Titanium Coated Endcaps for the Cube Fusor

This area is for discussions involving any fusion related radiation metrology issues. Neutrons are the key signature of fusion, but other radiations are of interest to the amateur fusioneer as well.
Post Reply
Jon Rosenstiel
Posts: 1494
Joined: Thu Jun 28, 2001 1:30 am
Real name: Jon Rosenstiel
Location: Southern California

Titanium Coated Endcaps for the Cube Fusor

Post by Jon Rosenstiel »

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
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)
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)
Tungsten boat with titanium pellets.
Tungsten boat with titanium pellets.
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.
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.
Ready to rock.
Ready to rock.
Before/after Ti coating.
Before/after Ti coating.
NPR comparisons.
NPR comparisons.
User avatar
Mark Rowley
Posts: 909
Joined: Sun Dec 29, 2002 12:20 am
Real name: Mark Rowley
Location: Sacramento California
Contact:

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Mark Rowley »

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

MR
User avatar
Jim Kovalchick
Posts: 717
Joined: Wed Apr 13, 2011 8:00 pm
Real name:

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Jim Kovalchick »

Wow!
User avatar
Liam David
Posts: 518
Joined: Sat Jan 25, 2014 5:30 pm
Real name: Liam David
Location: PPPL

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Liam David »

Jumping on the bandwagon, wow! Any operational difficulties with outgassing or was that not an issue with the cooling?
Jon Rosenstiel
Posts: 1494
Joined: Thu Jun 28, 2001 1:30 am
Real name: Jon Rosenstiel
Location: Southern California

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Jon Rosenstiel »

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
User avatar
Mark Rowley
Posts: 909
Joined: Sun Dec 29, 2002 12:20 am
Real name: Mark Rowley
Location: Sacramento California
Contact:

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Mark Rowley »

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 2:37 am, edited 1 time in total.
User avatar
Richard Hull
Moderator
Posts: 14992
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Richard Hull »

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
User avatar
Jim Kovalchick
Posts: 717
Joined: Wed Apr 13, 2011 8:00 pm
Real name:

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Jim Kovalchick »

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
User avatar
Jim Kovalchick
Posts: 717
Joined: Wed Apr 13, 2011 8:00 pm
Real name:

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Jim Kovalchick »

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
Posts: 1494
Joined: Thu Jun 28, 2001 1:30 am
Real name: Jon Rosenstiel
Location: Southern California

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Jon Rosenstiel »

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
Roberto Ferrari
Posts: 364
Joined: Tue Mar 02, 2004 12:21 pm
Real name: Roberto Ferrari
Location: Argentina
Contact:

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Roberto Ferrari »

Jon
A superb setup, as always.

But help me to understand. Wasn´t enough to use a titanium sheet?

Roberto
Jon Rosenstiel
Posts: 1494
Joined: Thu Jun 28, 2001 1:30 am
Real name: Jon Rosenstiel
Location: Southern California

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Jon Rosenstiel »

Jim,
Today I tried (twice) what you suggested, taking a reading at 40 kV after a 50 kV run. The changes were small, just the typical run to run differences.

I'm attaching a paper with info gleaned from the K J Lesker website. As I pretty much followed what they had done I would guess the Ti coating thickness on my endcaps would be in the neighborhood of 2000 angstroms. (200 nm, 0.02 micron) I think, just as with a commercial neutron generator, the coating will eventually burn off.

No idea about Pd, but according to the Lesker website “thermally evaporating palladium is difficult, if not impossible”. E-beam evaporation is the recommended method.

I recall Joe telling me that one could not sputter titanium as you describe, unfortunately, I don’t remember what the reason was.

Attached find results from today’s runs. I got brave and cranked her up to 60 kV. Wow again!

Jon Rosenstiel
Attachments
Today's runs.
Today's runs.
Dreamin' about the future.
Dreamin' about the future.
Tungsten boat EVS20A015W.pdf
(93.51 KiB) Downloaded 235 times
User avatar
Liam David
Posts: 518
Joined: Sat Jan 25, 2014 5:30 pm
Real name: Liam David
Location: PPPL

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Liam David »

The ultra-thin layer would explain why outgassing isn't an issue. Titanium's thermal conductivity is terrible at <10% of aluminum, so the thin layer allows the aluminum to pull the heat away quickly. I think a sheet would fare worse, both due to the thousand-fold greater thickness and worse thermal interface between metals.
Jon Rosenstiel
Posts: 1494
Joined: Thu Jun 28, 2001 1:30 am
Real name: Jon Rosenstiel
Location: Southern California

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Jon Rosenstiel »

Thanks Roberto.

The endcaps have a concave radius, and from my experience titanium sheet is nearly impossible to form.

JonR
User avatar
Jim Kovalchick
Posts: 717
Joined: Wed Apr 13, 2011 8:00 pm
Real name:

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Jim Kovalchick »

...also Titanium sheet outgasses terribly.
Jon Rosenstiel
Posts: 1494
Joined: Thu Jun 28, 2001 1:30 am
Real name: Jon Rosenstiel
Location: Southern California

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Jon Rosenstiel »

I wonder if titanium’s effect on neutron production is, in some way, related to its gettering action? During the coating process I’ve noticed that when the Ti pellets melt and start vaporizing chamber pressure drops about 2E-05 Torr.

JonR
User avatar
Richard Hull
Moderator
Posts: 14992
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Richard Hull »

You bet it is a getter! what can it form? Assuming the deuterium gas mass ratio to tramp gas is through the roof and it is in most high performing systems. There is only one gettered product Titanium:deuteron alloy deuteride deposition all over the place. We have called it wall loading and this is concentrated where a deuteron been hits the titanium. Gettering of a desired gas IS wall loading. Gettering of harmful, unwanted tramp gases is purifying an already decent vacuum. Both actions are desired, but to different end results. Such action creates a self-aiding bit of BOT. This is enhanced in beaming systems. Spheres do this via surface area deposition of fast neutrals, but at net reduced area delivering current. Cubes and crosses do this provided they have a cylinder cathode to do the focused high current beaming. Smaller cubes and crosses do better due to mean free path and confined targets.

Aluminum cylinder fusors maybe the best in this venue with cylinder cathodes and water cooled aluminum target ends with suitable copper post mounted targets just off the aluminum ends. I attach a simple suggestive diagram below the cube and the cross tend to have sharp union edges that are field disruptive throughout, are needless and act to attract deuterons at high field points. The cylinder keeps the concept pure or at least as pure as in possible. It might prove interesting to lengthen the cylinder cathode. Many of the target and cylinder iterations might benefit from threaded attachment for experimental change-out. For field concentration the concave targets could be much smaller than drawn in my example as they will stick out as high field targets set off the anode end plates.

Richard Hull
Attachments
Cylinder concept.jpg
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
Roberto Ferrari
Posts: 364
Joined: Tue Mar 02, 2004 12:21 pm
Real name: Roberto Ferrari
Location: Argentina
Contact:

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Roberto Ferrari »

Jon, Jim, Richard
Thanks for your comments.
Being unable to assembly a PVD, what about heating a titanium wire in a high vacuum, as in sublimation pumps?
Some will condense in an adecuately positioned piece.
Am I wrong?
User avatar
Jim Kovalchick
Posts: 717
Joined: Wed Apr 13, 2011 8:00 pm
Real name:

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Jim Kovalchick »

Roberto,
I recommend going to the K J Lesker site that Jon referenced. I looked into it yesterday. Sounds like Ti is pretty hard to work with because of tendency to spit.

Jim K
Jon Rosenstiel
Posts: 1494
Joined: Thu Jun 28, 2001 1:30 am
Real name: Jon Rosenstiel
Location: Southern California

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Jon Rosenstiel »

Roberto,
I tried what this guy in the video shows, and it did result in a thin coating. But it's extremely slow, and the titanium wire filaments burn out much too easily.

https://youtu.be/-lh1LhoRBaY

JonR
Roberto Ferrari
Posts: 364
Joined: Tue Mar 02, 2004 12:21 pm
Real name: Roberto Ferrari
Location: Argentina
Contact:

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Roberto Ferrari »

Jim and Jon,

Understood, thanks.
Roberto
Post Reply

Return to “Neutrons, Radiation, and Detection (& FAQs)”