Tandem Mirror & DEC Synergy

The open-ended tandem mirror and direct conversion fit together: the exhaust the mirror cannot help but produce is exactly what DEC wants to eat.

A weakness turned into a feed

Closed devices like tokamaks confine plasma in a torus with no natural exit; extracting a directed particle stream for DEC is awkward. An open-ended tandem mirror is the opposite: plasma streams out the ends by design. What is a confinement challenge — end loss — becomes the very thing a direct converter needs: a directed, high-quality beam of charged particles delivered straight into the expander and the DEC train.

How the pieces reinforce each other

• The plug at 26.49 T builds the electrostatic barrier that confines ions and shapes what leaks out.
• The throat at 17 T and the expander turn that leak into a spread, directional beam.
• The DEC train recovers that beam's energy directly, so the end loss is not wasted but harvested.
• The same ultra-high field that confines the plasma also powers the MHD conversion stage.

Why this is hard to replicate elsewhere

A direct converter needs a directed beam; only an open geometry naturally provides one. Bolting DEC onto a closed device means engineering an artificial exit and diverting plasma to it, giving up much of the benefit. The tandem mirror's synergy with DEC is architectural, not incidental — the machine and the converter were, in effect, designed for each other.

The consequence for MetroVolt

This synergy is why the burner can plausibly convert the majority of its energy directly and reject only a small residual as heat — the foundation of its near-zero-water, load-adjacent siting. The tandem mirror is not merely compatible with DEC; it is the confinement scheme that makes the whole DEC-first strategy coherent.