NAA Tungsten

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.
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Richard Hull
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Re: NAA Tungsten

Post by Richard Hull » Fri Jul 03, 2015 8:53 pm

Electronci drift is there, to be sure and this is due to the A to D converters. This is taken up and corrected for by using a check source each data accumulation session to adjust your amplifier detection threshold and or gain to center the check source's known peak precisely prior to running an unknown or re-running a long, low count re-count days later. Part of the art of gamma spec work.

Again, much excellent gamma spec work has been done here in this forum over many years with activated materials.

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.

George Dowell
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Re: NAA Tungsten

Post by George Dowell » Sat Jul 04, 2015 5:20 pm

Jon Rosenstiel wrote:Very nice work George... nice clean spectra. What are you using as a neutron source?

Jon Rosenstiel
Hi Jon.

More to come but the working conditions in a nutshell were/are:



Target- 70g WC (tungsten carbide) tool part.

Source- isotopic @20e8 n/s (11/2014), distance 5”".

Moderator- 2"” 200 series S.S., 1""” air gap, 2” water.

Time on source 37 Hr.

Cooldown in hot cell/ transportation cycle- 4 Days



Detector- Bicron 1.75M2/2 FWHM 6.3% @ 661.7 keV-in custom lead shield,

Detector Base- custom made 14 pin base with 1 transistor preamp (Note1)

MCA- URSA II @ 4K channels set for 0-4000 keV range. Run times 1 hour, 6 hour, 12 hour, repeated on 24 hour cycle.











Note 1- I'’ve adopted 2 versions of this base as a standard for 3M14 based integral tube/crystals such as the Bicron. One includes the preamp, the other is all-passive. Both versions now standardized to include only SHV connectors for HV and BNC connectors for Signal.-



Link to PMT Base project, 2N3906 transistor is a good fit:

http://www.qsl.net/k/k0ff/PMT%20Base%20 ... %20PREAMP/



Same base without preamp, gives really good overall performance:

http://www.qsl.net/k/k0ff/PMT%20Base%20 ... %20PREAMP/







George Dowell

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Re: NAA Tungsten- @5 Half-Lives

Post by George Dowell » Sun Jul 05, 2015 4:08 pm

Two 12 hour scans, separated by 5 half-lives in time, subtracted from one another. The first scan was the baseline activity, taken as soon as the sample was available and was loaded as "LIVE SPECTRUM" to make this picture.

For 5 more days, another 12 hour scan was taken and saved. Activity at the 5 half-life point has all but vanished. That scan was loaded as "BACKGROUND SPECTRUM" and subtracted from the first scan via the URSA II software function.

This picture then represents the difference between the original scan and the 5 half-life scan. This also removes the minor background counts from distant K-40 and Tl-208 (from Th-232) sources. Essentially the idea is to show what was in the sample when it arrived but is no longer there 5 half-lives later.

I was expecting to see residual W-185, but so far it's presence has eluded the investigation.

The data will be uploaded to the aforementioned remote site so if anyone wants to, they can download the URSA II program designed for your computer platform and then download my raw data .usf files.



George Dowell
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Run#2-MINUS-Run@27-5H-L-ApartAnnotated.jpg
Difference spectrum- Activity Day 0 vs Day 5

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Re: NAA Tungsten

Post by George Dowell » Sun Jul 05, 2015 6:38 pm

Richard Hull wrote:Electronci drift is there, to be sure and this is due to the A to D converters. This is taken up and corrected for by using a check source each data accumulation session to adjust your amplifier detection threshold and or gain to center the check source's known peak precisely prior to running an unknown or re-running a long, low count re-count days later. Part of the art of gamma spec work.

Again, much excellent gamma spec work has been done here in this forum over many years with activated materials.

Richard Hull

Understood Richard and thanks for mentioning that.

For this study the probe was stabilized to operating temperature for about 1 week before, and the MCA has not been shut off since. Of course hour by hour and day to night temperature fluctuations are still present.

The initial energy calibration was done with Cd-109 (Ag-109m X-Rays ~22keV), Am-241 @ 59.5, Cs-137 @ 661.7 and Co-60 @ 1173.2, 1332.5 and the sum peak checked at 2505.7. This particular MCA will allow 12 point calibrating, but I always keep the # points to a minumun, to bracket the area of energy being studied.

I acknowledge the work done by the advanced amateurs here on FUSOR.NET and can credit their input for helping me to get started since I joined here in 2003.

George Dowell

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Richard Hull
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Re: NAA Tungsten

Post by Richard Hull » Sun Jul 05, 2015 8:59 pm

George, my posting was for the fellow who posted wondering about drift in the instrument over time. I knew your calibration would be right on.

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: NAA Tungsten

Post by Roberto Ferrari » Sun Jul 05, 2015 10:57 pm

Richard
Thanks for the explanation.
George
Great work!

Regards
Roberto

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