Primary Coil strike rings

Hi guys,

I've been looking at a few of the images from nic.funet.fi, in 
particularly the wingate files, and was almost totally blown away!

Does anyone know the specs/locations of these coils?

All I can tell is that Wingate1.jpg is a magnifying setup, and 
Wingate2.jpg is a dual-coil system - bloody awesome!

Anyway, I've been noticing a few people chatting, aswell as seeing these 
in images, but Primary Coil strike rings - what technical info is there 
to know about them, other than that there higher than the primary (so 
there is no breakdown between), it's not a complete ring, and it's 

I'm mainly interested in the mathematical side of designs for these, 
aswell as coils in general.