Beam on Target Project (BOT 2021)

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: Beam on Target Project (BOT 2021)

Post by Mark Rowley » Tue Jan 05, 2021 7:51 am

Solid machined aluminum target holder. Not flimsy at all. Here’s a good shot of it with the Ti target seated in place. Due to the angle of the pic, the set screw is not easily visible (on the right side).

9817BC73-56CC-4A09-A92D-C1F0F6735A10.jpeg

The Ti target is about the size and thickness of a quarter.
The set screw wasn’t centered and it appears to have seated just above the lower edge of the target. So when it heated up, the tension caused it to snap out.

Details on the target:
Titanium (Ti) 24.26mm Metal Disc... https://www.amazon.com/dp/B07V3YL9X8?re ... b_ap_share

Mark Rowley

Jon Rosenstiel
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Re: Beam on Target Project (BOT 2021)

Post by Jon Rosenstiel » Tue Jan 05, 2021 4:54 pm

Mark,

Very nice indeed. Is your Ti target pure Ti or the usual 6Al-4V alloy?

JonR
I like old-timey heavy electronics that you don't have to hold down
with one hand while pushing the on/off button with the other.

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Mark Rowley
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Re: Beam on Target Project (BOT 2021)

Post by Mark Rowley » Tue Jan 05, 2021 5:30 pm

Thanks Jon
The seller claims 99.7% purity and no mention of any alloy content. His ratings are good so that's about all I can put trust in.

Mark Rowley

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Mark Rowley
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Re: Beam on Target Project (BOT 2021)

Post by Mark Rowley » Sun Jan 10, 2021 10:19 pm

Just some eye candy shots today while waiting on the quartz tubing.

This was a very low power run while I was learning how to maximize the differential pumping arrangement. As you can hear in the video I was getting a small smattering of neutrons (louder beeps).

https://youtu.be/sWgvnNpuL7k

Through the viewport
48084695-977B-4EEC-91FB-687594CB9F98.jpeg


The camera was on the inside wall of some lead shielding. Note the X-ray interference.
EA6B6264-C020-4197-A231-9BAB8619CD91.jpeg

Mark Rowley

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Mark Rowley
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Re: Beam on Target Project (BOT 2021)

Post by Mark Rowley » Sun Jan 17, 2021 4:43 am

Finished the ECR yoke and adjusted it to ~890 gauss at the center using a Hall effect magnetometer. It’s fairly stable within the 19mm diameter of the quartz tube and begins to change a bit as you get closer to the yoke.

This one part made a substantial difference at maintaining a plasma to 1mTorr and below. Even by opening the Varian HS-2 diff pump to full throttle I couldn’t extinguish it. This effect in concert with the crude capillary type differential pumping should make the ion source quite stable during sustained long term operation. Heating is almost non existent with the quartz and microwave leakage is zero when measuring past 6” from the exciter coupling.

Here’s the deuterium plasma with the TC gauge bottomed out.
D3FCAD19-97F5-4F1E-928A-2004D1B2996C.jpeg


Better shot of the ECR yoke with deuterium plasma at 50mTorr. This was taken before the yoke was properly dialed in.
42F75883-9453-495D-973A-CD0C849F768A.jpeg

Still lots to do. The magnetron supply is still in “oven” pulse mode but throttled back with a ballast resistor and a 0.2uF cap. The entire power supply will be re-arranged in a week or so to provide continuous DC. Just waiting for parts. Electron suppression is also on the immediate to-do list.

Gotta say, so far this project has been (and will continue to be) a phenomenal learning experience. I highly encourage anyone to proceed in this direction after the fusor. And what’s especially cool is the potential of applying this tech back to the fusor after ion source tech is learned. Lots of fun to be had.

Mark Rowley
Last edited by Mark Rowley on Sun Jan 17, 2021 9:29 am, edited 1 time in total.

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Richard Hull
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Re: Beam on Target Project (BOT 2021)

Post by Richard Hull » Sun Jan 17, 2021 8:58 am

A learning experience or even a phenomenal learning experience is a great understatement! You will be richer for the effort, regardless. I notice the glass accelerator tube fluorescing due to UV. Now what wavelength? Long UV no problem. Short wave UV with glass again, no problem. Short wave UV with Quartz tube, a real problem. Vacuum UV with Quartz or glass probably not too bad. You know to how to suppress the x-radiation, I would be sure to avoid the UV once a Quartz tube is used.

The images are great and I love the work you are doing 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.

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