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.
Roberto Ferrari
Posts: 357
Joined: Tue Mar 02, 2004 5:21 pm
Real name: Roberto Ferrari
Location: Argentina
Contact:

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Roberto Ferrari » Wed Feb 17, 2021 11:26 pm

Jon
A superb setup, as always.

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

Roberto

Jon Rosenstiel
Posts: 1440
Joined: Thu Jun 28, 2001 5:30 am
Real name: Jon Rosenstiel
Location: Southern California

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Jon Rosenstiel » Thu Feb 18, 2021 12:11 am

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
2-17-2021.png
Today's runs.
2-17-2021 power trend line.png
Dreamin' about the future.
Tungsten boat EVS20A015W.pdf
(93.51 KiB) Downloaded 31 times
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.

User avatar
Liam David
Posts: 197
Joined: Sat Jan 25, 2014 10:30 pm
Real name: Liam David
Location: Arizona

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Liam David » Thu Feb 18, 2021 12:42 am

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: 1440
Joined: Thu Jun 28, 2001 5:30 am
Real name: Jon Rosenstiel
Location: Southern California

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Jon Rosenstiel » Thu Feb 18, 2021 12:53 am

Thanks Roberto.

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

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.

User avatar
Jim Kovalchick
Posts: 528
Joined: Thu Apr 14, 2011 12:00 am
Real name:

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Jim Kovalchick » Thu Feb 18, 2021 1:36 am

...also Titanium sheet outgasses terribly.

Jon Rosenstiel
Posts: 1440
Joined: Thu Jun 28, 2001 5:30 am
Real name: Jon Rosenstiel
Location: Southern California

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Jon Rosenstiel » Thu Feb 18, 2021 4:12 am

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
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.

User avatar
Richard Hull
Moderator
Posts: 12927
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Richard Hull » Thu Feb 18, 2021 6:47 am

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

Roberto Ferrari
Posts: 357
Joined: Tue Mar 02, 2004 5:21 pm
Real name: Roberto Ferrari
Location: Argentina
Contact:

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Roberto Ferrari » Thu Feb 18, 2021 8:45 pm

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: 528
Joined: Thu Apr 14, 2011 12:00 am
Real name:

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Jim Kovalchick » Thu Feb 18, 2021 9:23 pm

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: 1440
Joined: Thu Jun 28, 2001 5:30 am
Real name: Jon Rosenstiel
Location: Southern California

Re: Titanium Coated Endcaps for the Cube Fusor

Post by Jon Rosenstiel » Thu Feb 18, 2021 10:06 pm

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
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.

Post Reply

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