Field reversed configuration confinement enhancement through edge biasing and neutral beam injection

Area of Science:

• Plasma physics
• Fusion energy research
• Magnetic confinement fusion

Background:

• Field Reversed Configurations (FRCs) are a promising magnetic confinement approach for fusion energy.
• Traditional FRCs often suffer from spin-up and rotational instabilities, limiting confinement.
• Achieving stable, long-lived FRCs is crucial for their viability as fusion reactors.

Purpose of the Study:

• To investigate methods for improving confinement and stability in FRCs.
• To explore the effects of plasma gun edge biasing combined with neutral beam injection on FRC properties.
• To determine if these techniques can overcome inherent FRC limitations like spin-up and instabilities.

Main Methods:

• Utilized the C-2 device, combining plasma gun edge biasing and neutral beam injection.
• The plasma gun generated an inward radial electric field to counteract FRC spin-up.
• Monitored FRC behavior, including stability, confinement times, and plasma lifetimes.

Main Results:

• Achieved FRCs with significantly improved confinement.
• Observed stabilization of the n = 2 rotational instability without external quadrupole fields.
• Reported a 2-4 fold improvement in FRC confinement times and extended plasma lifetimes up to 4 ms.
• Identified E × B shear in the edge layer, potentially improving particle transport.

Conclusions:

• Plasma gun edge biasing and neutral beam injection are effective in enhancing FRC confinement and stability.
• These methods successfully mitigate FRC spin-up and rotational instabilities, leading to near-axisymmetric configurations.
• The observed improvements in confinement and lifetime suggest a promising pathway for advancing FRC technology for fusion energy.