Voltage level for static E-feild

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Andrew Haynes
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Voltage level for static E-feild

Post by Andrew Haynes » Fri Dec 13, 2013 3:18 am

Hi, I'm trying to make a ion gun, and was wondering at what voltage level would a 0.5mm needle emit electrons. Was planning to run it in a vacuum of about 0.1-0.5psi with a gap to target of 0.5-1mm.
I can get access to a 250nm UV lamp and was wondering if that would lower the threshold, and if the gas would effect the operation(if they become positive and get attached to the anode).

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Andrew Haynes

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Richard Hull
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Re: Voltage level for static E-feild

Post by Richard Hull » Fri Dec 13, 2013 4:47 pm

You would only need a kilovolt or so off a needle at that pressure, but your ions would not go far, unfortunately, as the mean free path would be only a couple of millimeters.

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Steven Sesselmann
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Re: Voltage level for static E-feild

Post by Steven Sesselmann » Fri Dec 13, 2013 11:58 pm

Andy,

If you can rig up a system with differential pressure, so the gas pressure around the needle is higher, then you can generate ions at relatively low voltage and extract them into a chamber of lower pressure.

You place the needle cathode above an anode disc with a small hole, leading into a chamber of lower pressure.

Steven
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http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG

Andrew Haynes
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Re: Voltage level for static E-feild

Post by Andrew Haynes » Sat Dec 14, 2013 10:41 pm

Thanks you two for the info.
S_Sesselmann would that arrangement work without the difference in pressure?, what voltage level could it be with the right pressure variables?
I've added the idea to the drawing its a easy voltage doubler, and plan on useing a Rocker 300, 220V/50Hz oil free vacuum pump if the 300 means something....,
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Steven Sesselmann
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Re: Voltage level for static E-feild

Post by Steven Sesselmann » Sat Dec 14, 2013 11:54 pm

Sorry Andy, I don't quite understand your diagram, but in regards to the vacuum , you are going to need something better than a rotary pump, if you are going to experiment with ion optics. As Richard already explained, you need a high enough vacuum for the ion to have a sufficient mean free path.

Steven
http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG

Andrew Haynes
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Re: Voltage level for static E-feild

Post by Andrew Haynes » Sun Dec 15, 2013 5:22 pm

The path doesn't need to be long, from one end cap to the anode will be 1mm or less, or just don't want a arc discharge.
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Steven Sesselmann
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Re: Voltage level for static E-feild

Post by Steven Sesselmann » Sun Dec 15, 2013 9:40 pm

Andy,

Well in that case you will get an arc discharge of high current and low potential.

Not sure what you are trying to achieve with this experiment...

Steven
http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG

Andrew Haynes
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Re: Voltage level for static E-feild

Post by Andrew Haynes » Sun Dec 15, 2013 10:23 pm

S_Sesselmann

I'm trying to make electron get accelerated from the anode to the end cap, but still not have a conductive path between the two. I thought that if the vacuum was good enough a electron won't start a averlance (spelling).
If I run this connected to a 15kv nst the voltages should add up , once the ac is reciftered, it should be easier than high frequency or having caps and diodes handle the full voltage

If not I can use salt water, but the efficiency will be lower.

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Andrew Haynes

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