Plug Plasma Buildup

Each plug carries a dense, hot plasma whose charge separation raises the ambipolar potential; building it is the central operational challenge.

The plug potential is only as tall as the plug plasma that makes it. Each plug must sustain a dense, hot plasma inside the 26.49 T field, fueled and heated independently of the central cell, so its density and temperature can be set to build a potential above the central-cell ion energy near 90 keV. Building and holding that plug plasma is the operational heart of the tandem mirror.

The plug plasma is created by a combination of gas or pellet fueling and dedicated heating — neutral beams and RF aimed at the plug region. The control challenge is that the plug must stay dense and hot continuously; any sag in the plug plasma lowers the potential and lets central-cell ions leak, which cools the central cell in turn.

What the plug plasma must sustain

• High density inside the 26.49 T field
• Ion temperature sufficient to raise the potential above ~90 keV
• Symmetric operation at both machine ends
• Continuous, steady-state maintenance
• Stability against loss of the confining potential

The regime gate

This is where the plug-regime gate bites. The combination of density, temperature, and field the plug plasma is asked to hold sits 166–830x beyond any operated device, so its buildup and stability cannot be post-dicted from experiment. Simulation describes it; no machine has yet run close enough to validate that description. The plug plasma is the burner's most consequential unproven element.

All figures are design-and-simulation values for an unbuilt machine.