The Turn Of The Century Electrotherapy Museum http://www.electrotherapymuseum.com   Tesla / Oudin Coil with 6" Copper Sphere Topload This simple unit has quickly become one of my favorites.  The secondary coil is only 18" high, wound with 27 gauge magnet wire.  The primary has only an 8" OD and is wound with a half dozen turns of 1" copper ribbon separated by 3/16" thick rubber.  Don't try this at home - I'm drawing off an arc to a stainless steel glove on my right hand! Discharge length is over two feet.  The streamers issue all around the sphere covering an area of over 60 inches with 1.5 KW input power.  (Current-limited, two 2kV MOT transformers with secondaries in series). The spark gap is a 2-series stationary gap made from 3/4" diameter tungsten mounted to 6061 Aluminum heat sinks. Click here for a movie!