The Magnetic-Well Question

Tandem mirrors need a stable configuration at useful plasma pressure; whether a sufficient magnetic well exists at feasible β is unresolved.

Stability at pressure

Magnetic confinement must be stable: the plasma should sit in an effective magnetic well so that pressure-driven instabilities do not eject it. In a tandem mirror this is achieved through field shaping. The open question is whether a configuration provides an adequate well at the plasma pressure (β) MetroVolt needs for useful output.

High β is desirable for power density but stresses stability; low β is easier to stabilize but reduces output. The design must find a point that is both stable and productive. Whether that point exists at feasible field and geometry is part of the same open question as plug confinement.

Why simulation is not the last word

Stability at the relevant pressure involves kinetic and geometric effects that models capture imperfectly. This is a measure-it question. The test unit is built precisely to observe whether the configuration holds at the intended β.

• Need: a stable well at a productive β.
• Risk: no feasible point that is both stable and high-output.
• Resolution: direct measurement on the ~2032 test unit.

Until then, MetroVolt treats the stable-well assumption as a design premise under test, not a settled fact.