tabletop neutron generator

For the design and construction details of ion guns, necessary for more advanced designs and lower vacuums.
Rapp Instruments
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tabletop neutron generator

Post by Rapp Instruments » Sun Jun 05, 2016 7:10 pm

Hi,
I justed finished a small neutron source for detector testing. The function was proved with indium- and silver-activation. The source works with a simple canal-ray ion source and a titan target. The working gas is deuterium from a lecture bottle. The accelerating voltage is arround 100 kV, the target current only some 10th microamps. Both HV-supplies, for the ion source (max 25kV) and accelerating (max 120kV) are simple homemade device, flyback inverters with voltage multipliers. The moderator is made of PE-HD. In spite of the low power and current the activation is remarkable, 90 counts for silver and 30 counts for indium.

Thomas
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Werner Engel
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Re: tabletop neutron generator

Post by Werner Engel » Sun Jun 05, 2016 7:37 pm

The plastic hose and the small design does solve a lot of Isolation issues - congratulation!
I can't see the RF generator for the ion-source - or am I missing something?
How did you solve the isolation problem between the RF coil and the next KF fitting?
Great work!

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Re: tabletop neutron generator

Post by Rapp Instruments » Sun Jun 05, 2016 9:19 pm

Hi Werner,
the copper coil you see is not a rf-coil but a capillary tube to feed the deuterium to the canal ray ion source. The ion source is driven by dc current (20kv, about 200..300µA). Construction drawing will following.

Thomas

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Re: tabletop neutron generator

Post by RobertTubbs » Mon Jun 06, 2016 4:05 am

Nice work, Rapp, your posts are always an enjoyable read.

Keep the updates coming.

RT

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Richard Hull
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Re: tabletop neutron generator

Post by Richard Hull » Mon Jun 06, 2016 6:17 pm

Really sweet beam on target fusion effort! Thanks for your continuing efforts and sharing with the group here.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

Rapp Instruments
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Re: tabletop neutron generator

Post by Rapp Instruments » Mon Jun 06, 2016 8:38 pm

Hi,
a schematic of the source

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and a image of the tiny ion beam

Image

Thomas

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Richard Hull
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Re: tabletop neutron generator

Post by Richard Hull » Tue Jun 07, 2016 4:52 am

It looks as if the system is, effectively, differentially pumped due to the fine holes in the anode and cathode to the right as the glow in the right half seems rather bright, (higher pressure) and the deuteron stream is nice an dull pink in color, (lower pressure). Am I correct here?

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

Rapp Instruments
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Re: tabletop neutron generator

Post by Rapp Instruments » Tue Jun 07, 2016 7:20 am

Hi Richard,

you are quite correct. Mostly because of the fine cannel in the cathode the pressure in the accelerating space is low enough. Otherwise there would be a discharge between cathode and the suppressor. The fine hole in the anode and the long capillary (0.8 mm ID, 50cm long) helps to regulated the pressure with the throttle valve .

Thomas

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Werner Engel
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Re: tabletop neutron generator

Post by Werner Engel » Tue Jun 07, 2016 5:58 pm

I'm using a similar device to prevent the plasma from igniting through from the chamber back to the MFC.
It's just a small piece of tiny steel pipe, connected to a KF seal ring.

I think I will call it "plasma backdraft restrictor - design ENGEL" ;-)
Sounds nice- does it?

I think Steven Sesselmann could also use it.
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Richard Hull
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Re: tabletop neutron generator

Post by Richard Hull » Wed Jun 08, 2016 6:03 am

I always liked well thought out differential pumping schemes that relied on controlled leaks between chambers, rather than two pumping systems.
Really cool trick, guys.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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