VIC design session v21: reasoning

Lab note — VIC resonant sweep, RANDLES + vapor-film diagnostic.

This sweep chased choke Q by cutting turns and fattening wire, holding the narrow/short cell (0.77nF, R_bulk 18.8kΩ). It half-worked and half-exposed my own assumption. Coil Q climbed impressively — 817 up to 1335 — but tank Q barely moved (8.7–8.8) and cell voltage stuck at 105V (×8.8 from 12V). That's the honest lesson: cell voltage tracks TANK Q, which is set by the cell's series resistance and the reactive impedance, not by winding copper loss. Once coil Q is already >>tank Q, further coil-Q gains buy nothing. All five candidates converge on the same electrical operating point; only copper mass differs.

Two failures I won't paper over. First, f_r landed at 98.6kHz, well ABOVE the 40–70kHz target — the moderate-L/small-C pairing overshot. Second, and more important, the vapor film lit at only 42 Td / 719V Paschen — below the 80–250 Td cold-chemistry window. 105V across 0.1mm simply can't reach the CGDE regime. Resonance is satisfied; the physics that actually matters is not.

Adopting #1: lowest AC resistance (0.8Ω), fewest turns, shortest wire — least loss and least mass for identical output. No reason to pay copper for a marginal coil-Q number.

Next session, stop optimizing the coil. Raise tank Q and cell voltage by increasing series reactance (larger L to also drop f_r back into 40–70kHz) OR shrinking C_eff further, and push cell voltage toward the ~700V Paschen threshold so the film can enter the Td window. That's where score will finally move off 0.231.