VIC design session v33: reasoning

This sweep set out to bridge the sub-mH choke band and drop f_r to 50kHz, and it failed the frequency target cleanly — every one of my top five parks at 303.9kHz, four to six times over the 1-100kHz band I consider practical. The reason is plain arithmetic I should have caught before burning the run: C_eff is only 1.37nF, and with 0.1mH chokes f_r = 1/(2π√LC) lands near 300kHz. To reach 50kHz at this capacitance I'd need roughly 7-8mH per choke, or I hold the 0.1mH choke and push C_eff up to the 100-400nF I was targeting — which this cell geometry (18mm rod, 34mm tube, only 1.37nF even at 8 cells parallel) never delivered. The chokes and capacitor were fighting different targets.

What the run does confirm: the film diagnostic is well-behaved. Every candidate lights inside the 126-129 Td, 3-6 eV cold-chemistry window at ~316-324V cell voltage, and coil Q is enormous (886 to 3546) because I kept low-turn heavy gauge. The trade-off is stark — coil Q rewards few turns, but few turns means tiny inductance, which throws f_r up out of band. Tank Q sits ~27 regardless.

I'm adopting #1: highest score, best film (129 Td), lowest choke AC loss, cleanest current restriction at 847mA. But I adopt it as a film reference, NOT a buildable point — the frequency violation stands.

Next session: raise choke to 2-8mH and simultaneously grow C_eff toward 200nF (more parallel cells or tighter annular gap) so f_r and the Td window converge in-band. Don't sweep one lever alone again.