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2024-11-27, 07:39:43
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img  darkspeed
Triode driven spark gap « on: 2010-07-01, 20:40:53 »
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I am thinking of actuating a spark gap with a high power triode.. in place of the rotary spark gap in series

Anyone here done this before?

Anything to look out for in doing so.. stress on triode?
   
img  BEP
Re: Triode driven spark gap « Reply #1 on: 2010-07-01, 21:46:07 »
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If you wish to replace the spark gap with a tube then use a trigatron.
If you wish to control an open spark gap, that gap needs a trigger element. That element can be driven by a more conventional triode which outputs to a coil with a HV secondary.

Example: You can use a trigger voltage (very low current/power) of 8kV to trigger a very high amperage/lower voltage open spark gap - or the inverse.

Just look at how trigatrons are made and work. A vacuum is nice but not completely required.
   
img  Peterae
Re: Triode driven spark gap « Reply #2 on: 2010-07-01, 22:14:33 »

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Corona Oscillator and Triode with Gain

http://sparkbangbuzz.com/corona-osc/corona-osc.htm
   
img  BEP
Re: Triode driven spark gap « Reply #3 on: 2010-07-01, 23:39:37 »
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Ah, Yes!

K7NS... I know him through HAM activities. The guy makes many things from almost nothing. I built this one, the TEA laser, the flame triode and magnetic amplifiers. His projects are a treat.

If I told folks you could build a spark gap with a trigger or grid they wouldn't believe me  :D The 'more fun' projects came from this guy and others.
   
img  darkspeed
Re: Triode driven spark gap « Reply #4 on: 2010-07-01, 23:49:47 »
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W.W. I have a number of trigatrons on the shelf but they dont shunt the arc until the voltage drops in the cap bank. - im running off of a 6kv/100uf bank

I need a way to modulate the spark gap - my theory was that the gap wont make unless the heater in the triode is emitting.

Also it fills the need for absolute rectification unless the tube arcs over.

I helped build a GU5B VTTC and was thinking of trying one of these as it has a friendly 12.6v filament (25a) and a 5kv range although we dumped 10kv through one and it just smiled back
« Last Edit: 2010-07-02, 00:08:22 by darkspeed »
   
img  BEP
Re: Triode driven spark gap « Reply #5 on: 2010-07-02, 00:48:15 »
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Quote from: darkspeed on 2010-07-01, 23:49:47
W.W. I have a number of trigatrons on the shelf but they dont shunt the arc until the voltage drops in the cap bank. - im running off of a 6kv/100uf bank

?? - Slow ionization buildup?

Quote
I need a way to modulate the spark gap -

Modulate it? AM - FM - PM or just stop conduction when you need?

Quote
my theory was that the gap wont make unless the heater in the triode is emitting.

For heater type, yes. Since I doubt you have radioactive heater tubes on your shelf there is one option.... A trigger. The trigger is just another electrode. All it does is ionize the air to allow the main electrodes to begin conduction.

Quote
Also it fills the need for absolute rectification unless the tube arcs over.

I helped build a GU5B VTTC and was thinking of trying one of these as it has a friendly 12.6v filament (25a) and a 5kv range although we dumped 10kv through one and it just smiled back

Cute little puppies, aren't they. This past winter I had a discharge of 125kA through one little tube. The tube liked it. The caps puked while the load vaporized (iron pellets). Ever smell burned iron? Strange.
   
img  the_big_m_in_ok
Re: Triode driven spark gap « Reply #6 on: 2010-07-02, 00:51:50 »
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Quote from: darkspeed on 2010-07-01, 20:40:53
I am thinking of actuating a spark gap with a high power triode.. in place of the rotary spark gap in series

Anyone here done this before?

Quote from: WaveWatcher on 2010-07-01, 21:46:07
If you wish to control an open spark gap, that gap needs a trigger element. That element can be driven by a more conventional triode which outputs to a coil with a HV secondary.

Example: You can use a trigger voltage (very low current/power) of 8kV to trigger a very high amperage/lower voltage open spark gap - or the inverse.
A Xenon lamp works like a spark gap according to this:

http://www.autolamps-online.com/gasdischarge/faq1to5centre.htm

EMI may be less than a spark gap and electrodes won't erode from the high temperature arc---since there are no electrodes, right?

Just an idea.

--Lee
« Last Edit: 2010-07-14, 21:18:00 by the_big_m_in_ok »
   
img  darkspeed
Re: Triode driven spark gap « Reply #7 on: 2010-07-02, 01:43:31 »
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Im looking to drive the triode from a function generator at variable frequencies and pw.

I have a few radioactive passive spark gaps but nothing with a heater. ib-22's

The goal was to get the gap so close that it would ionize the gap when the triode started to conduct.

I am testing different materials in the spark gap  - i just need a way to test them at specific freq.
   
img  BEP
Re: Triode driven spark gap « Reply #8 on: 2010-07-02, 03:44:09 »
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Hmmm.....

I can make a triode fire a gap, but stop it? Once the gap starts conducting it won't stop until voltage drops low enough for the ionization to fail. Your best bet is the triode with gain idea - above.

Then you can reverse bias the control loop to stop the oscillation. As far as I know, The only way to stop the output during a pulse is to short it with another gap.
   
img  darkspeed
Re: Triode driven spark gap « Reply #9 on: 2010-07-02, 04:19:24 »
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Ok I must not have explained that correctly..

Im talking about spark gap and GU5B in series with the capacitor bank

The spark gap is set very close but it can fire because the triode is in series

When the triode conducts the gap fires
   
img  Grumpy
Re: Triode driven spark gap « Reply #10 on: 2010-07-02, 05:47:57 »

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how about a triode and shut it off with a delay line (the reflection) this will set the pulse width as well.  You just need to turn the triode on - it will be independent of the gap.
   
img  darkspeed
Re: Triode driven spark gap « Reply #11 on: 2010-07-02, 05:53:11 »
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Delay line on triode grid? and still have the gap and triode in series?
   
img  Grumpy
Re: Triode driven spark gap « Reply #12 on: 2010-07-02, 14:49:04 »

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Quote from: darkspeed on 2010-07-02, 05:53:11
Delay line on triode grid? and still have the gap and triode in series?

I used delay lines with spark gaps and they quenched better than with strong magnets across the gap.  Same setup as an avalanche transistor.   Can't say if it will work with every switch, but I do not see why it won't.
   
img  darkspeed
Re: Triode driven spark gap « Reply #13 on: 2010-07-02, 20:52:15 »
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I still dont get it - can you draw it out?
   
img  BEP
Re: Triode driven spark gap « Reply #14 on: 2010-07-02, 21:44:57 »
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On the run right now but...

http://www.slac.stanford.edu/cgi-wrap/getdoc/slac-tn-69-019.pdf

Not many folks do this ....

For the delays discussed.... Maybe a 'Retarding Field Tube'. I'm sure it is a 'roll your own' tube.

A serious piece of work using a Vircator and a bit overboard but includes usable principles....
http://etd.lib.ttu.edu/theses/available/etd-06272008-31295018735059/unrestricted/31295018735059.pdf
   
img  darkspeed
Re: Triode driven spark gap « Reply #15 on: 2010-07-02, 22:23:15 »
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Well i tested it at 1kv with a triode and yes it works.. but not like expected..

With a non quenched gap above a freq. the spark gap remains ionized even when the triode is open

Raising the kv to 5kv will only make this worse so my next step is the 5kv triode and the nitrogen quenched gap

I wonder if the peach cloud in the exhaust pipe would show up on film?

Yes I am isolating my nitrogen so I dont take a permanent nap.
   
img  Grumpy
Re: Triode driven spark gap « Reply #16 on: 2010-07-02, 23:13:10 »

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delay line avalanche transistor (switch) (delay line is a length of coax)

Vout1 is positive

Vout2 is negative

Length of delay sets pulse width and shuts off pulse when the reflection along the delay line hits the switch

Can you shut it off with a negative trigger pulse?  If so, then differentiate a square trigger and the negative pulse that results will shut it off (if it is enough - might not be as differentiation lowers amplitude and there is little current in the trigger also)
   
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