Hi Marco, All,
    The fastest quenching gas switch is hydrogen at high pressure.
There is an alternative.  A powder filled switch.  Try calcium
carbonate (or powdered limestone) and space your electrodes close
together.  A large surface area helps also.  see the following:

    +ACI-Novel Short Recovery Time High Voltage Switch+ACI-, M. Dufour et.
al., Institute of applied Physics, Berne Switzerland.

Quench times down to a few microseconds have been achieved with 0.02
uF charged to 25 kV at 3 Hz.  You should be able to go faster with a
larger surface area.

This is all I can say about this subject.

-----Original Message-----
From: Tesla List +ADw-tesla+AEA-pupman-dot-com+AD4-
To: tesla+AEA-pupman-dot-com +ADw-tesla+AEA-pupman-dot-com+AD4-
Date: Monday, January 04, 1999 4:49 PM

Original Poster: +ACI-Marco Denicolai+ACI-

I am designing a TC with a 62 kHz oscillating frequency. As I would
like to
quench at the first notch with a rotary gap, I supposed I can set my
coupling coeff. so that the first notch will come after about 5
oscillations at 62 kHz. That makes about 80 us to reach the first

So the quest is how to achieve such a short quenching time.

+AD4-From available literature I found that a spark can possibly form when
electric field exeeds 40 kV/cm and surely forms when it exeeds 70
So, if you write down how the stationary and rotating electrode
evolves with time, and calculate the time the electric field is
than 40 kV/cm, you should get a rough figure of your quench time.

I did that and for a peak voltage of 60 kV, rotating speed of 6000
rotor diameter of 12+ACI- I got a quench time of over 500 us (+ACE-). Because
cannot reasonably increase either speed or rotor diameter, I took the
book's solution and designed to insert a static spark gap in series
the rotary one.

By doing that I plan to decrease the voltage at the RSG down to 15 kV:
way the theoretical quench time drops down to 100 us, that gives at
some hope to achieve the required 80 us.

I was thinking to use a high resistance voltage divider to have 15 kV
the RSG and 45 kV on the static gap. The static gap would be a series
sections, to easily set its trigger voltage. The voltage divider
also remove a part of the randomness involved in air gap trigger

Any suggestions or comments about the above story?

Thanks to everybody.