This is a short video of my 2.875" dia 13" tall coil #28.
The top is loaded with two salad bowls with a 3x12" 
styrofoam center with alum tape. 15kv30ma neon with 3/16"
copper primary 30deg 12 turns.
6 stationary copper gaps @ 32mils each. Two 2.3nf ceramic
caps in parallel.
Arcs are approximately 18"
Although it looks like it, my hand is not in the primary.
dave huffman
huffman@fnal.gov