New Rhodium counter system and moderator for fusor V

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Finn Hammer
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Re: New Rhodium counter system and moderator for fusor V

Post by Finn Hammer »

Richard,

Thank you for a comprehensive detailing of the decay curves.

Edit:
I read the numbers wrong in the silver section of this analogy, and this lead to a lack of, well, analogy.
In short, I misstook the half life of Ag107m instead of from Ag108 and this removes the basis of any analogy.
Sorry for that, better luck next time.

Just disregard the rest of this post:
--------‐--------------------------------------------------------
In a way, (Although not at all) it is like activating a sandwich of 2 different metals, one with a large neutron capture cross section and a fast decay, like silver, together with another metal with a small neutron capture cross section but with a slow rate of decay, like copper.

In this analogy, I discard the 69% of Cu63 because it produces Cu64 with a 12.8 hour half life and thus does not come up to detectable levels within the short run times we use here, instead base the analogy on the 31% of Cu65, which turns into Cu66 with a 5 minutes halftime and a neutron capture cross section of 2.3 barns.

In this analogy, the 2 silver isotopes Ag107 and Ag109 which both have comparatively large neutron capture cross sections, 35 vs.89 barns, and relatively short decay half lives of 44 sec. vs. 39 sec. and due to the close coincidence in decay time, they will look almost identical on the graph.

With a run time at max. flux of 45x5=225 sec. the silver isotopes have been brought up to the full level of saturation that the present flux enables, whereas the copper is only within 13% of the saturation which it would take 25 minutes to reach.

Measuring the combined decay profile would yield a similar profile as the Rhodium decay, where the silver decays to near zero in 225 seconds after which the copper dominates for another 22 minutes.


As a note to your axis labelling, I find it unnecessarily complicated that you label the x-axis in multitudes of 5, (so that 4 divisions of five denoted as 20 really means 100) I would like to see the time in seconds directly.
Similarly on the Y axis: why not just label it in CPM directly? Just my 7 cents.

Cheers, Finn Hammer
Last edited by Finn Hammer on Thu Aug 05, 2021 4:18 pm, edited 2 times in total.
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Jim Kovalchick
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Re: New Rhodium counter system and moderator for fusor V

Post by Jim Kovalchick »

I find this diagram helpful in understanding Rh activation and decay. The Rh 104m stuff muddies the waters because of it does not release betas (at first) meaning that even if your detector sees the gammas it likely won't do it with the same efficiency. Ultimately Rh 104m becomes Rh 104 and then will decay with betas. This latter part probably won't be seen unless you activated with big flux and/or your background is very small. I know that deep in the caverns of my brain is the knowledge to write up the time function curves for activity of each isotope, but I am afraid of what else I might find in there if I go looking.
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Re: New Rhodium counter system and moderator for fusor V

Post by Richard Hull »

Thanks for posting this update, Jim. This decay diagram is far more elucidating than the complex diagrams at the rear portion of the table of the isotopes. It was hard to get it in my head that as RH104 was being made, (my super hot 2.4 MeV beta emitter), the 104m was also being made, but as noted, to a far lesser degree. What was tough for me was that the Rh104m would also decay into Rh104. Due to the weakness of activation of the 11 cross section of Rh104m, the muddiness is bad, but not terrible so far as my graphs of 10minutes, (600 seconds), are concerned. The trail-on betas from Rh104m decaying to Rh104 would be far fewer than the 144 cross section of promptly produced Rh104 would be. Still, it is rather bizarre. It turns out far more bizarre than silver's double decay. Rhodium remains the number one fast 100% isotopically pure activation metal of choice.

It is to be noted that at the death of Rh104m there would be a barely detectable beta only signature of Rh104 going on for another 210 seconds until this tiny Rh104 emission would cease. (to be detectable to any counting agency)

It is important to remember that, due to the exponential nature of radioactive decay, in theory only, no radioactive would ever cease to decay. The half-life is a convenient, measurable, calculable value convenient to our linear brains. Nature loves and nurtures the exponential while shunning the linear.

This is about as complex a story of activation and decay as one might encounter with a low grade neutron source which might be actually observable at the amateur level.

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Re: New Rhodium counter system and moderator for fusor V

Post by Richard Hull »

Re: Finn's posting....The silvers have far different decay times for the product isotopes of Ag108 of 2.4 minutes, (144 seconds) and Ag110 of 24.4 seconds. I think you are looking at the metastables which cannot be produced via neutron activation of silver. (look at the method of production column for the two silver metastables). Sometimes if the item immediately below the stable activation element is a metastable it can't be produced by neutron activation. In the case of the silver metastables they are only produced by the decay of a cadmium or Ag metastable radioactive isotope. There are catch 22s in this biz. In the case of stable silver 109 there is a cross section of 3 to neutron bombardment to Ag 110m with the incredibly long half time of 255 days! Needless to say, this nice beta emitter will not be activated or seen at the normal exposure times by the amateur. As a point of amusement, you will note that like rhodium, the production of Ag110m will see it decay to Ag110 the original product of Ag109 with the high cross section.

Richard Hull
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Re: New Rhodium counter system and moderator for fusor V

Post by Jim Kovalchick »

With Rhodium I wonder if activating only to saturation of Rh 104 would help clean up the muddied decay back end. In others words, after 5 half lives of Rh 104, stop activating and prevent Rh 104m from catching up to it's potential relevance.
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Re: New Rhodium counter system and moderator for fusor V

Post by Richard Hull »

With my current setup it would be tough as the Rhodium covered GM tube is buried in the block moderator. I would have to dismantle the block moderator half way, take out the HDPE block with the tube and rhodium in it. Next, run the fusor up to peak over some number of minutes and quickly with the HV at 44kv, replace the tube and rhodium, reassemble the block moderator around it and run the system for 4-5 minutes at peak. Then shut down and count.

I would have to have a monolithic moderator like my large 3He moderator where it is easy to slip the tube in and out during operation. I might just try it, but the closeness to the fusor will be lost and the numbers would be down across the board. Still, that would be better than a poke in the eye with a sharp stick.

Richard Hull
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Re: New Rhodium counter system and moderator for fusor V

Post by Jim Kovalchick »

Richard,
...or alternatively shadow your rhodium with a sleeve of cadmium until the activation time. Yank out the cadmium and activate.
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Re: New Rhodium counter system and moderator for fusor V

Post by Finn Hammer »

Jim, Richard, all,

Forgive me for chiming in on a subject which is way over my head, but I am really trying to understand.

I notice something in Jim's chart which is not obvious in Table 1 from "Table of Isotopes"

From Jim's chart, it is demonstrated, that Rhodium 103 is elevated to Rh104 by a cross section of 133, and to Rh104m by a cross section of 11.

Jim's chart
Jim's chart

The Rh104m isotope decays to Rh104 via gamma radiation by a process called Isomeric Transition, which as far as I can tell, is caused by rearrangement of the protons and neutrons in the nucleus, to attain a lower energetic state. They "tug in", so to speak.

Then the Rh104 decays to Palladium104. 98.1% goes directly via Beta- radiation, the rest arrives at slightly elevated states, from where they emit gamma radiation to also land at Palladium104.

Woops, one step up in atomic number, same atomic weight, what happened?

Udklip.JPG
Udklip.JPG (23.05 KiB) Viewed 5614 times

There are 45 protons and 58 neutrons in Rh103
There are 45 protons and 59 neutrons in Rh104
There are 46 protons and 58 neutrons in Pd104 (stable)

So the newly captured neutron is converted to a Proton, to the benefit of the ejected electron which is detected as Beta radiation.

Udklip2.JPG

Whenever we activate an element that returns from it's emancipated state by emitting Beta- radiation, we cause it's transformation into the next element up the ladder of atomic numbers.

Lets have a look at Silver.

Udklip3.JPG
Udklip3.JPG (21.98 KiB) Viewed 5614 times

There are 47 protons and 60 neutrons in Ag107
There are 47 protons and 61 neutrons in Ag108
There are 48 protons and 60 neutrons in Cd108 ((as good as) stable)

There are 47 protons and 62 neutrons in Ag109
There are 47 protons and 63 neutrons in Ag110
There are 48 protons and 62 neutrons in Cd110 (stable)

Does this have any relevance, am I regurgitating common knowledge?

All of this is new to me, and certainly the fact that when activating elements by neutron bombardment, we are not cycling them between the same states, but actually transforming them into the next element up the ladder.

We are alchymists!

Cheers, Finn Hammer
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Re: New Rhodium counter system and moderator for fusor V

Post by Dennis P Brown »

The weak force is a fascinating beast and powers many fusion processes.
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Re: New Rhodium counter system and moderator for fusor V

Post by Richard Hull »

Law #1....A neutron is not made up of a an electron and a proton! Law #2 - There are no electrons in the nucleus......

Lo and behold!....When any radioactive elemental isotope beta decays there is an electron released from within the nucleus. What?! Lo and behold #2 A neutron disappears and a proton appears. What?! This bumps the new, beta decayed isotope up one notch in atomic number. Amazing ain't it! You are not allowed to believe a neutron is a combination of a proton and electron resulting in a zero charge or neutral particle.

We observe no atom can be made after hydrogen without a neutron or 2 or 10 or 45 of 'em or more!! No heavy radioactive element in the entire periodic chart out near the end, that doesn't self fission will emit a single neutron! They are jealously guarded. All radioactives would happily emit an electron (beta), a photon (gamma and x-rays) and an entire helium nucleus, but never a neutron. The neutron is the key within the nucleus for atom building and ultimately their destruction.

Neutron manufacture on most any scale in the universe are fused in an idealized solar plasma of protons and electrons. Remember, once again, never think a neutron is a union of a proton and an electron. It is considered "wrong think" and certainly "wrong speak" (Neutrons are made up of quarks, take their word for it or forever remain an outcast in nuclear physics)

The neutron is the first radioactive isotope on most modern periodic charts! A lone flying neutron has a half life of 12-13 minutes. Once outside of its protective nuclear cocoon via fission or collision, the neutron then decays into a proton and an electron with a virtually massless, hyper velocity neutrino needed to balance the energy-mass books. Remember, again, the neutron is not a union of a proton and an electron.

The neutron, with a charge of zero and having the mass a bit greater than a proton will, in a gravitational field, follow a ballistic trajectory just like a rifle bullet until it decays rejoining the world as a hydrogen atom at STP having swiped or shared a needed electron and a high velocity electron.

The upshot is, a beta decay bumps the daughter product up one atomic number. Nuclear alchemy? Yes indeed. It's fact Jack!

There is so much out there in nuclearland.... IT, EC, beta decay, alpha decay, photon decay and alteration, auger electrons, etc. Plenty of spreads and toppings to choose from for you nuclear sliced bread. Quite a smorgasbord....

Richard Hull
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Re: New Rhodium counter system and moderator for fusor V

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Yes, the electron can't be confined in a nucleus or at least under normal conditions. The weak force converts one type of quark into another, and the excessive energy shakes the fabric of space and time so an electron (with a lot of K.E.) is created as well as a neutrino. The reverse process can occur but only within collapsing star cores when neutron stars are created and where their electrons and protons are converted into neutrons. A neutron star is just a huge pile of neutrons (maybe a sea of electrons here and there as well as ...maybe ... a sea of quarks in the center.) Nature is strange and wonderous and that we can peak a glimpse into these secrets is just incredible.
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Re: New Rhodium counter system and moderator for fusor V

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Trying to help Finn understand some of the intricacies of activation has led the thread into theoretical nuclear discussions.

The neutron like all quantum ruled particles has a sphere of influence or existence. Up close and personal, the neutron is not neutral, but presents lobed charge regions that move about with both localized positive and negative charges presenting constantly. Back off far enough and it appears neutral.

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Re: New Rhodium counter system and moderator for fusor V

Post by Finn Hammer »

Richard, all,

Let's end it here, and my apologies for hijacking the thread.
Back to Rhodium activation!

Cheers, Finn Hammer
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Re: New Rhodium counter system and moderator for fusor V

Post by Dennis P Brown »

Finn, if anyone hi-jacked this thread it was me but I do feel that being a site that does try to bring useful information to people here, discussions about the underlying physics is part of the forum's function. I should add, thanks' to Richard's thread here, that I have finally (about time, one would think) realized why I failed at activation even though I had far more neutrons then needed. So after following this thread I am determined to correct that mistake and see what occurs.

In any case, back to regular scheduled programming ... ;)
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Re: New Rhodium counter system and moderator for fusor V

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Finn is a hard worker and a doer. I appreciate that. He wants to learn. I really like that. I will bend over backwards and interrupt my own thread to see to it he is pointed in the right direction. Activation and interpreting the tables and charts are all part of the continuing fusion effort that I talk about all the time. Making a fusor and doing fusion should be a starting point in the nuclear physics effort. Improving the fusor, understanding it better, using the fusion as a study in activation are all follow-on goals that should interest any person spending the long-buck with the verve to do and learn more.

Anytime Finn, anytime... Interruptions that forward learning are to be sought out, and welcomed.

By the way, EC (electron capture), makes a neutron in the nucleus and sends the new isotope "down chart" as a proton disappears. Down one atomic number. But....Remember, a neutron is not a proton and an electron. An orbital electron is swiped from the shell and sucked into the nucleus, (captured). Remember, there are no electrons in the nucleus. This EC process is done when a nucleus is unstable due to too few neutrons or is overloaded with protons. Take your pick on which rules the roost here as to the real cause. ( think the neutron is the king here...too few)

Does this tell us, (dare we say it), the neutrons are the source of glue that hold the atom together? No...No....No!!!!! It is the strong force, #!@^**%!&. If the strong force is so strong as to overpower the proton-proton repulsion in the nucleus why do we need the neutrons? "Sit down and shut up and listen up to what I say, you poor dumb student!" Students who ask questions are always to be desired. They change science and expand it.

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Re: New Rhodium counter system and moderator for fusor V

Post by Finn Hammer »

As a reference to the mechanism of neutron capture in Rhodium, Jim posted a nice graphic, depicting the most relevant stages of the incident.
Jim, would you mind sharing which publication this chart originates from.
It would seem most usefull to be able to view that particular level of detail for other elements too.

Cheers, Finn Hammer
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Re: New Rhodium counter system and moderator for fusor V

Post by Jim Kovalchick »

Finn, my source of the rhodium decay scheme was from a document that is mostly beyond relevance to our activation interests as it related to use of rhodium's use as an emitter in a self-powered detector.

All the information in the scheme is available in Table of Isotopes. I don't own a copy, but I have the IAEA app on my phone. I highly recommend it.

Jim K
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Re: New Rhodium counter system and moderator for fusor V

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Sadly, as I noted the table of the isotopes has this listed in two separated step diagrams in the back of the book. Only an expert might follow the decay scheme in the back of the T.O.N. A careful following of the front section daughters and product listings will make it clearer. However the one Jim presented gave a good diagram of the cat chasing it own tail, circumnavigation through Rh104.

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Re: New Rhodium counter system and moderator for fusor V

Post by Richard Hull »

At Finn's suggestion I hereby attach a more readable activation graph in CPM and seconds for those struggling with the 5 second sample rate graphs of the past. I will endeavor to, in future, supply this type of graph.
The graph is from the best run of HEAS 2021. Folks were there watching this happen!

edit: old graph had wrong x axis values. Here is the proper graph 11/5/21

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Re: New Rhodium counter system and moderator for fusor V

Post by Richard Hull »

I post this as a duplicate post from one of Finns postings to explain in some detail the reason for the long continued counting of rhodium well past its 5 X 44 sec half life of ~220 seconds, provides the TIER is high and exposure time is over 5 minutes...

I have never loved rhodium for its fast decay but solely for its fast activation at lower neutron outputs. With Rhodium, a terrible fusor will activate with zero need for any statistical analysis. It is up and hot fast. A fast decay mean a fast activation and the high cross section means a lot of activation per unit TIER.

In these rolling discussions in my recent runs of fusor V, we discussed that activated rhodium actually generates more Rhodium 104 via activated Rh104m and will not die dead even at 600 seconds if you have the snort to blast it hot and long enough. Even I saw that at only 500k n/s TIER with 6 minute activations...It was discussed with Jim Kovalchick coming to the rescue on why this is so with his diagram that followed the long, yet unsuspected chain of rolling activations. Like a giant nuclear echo! But, like all echos they can't live forever.

Refer to Jim's very handy diagram at

viewtopic.php?f=13&t=14084&start=20

It can be seen that if you expose Rh103 for a long time 10 minutes or more, you will generate enough to 104m to keep a statistically detailed, low background adroit GM counting of betas for as long as 20 minutes! following the irradiation of Rh103 is stopped due to Rh104m generating more Rh104 with its 44 sec half life. This is the Beta echo. Totally unexpected, but real and keeps even a 500k n/s TIER exposure counting above background past 600 seconds. More n/s TIER and longer exposure times will show far more prominent above background counting stringing out much longer.

I attach a modified diagram of the echo effect. Even the weak gammas will be counted from Rh104m

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Re: New Rhodium counter system and moderator for fusor V

Post by Richard Hull »

Well, it is cold here and the current lab temp is 30 degrees. Here is the first and last Rhodium activation of 2022, until more temperate lab conditions exist, probably in the early spring.

The fusor worked much better in the cold than over the last week of operation. over 97,000 CPM at peek operation on 3He system.. 8 - 9 mrem/hr on Remball, 8.1 - 9.3 mrem/hr on PNC-1. 589,000 n/s TIER
The run:
41kv, 10.5 ma, 10.7microns on fusor V. 12 X 129= 1548 cpm on the puny 6 sqcm, 2pi emisson of Rhodium against a 4.1X12 = 49.2 cpm back ground. Result, ~32X background...solid activation on a tiny scrap of Rhodium. I have activated my 6 sqcm of rhodium at 56,000 TIER!

Graph of Rhodium activation below.

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Re: New Rhodium counter system and moderator for fusor V

Post by Matt_Gibson »

This run is very close to what my setup runs…Looks like I shouldn’t have much trouble with activation once I get my Hdpe here. I was afraid that I was going to need higher voltages (my psu can provide -40kV @ 15mA)

-Matt
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Re: New Rhodium counter system and moderator for fusor V

Post by Richard Hull »

30kv in a good system, well run, will give unequivocal activation of silver. I hope to being inducting you into the Elite fusioneers soon.

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Fusion is the energy of the future....and it always will be
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Re: New Rhodium counter system and moderator for fusor V

Post by Matt_Gibson »

Richard, you can count on it ;-) As soon as my Hdpe arrives, I’ll be back.
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