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Registered Member #10944
Joined: Mon Mar 11 2013, 09:40AM
Location:
Posts: 3
HERF devices are really interesting to me and I definitely want to build something. I'm not poor, but I also can't justify spending thousands on a whim. The main barrier to entry that I can see are decent capacitors, so my first mission is to build some decent caps.
First off, how much capacitance is actually needed? What I mean is, would it be more important to have high capacitance 100kv or low capacitance 500kv for the purpose of efficient HERF usage?
Here was my first idea for building a capacitor, please give me some feedback on whether I'm heading in the right direction or whether there's an easier/cheaper way to go:
container: 7 gallon bucket (~19" height, ~10" diameter) conductor: aluminum foil, 18 inches wide insulator: electrical grade polyester film, 1400 gauge (20kv rated minimum, hopefully higher?), 19 inches wide top it off with some mineral oil and call it good?
I've also seen it mentioned a few places that some people were using spools of coax as a capacitor, with the shielding and inner wire acting as the conductors. Much of the cable I've seen though has limited specs available, and wildly varying data....and I don't really feel like burning up coax in my garage.
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
What about using multi core HDD cable, that has inter-pair breakdown strength in the 10KV range for 40 wire, and you can source it easily enough. Folks use it for glow discharge plasma devices..
Another thought is to use bell wire, that is fairly cheap and good for a few kV if pristine and not nicked or sharply bent.
Registered Member #10944
Joined: Mon Mar 11 2013, 09:40AM
Location:
Posts: 3
Thanks for the replies guys. PVC sounded promising at first, but I think 50kv/mm is a bit optimistic, and running some quick numbers in my head I think the value is less than mylar regarding the amount of dielectric strength per dollar.
With the PVC I'd have to run it extra thick and lose out on capacity, too. If I come across some for cheap though it's still a hell of an idea.
I'd like to treat the foil somehow too that isn't incredibly labor intensive. Poke holes in it with a roller or something like that. I wonder if some kind of chemical etching could be used to increase the surface area without making it too fragile to handle?
Registered Member #4266
Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874
I'd like to treat the foil somehow too that isn't incredibly labor intensive. Poke holes in it with a roller or something like that. I wonder if some kind of chemical etching could be used to increase the surface area without making it too fragile to handle?
If you can find some Barium Titante or Calcium copper titante it will increase the capacitance by factor of 1000-10000 respectively if you had a lay between the two plates. About 50kv running it at half had no breakthrought, at 60kv two sheets didn't arc
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
I would construct a marx generator for this purpose. Then you only need low voltage capacitors for each stage of the marx generator (i.e. 40kV per stage) for a total of 10 stages and a theoreticaly output pulse of 400kV.
The output of this can then be channeled into a horn antenna (or similar) as required, although the horn antenna has to be capable of withstanding the voltage.
Typically, EMP pulse generators are designed with marx generators and designed so the total output impedance is 50 ohms. Then its easy to couple efficiently to a 50 ohm antenna. Although easy is a relative term.
Note, a marx generator by itself creates a wideband EMP wave when fired.
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Building capacitors for HERF usage...
