DEC Conversion Efficiency

Direct conversion is not thermal-cycle-limited, but real efficiency depends on staging, electrode losses, and the un-converted neutron fraction.

The appeal of direct conversion is that it is not bounded by the Carnot limit of a heat engine. In principle a charged ion can give nearly all its kinetic energy to the collecting field. In practice the achievable efficiency of the DEC is set by how finely the energy band is staged, how much beam the grids intercept, how much is lost to secondary electrons, and how much power never reaches the converter at all.

The 5.44% neutron fraction is the clearest un-convertible share: neutrons carry no charge, cannot be decelerated electrostatically, and deposit their energy as heat in the shielding. Any accounting of the burner's power path must set that fraction aside as thermal, not direct. What the DEC works on is the charged-particle stream that survives the expander.

What sets the efficiency

• Number of collector stages and how well they match the energy band
• Grid transparency and ion interception losses
• Secondary-electron emission at the electrodes
• Energy spread delivered by the expander
• The 5.44% neutron fraction, which bypasses direct conversion

Honest framing

No specific efficiency figure is asserted here because it is a design-and-simulation quantity that depends on choices still open, and stating a single number would overclaim. What is firm is the structure: direct conversion escapes the thermal ceiling but carries its own losses, and the neutron fraction is thermal by necessity. The burner's power case rests on the charged-particle channel being large — which is exactly why D–³He was chosen.

All statements are design-and-simulation findings for a machine not yet built.