WFC design session v35: reasoning

Lab notebook — WFC resonant sweep, 432 candidates, 2026-08-03.

This grid was supposed to slide V_cell into the 80–250 Td cold-chemistry window by trimming peak drive to 24V at low duty while holding the cold (8°C), ultra-pure (0.5ppm Na+), passivated (×0.4) Randles floor. It didn't get there. Every top candidate lights its 0.1mm vapor film at 293–301 Td — Townsend-avalanche, but sitting just ABOVE the 250 Td ceiling I want. So the scoring is rewarding "closest approach from the hot side," not a clean hit. That's the headline trade-off: pushing peak_v lower to drop Td also drops V_cell out of the film's Paschen breakdown (719V), and I lose the discharge entirely. The window is narrow and I'm skimming its upper edge.

Q is comfortable (30–31 tank, ~125 coil) and the band is fine (92–95 kHz, well inside limits), so neither is the binding constraint — the Td landing is. One honest caveat: τ_EDL reads ~25,000 carrier cycles to charge the double layer. If that number is right, the EDL never settles within a burst, and the "displacement current 97.6%" split is a steady-state figure the pulse never reaches. I don't fully trust that sub-model yet.

Adopting #1: smaller 12/16mm cell, 293 Td (closest to window), best breakdown margin per volt, lowest 2%-duty average current (14mA). Tighter geometry, same Q.

Next session: hold #1 geometry, sweep film thickness 0.05–0.15mm and peak_v 18–24V to walk Td down through 250 without extinguishing Paschen. And re-derive τ_EDL before I believe the current split.