WFC design session v31: reasoning

Lab note — annular-gap widening sweep, 7776 candidates.

The stated goal was to slide the 0.1mm vapor film down into the 80–250 Td cold-chemistry window by opening the gap to 6–9mm at ~800V. Honest verdict: I didn't get there. Every top candidate lit at ~396 Td in the townsend-avalanche regime — roughly double the top of the CGDE band — because widening the gap to 8mm also pushed cell voltage to ~993V, and Td scales with field. Wider geometry lowered C_eff (3.04nF at 28mm tube) and dragged resonance UP to 64.5kHz, well off my 45kHz target. So this sweep traded my frequency band away without buying the discharge regime I wanted. The scoring plateau at 0.594 is the model rewarding good resonance and inhibited leakage (leak score 0.08, displacement current 96.9%), NOT a window hit.

The Randles side is genuinely strong: 0.5ppm Na+ at 5°C with de-activated surface gives λ_D 102nm, breakdown margin ×525, and Faradaic leakage held near the floor. That half of the physics is working.

Adopting #1 provisionally — best score, lowest duty (2%, 25mA average input), tank Q 20.7, 1.23A circulating (rate the switch/wire for that, not the 25mA). It's the cleanest resonator even though it misses the Td window.

Next session: decouple voltage from gap. Hold gap at 8mm but drop cell voltage toward 800V by lowering the multiplication (48V drive × ~16, or looser coupling) to bring 396→~250 Td, then re-widen tube diameter to claw C_eff back up to resonate near 45kHz. Sweep film thickness 0.05–0.2mm too — Td is thickness-sensitive and I fixed it at 0.1mm.