Spark gaps -- making and triggering

Ignoramus29428 · 2006-04-04T17:43:31+00:00

I finally picked up the caps from Fermilab. Each of them weighs about40 lbs and they look nice, very cute color also. So... I would like to make some sort of a pulse discharge thingy fromreadily available materials. Can crushing would be my first choice. My plan is as follows, to use copper pipe as conductor. I bought someHV diode stack (4 7.5 kV diodes) and a HV probe. The first thing to make would be a reliable system for discharging thecaps safely, and test it at low voltages. I would probably want to usetwo 12 MEG Victoreen resistors in series a permanently attachedbleeder.With four 1 uF caps, RC would be 2*12,000,000 * 4/1000000 = 96, whichis hopefully acceptable, and power dissipation in the resistors willbe about 3W per resistor.My main questions concern the spark gap. How to practically make adecent spark gap, and also how to safely trigger it. For instance, would 3/4" brass balls such as McMaster item 9617K47, beadequate? If not, I have 3/16" tungsten electrodes. Would they make anadequate spark gap?If not, can I use sections of, say, 1" copper pipe, placed at somedistance with their axes perpendicular?Also, what is the best way ot safely triggering a spark gap. Myunderstanding is that there is a rule of one inch per 15 kV. Wouldmaking the gap 1.5" and injecting some argon into it be a safeand effective triggering method?I am going to do a lot more reading and I will post my "design" hereand get it to pass some consensus before implementing it. i

Apr 04, 2006 43 Replies

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Winfield Hill 20 years ago

Just be sure the un-powered state shorts the capacitors.

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Cydrome Leader 20 years ago

There's alot of energy involved.

And lots of people don't know what they're doing.

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Doug White 20 years ago

When I was in High School, a friend had a "rechargeable cherry bomb". It was something on the order of 200 uFd at 10kV. We'd charge it up and fire it with an ignitron tube through a 1/2" gap. It made one heck of a bang.

The other fun thing was discharging a large HV cap in small containers of water. The resulting shock wave would throw water up in the air and shred the container. This was in the days of metal frozen orange juice cans, which his family would empty every morning at breakfast. When my friend got home from school, he'd shred the day's can with a smaller capacitor (2 uFd @ 20 kV?). The plan was to make a metal sculpture out of the results, but I don't recall that he ever got around to that part.

Doug White

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