WFC design session v28: reasoning

This sweep set out to pin the 150 Td cold-window from the density side, and I'll be honest: it didn't get there. Every top candidate lands at 572 Td (1434V film) or 1144 Td (2868V), well above the 80-250 Td target. The cold high-εr water raised C_eff and dropped f_r to 30.26 kHz nicely, and the 227nm Debye length gives a healthy ×280 breakdown margin — but the 0.1mm vapor film still lights in the streamer regime, not the diffuse CGDE glow I want. The scoring plateaued at 0.695 across all five because the film physics saturates before the resonant levers can pull it back.

The real trade study here is Q vs. duty vs. field. Tank Q sits at 23.9 (coil Q 73.7), giving ×23.9 voltage gain — good, but the 1.14A circulating current is the true design constraint; that's what sizes my Litz and switch, not the 23mA average. Duty is purely an average-current knob: candidates #1-#3 are the SAME cell at 2/5/10% duty (23/57/114mA). Doubling drive (#4-#5) doubles field and Td but halves margin — wrong direction for cold chemistry.

I'm adopting #1: 60V drive, 2% duty, 23mA average. Lowest current draw, ×280 margin, and if I'm going to be off the cold window anyway, I'd rather be off it gently and safely while I fix the film model.

Next session: I need to LOWER the film field — widen the vapor gap assumption, or drop cell voltage below ~600V (near film Paschen 719V) and recover polarization through more series cells rather than brute volts. Sweep film thickness explicitly.