Fusor 2020 Activation Experiments

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Mark Rowley
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Fusor 2020 Activation Experiments

Post by Mark Rowley »

Conducted a couple activation experiments this afternoon. I wanted to try silver activation for the first time followed by a gamma spec of indium activation.

Both samples were exposed to a TIER neutron flux of roughly 1.30E+6 (1,300,000 n/s) for 3 minutes. The silver foil was 3x3” and the indium was 2.5x2.0”. Both were about 17cm from the grid.

Silver Decay Results
Minute One: 910 counts
Minute Two: 243 counts
Minute Three: 127 counts
Minute Four: 118 counts
Minute Eight: 79 counts
Minute Ten: 56 counts
Minute Thirty Six: 37 counts (almost background)

Indium Gamma Spec Results
My gamma spec system consists of:
Theremino MCA Software
Gamma Spectacular GS1100-Pro
Bicron 1.5x1.25” NaI(TI) scintillator

I was hopeful to just get the 417keV photopeak but surprised and quite pleased to see the following as well:
138keV
819keV (the peak eventually became more pronounced)
1097keV
1294keV

1508keV and 2112keV could be in there as well but it’s very close to looking like the typical ground noise.

Here’s a screen shot of the spectra chart:
47070F42-9018-438D-A8F6-DCCA0C821F45.jpeg

For comparison and guidance, I used this activated Indium photopeak chart from Carl Willis:
DEE2D257-01AB-4D64-BD59-45006172AD86.jpeg

The indium foil in the lead castle:

BE71D1CB-0263-491A-950C-DD8DB1C8583C.jpeg

The overall run was about 4 minutes. BTI results were from about 20cm distance resulting in 45 bubbles.

EB449367-A1EE-4F4C-8934-F338C5F4FE5E.jpeg
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Re: Fusor 2020 Activation Experiments

Post by Mark Rowley »

Conducted another Indium foil activation run.
5 minutes exposure time
Estimated neutron TIER of 1.5E+6
55kV
3mA
45mTorr D2

Of note, 3hrs after activation it’s still roughly 150cpm over background.

Time lapse MCA spectra acquisition of 2200 seconds can be seen here.

https://youtu.be/qDzF7zwMZnk


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Mark Rowley
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Joe Gayo
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Re: Fusor 2020 Activation Experiments

Post by Joe Gayo »

Mark,

You probably have this mentioned elsewhere, but I can't find the post(s): What are the dimensions of the moderator, materials, and location relative to the cathode ("on-axis" with beam?). If you have time, a diagram would be great!

I'm in the process of redesigning my activation setup and looking for inspiration/reference point.

Joe
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Dennis P Brown
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Re: Fusor 2020 Activation Experiments

Post by Dennis P Brown »

Very impressive data collection system and display; the gold standard of the bubble detector is a perfect check/calibration. Very impressive. Current images of the setup/fusor would be a nice touch.
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Richard Hull
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Re: Fusor 2020 Activation Experiments

Post by Richard Hull »

I just put up a PDF file of my recent Moderator rebuild in the Neutron forum. It might be of interest.

viewtopic.php?f=13&t=13553

If you have a neutron source and want to do activation, the very best way to do this is to place what is to be activated virtually touching the fast neutron source and surround both with moderator. This is tough with a fusor and expensive with polyethylene. A typical small neutron source is placed in a plastic, weighted vial with the material to be activated and sunk into the middle of a nice clean 5 gallon paint can of water. This is ideal if you have a small source. These 5 gallon polypails are sold at large hardware outlets and harbor freight very inexpensive, too.

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
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Re: Fusor 2020 Activation Experiments

Post by Mark Rowley »

Hi Joe,
My apologies for not replying to this sooner. I got your pm and remembered you question.

My moderator is a 9x8x8” cube of standard craft store paraffin wax. The center of the cube to the grid is about 7” and I generally place activation items at 5.5”. I haven’t experimented with any closer proximities but 5.5 seems to be working well. Just yesterday I easily activated silver utensils and an ingot after a couple minutes of flux time at that distance.

It’s very close to being in axis to one of the beams, just a couple degrees off.

In this picture you can see one at a little past the 6:30 mark. Trajectory puts its very close to dead center of whatever I’m activating. Of note, the picture is just a low power / non activation run for photos only. When fusing, the entire chamber is in a lead box.

9F020097-00A9-48D2-BDF0-75F04C1ED9CF.jpeg
Here’s a pic of the paraffin cube with the CHM11:

5FE8305D-B2CB-4804-BE35-CB19A790F405.jpeg

Mark Rowley
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Richard Hull
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Re: Fusor 2020 Activation Experiments

Post by Richard Hull »

Wow! That is a gang o' paraffin! I bought 100 lbs of paraffin in 1999 from "Missey's Candles" on line. I was going to use it, but it was too much of a fire hazard, (fuel you know), to have in my home- attached lab. So I went with water moderation and now, as seen, in my fusor V postings, HDPE. Carl Willis put out a lot of moderation posts between 2003 and 2010 related to water, paraffin, heavy water, HDPE and even carbon. HDPE came out on top. You have more than enough paraffin to do the job there.

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
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Re: Fusor 2020 Activation Experiments

Post by Mark Rowley »

Richard,
Your HDPE arrangement has been nagging me to replicate it. If I can get similar pricing I’ll make the purchase next week.

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Richard Hull
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Re: Fusor 2020 Activation Experiments

Post by Richard Hull »

What will you do with all that paraffin!? I think Carl noted that paraffin also acted as a neutron absorber in large quantities. But I guess any large moderator assembly might do that
I had two 50 lb sacks and sold one at HEAS 2018. The other still sits outside under my lab porch overhang area. In all this heat, (20 straight days of 90+ with near 100% humidity), most all the slabs have merged into one 50 lb wad, just due to their mass.

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
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Re: Fusor 2020 Activation Experiments

Post by Mark Rowley »

Richard, the picture makes it look like a lot but it's only a moderate stack measuring 9 x 8 x 8". Each block measures 1.5 x 2.5 x 9 " and is practically feather light. With a coupon I think it was only about $25 worth from Hobby Lobby. The whole thing probably weighs 5 or 6lbs at best.

I'm fairly sure your stack of HDPE is actually larger (18 x 6 x 6"). I'm considering a slightly smaller HDPE stack at 14 x 6 x 6" as 14" slabs seem to be a bit more easy to come by.

I've also read and heard from quite a few reliable sources that too much moderator will absorb the neuts. I may have seen Carls post about it awhile back as well. Good info and that was taken into consideration with the 9 x 8 x 8" stack of paraffin.

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Re: Fusor 2020 Activation Experiments

Post by Mark Rowley »

-Manganese 56-
Since 2009 I’ve always been impressed with the Manganese activation experiment conducted by Carl Willis (https://youtu.be/ng6NOH8S7Bk). I’ve attempted it with weak static sources with no luck. Since the fusor has been operating fairly good lately I gave it a shot exposing a small 1.2” puck of manganese dioxide for 5 minutes at a neutron TIER of roughly 1.7E+6.

Once complete, it was quickly put in the gamma spectrometer which instantly displayed a strong 850keV photopeak.

Time lapse MCA spectra acquisition of 2000 seconds can be seen here.

https://youtu.be/AfX5w53ZB1s

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Re: Fusor 2020 Activation Experiments

Post by Richard Hull »

Fabulous work Mark! I have to get my numbers way up before I get to manganese activation. I remember Carl used the sulfate dissolved in a gallon jug. The water was the moderator as well with the saturated solution of manganese sulfate. That was really cool....A two fer...

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
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Re: Fusor 2020 Activation Experiments

Post by Mark Rowley »

-Copper 66-
This has been a tough nut to crack. I got some promising results this afternoon but nowhere near the nice photopeak I had with Mn56. To do so would’ve required a good 10+ minutes of flux time at the same neutron numbers (or higher) as I did with Manganese. Unfortunately at 1.5 to 2E+06 I’m limited to under 5 minutes due to chamber heating. Today’s copper activation experiment resulted in 3.5 minutes of activation time at an approximate neutron TIER 2E+06. I shut off the activation run when the chamber hit a surface temp of 160F.

-Gamma Spec Results-
For both background and the 1x1.5” copper plate specimen,count times were 1500 seconds respectively.

Normal background in the lead gamma spec castle was 3.0cps with a 1.5x2.25” NaI(TI) Bicron pmt.

The copper specimen registered 6.8cps when initially placed in the chamber. After 500 seconds it decayed to 4cps and at 900 seconds, 3.8cps. By 1500s seconds it was at 3.3cps.

Photopeaks at 511keV and 1040keV can be clearly seen. When equivalent background is subtracted, the 1040keV peak is more pronounced and the 511keV Is reduced by the removal of the natural lead induced photopeak at the same energy.

Total background counts:4592
Total counts with activated copper: 5575
Total counts over background: 983

I referenced Carl and Jon’s 15 year old copper activation experiment for general guidance.Their excellent report can be seen here:

viewtopic.php?f=13&t=5607&p=37584&hilit ... ion#p37584

A time lapse video of the gamma spec run can be seen here. Due to camera issues, it’s only 900 seconds of the 1500sec run.

https://youtu.be/xD3GXA-_Oqw

B41D2450-B885-444E-ABA8-B8A78558DC16.jpeg
40674412-DB30-4CDC-9ECE-51D2CF1DD55E.jpeg

This is the copper sandwiched between HDPE slabs. The copper plate is exactly 17cm from the grid.
11C21D28-79F1-4BEC-8A85-659FD77D6312.jpeg

Lead Castle,Activated Copper Plate and PMT
2AA7512B-5BB0-4389-B255-AD732D4B5ABC.jpeg

Once I get the cooling issue resolved I’ll try again for larger photopeaks.

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Richard Hull
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Re: Fusor 2020 Activation Experiments

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Wow! You got copper to give it up! Great work and great fusor!

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
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Re: Fusor 2020 Activation Experiments

Post by Jon Rosenstiel »

Great results with the copper, Mark. I think you’re close to being able to activate aluminum.

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Re: Fusor 2020 Activation Experiments

Post by Mark Rowley »

Thanks!
Hmmmm, you piqued my interest Jon. Background noise in the 1.78meV region of the gamma spec system is comparatively nil, just natural K40 at 1.46meV. This should assist with detecting a low yield activation, which no doubt would be the case.

If I can get the cooling under control for a solid 5 minutes, I’ll give it a shot.

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Re: Fusor 2020 Activation Experiments

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Today’s run activated a small amount of aluminum powder to create the short lived isotope of Al28. This isotope has a gamma energy of 1.78MeV.

The activation consisted of a 10 minute exposure to a roughly estimated neutron TIER of 1.5E+6. During this time a small sachet of aluminum powder(pictured) was situated in an HDPE moderator 17cm from the fusor grid.

Following activation, the aluminum sample was quickly placed in the gamma spectrometer lead castle for a 606 second assessment run. Almost immediately a distinguishable photopeak was evident at the expected Al28 gamma energy of 1.78MeV. Just to the left the natural K40 peak can be seen at 1.46MeV.

Total counts during the 606 second run was 2377.

I conducted three background counts using the same time span. They were 1875, 1856, and 1889. Using 1875 as the average, the activated assessment registered 502 counts over background.

When the aluminum sample was placed in the spectrometer, it averaged approximately 7cps and decayed to 3.9cps after 606 seconds. An hour afterwards the sample was indistinguishable from normal background (~3cps).

Once again, many thanks to Jon R for sharing the cooling maze modification. This 10 minute run never peaked over 24 deg Celsius!

Mark Rowley
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Re: Fusor 2020 Activation Experiments

Post by Richard Hull »

Mark, you are becoming the activation hero!

I have a great Canberra gamma spec, but prefer the instant gratification of a beta activation where an embedded GM counter is the best for demo work before a group of spectators. As the fusor lab is unheated, my valuable 3 and 5-inch NaI:Tl Bircon heads and gamma spec system is located upstairs in my heated home. In spite of having the nice gamma spec system I have never once used it on any activation over the last 15 years of activation work! Figure that one out! I tend to use it to sniff out rock samples and the relative amounts of various natural radio nuclides.

Great work and I love the continuing efforts on your part and fabulous detailed reports.

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
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Re: Fusor 2020 Activation Experiments

Post by Mark Rowley »

Thanks Richard
Knowing that I only had about 2.5 minutes with it’s half life, in short order I had to this:

Turn off the fusor
Turn off the fuel supply
Disassemble the moderator
Remove the irradiated sample
RUN to the house from the backyard lab
Put it in the spectrometer
Stack a few lead bricks
And turn on the spectrometer

In all that wasted time I lost a significant portion of it initial activation to necessary chores. Doubt I’ll ever move the spectrometry system into the shop.

Like you, I do enjoy silver and indium. Silver’s instant flurry of beta decay totally sends a nice message to visitors. I recently activated some sterling Ag items for some folks showing their subsequent activity with a TBM-3S pancake unit. Fun and undeniable results. Reminds me of the old irradiated dimes from the 1965 worlds fair.

Not sure what’s left to activate but for now my only remaining goal is to get a larger photopeak from Cu66 at 1.4MeV.

Suggestions are welcome!

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Re: Fusor 2020 Activation Experiments

Post by Richard Hull »

As you know, and as I have told it, Even in my lab, I had to race to the lab NIM bin counter for silver measurements in the past. Thus, my custom Arduino counting system and moderator-embedded GM detector on Fusor V.

Copper is a bold stroke by any measure. Cut time by pre-starting your gamma spec. open doors and warn the wife you are coming through at high speed. You could even have an assistant press the collect button the minute they here you rush into the house. You won't foul the collection by having it run a few seconds before you arrive Have every thing set for speed. Cutting a number of seconds off the dash will really help. Don't trip in the dash and fall, it ain't worth it.

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
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Re: Fusor 2020 Activation Experiments

Post by Jon Rosenstiel »

Mark,

As to your copper count conundrum, maybe try copper metal powder in a Marinelli beaker. I think they run somewhere around $15.00 each.

https://www.drct.com/dss/accessories/be ... eakers.htm.

Jon R
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Mark Rowley
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Re: Fusor 2020 Activation Experiments

Post by Mark Rowley »

Hi Jon,
Not a bad idea. The site looks like a good overall resource too!

I’ve yet to give the copper bar a nice long exposure with the new cooling system. Tonight or tomorrow I’ll flux it with a good 15 minute run and see what turns up. Stay tuned!

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Re: Fusor 2020 Activation Experiments

Post by Mark Rowley »

Much better results with Copper activation. 10 minutes of flux time at a rough TIER estimate of 1.7E+6 n/s.

The Cu66 photopeak at 1.04MeV is very pronounced at 346 seconds.
25C73F18-3B91-4050-AA8B-97CA8D288DB8.jpeg

At 1000 seconds shown with natural background in gray.
258EC9EA-3CD1-4B9E-BA48-0D97FC457B4C.jpeg

This is a 1000 second natural background count with a non-irradiated copper sample of the same size.
5DE5F551-84ED-4648-973A-6A80F52E3338.jpeg

Total counts from irradiated sample: 5039
Total counts from non-irradiated sample: 3298
Total counts over background: 1741

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Re: Fusor 2020 Activation Experiments

Post by Mark Rowley »

More progress with Copper activation today. The chart shows results after 533 seconds in the spectrometer. The 1.04MeV photopeak decayed to about nothing after 90 minutes however the 511keV is still cranking out gammas well above the natural artifact.

Flux time was 10 minutes.

Mark Rowley
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Re: Fusor 2020 Activation Experiments

Post by Jon Rosenstiel »

Way cool Mark,12.7-hour Cu-64 spittin’ out the positrons. Just think how large that 511 peak would be if you could activate your copper sample for 24-hours.

Jon Rosenstiel
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