Dysprosium activation runs planned

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
User avatar
Richard Hull
Site Admin
Posts: 10810
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Dysprosium activation runs planned

Post by Richard Hull » Mon Jun 11, 2018 9:13 am

I have spent the last three days getting fusor IV up to operating levels that will allow my activation of dysprosium. I will need at least a million neuts per second isotropic, I figure. I got it up to 800,000 n/s today.

I ordered two of Metallium's Dy coins and hope they will arrive soon as they shipped last Thursday. I mentioned this in my last FAQ here...

viewtopic.php?f=31&t=12251

I am big on Dy due to its cross section of 800 barns and 2000 barns to its metastable isotopes.

I have Dy in my element collection petting zoo, but it is a largish rod about 1" in diameter and 1" long. I didn't want to cut it up, so I ordered the coins. I might try and use my jewelers rolling mill on one of the coins to create a foil. (Larger surface area) I fear, however that the "coining" process might have terribly hardened the Dy and rolling might just crack the coin. I have rolled out a lot of silver and indium foil in the past. Indium is nasty as it needs to had a good layer of its protective oxide or is sticks to the rolls. I need to leave it out about 24 hours after each pass to acquire new oxide.

I went to Metallium's, "contact us", e-mail and asked about foil or a thin larger surface piece of Dy and got a quick response that the owner was out of town and that he would get back. Two weeks passed and nothing.....I re-e-mailed and never got a reply. Hmm. The coins were in stock and I just gave up and ordered them. They are supposedly about the size of a U.S. penny. Two placed side by side would give a decent surface area, But I will try and roll one.

I will keep in touch on this.

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.

User avatar
Frank Sanns
Site Admin
Posts: 1553
Joined: Fri Jun 14, 2002 6:26 pm
Real name: Frank Sanns
Location: Pittsburgh, PA USA

Re: Dysprosium activation runs planned

Post by Frank Sanns » Mon Jun 11, 2018 3:43 pm

Work hardening is a problem when mechanical energy is put into most metals. There is a limit to how much working a metal can take before it loses its ductility and becomes brittle. For this reason, it is essential to anneal most metals when working them. Some of the softer metals will self anneal with time but most require a good dose of heat.

It looks like a flash up somewhere between 600C and 1000C should do it for you. In general a torch is used to fan the item with heat until the very first signs of high temperature oxidation is happening. This is about right with items like gold, silver copper and other metals, to indicate high enough temperatures to anneal have been met.

Annealing resets the hardness so it can be implemented between each pass through the roll mill. I imagine some fairly thin foils could be made.

User avatar
Rich Feldman
Posts: 962
Joined: Mon Dec 21, 2009 11:59 pm
Real name: Rich Feldman
Location: Santa Clara County, CA, USA

Re: Dysprosium activation runs planned

Post by Rich Feldman » Mon Jun 11, 2018 4:16 pm

Fusors and rolling mills, how about that! Is physical thin-ness desirable to reduce the activated metal's self-shielding of decay radiation?

There's stainless steel foil sold for wrapping air-sensitive materials in the furnace, when things need that kind of annealing. Certainly not news to an old jewelry rolling mill owner like Richard. I can attest that niobium C-103 alloy is outstandingly workable. Cold forged my wedding ring from 3/8" length of 3/8" diameter solid round rod, using a hammer & punch & mandrels. No annealing and no evidence of cracking.

You know the penny-rolling mills set up at tourist sites? Seems like the coins come out elongated 3:1, even more than being run over by a train. Multiple passes might create even more elongation. Then you could see if the distorted grain structure makes the metal anisotropic with respect to neutrons or decay radiation. Like the magnetization of transformer steel sheets, as discovered more than 100 years ago. If you know the answer then the experiment isn't actually science. :-)
.
7766.PNG
Richard Feldman

User avatar
Richard Hull
Site Admin
Posts: 10810
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: Dysprosium activation runs planned

Post by Richard Hull » Tue Jun 12, 2018 5:08 am

I received the dysprosium coins today and lashed my myself to the mast of fusor IV for 4 hours. Results below.

Regarding Frank's discussions on annealing....(Solution for work hardening). Having earned good money as a custom jewelry maker working mostly in silver, gold and platinum in the 70's as a money making hobby, I have annealed many metals many times while rolling or planishing them.

As I thought, the coins had a nice finished surface. However, the rim was horrid and grainy.. Even before I attempted to roll one, I feared I was right. I had rolled in three passes barely taking the coin out of round before cracks appeared at the edge, all around. I ceased rolling at that point.

Set up

I am smart enough to know a little material science and consulted a number of references I have on the rare earth metals properties. Dysprosium is touted to be a soft and malleable metal. Great! Fly #1 in the ointment...Reading a bit further "However, very small inclusions beyond high purity as little as .3% can change dysprosium's working characteristics considerably". ( my coins are warranted to have 1% garbage in them - 99% pure). Fly #2 in the ointment.... All rare earths are rapidly attacked by moisture and oxygen. However, about half of them, dysprosium among them, are relatively stable at room temperature in moderately dry air over a period of years. Annealing?? Well is is stated that at 300 degrees C dysprosium rapidly oxides in air and turns to the oxide near 800 deg C. It has to be annealed under vacuum or inert atmosphere and cooled slowly in same. Annealing is sort of out of the picture assuming my 99% sample can be annealed at all!

I stuck the two coins on a a cardboard holder that would place them in my less than ideal neutron oven so they could be very quickly removed and placed under a 2 inch mica GM detector connected to my NIM system for counting.

Three runs on Fusor IV

I really wanted the Dy to work out so I went far beyond any activation session I have ever run. I ran my system for 1 hour at an average isotropic emission of 780,000 n/s As I vary the voltages and pressures over the hour, I run one minute counts, record the data for that minute and then adjust the voltage, usually upward and the pressure of D2 upward. With each increased pressure, the voltage must be reduced until the walls absorb some of the D2 and allow the voltage to be raised once more. The weakest one minute count was 406,000n/s and the strongest was 1,305,000 n/s.

All of this was a tedious circus of continued control and adjustment. I have never done this long a run before. After 1 hour, I figured this would give me something to talk or cry about. So, I shut off fusor IV's voltage, and grabbed the Dy and raced to the NIM system. A 1 minute count was a bust for Dy as an activator. It read only about 1.5X my lab's background count! Statistically significant? Yes! In subsequent 1 minute counts, it lost counts as expected.

Frustrated and exasperated, I decided to run Indium as I had the fusor near peak operation at or beyond 1 million n/s. I have both indium and silver foil in machined aluminum rings that are exactly the diameter of the GM detector. I was pretty burned out after the hour long bout with the Dy.
I ran a 13 minute activation run using the same technique as with Dy. The result was that the average of 10 one minute data runs, I produced 956,000 n/s where the weakest minute run was 796,000 n/s and the best was a near record of 1,500,000 n/s. **NOTE the fusor system was left running and at full power between all data runs. I just recorded a one minute timed data result (voltage, current, pressure, count), then I would quickly raise or lower the voltage and pressure, hit the counter reset button for another timed run and so on. Thus 10 one minute runs took 13 minutes at optimum run conditions, just like the Dy run. I again killed the voltage after the last run and raced for the GM/NIM system. The result was better, of course, and I activated indium to 2.1X lab background. A longer run would have been better, but I was sweaty in the Virginia muggy 90 deg heat in the sealed lab. In short, I was pretty blown-out.

Still, fusor IV was working so fabulously I persevered and ran Silver. I did a total of 5 0ne minute runs over 8 minutes. Only the fusor's 1 mega runs kept me going. The average run was 1,200,000 n/s. The weakest run was 978,000 and the best was 1,690,000 n/s (record?)! the GM/NIM count was 3.6X background!

I shutdown the system (takes about 25 minutes until totally down), and sat reducing and crunching three pages of data, given above, swilling water and eating the boiled egg and bologna sandwich my wife brought out to the lab 2 hours ago.

Bottom line....As noted in my FAQ... If you can't snag rhodium, silver is the penultimate activation material for the amateur, would-be fusioneer who can't count neutrons or afford a bubble detector. Indium is a good one but not as good as silver before a GM counter.
***Note all activation work takes a gang o' neutrons from a fusor. first pass fusioneers rarely even come close to activation output levels.
It should also be noted that mica windowed GM tubes are primarily alpha-beta counters and are particularly bad at counting gamma rays. Maybe only 1-2% are typically counted. Thus, I cannot speak to any gammas from the above runs.

Oh....Did I say? Dy is crap! I fear that all I got was surface betas from just 28% of the metal's surface mass. and got less than 1/2 of the total I could have got had I ran for the needed 2 hours to bring it up to 1/2 life emission rate. Oh well....Now we know.

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.

John Futter
Posts: 1288
Joined: Thu Apr 22, 2004 2:29 am
Real name:
Contact:

Re: Dysprosium activation runs planned

Post by John Futter » Tue Jun 12, 2018 7:16 am

My only introduction to dysprosium was at work to make some ion source targets for a Dy beam
the rod i had was as hard as. Hard on lathe tooling harder on cobalt drill bits but i did get what i wanted
cutting a bit off in vice to put in the lathe saw a new hacksaw blade dulled to oblivian

User avatar
Richard Hull
Site Admin
Posts: 10810
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: Dysprosium activation runs planned

Post by Richard Hull » Tue Jun 12, 2018 6:06 pm

One thing about all the books, they don't often go into how various impurities in the rare earth metals affect working the metal. They paint with a broad brush. It is very rare to find a rare earth metal better than 99% pure. Therein, lies the rub that gives the lie to the first sentence, "the pure metal is soft and ductile."

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.

User avatar
Rich Feldman
Posts: 962
Joined: Mon Dec 21, 2009 11:59 pm
Real name: Rich Feldman
Location: Santa Clara County, CA, USA

Re: Dysprosium activation runs planned

Post by Rich Feldman » Tue Jun 12, 2018 6:48 pm

Hooray for Richard, persevering in the Virginia heat to squish dysprosium coins and get activation data !

Sounds like separation & purification of the rare earths is pretty new in the history of metallurgy.

Not wanting to hijack your thread, Richard, here's a related story about zirconium.
In the ground it's always associated with hafnium, and they're pretty hard to separate.
The composition standards for Zr metal and its alloys have a special exception for Hf:
zr.PNG

Then came atomic energy and nuclear reactors. Zr and Hf are as nuclearly different as they are chemically similar.

Suddenly there was an important demand for hafnium-free zirconium, and the specialty metals industry learned how to make it.
It's said that surplus hafnium was piling up at Wah Chang Corp, in Oregon, and the company president wanted to find a use for it. That led to development of niobium C-103, a rocket engine alloy that's still important today.
Richard Feldman

Post Reply