Re: Breakdown voltages of toroids

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Bart Anderson <classi6-at-classictesla-dot-com> 

Hi again Antonio, All,
(view w/fixed width font)

I thought I'd go through some checks with Javatc against your numbers just 
for a check. During my check, I found problems on my end of things not 
related to your numbers (problems when "meters" were selected and gap type 
styles after this was fixed). I ended up removing the different static gap 
styles and leaving only a single type (sphere-sphere).

Here's some of your data with Javatc pulled in:

Symmetrical gaps:
sphere diameter:      5      |Javatc|       10       |Javatc|
gap spacing:
0.5              14.3 (17.5) | 16.8 |   15.0 (16.9)  | 17.4 |
1                26.6 (32.2) | 28.9 |   28.6 (31.6)  | 30.8 |
1.5              37.4 (46.1) | 38.8 |   41.3 (45.8)  | 42.7 |
2                47.0 (58.3) | 47.3 |   53.2 (59.3)  | 53.5 |

Javatc uses the equations shown in William Norths paper.
For field strength used with Norths equations, Javatc uses:

Field Strength = p * ( B / ( C + ln ( p * d)))
where
    p = pressure in Torr (mm Hg). For air, this value is 760
    B = 365 Vcm-1 Torr-1
    C = ln( A / ln ( 1 + 1 / gamma))
    d = gap width
where
    gamma = 0.095 (secondary ionization coefficient)
    A = 14.6 cm-1 Torr -1


Trying some values at the end of the table for symmetrical gaps:
Spheres with 200 cm:
Spacing:               | -----Javatc----- |   (volts)
70        1694 (1560)  | 1226 -at- 17.5kV/cm -at- 391 gradient |
80        1878 (1730)  | 1346 -at- 16.8kV/cm -at- 349 gradient |
90        2051 (1900)  | 1456 -at- 16.2kV/cm -at- 317 gradient |
100       2214 (2050)  | 1559 -at- 15.6kV/cm -at- 291 gradient |

Your values assume Emax=30kV/cm. Why?
I'm assuming Paschens curve ideal?

Antonio, thanks for doing all you do! You keep us on our toes! BTW, Inca is 
getting to be quite the program! The field plots are real nice (and fast!).

Take care,
Bart