Future smaller Fusor or fusor 3.0

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Dennis P Brown
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Future smaller Fusor or fusor 3.0

Post by Dennis P Brown »

I would like to try activation. My current fusor, while great for testing detectors has far too few neutrons (200 k/sec) to do detectable activation. More problematic, the distance from the center of the fusor to the wall is rather large. Also, having such a large active plasma region would, I'd think, also work against me for activation - the flux is too low thanks to that large plasma/neutron generation region at such low pressure.

As such, I guess building a smaller unit that will operate at higher pressure (more D2) and allow closer sample exposure to the neutron flux that is created and this might be the best way to go.

For this reason I obtained some smaller parts - a 60 mm 'T' and adapter flange system to run it in place of my large fusor (yes, a bit of an odd ball size - guess that's what makes it cheaper.)

Need to do more machine work and then tests on both the HV insert and window to confirm they will be vacuum tight. Next, make a cathode wire cage and couple it to the insert end.

Then get the higher voltage transformer (can do up to 80 kV) up and working. As for the x-former, tests will be at very low voltages and likely I will limit the system to 60 kV in any case. The x-ray problem concerns me even with proper shielding.

When all this is finally done, I hope I will be able to get a significantly greater neutron flux and be able to get a test sample closer to said flux. This will, if all goes well, enable activation of Indium or maybe silver.

Still have to get a pancake probe up and working with my computer interface system. A lot still to do with many other claims on my time.

Aside: the fast detector and new gamma/x- ray scintillation detectors are definitely going be put further down in the 'to be done list'.
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Future fusor 3.0 - parts
Future fusor 3.0 - parts
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Dennis P Brown
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Real name: Dennis Brown

Re: Future smaller Fusor or fusor 3.0

Post by Dennis P Brown »

Quick Update - I did the machine work on the surplus blank for the fusor 'window'. Used a lathe, a lot of cutting oil, and often water cooling of the cutting bit. The issue with surplus is one buys what is available; no flanges with windows of the correct size were being sold but a blank-off was available. So, despite my very marginal lathe skills, I placed the blank onto the lathe, made a rough pencil mark for where to start the cut and a lot of high pitched noise and metal flakes later, done - harden stainless steel is no fun to cut. See pics.

Hope it seals well. Also, finished the new cathode - an easy bend of a section of steel rod that took less than ten minutes and only an aluminum rod as a guide, a vice, and pliers. Yes, a 'home made' high voltage feed-thru. Until I am certain this new fusor works, will keep my commercial HV feed-thru on its current assembly.

The new small fusor has an adapter port that will fit on my current vacuum station. I will have to remove my large chamber. Then install and vacuum testing. If all goes well sometime this week, a real fusor run and test of neutron output (compared to values for the large chamber.)
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Blank being cut
Blank being cut
Port Window nearly cut through (flipped side)
Port Window nearly cut through (flipped side)
Finished black-off with O-ring seal, and Window port
Finished black-off with O-ring seal, and Window port
New Fusor 'T', window & flange, electrode and cathode
New Fusor 'T', window & flange, electrode and cathode
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Richard Hull
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Re: Future smaller Fusor or fusor 3.0

Post by Richard Hull »

Great work! Sunday afternoon Quarterbacking..... If you had a 1" drill with 1/2 inch shank and a chucked tail stock plus a boring bar, things would have proceeded rapidly. Bore the 1" hole or even a 3/4" hole and bore out the already through-hole to suit. Again, you would need the above items to do this.

Working SS is all about keeping the tool sharp and the speed right on and proper. Carbide tools are nice but the best cobalt high speed steel is much easier to keep sharp as work proceeds.

As Hickok45 would say after a success...."got th' job done...Got th' job done." That is the bottom line in any endeavor not matter the process.

I hope your smaller chamber works out well.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Dennis P Brown
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Real name: Dennis Brown

Re: Future smaller Fusor or fusor 3.0

Post by Dennis P Brown »

The difference between an amateur and a competent machine worker. Richard, that would have been far easier.

Looks like something is leaking really badly - so, need to do some tests on the various face plates & o-rings and find the issue.

Now that I have the proper voltage for the pancake probe, will get a better handle on the x-ray threat once I get this new fusor operational (will still be using the 32 kV PS.)
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Richard Hull
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Re: Future smaller Fusor or fusor 3.0

Post by Richard Hull »

I would tend to suspect the viewport addition. Regular, blanked off ISO fittings, in my experience, seal well. I liked them over conflat, but was worried about elastomer seals in high temperature fusor use. This was probably not warranted, but nonetheless, I went with conflat.

I am sure you de-greased all items after machining.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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