Is there a voltage between two bifilar non-inductive flat spiral
pancake coils parallel to each other and rotating in opposite
directions?  By non-inductive I mean that the conductor is doubled,
then wound into a spiral, so currents in adjacent filaments are in
opposite directions. The winding of the coils as seen from axis of
rotation is opposite as well, i.e. one spirals clockwise out, and the
other spirals clockwise in, so there are numerous apparent points of
intersection as the coils rotate.  Another question: why are
non-inductive pancake coils used in plasma studies?  Is it because of
high frequencies, or because it is necessary to have a tight magnetic
field?

In the absence of an ?answer? yet, here?s a stab.

One could set up a standing wave in such a coil so another identical
coil in proximity would respond with a standing wave imposed on it.
Rotation at high speed would rotate the wave pattern hence perhaps
confine a plasma. So rather than feedback in response to
instabilities, incipient instabilities would be automatically
suppressed and bunching be promoted.

Best