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I've recently gotten into eletrochemistry, and I found out that if you break through \$\epsilon_{0}\$ with a high enough voltage you can ionize various gasses. I've already wound a 1:1250 EE core that I plan to operate at 350 kHz on a 25 V supply which should give me 31.25 kV in the arctube, but there's this problem where I think I need to rectify the output and uh, I have yet to see a 50 kV diode.

Is there a way to do it that I'm just not remembering? I thought there was a way to do that back in the vacuum tube days.

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    \$\begingroup\$ There was. Start with 1kV AC (or whatever you CAN find a diode for) and build a Cockroft-Walton multiplier. Each diode only sees the original AC voltage. \$\endgroup\$ – Brian Drummond Jul 28 at 13:46
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    \$\begingroup\$ There are rectifier stacks that can handle (say) 100kV. Forward voltage might be 120V meaning that they're 100+ individual diodes in series. \$\endgroup\$ – Spehro Pefhany Jul 28 at 13:51
  • \$\begingroup\$ @BrianDrummond Cockroft-Walton multipliers aren't that good for high multiplication factors, if I remember right. \$\endgroup\$ – Hearth Jul 28 at 13:51
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    \$\begingroup\$ Good luck with that transformer not breaking down under 31kV... At 100kHZ normal insulation will not do well even if rated for 31kV. \$\endgroup\$ – MadHatter Jul 28 at 19:14
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    \$\begingroup\$ Are you sure what you are getting into? I once had 30 kV punch through Teflon insulation that was not thick enough (supply for a MALDI TOF mass spectrometer). \$\endgroup\$ – Peter Mortensen Jul 28 at 23:42
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There are rectifier stacks that can handle (say) 100kV. Forward voltage might be 120V meaning that they're 100+ individual diodes in series.

Here is some data from a random Chinese supplier (no experience with those guys, but it should give you an idea):

enter image description here

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  • \$\begingroup\$ Thank you very much, I have about 200 FFSH20120A SiC Diodes I guess I can sacrifice. You know those things are expensive, but I'll only lose a volt each, so to handle 12kv it'll only cost me 10V. \$\endgroup\$ – user14828 Jul 28 at 14:10
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    \$\begingroup\$ You answered my first question on this message board, how to drive a MOSFET with a push-pull (emitter follower). That was great and thanks again. I've actually improved on that circuit since then adding 2 additional shunted transistors to equalize the voltage at the output, you know, the diode drops. \$\endgroup\$ – user14828 Jul 28 at 14:18
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    \$\begingroup\$ What's the motivation to use SiC rather than silicon diodes? \$\endgroup\$ – pericynthion Jul 29 at 1:26
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    \$\begingroup\$ @pericynthion Performs better at higher voltages. You can get away with less diodes. \$\endgroup\$ – DKNguyen Jul 29 at 5:11
  • \$\begingroup\$ Seems like the SF4007 or similar would work fine, not have significant forward conduction loss at these operating voltages, can handle the switching frequency and would be a lot cheaper. The SiC Schottkys would have lower switching loss though and I was wondering whether the OP expected that to be relevant. \$\endgroup\$ – pericynthion Jul 29 at 15:02

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