Electron gun- what's wrong here?

For the design and construction details of ion guns, necessary for more advanced designs and lower vacuums.
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Steven Sesselmann
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Re: Electron gun- what's wrong here?

Post by Steven Sesselmann » Tue Aug 23, 2016 12:56 am

David,

That's correct, whatever power supply you use to heat the filament needs to float, so you need an isolation transformer.

In a fusor situation it is unlikely that you will need 10's of kV isolation because (as you discovered) you only need a few hundred volts to 1000V on the filament to make it emit electrons, those electrons will ionise some gas and keep your fusor lit at low pressures.

Steven
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David Kunkle
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Re: Electron gun- what's wrong here?

Post by David Kunkle » Wed Aug 24, 2016 11:59 pm

Is there any problem with using a battery for the filament PS? I had a 12V lead/acid motorcycle battery in mind. The whole battery would be floated to whatever HV potential is used on the filament.

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Steven Sesselmann
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Re: Electron gun- what's wrong here?

Post by Steven Sesselmann » Thu Aug 25, 2016 12:15 am

David,

No problem at all, I do the same on my rig, floating two 18V cordless drill batteries to power an MFC a USB hud and a DAQ.

Check the current draw and work out how long the battery will power it.

Steven
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David Kunkle
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Re: Electron gun- what's wrong here?

Post by David Kunkle » Thu Aug 25, 2016 4:35 pm

Thanks. Just wanted to make sure. It sounded OK in my head, but on the other hand, I could do without a battery exploding. I'll just make sure it's electrically insulated well enough from everything else.

My filament will use 6W @ 12V. So it should last many, many times longer than I need before I'd have to recharge if I go with the motorcycle battery.

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Rich Feldman
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Re: Electron gun- what's wrong here?

Post by Rich Feldman » Sat Aug 27, 2016 7:09 am

>> I do the same on my rig, floating two 18V cordless drill batteries to power an MFC a USB hud and a DAQ.

You can also electrically float a cordless drill with _no_ batteries, and use its motor as a generator.
DSCN0973.JPG
As shown on fusor.net in 2010: viewtopic.php?f=11&t=4771&p=27609
The old image thumbnails have not been treated nicely.
Richard Feldman

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