic-confinement mode using an edge biasable electrode.
• To demonstrate a method for preventing magnetic confinement saturation.

Main Methods:

• Utilizing a cylindrical partially magnetized E×B plasma device.
• Implementing an additional biasable electrode at the radial edge.
• Applying a positive voltage to the electrode to create an asymmetric electron-loss channel.
• Measuring plasma density profiles and edge-to-center density ratios.

Main Results:

• Successful suppression of the gradient-drift driven instability was achieved.
• A transition to a high-magnetic-confinement mode was experimentally observed.
• Applying voltage to the electrode created an asymmetric nonambipolar flow, breaking spatial symmetry.
• Plasma density in the core increased up to four times compared to the unstable state.
• A reduced edge-to-center density ratio of 0.16 indicated improved core confinement.

Conclusions:

• Asymmetric nonambipolar flow, induced by an edge electrode, effectively suppresses gradient-drift instability.
• This method enables the transition to a high-magnetic-confinement mode in E×B plasmas.
• The findings demonstrate a viable strategy to prevent magnetic confinement saturation.