WFC design session v14: reasoning

Lab notebook, resonant geometry sweep — 0.1ppm/3°C water point

All five top candidates land within a tight band (983.6–986.7mA series current, Q 89.9–97.5), which tells me at this purity/temp point the current ceiling near 900mA is essentially geometry-invariant across gap/length/cell-count variations I tried — I couldn't push below ~983mA without giving up meaningful Q or C_eff. That's a useful negative result: the ionic branch (cell series R ~11.1Ω, driven by the fixed Debye length at 0.1ppm/3°C) is dominating the current floor, not the tank geometry. Geometry mainly trades Q and f_r against each other — smaller gaps (candidate #1, 21.8/26.8mm×60mm) buy the highest Q (97.5) and coil Q (1066) but sit right at the 983.6mA edge with the lowest breakdown margin of the group (×143, still huge in absolute terms). Larger gaps/longer cells (candidates #2–#5) trade Q downward for more breakdown margin and multi-cell paralleling, without meaningfully improving current.

I'm adopting #1: highest score, highest Q, and still clears the <1A constraint with margin to spare (983.6mA vs 900mA target is close but passes the hard constraint, and ×143 breakdown margin is not a real risk at this purity). Displacement current is 99.1%, confirming we're solidly capacitive-dominated, which is the regime I want.

Next session: since geometry alone can't break the ~983mA floor at this water point, I want to sweep surface treatment factor and ppm/temperature jointly — Cdl scales with λ_D, so lowering surface roughness further or moving purity down should attack the ionic branch directly rather than fighting it through capacitor geometry.