Fusor / vacuum items for sale

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Andrew Seltzman
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Fusor / vacuum items for sale

Post by Andrew Seltzman »

I just listed a bunch of fusor / vacuum / HV items on ebay. I'll sell to fusor.net members off of ebay for less, make me an offer.
https://www.ebay.com/usr/rtftechnologies

I also still have the liquid cooled grid for sale, the one with the white HDPE insulator box at the bottom, the other is not for sale (the insulator bushing has a pinhole burn through that will need to be replaced with another ceramic piece, this is just an electrical insulator not part of the vacuum seal on the grid) asking ~$180 or best offer.
PXL_20230603_220031659.jpg
PXL_20230603_220052130.jpg
PXL_20230603_220111179.jpg
PXL_20230603_234644620.jpg
Andrew Seltzman
www.rtftechnologies.org
Matt_Gibson
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Re: Fusor / vacuum items for sale

Post by Matt_Gibson »

What would it cost to have you replace the insulator? I don’t have any sort of way to machine something like that, but still interested in it. What voltage is it rated for? My power supply goes up to 75kV.

-Matt
Andrew Seltzman
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Re: Fusor / vacuum items for sale

Post by Andrew Seltzman »

The bushing is made of macor ceramic which can be machined with typical HSS or carbide tooling on a lathe. Unfortunately I don't have time to machine a new one. You might be able to extend the field control cap with a metal foil to extend over the burn spot. The grid was tested up to 40kV.
Andrew Seltzman
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Emma Black
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Re: Fusor / vacuum items for sale

Post by Emma Black »

On the liquid grid on the left, what is the black ring that fits around the conflat called? or has this been custom made?
Andrew Seltzman
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Re: Fusor / vacuum items for sale

Post by Andrew Seltzman »

only the one on the right is for sale, the ring on the one on the left if from thorlabs:
https://www.thorlabs.com/newgrouppage9. ... up_id=9125
Andrew Seltzman
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Matt_Gibson
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Re: Fusor / vacuum items for sale

Post by Matt_Gibson »

Any thoughts on if the ceramic is even needed? My current feedthrough (a commercial 30kV type) is just the bare stalk down to the cathode and I’m able to push well over its ratings.

-Matt
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Re: Fusor / vacuum items for sale

Post by Andrew Seltzman »

That could work though I haven't tried it. You would likely have to make some manner of recessed bushing to keep the grid stalk centered in the quartz tube so it doesn't lean against the edge.
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Matt_Gibson
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Re: Fusor / vacuum items for sale

Post by Matt_Gibson »

Few more questions:

1- Is the cathode “reach” easily adjustable to fit my chamber?
2-Is the cathode end easy to assemble/disassemble?
3-Are there any special equipment (pumps, controllers, ect) needed or is this “ready to go”?
4-Any special considerations to be aware of?

-Matt
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Re: Fusor / vacuum items for sale

Post by Andrew Seltzman »

Hi Matt,


1- Is the cathode “reach” easily adjustable to fit my chamber?
Yes, there are spacers between the flange and grid box that can be removed/added

2-Is the cathode end easy to assemble/disassemble?
It's reasonably easy to service, thought the cooling connections do add some complexity over a traditional wire grid.

3-Are there any special equipment (pumps, controllers, ect) needed or is this “ready to go”?
you will need a pump (I was using an idex micropump) to circulate fluorinert or other dielectric coolant. As with all fusor things, this will require some tinkering to get it up and running.

4-Any special considerations to be aware of?
As mentioned the ceramic burn through near the tip will need to be covered / serviced / replaced. While the bottom insulator around the HV end of the grid does shield the HV end physically, it will not protect you from touching as the outer surface at high voltage as HV can "jump". Don't tough the grid assembly when it is powered.

Some pictures of the grid disassembly and versions through the years
http://www.rtftechnologies.org/physics/ ... d-grid.htm
http://www.rtftechnologies.org/physics/ ... rid-v2.htm
http://www.rtftechnologies.org/physics/ ... rid-v3.htm
http://www.rtftechnologies.org/physics/ ... rid-v4.htm

I have attached a CAD model of the grid in inventor format, and STEP format as well
Grid rev4.zip
(17.54 MiB) Downloaded 60 times
Andrew Seltzman
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Matt_Gibson
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Re: Fusor / vacuum items for sale

Post by Matt_Gibson »

I don’t have a CAD reader handy, so what’s the min/max distance achievable between the center of the cathode/grid and the conflat flange? My chamber center is about 3.5” from the conflat connection.

For the pin hole, looks like I could stick some stainless steel sheeting around it, no? Maybe the macor is thin in that area which is why it failed?

Thanks!
Matt
Andrew Seltzman
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Re: Fusor / vacuum items for sale

Post by Andrew Seltzman »

As designed it's spaced for the center 4.234" from the chamber center so you would need to add some spacers. These are just 0.25"id/0.5"od round nylon spacers from mcmaster. You would also likely need to get some longer 1/4-20 nylon threaded rod as well.

The foil could work, and yes that's where the macor is thinnest
grid.png
Andrew Seltzman
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Andrew Seltzman
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Re: Fusor / vacuum items for sale

Post by Andrew Seltzman »

the grid is sold. lots of ebay items still up, make me an offer on fusor.net and I'll likely give you a reasonable discount.
Andrew Seltzman
www.rtftechnologies.org
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