Gas & Gaps

• To: tesla-at-pupman-dot-com
• Subject: Gas & Gaps
• From: Scott Stephens <stephens-at-enteract-dot-com> (by way of Terry Fritz <terryf-at-verinet-dot-com>)
• Date: Wed, 16 Sep 1998 17:44:58 -0600
• Approved: terryf-at-verinet-dot-com

Since the list is discussing gas qualities, I'll share a few notes I've
recently taken:

Electronegative gas, like SF6 (oxygen? chlorine?) has twice higher standoff
voltage, but inert Ar & Xe quench faster

Pressure increases standoff voltage linearly to 6 bar

Mercury and heavy inert gas (Ar, Xe) has lower forward voltage (10 - 40
volt) drop, but cathode damage (sputtering) happens around 100V, with high
currents. Insulators get metalized & shorted.

Hydrogen has higher drop, 100V, but faster recovery time, and has higher
(600V) sputtering damage threshold

Metals make diffuse-to-arc transitions similar to vapor pressures:
Mercury has best diffuse-to-arc discharge, happens at lowest voltage.
Cadmium, sodium, copper and iron with the highest vapor pressure vs.
temperature
All suffer from poor 10's ms quench times, limiting pulse rates to
100's/second.

Ionization probability vs electron collision energy curves list argon,
nitrogen, mercury, neon, helium, respectively, over a 2-1 range with argon
the easiest to ionize.





surface discharge:

multi-channel

fast cooling/quenching-.2 - ,5 ms 2-5A/channel


surface conditioning of G10-3 orders magnitude, 500 shots

alumina 1/4 erosion of g10, g10 channels dropped to 1/4

fast switching & low jitter, no trigger electrode flashback/isolation

glass, ceramic & alumina

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