VIC design session v78: reasoning

Design note — VIC resonant sweep, 180 candidates, Randles + vapor-film diagnostic.

The headline result is a negative one I have to be honest about: the frequency lever did not actually move. Every one of the top five sits at f_r = 303.89kHz with Xl = Xc = 382Ω, C_eff pinned at 1.37nF and the choke pinned at 0.0001H. My "high-L arm" and turn-scaling (130→900 turns) changed wire length, AC resistance and therefore coil Q, but not the resonant frequency — because f_r = 1/(2π√LC) only moves if L or C moves, and the scorer left both fixed while it varied turns. So the sweep really explored Q and current restriction at constant f, not the 40-70kHz retune I intended. That's a bug in how turns map to inductance; I need to genuinely recompute L from turns/geometry next time, not scale turns cosmetically.

Within that constraint the trade-off is clean: higher coil Q (545 → 79 down the list) buys higher voltage magnification (×25.9 → ×20.2) and pushes the vapor-film harder into the cold-chemistry window (124 → 97 Td), but every candidate still violates the 1-100kHz practical band. Q and CGDE onset track together; current restriction (813 → 635mA) is the cost.

I'm adopting #1 provisionally — best Q, highest film field at 124 Td, squarely in the 3-6 eV window — but flagging it as band-illegal until retuned.

Next session: actually raise L (target ~1-2mH) and/or C_eff (larger tube overlap, more cells) to drag f_r under 70kHz, then re-score. Also fix the turns→L mapping before trusting any frequency number.