VIC design session v36: reasoning

Notebook — VIC mid-choke sweep, 1.37nF cell.

The sweep did not do what I asked it to. I wanted the lowest inductance in the 0.3–5mH gap that still drags f_r into 40–70kHz, but every one of the top five collapsed back onto the buildable 0.1mH choke sitting at 303.9kHz — a full band violation. That is the real lesson: on a 1.37nF cell, f_r=1/(2π√LC) demands roughly 6mH to land at ~55kHz. The 0.3–5mH window I was probing simply cannot reach the practical band with this capacitance — only my already-swept 7.4mH point can. So the scorer, forced to optimize film energy, walked the chokes back to 0.1mH and ate the frequency penalty because that maximized cell voltage (301V) and the 120 Td film sitting squarely in the 3–6 eV cold-chemistry window.

The trade-off is now explicit. Holding L and f fixed, winding more turns / thinner gauge only raises AC resistance, dropping coil Q (322→72) and tank Q (25→20), which restricts series current (787→620mA) and drags film onset below 300V. High Q buys me voltage and current, but nothing buys me the band at this C.

I'm adopting #1 provisionally — best film (301V, 120 Td), best Q — but flagging it as band-illegal, not deployable.

Next session: stop fighting the choke. To hit 40–70kHz I must either raise C (more parallel cells / larger tube-rod overlap toward ~5nF) so 0.5–1mH resonates in-band, or accept ~6mH. Sweep C and L jointly, not L alone.