Apparatus for Making a Deuterated Target

For the design and construction details of ion guns, necessary for more advanced designs and lower vacuums.
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Mark Rowley
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Re: Apparatus for Making a Deuterated Target

Post by Mark Rowley » Fri Jul 02, 2021 8:35 pm

Custom o-ring seals are doing great. Deepest vacuum with the Yellowjacket pump has been 7mTorr which means a secondary diffusion pump would bottom this out to sub-milliTorr levels with ease.

9mTorr is after about a minute of pumping time.
D3EF3112-4179-43A3-9972-2B2164C999A6.jpeg
Later today will be a stress test of the viton o-rings under heated conditions. Fairly sure I’ll be needing a longer quartz tube.

Here’s the tube furnace which will be incorporated with the setup. Operational temps will be roughly 900 Celsius. My concern with this arrangement is it’s considerably slower cool down time. A redesign allowing for an immediate drop-down arrangement may be required.
DCF66817-50BB-413A-9CAD-54644CB32E89.jpeg

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Mark Rowley
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Re: Apparatus for Making a Deuterated Target

Post by Mark Rowley » Sat Jul 03, 2021 4:53 am

So far a surprising success. The o-ring areas remained very cool with forced air blowing over the heat dissipators. Even at 900 Celsius neither o-ring area exceeded 35 Celsius (95F)… even after several hours.
6800B259-B9AC-479F-A96F-6CC179E4436E.jpeg

Shown here is the back side of the furnace with forced air blowing over the dissipators. The glowing red alumina heating element can easily been seen in this shot.
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This is a comparison between a treated and untreated piece of titanium sheet.
64288EE6-12EE-46B2-8DD1-F45E0A30E885.jpeg

Being a first attempt, the system was gently operating at a reduced duty cycle. The titanium was only maintained at 900 Celsius for just under 2hrs. 100mL of deuterium was not enough to bring the chamber up to 1 atm, but it got fairly close. In the future I’ll use a 150mL reservoir and push the heating duration closer to 3 or 4hrs.

As of now the next step is to install the treated titanium in the fusor.

Mark Rowley

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Richard Hull
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Re: Apparatus for Making a Deuterated Target

Post by Richard Hull » Sat Jul 03, 2021 7:46 pm

This is fabulous stuff! You really lay it out with a great balance of plenty of images and explanatory text. I remain amazed at your doggedly pursuing the issues that interest you and those of us witnessing your many and continued efforts. A shining example of open source sharing.

You note the 7mtorr yellow jacket number. That is what I got at my best with my old yellow jacket pump on fusor II and III. For a well kept refrigeration pump they are rather fantastic. One of the few I ever had that performed on a par with a good welch belt drive, (which I consider the gold standard).

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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Mark Rowley
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Re: Apparatus for Making a Deuterated Target

Post by Mark Rowley » Sat Jul 03, 2021 9:56 pm

Thanks Richard. It’s a definitely a fun pastime, and yes.. the Yellowjacket is a great pump. Thanks again for the recommendation! It must’ve been around 2002 or so.

RESULTS
I decided to install the titanium in the fusor by using a slide-in aluminum sleeve.
B2EE93F5-63E9-44D4-A82E-235526838B92.jpeg
Even though the fusor is water cooled, I expected this to heat up rather quickly causing the typical associated issues. There’s just no way to firmly attach the titanium to the cooled fusor wall without extensive machining.

So today’s run provided promising yet inconclusive results.
For a freshly opened chamber and subsequent pump down, the fusor instantly yielded a TIER of about 5.4E+5 n/s at 55kV / 0.3mA!! Never before have I seen those numbers at such low current and within seconds of switching on the power.

So here’s where it became expectedly troublesome. As I ramped up the voltage and subsequent current, it began to plateau just under 2E+6 n/s. Increasing the voltage any further resulted in a diminished neutron yield. This was not the case under normal conditions as any increase of voltage resulted in considerably more neuts. It’s fairly clear target heating was poisoning the conditions within the fusor. It’s somewhat reminiscent of how things behaved before cooling was added to the design.

So where to go from here? Well, I still have some unrelated projects to complete with Fusor2020 so I’ll remove the titanium target and restore it to normal operating conditions. Once done with the other projects (psu modification and Maciek’s track detectors), Ill make some new deuterated target material and install it in the BoT for testing. Afterwards, a cube fusor may be in the works. Seems like it’d be easy to make water cooled endcaps where titanium targets could be firmly secured to their respective chamber sides. A cylindrical grid would be used to create opposing deuteron beams to hit each deuterated target (similar to Jon’s titanium coated endcap design. Definitely no shortage of projects for the foreseeable future!

Mark Rowley

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