[TCML] small ionizing source on top of toroid

[Bert Hickman]

Frosty wrote:
> I remember reading once that it is thought that natural lightning can
> achieve such huge 'spark lengths' at relativley low voltages because of
> avalanche break down from (ionizing) cosmic rays. Does any one know what
> sort of energies/radiation intensities would be required to actually cause
> runaway break down on the tesla coil level? I dont think americium would be
> too effective because it emmits alpha particles (I think), which cant go
> more than a few cm in air.
> 
> Cheers,
> Jesse
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Hi Jesse,

The problem with natural lightning is that, even though immense voltages 
  are present, the measured E-fields (before breakdown) within storms 
are not sufficient to trigger avalanche breakdown. Without this initial 
stage, the following stages (streamers, stepped leaders, return stroke, 
etc.) that eventually culminate in a lightning bolt, will never develop. 
Extensive atmospheric cosmic ray showers (EAS) and, more recently, lower 
energy background cosmic rays have been proposed as possible sources of 
large numbers of high energy secondary electrons that can "run away" in 
the presence of ambient E-fields.

"Runaway" electrons require an initial energy of 100 keV or higher, 
typically in the range of ~100 keV - 10 MeV. When high energy cosmic 
rays collide with our atmosphere, electrons can be generated from the 
decay of daughter particles, electron-positron pair production, Compton 
scattering, bremsstrahlung, and collisional ionization. Here's a 
web-accessible paper that describes one of the theories:
http://www.phy.olemiss.edu/~jgladden/phys510/spring06/Gurevich.pdf

Certain radioactive isotopes undergo beta decay that generates electrons 
(or positrons) that could trigger runaway breakdown. An example would be 
Phosphorus 32, a high energy man-made beta emitter, where the electrons 
have an average energy of 0.69 MeV and a maximum energy of over 1.7 MeV. 
These electrons can travel up to 20 feet through air, and they'll also 
generate high energy X-rays if the specimen is placed near a dense metal 
foil.

If these relativistic electrons are released near the surface of a TC 
topload, the ambient E-field might be sufficient to support runaway 
breakdown and spark breakout at lower output voltages than normally 
required. However, as Dave mentioned earlier, it would also be 
potentially quite hazardous from a radiation safety standpoint, even if 
you could obtain the appropriate isotopes and meet regulatory/safety 
criteria.

Bert
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