[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: 20 joules at 100 bps vs 4 joules at 500 bps

Original poster: Bert Hickman <bert.hickman@xxxxxxxxxx>

Marco and all,

That's really an excellent summary! Although the "average field" is considerably lower, the E-field near the tips of streamers must still be significantly above 30 kV/cm to support further growth. Further streamer-leader propagation can occur as long as the terminal voltage rises fast enough to overcome increasing path resistance as the leader channel cools. Smaller coils run out of voltage, limiting maximum discharge length.

BTW, it's probably a good idea to begin consistently calling the easily seen discharges from TC's "leaders", and the much fainter/fuzzier discharges at the leader tips "streamers". This will allow us to be more consistent when discussing spark breakdown, especially if referencing the literature. Spark breakdown is difficult enough without having to continually (re)define what is meant when discussing TC discharges...

Bert

Tesla list wrote:

Original poster: "Denicolai, Marco" <Marco.Denicolai@xxxxxxxxxxx>
Hello Jim, all,
Based on my readings there are 3 different situations for breakdown:
- small gaps (some cm), Efield required 30 kV/cm, breakdown with avalanche (Townsend).
- medium gaps (< 1 m), Efield required 5 kV/m, breakdown with stable streamers and final jump.
- large gaps (> 1 m), Efield required only 1 kV/m, breakdown with leader-streamer phases and final jump.
These phenomena are very well documented, although usually with different names and in not such a clear manner. So, for a 2 m breakdown you need a 30 kV/m on the toroid surface, then at least some 5 kV/m within 1 m from it and the rest of the travel will succeed if 1 kV/m can be ensured.
Best Regards

----------
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Wed 8/3/2005 7:38 AM
To: tesla@xxxxxxxxxx
Subject: Re: 20 joules at 100 bps vs 4 joules at 500 bps
Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>
 >Really is true... there IS a minimum sparking voltage.  As you keep
 >dropping the pressure, eventually you get a glow discharge, but never
 >a spark, or possibly current flow from field emission.  We depend on
 >this all the time for high power RF stuff operating in low pressures
 >(like Martian atmosphere... CO2 and Argon at about 5-10 torr...)