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  • #1655
    Henning
    Participant

    Focus Fusion’s Twitter account is promoting a Kickstarter project for an very fast high voltage opening switch: https://www.kickstarter.com/projects/fusionnow/fusionnow-high-gain-nuclear-fusion-without-the-wai

    I know that the LPP experiment needs a very fast high current (~1 MA, ~40kV) closing switch. This is done by using a spark plug to ionise switch gas: https://www.flickr.com/photos/focusfusion/5288439873/

    How important is an opening switch for the experiment, which uses an electron beam instead of ionized gas (spark)? And how does the electron-beam switch scale current-wise? It’s supposed to handle big voltage in some future versions (maybe 100MV), but at LPPX we need high amperage.

    Maybe it’s useful for triggering the spark for the spark plug, with the high voltage distribution system: https://www.flickr.com/photos/focusfusion/5289042430/

    But then that doesn’t help to break down the current in the spark switch itself.

    #13575
    delt0r
    Participant

    If you can do a fast opening switch then inductive storage becomes pretty attractive. However fast opening switches just don’t exist. Lots have tried. Diamond switches seems to hold some promise, but haven’t yet delivered. There are a number of reasons fast opening switches are much harder than fast closing switches. For example is it much easier to have a fast breakdown and a increases in charge carriers, but you can’t make a ionized gas recombine and stop conducting without reducing the current to near zero.

    As for the kickstarter. Well it looks like rubbish. No details, and sounds like pie in the sky. Also it sounds like the person doesn’t know what they are doing. I got personally spammed about it.

    #13576
    Henning
    Participant

    I think it’s just a vacuum tube with an electron beam, where the electron beam hits a conducting plate and gets diverted when switched off. So as the Kickstarter project says, not much more than a TV tube (cathode ray tube). Nothing fancy, might have been in use since the 30s.

    #13577
    delt0r
    Participant

    And because of space charge effects, inductive effects and others, you can’t make them fast with high stand off voltage and high current. Its not like high power vacuum tubes aren’t a thing. They still are and often need very fast closing switches to prevent arcing and permanent damage.

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