Titanium Coated Endcaps for the Cube Fusor

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Jon Rosenstiel
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Titanium Coated Endcaps for the Cube Fusor

Post by Jon Rosenstiel » Tue Feb 16, 2021 11:32 pm

A while back Joe Gayo suggested I try coating my cube’s endcaps with titanium, mentioned I might be surprised at the Ti coating’s effect on NPR. (Neutron Production Rate) As usual, I was a little skeptical, but the fire was lit and I decided this would also be a good opportunity to finally put together something that’s been on the back burner for better than a decade.

That something was a PVD (Physical Vapor Deposition) coating system. Over the years I had gathered most of the stuff I needed… high current vacuum feedthroughs, bell jar with shield, transformer out of an old Nor-Cal vacuum coater, etc., etc. (The transformer is a real beast, 208 V input, 5, 7.5, and 10 V output taps… rated at 4 KVA)

The coating process was somewhat intimidating as it takes lotsa’ heat to melt and vaporize titanium. Power into the 0.015” thick tungsten boat was close to 1 kW. (2.9 V, 330 A) Actual coating time for each endcap was 7-minutes.

Ok, enough about the coater, on to the results. An NPR of 2.8E+06 n/s at 40 kV, 10 mA was reached after 34-minutes of conditioning. This equaled the best the cube had ever achieved.

The next day, after 25-minutes of operation, NPR at 40 kV, 10 mA was 3.2 to 3.4E+06 n/s. Wow!

On the third day of conditioning/operation I upped the input power to 50 kV, 10 mA. During a 5-minute silver activation run TIER averaged 6.8E+06 n/s. (Previous best for the cube was 4.5E+06 n/s. Previous best for my spherical fusor was 2.1E+06 n/s) About an hour later I did another 5-minute silver activation run. Average TIER for that run was 7.3E+06 n/s. (At one point maximum TIER was close to 8.0E+06 n/s) Unbelievable!

I shot a short video of the silver activation and placed it in my Dropbox, link below. Note that the Ludlum 12’s range switch is on X100.

https://www.dropbox.com/s/m0dulrngru5z6 ... n.mp4?dl=0

Jon Rosenstiel
Attachments
001.jpg
400 A, 50 V copper feedthroughs. The boat holding blocks were machined from C14500 tellurium copper. To the left of the tungsten boat is a 5 kV feedthrough used for glow cleaning. Just under the sample holder is a shutter attached to a rotary motion feedthrough. The shutter protects the endcap from the gas (oxides) that titanium emits upon first heating. Behind and to the left of the baseplate is a molecular sieve and its pink balloon reservoir. (Used to dry the argon glow-cleaning/backfill gas)
002.jpg
Tungsten boat with titanium pellets.
003.jpg
Stainless steel shields to protect bell jar from heat and from becoming coated with titanium. Slot allows shutter to open fully. Square viewport with sacrificial glass window.
004.jpg
Ready to rock.
005.jpg
Before/after Ti coating.
006.png
NPR comparisons.
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: Titanium Coated Endcaps for the Cube Fusor

Post by Mark Rowley » Tue Feb 16, 2021 11:58 pm

All I can say is wow!!!
Extremely impressive work Jon

MR

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Jim Kovalchick
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Re: Titanium Coated Endcaps for the Cube Fusor

Post by Jim Kovalchick » Wed Feb 17, 2021 12:22 am

Wow!

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Liam David
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Re: Titanium Coated Endcaps for the Cube Fusor

Post by Liam David » Wed Feb 17, 2021 12:57 am

Jumping on the bandwagon, wow! Any operational difficulties with outgassing or was that not an issue with the cooling?

Jon Rosenstiel
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Re: Titanium Coated Endcaps for the Cube Fusor

Post by Jon Rosenstiel » Wed Feb 17, 2021 1:29 am

Thanks guys.

Liam, as of yet I haven't noticed any issues with outgassing, she's been quite stable. Did have lots of outgassing/runaway problems (not sure which it was) with a titanium cathode. Now I'm wondering about how well an embedded titanium target (al la Mark Rowley) would work.

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: Titanium Coated Endcaps for the Cube Fusor

Post by Mark Rowley » Wed Feb 17, 2021 5:52 am

Funny you should mention that Jon. I just finished a brief chat with Tim Koeth about deuterium loading of titanium targets. Building the loading apparatus seems remarkably simple and most of the parts are ready to be assembled. But first things first... gotta finish the latest set of modifications to the BoT. And that should be done in the next couple days. Stay tuned!

Mark Rowley
Last edited by Mark Rowley on Wed Feb 17, 2021 7:37 am, edited 1 time in total.

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Richard Hull
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Re: Titanium Coated Endcaps for the Cube Fusor

Post by Richard Hull » Wed Feb 17, 2021 7:07 am

Fabulous piece of work, as always, Jon. The numbers are out of sight!
For the newbies following this please do not believe that all you need is a 10ma supply to do what Jon is doing at 10ma. You will always need "reserve" current capability against startup and unforeseen issues that always pop up. In addition, like Jon and many others who have long worked fusion in fusors, you will need lots of operational experience in your first device and apply that to any future modifications and new systems you build.

Jon is and has always been the number one and most capable at advancing the art here. An expert machinist, he can and does turn ideas into metal that works fusion. He has a fabulous grasp of critical measurements in the area of radiation. His ingenuity is of the first order. I can't say enough about his work through the years 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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Jim Kovalchick
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Re: Titanium Coated Endcaps for the Cube Fusor

Post by Jim Kovalchick » Wed Feb 17, 2021 9:22 am

Jon,
I am curious about the shape of your TIER vs voltage curve for your new Ti end caps. There is a remarkable change between 40 and 50 kV. Did you try taking another reading at 40 kV after your run at 50 kV? I would have guessed that the primary influence on the shape of the curve is reaction cross section and that effects of functional efficiencies would be more linear. I wonder if taking another reading at 40 kV after having run at 50 would show higher numbers at 40 at least temporarily because wall loading that happened at 50.

Jim K

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Jim Kovalchick
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Re: Titanium Coated Endcaps for the Cube Fusor

Post by Jim Kovalchick » Wed Feb 17, 2021 6:40 pm

Jon, it doesn't seem like there needs to much Ti on your end pieces to see the effect. That may be why outgassing is not a problem. Do you think the Ti will eventually burn off?

Do you think the same effect could be achieved with Pd instead of Ti?

I wonder if the fusor itself could be used to sputter coat the inside of the chamber to see this effect. For example, incorporate a small bit of Ti or Pd into a tungsten grid and light it up. I am already imagining a problem with not getting the deposition where you wanted because of the beams. One solution may be to turn the grid during the sputtering and then return it to dead center for the test.

You have my brain spinning.

Jim K

Jon Rosenstiel
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Re: Titanium Coated Endcaps for the Cube Fusor

Post by Jon Rosenstiel » Wed Feb 17, 2021 10:45 pm

Thank you for the kind words Richard, but you guys never get to see all the stuff I screw up and have to toss out.

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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