Really big VTTCs

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: David Speck <dave@xxxxxxxxxxxxxxxx>

List,

I asked this question a couple of years ago, but never really got a 
definitive answer.
I've seen experimenters construct disruptive coils with secondaries 
from a few inches long to 60 feet tall.  Current SSTCs are 
approaching or surpassing the performance specs of the disruptive 
coils every day.

By comparison, VTTCs seem to have topped out at a 4" x 20" secondary, 
driven by one to four 833A tubes.  The consensus seems to be that you 
can get just about as good performance from one 833A as with 4 of 
them, if you design the coil right.  Perhaps 36" discharges seem to 
be the limit for VTTCs on a good day.
Is there some physical or electronic limitation to the design and 
construction of a really big VTTC?  With the availability of big 
surplus power tubes (10 kW or more) on eBay, and the possibility of 
multiple parallel free MOTs for input power, is there a physical 
reason why no one has built a 12 x 60 or 18 x 90 VTTC?
Ten foot sword like discharges would be neat to watch!

Dave