Direct-Converter Collector Electrodes
Biased electrodes — historically a venetian-blind geometry — intercept the ion stream at grazing angles and collect charge while shedding secondary electrons.
Catching ions, not electrons
The collector must stop ions and hand their charge to an external circuit, while keeping electrons and secondary particles from short-circuiting the voltage. The classic solution is a set of angled ribbon electrodes — a venetian-blind arrangement — that ions strike at a grazing angle. The geometry suppresses secondary-electron escape and spreads the impact over a large surface to limit heat flux.
Electron suppression first
Before ions can be sorted by energy, the co-streaming electrons must be removed, or they will neutralize the collected charge. An electron-suppressor stage reflects electrons back while letting the heavier, faster ions pass into the energy-sorting grids. Only then does energy-selective collection work.
Surviving the flux
- Grazing incidence spreads heat load and reduces sputtering
- Angled ribbons trap secondary electrons geometrically
- Electrode material and cooling set the lifetime
- Large collector area follows from the expander expansion ratio
The collector is a plasma-facing, high-voltage, actively cooled structure — a demanding combination. Its design couples to the expander flow upstream and the power electronics downstream. In the burner study it is modeled from the mirror-program heritage that demonstrated direct conversion experimentally, adapted to the burner's exhaust parameters.
Collector performance sets the ceiling on how much of the exhaust energy becomes electricity, so its geometry, cooling, and voltage handling are optimized alongside the expander that feeds it rather than in isolation. It is one of the components the test unit is meant to exercise on real burner-scale exhaust.