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Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
I bought a reel of diodes last week. 5 thousand!
They are SF4007TR diodes. *Ultrafast *1kV *Glass *1A continuous *30A pulse *Avalanche diodes!
Pretty much the perfect diode.
I was thinking of what I could use these for, and I got to thinking; how cool would a 2 million volt CW be?! Now obviously it's not going to be possible to draw arcs at that voltage, but with 50x 40kV stages that's 2MV, or 8 foot sparks! Though maybe only about 2 sparks a second, but that's still really cool.
My only problem is the capacitors. I don't trust homemade foil caps with this task, mainly because they are very "leaky". Where would I find 100 50kV caps?? I'm thinking surplus, but I have no clue where to look...
Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
Well I never planned on drawing any continuous currents from it, so voltage drop is irrelevant. It would have time to reach full charge and then spark, but since it's a cw it'd charge up a lot faster than a marx.
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061
Also you will need series resistors between stages or the surge currents will blow every diode if even one fails under load.
(learned this the hard way!!!!)
These look like the same ones I bought from CPC a while back, IIRC they are fairly robust and good to >60 khz BUT don't take surge currents gracefully.
Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
Oh I'm well aware of that, but one hv resistor on the end gives better results than ones on the diodes. But with 8' flashover, i think the former may not be an option!
Well, this project is just a pipe dream until I can find the caps I need...
Registered Member #311
Joined: Sun Mar 12 2006, 08:28PM
Location:
Posts: 253
The problem with big CWs, apart from corona losses, is that the ratio of stray capacitance to the stage capacitance forms a potential divider, reducing output gain per stage. I doubt 50 stages will give any more output than 30-40.
Registered Member #3610
Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506
It's just the nature of the beast that you get diminishing returns as you add additional stages. CW multipliers with more than about 10-15 stages are generally not very practical. You get to the point where the losses start to overtake the gains.
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Really big CW
