Activation Twofer. (Molybdenum > Technetium)

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.
Jon Rosenstiel
Posts: 1386
Joined: Thu Jun 28, 2001 5:30 am
Real name: Jon Rosenstiel
Location: Southern California

Activation Twofer. (Molybdenum > Technetium)

Post by Jon Rosenstiel » Tue Jul 03, 2007 5:25 am

Two gamma emitting isotopes for the price of one activation run… such a deal!

The activation target was Mo-100, one of molybdenum’s seven naturally occurring isotopes. The activation product, 14.6-minute Mo-101 decays via beta / gamma emission into 14.2-minute Tc-101, which in turn decays via beta / gamma emission into stable Ru-101.

First pic shows the UHMW “neutron oven” in position resting on my fusor’s specimen shelf.

Second pic shows the oven with the reflector plug removed.

Third pic shows the moderator, (in back), with the reflector and its plug.

Fourth pic shows how the machined recess in the moderator allows it to sit down close to the fusor so it will intercept as many neutrons as possible.

Fifth pic shows the molybdenum disc used in this experiment.

Sixth pic is Mo-101’s and Tc-101’s gamma spectra.

Jon Rosenstiel
Attachments
Mo Activation 001.jpg
Mo Activation 001.jpg (64.26 KiB) Viewed 102 times
Mo Activation 003.jpg
Mo Activation 003.jpg (40.99 KiB) Viewed 102 times
Mo Activation 004.jpg
Mo Activation 004.jpg (33.54 KiB) Viewed 102 times
Mo Activation 007.jpg
Mo Activation 007.jpg (38.1 KiB) Viewed 102 times
Mo Activation 011.jpg
Mo Activation 011.jpg (42.83 KiB) Viewed 102 times
Image1.gif

User avatar
Richard Hull
Moderator
Posts: 11840
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: Neutron Activation Twofer

Post by Richard Hull » Tue Jul 03, 2007 2:29 pm

Fabulous! Just starting to run out of superlatives, Jon!

You have now had an element I have never had Technetium!....Albeit, a fleeting ownership.

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.

Jon Rosenstiel
Posts: 1386
Joined: Thu Jun 28, 2001 5:30 am
Real name: Jon Rosenstiel
Location: Southern California

Re: Neutron Activation Twofer

Post by Jon Rosenstiel » Tue Jul 03, 2007 4:09 pm

Thanks for the kind words, Richard.

Finding technetium was totally unexpected, it was something I had not even remotely considered in my molybdenum activation attempt.

There I was, sitting on a stool in front of my MCA’s screen watching Mo-101’s gamma spectrum develop when out of the blue this unknown peak starts growing at a rapid rate, quickly passing up and leaving in the dust Mo-101’s gammas. I frantically searched the on-line gamma catalogs looking for some other molybdenum isotope that was responsible for this interloper. I found nothing. Then I noticed that right in the middle of each search sat Tc-101. Hmmm… the energy matched, the half-life matched, and technetium sat just to the right of molybdenum in the periodic table. Bingo!

Jon Rosenstiel

Starfire
Posts: 1482
Joined: Wed Oct 24, 2001 6:14 pm
Real name:

Re: Neutron Activation Twofer

Post by Starfire » Tue Jul 03, 2007 10:14 pm

Yet again - cutting edge Jon - like Richard, I've run out of words.
My respect.

Jon Rosenstiel
Posts: 1386
Joined: Thu Jun 28, 2001 5:30 am
Real name: Jon Rosenstiel
Location: Southern California

Re: Neutron Activation Twofer (Make that Three-fer)

Post by Jon Rosenstiel » Wed Jul 04, 2007 6:07 pm

I threw the molybdenum disc back in the neutron oven for 40 minutes at 3.5E+06 n/s, then waited 45 minutes before starting a 6-hour count.

Attached spectra shows the remnants of 14.2-minute Tc-101, and a nice strong peak at 140.5 keV, which is 6-hour Tc-99m, one of the decay products of 65-hour Mo-99.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

The following added 9 hours later...

In the second chart below are the results of another 6-hour count that was started 15.5 hours after the finish of the activation run. Note that 6-hour Tc-99m is stronger than it was in the earlier count, and note the complete absence of 14.2-minute Tc-101.

Jon Rosenstiel
Attachments
Image1 (2).gif
Image1 (2).gif (10.47 KiB) Viewed 102 times
Image2.gif
Image2.gif (9.45 KiB) Viewed 102 times

Jon Rosenstiel
Posts: 1386
Joined: Thu Jun 28, 2001 5:30 am
Real name: Jon Rosenstiel
Location: Southern California

Re: Neutron Activation Twofer (Mo K-shell x-rays)

Post by Jon Rosenstiel » Wed Jul 04, 2007 6:23 pm

While I'm at it I may as well share the x-ray spectra I got from this same molybdenum disc.

Detector: EDAX SiLi
Exciter: Oxford Rh anode XRF tube at 25 kV, 30 μA, 30 seconds.

Jon Rosenstiel
Attachments
Mo x-rays.gif
Mo x-rays.gif (7.04 KiB) Viewed 102 times

Starfire
Posts: 1482
Joined: Wed Oct 24, 2001 6:14 pm
Real name:

Re: Neutron Activation Twofer (Make that Three-fer)

Post by Starfire » Wed Jul 04, 2007 6:51 pm

Again, Jon this is great work - in a sense it is pioneering as no amateur has progressed so far - it also has an exciting aspect of discovery, as you were not aware nor expected theTechnecium isotopes - You must be covering almost all the energy spectrum - How far up can you now analyse?

Perhaps, Lead to Gold is just arround the corner :)

Jon Rosenstiel
Posts: 1386
Joined: Thu Jun 28, 2001 5:30 am
Real name: Jon Rosenstiel
Location: Southern California

Re: Neutron Activation Twofer (Make that Three-fer)

Post by Jon Rosenstiel » Wed Jul 04, 2007 8:11 pm

John,
I imagine someone that has been trained in nuclear physics would know to look for technetium isotopes… I haven't been trained in nuclear physics, so I don’t think that far ahead. To me this is a good thing… I get to learn by the doing. There’s lots of excitement in the air while “the chase is afoot”.

I’m reminded of something Richard Hull posted several years back that he referred to as “The Franklin Imperative”….

“There is no illumination so bright as that which is borne out in experiment and no knowledge so gained that is more tightly held by the experimenter”.

I haven’t managed to turn lead into gold yet, but I have been able to transmute gold into mercury. But I think this is what one would call a “lose-lose situation”.

Jon Rosenstiel

George Schmermund
Posts: 262
Joined: Wed Aug 16, 2006 12:51 am
Real name: George Schmermund
Location: Carlsbad, CA

Re: Neutron Activation Twofer (Mo K-shell x-rays)

Post by George Schmermund » Wed Jul 04, 2007 8:26 pm

I'm a hard-core advocate of using XRF (ED or WD) for doing elemental identification and analysis. Your data showing almost 50K counts on the K alpha peak in 30 seconds using only 30 micro-amps of tube current is a good representation of the power of this method. Your XRF spectrum is also clean and unambiguous.

Your demonstration is almost enough to push me over the edge. It might be time to extricate some spectroscopy stuff from out of the attic and get my feet wet again. Thanks for the stimulation, Jon.
Anything obvious in high vacuum is probably wrong.

Jon Rosenstiel
Posts: 1386
Joined: Thu Jun 28, 2001 5:30 am
Real name: Jon Rosenstiel
Location: Southern California

Re: Neutron Activation Twofer (Mo K-shell x-rays)

Post by Jon Rosenstiel » Wed Jul 04, 2007 9:32 pm

George,
Hopefully this super-clean spectra from manganese-dioxide will push you over the edge.

Jon Rosenstiel
Attachments
Manganese.gif
Manganese.gif (7.25 KiB) Viewed 102 times

Post Reply