Palladium and Fusion

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danielchristensen
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Palladium and Fusion

Post by danielchristensen » Wed Apr 19, 2017 8:06 pm

Hi Everybody,

Myself and two other students from the Northwest Nuclear Consortium (now incorporated as a 501 (c) (3) called Northwest Nuclear Laboratories) did research on the topic of palladium and fusion during this past school year. As of yet, we haven’t made any solid conclusions of efficacy, but I thought I’d share what we’ve done and found so far.

As has been mentioned in other posts, beam-target reactions make up a large portion of total number of fusion, and as more deuterium is embedded in chamber walls, the amount of fusion events goes up. Due to cost, our first research done in to metals that can absorb hydrogen tested titanium, which can absorb roughly 20x it’s volume in deuterium. It was shown that there was a 30% increase in neutron output when titanium was added to the chamber. Research done at the University of Wisconsin-Madison corroborates this (http://iec.neep.wisc.edu/usjapan/9th-US ... /Rusch.pdf). The material best able to absorb deuterium is palladium, which is capable of absorbing 900x it’s volume in deuterium.

In order to create a palladium target while keeping a reasonable budget, we widened two 5 gram ingots on an anvil to a surface area of roughly 1.5 square inches. A property of palladium that we found in background research is that once a temperature of 80 celsius is reached, it’s deuterium absorption ability increases markedly. Our reactor has a water cooling system which makes it impossible to reach the temperature at which absorption starts in earnest, so that the shield’s main component, borated paraffin, doesn’t melt. Melting the shield is frowned upon. To get around this, we designed and implemented a device into our fusor that acted to thermally isolate the palladium sample from the cooling system.

On the conflats that are inline with plasma, there were existing holes used to mount titanium for experimentation, which we took advantage of these holes when constructing the isolator. In these holes, we inserted threaded rods which were used to mount ceramic standoffs. To these standoffs, we mounted a stainless steel disc, and to the disc we mounted the palladium. The palladium was moderately convex and was attached in such a way that there was maximum contact. Palladium has similar thermal expansion to steel, so we expected relatively good thermal coupling. We intended for the palladium to be heated by the plasma’s thermal load.

In actuality, there was an issue with the thermal coupling of the palladium. While there was little thermal expansion, deuterium absorption caused enough expansion for the sample to bow away from the steel plate and only be coupled by the two mounting screws. This caused a runaway effect, where the palladium heated much more rapidly than the rest of the device. We came to the conclusion that the palladium was getting so hot that it was evaporating and being ionized by the beam. Heavy ions in the plasma cause elevated current draw, which could result in premature breakdown of diodes in the Cockcroft Walton. That’s bad.

As shown in the attached data, there was a drop of nearly 50% in neutrons. These numbers don’t represent isotropic emission, just what the detector saw. We are at the moment attributing the stark decrease in neutrons to the presence of palladium ions in the plasma, draining much of the energy that would be going to fusion. We don’t think that these figures show that palladium won’t work, and when we do more research with different conditions that we may very well get an increase in neutron flux. We’re looking into using vapor deposition to get near perfect thermal coupling as an alternative method of introducing palladium.

I’m happy to address any questions or concerns,
Daniel Christensen
Attachments
Pd Graph.PNG
Palladium Fusor Data

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Richard Hull
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Re: Palladium and Fusion

Post by Richard Hull » Thu Apr 20, 2017 5:52 am

Daniel, Thanks for the report on your work thus far. My original paladium "boosting" idea of years past was to possibly heavy plate or foil line palladium over the entire inner shere of the fusor to trap and hold fast neutral deuterium atoms which are all doomed to hit the walls. Electron bomabardment would pop out some of these atoms as ionized deuterons and undergo full energy acceleration having been ionized at or near the shell.

Until an 80% or greater covering on the entire interior shell wall is done with palladium I would still hold for a net increase in fusion. I have been musing over how to do this for some time.

A true, focused, high current deuteron beam on palladium target just might do what you observe due to the concentrated beam current. However, such high current density beams are rare over the vast surface area of a spherical fusor.

Again, thanks for your experimental input and findings.

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.

danielchristensen
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Re: Palladium and Fusion

Post by danielchristensen » Thu Apr 20, 2017 5:24 pm

Richard,
What you mention about a high focus beam in a chamber is exactly what we have at the NWNC. Instead of a geodesic poissor, we simply have four titanium washers in the shape of a cylinder which forms a single beam. I've attached a picture of what we have running currently.
Daniel
Attachments
NWNC Fusor Beam.png
NWNL Fusor Beam

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Richard Hull
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Re: Palladium and Fusion

Post by Richard Hull » Thu Apr 20, 2017 9:23 pm

Nice Beam! Yep, that's a real local area heater/sputterer. I agree, you probably have a lot of palladium atoms/ions freed into the chamber.


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.

Roberto Ferrari
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Re: Palladium and Fusion

Post by Roberto Ferrari » Sat Apr 22, 2017 6:33 pm

Hi Daniel

Would you be so kind to publish a diagram showing the electrodes distribution?
Thanks and good luck with your setup.
Roberto

Bruce Meagher
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Re: Palladium and Fusion

Post by Bruce Meagher » Sat Apr 22, 2017 9:29 pm

Daniel,

Congrats to you and the other students at the Northwest Nuclear Laboratories for pursuing innovative fusor research. I look forward to seeing your future reports.

A couple things you might consider in your continued research. As you’re probably well aware the stopping power of a charged particle is described by the Bethe-Bloch formula. I believe 50keV deuterons have a CSDA range of less than 0.5 micron in titanium, and in palladium that number drops almost in half (if I did the math correctly). Beam on target fusion is only happening very close to the surface and the D-D fusion cross section falls off with depth.

In "Development of a sealed-accelerator-tube neutron generator” by Verbeke et.al. the researchers state: "The neutron production efficiency of materials depends mainly on their capacity to retain deuterium and tritium and on their stopping power...Other metals (talking about metals other than Ti) form hydrides of atomic ratios up to 3, and even for 3.75 for thorium, but their higher Z and thus higher stopping power results in an overall lower neutron production efficiency.” The paper "Deuterated target comparison for pyroelectric crystal D–D nuclear fusion experiments” by Gillich et. al. has a nice table on theoretical neutron production rates (for a particular flux and energy) for several different deuterated targets that might be instructive as a comparison (although PdD2 isn’t included). It also has a nice graph of fusion cross section vs depth for their target.

You state that you wanted the target heated to get better deuterium absorption. Do you believe absorption is the dominate process at the fusor pressures / temps vs implantation? Have you considered that elevated temps with the very, very thick target might keep the overall loading low because any implantation just moves away from the surface?

Some fun experiments you might consider in the future:
- Try a few micron layer of Pd deposited a copper disk. Compare cooled vs heated.
- Repeat with Ti.
- Get a couple of commercial deuterated targets and place them in your two beams (then you’d know how good it could be).
- Use RBS or ERDA to measure the deuterium loading vs depth after your runs (there might be local university / company with that capability)
- Measure the beam current hitting your target
- Measure the beam energy spectrum

With the last two you could even simulate the expected BoT fusion rate component of your fusor.

I’ve been slowly working on a small BoT system myself, and although I’m only interested in cooled Ti targets these are some of the things I’m hoping to measure.

Again, congrats on your work.

Bruce

danielchristensen
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Re: Palladium and Fusion

Post by danielchristensen » Mon Apr 24, 2017 4:07 am

Roberto,
I've attached an image of the electrode that I think will answer your question. Also, note that the vessel is at ground and the ring is at ~50,000VDC.

Bruce,
Thank's for the info on stopping power, we haven't taken that into consideration yet. The reason we looked to heating was that when we first tried to run with palladium at low temperatures, we saw no notable change in flux. We also didn't really look into/consider that how deep the deuterium was being embedded could affect things. We actually have considered pursuing some of the experimental ideas you've suggested, namely trying a thin palladium coating on a target and finding beam current. Like I mentioned in the original post, we will probably be trying a target coated in vapor-deposited palladium. More towards the beginning of the project, Jake Hecla made the suggestion to try using a Faraday cup to measure beam current. If we made a reasonable estimate of the deuterium density, we do some math using both figures along with ENDF cross-sections to figure out a theoretical BT reaction rate. Good luck with your BoT effort!

Daniel
Attachments
NWNL Fusor 2.jpg
Interior View of NWNL Fusor

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