PAA Selenium

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Using PAA ro measure Selenium concentrations.

According to Krouse<ref name="Krous1962"> H.R. Krause and H.G. Thode,"Thermodynamic Properties and Geochemistry of Iosotopic Compounds of Selenium",.Can. J. Chem., vol 40, pg 367</ref> , the fractional concentration of Se-82/Se-76 in plant material is observed to be less than from primordial (meteoric) concentrations by as much as 1.2%. Anaerobic bacteria are known to reduce selenates and senelites in biological systems. This may be the reason plant material has fractionation of selenium isotopes. They also observe excess concentrations of up to 0.4% in soil.


Plant material appears to detect environmental selenium.

Can one use plant material to measure the provenance of selenium?

Can one perform PAA measurements of Se-82 and Se-76?

Neutron knockout of Se-82

If you knock a neutron out of Se-82 you produce the unstable isotope Se-81 which Beta emitts with half life of 18 min and a meta-state that emmits a 103 keV gamma with a 57 minute half life.

[math]{82 \atop 34\; }Se (\gamma,n){81 \atop \; }Se[/math]

Other prominent photons

260 & 276 keV for the 57 minute half life isotope

Neutron knockout of Se-76

If you knock a neutron out of Se-76 you produce the unstable isotope Se-75 which has a half life of 119 days.

[math]{76 \atop\; }Se (\gamma,n){75 \atop \; }Se[/math]

The prominent photons emitted have the following energies

136, 264, and 279 keV


The article below describes how plant material and soil contain Se-76 to Se-82 ratios that differ from other natural samples by 1.5%. They argue that it is due to the bacteria living in plant material.

File:Krouse CanJournChem 40 1962 p367.pdf

Plant material is a natural way to sample the selenium content to determine if there are difference isotopic ratios due to the impact of human activities on the environment.

Experiments

Chlorine

It looks like Cl-35 is abundant as you see photon energies of 146 keV and 2127 keV (you can barely see 1176 keV) from Cl-34's decay (neutron knocked out of Cl-35).

The half life is 32 minutes.

Should check the half life from the run AccOnAlInDetASe-AinDetD_001.root using the calibration 

MPA->Draw("0.18063+0.960133*evt.Chan>> SeRun_008(8000,0.5,8000.5)","evt.ADCid==3");

Irradiation of Horse Mineral Supplement

Chlorine is a dominant signal

First, look at the peak around 146 keV 146 keV.png

Next I plotted the counts as a function of time to get an exponentially decaying graph. When doing an exponential fit here, the parameter "b" given by root will be the decay constant.

146 keV halflife.png

Root gives a value b = 3.59543x10^-4, which yields a half life of 32.1 minutes.


Now do the same for the 2127 keV line 2127 keV.png

Here are the counts plotted as a function of time Counts vs time 2127keV.png

Root gives b = 3.31508x10^-4, which yields a half life of 34.8 minutes.

Potassium is a potential signal

Looking at the spectrum for the fast irradiation sample, there are 2 prominent lines that could be from 38-K. The mechanism would be a single neutron knockout from a stable 39-K nucleus. The two most dominant energies of the three for 38-K are 2167 keV and 3936 keV and the half life is 7.63 minutes. Below is a fit to the energy spectrum histogram

2168 peak.png

Now check the half life


2168keV halflife.png

Root gives a value for b = -1.44513x10^(-3), which in turn gives a half life of 8 minutes

Next check the 3936 peak

3937 Peak.png

and check the half life

3937 halflife.png

Root gives a value for b = - 1.52044x10^(-3), which in turn gives a half life of 7.6 minutes

It seems very possible that 38-K could be in the sample of horse feed.

Possible Yb-167 in the Sample

Yb-167 has a half life of 17.5 minutes and can be produced by knocking a neutron out of Yb-168, which is stable.

I looked at the horse feed spectrum and compared the spectral lines for Yb-167, below is a table of those results:


Energy (keV) Spectrum Energy (keV) Half life (min)
90.84 89 18.23
106.18 105 18.0
112.88 113 18.86
132.02 137 19.2
161.29 161 17.3
203.75 204 17.27
280.5 281 17.0
290.89 289 16.7
323.5 322 16.6
354.0 354 16.7
375.9 378 15.5
387.0 388.4 19.1
398.1 402 16.1
688.5 691 15.6
733.2 736 17.1
920.32 922 16.6
977.9 980 16.9
1025.9 1028 16.9
1242 1245 17.5
1340.1 1341 16.5
1410.4 1413 18.6
1433.4 1437 16
1631.7 1630 19.6

The average of these half lives is 17.22 minutes, but it turns out this was just coincidental noise meaning we must overbin the spectrum.

Investigation of Se_B_002

Using the Se_B_002, I will investigate the peaks seen in the spectrum.

The first peak seen in the spectrum was at 74.1 \%pm%\ 2.947 keV. The half life was found to be 324.94 days. When doing the rad search I used a window from 69-79 keV and a half life window from 200-400 days.


Isotope Energy (keV) I(%) Half life
153-Gd 69.67 2.419 240 days
254-Es 69.7 not given 275.7 days
254-Es 70.4 not given 275.7 days
153-Gd 75.4 0.0783 240.4 days

254-Es doesn't really have a mechanism to produce this isotope. The nearest stable isotope would have to have greater than a quadruple neutron knockout, or a triple proton knockout.

153-Gd could possibly be produce from 154-Gd by knocking out a neutron, but the half life is still far off. The hottest decay lines for 153-Gd are 97.4 and 103.2 keV with I = 29 and I = 21.11 respectively. Neither of these lines are seen in the spectrum so it is unlikely that it is either of these isotopes.



The next clear peak is seen at 85.5 \%pm%\ 3.89 keV. The half life was found to be 99.1 days. When doing the rad search I set a range of energies from 75-95 keV with a half life range from 50-150 days. The possible isotope information is below

Isotope Energy (keV) Ig(%) Half life
257-Fm 75.0 0.200 100.5 days
174m-Lu 76.47 0.0638 142 days
170-Tm 78.63 0.00347 128.6 days
159-Dy 79.45 0.00048 144.4 days
168-Tm 79.804 10.53 93.1 days
258-Md 80.1 2.43 51.5 days
257-Fm 80.2 0.085 100.5 days
75-Se 80.94 0.0077 119.779 days
183-Re 82.9182 0.294 70.0 days
170-Tm 85.25474 2.5 128.6 days
182-Ta 84.6802 2.65 114.43 days
183-Re 84.7125 0.97 70.0 days
188-W 85.32 0.0024 69.4 days
160-Tb 86.7882 13.15 72.3 days
258-Md 86.9 0.5615 51.5 days
168-Tm 87.73 0.000016 93.1 days
127m-Te 88.26 0.084 109 days
123m-Te 88.46 0.092 119.7 days
175-Hf 89.36 2.4 70 days
258-Md 91.0 0.3018 51.5
148-Eu 92.6 0.019 54.5 days
151-Gd 93.21 0.0019 124 days
160-Tb 93.919 0.0566 72.3 days

The following isotopes have mechanisms that are larger than a 2 neutron/proton knockout and larger than 1n1p knockout: 257-Fm, 258-Md, 148-Eu.

First Observation of Se lines

Using the 44 Machine at 7 kW power and 44 meV incident electron energy to produce a bremsstrahlung spectrum with a mean energy of 15 meV. 


All runs lasting less than 214 seconds have time stamp that gives real time if you divide by clock frequency of 20 MHz.  The first 32 bits are used for a real time measurement.

Detector Efficiency

Below is the runlist for finding the efficiency of the detector at position R


Source Serial # Reference Date Activity Start Stop Live
Na-22 129743 7-01-08 9.427 microCi 15:49 16:19 1796.803
Cs-137 129793 7-01-08 1.006 microCi 14:25 14:56 1879.606
Mn-54 129807 7-01-08 11.77 microCi 15:00 15:30 1793.420
Co-60 129740 7-01-08 10.42 microCi 15:33 15:43 569.725

Below are the theoretical calculations for the theoretical decay frequencies

Na-22, 9.427micro Ci on July 1, 2008, half life 2.602 +/- 0.002 years, 99.937% for 1274.52 and 178.8 for 511 line , activity in March 31, 2016 =1.196micro Ci

= [math]\left (0.99937 \right )\left ( 1.196 \times 10^{-6} \mbox{Ci} \right) \left (\frac{ (3.7 \times 10^{10} \mbox{Hz}}{\mbox{Ci}} \right)= 44,224 Hz [/math] for the 1274 line
= [math]\left (1.788 \right )\left ( 1.196 \times 10^{-6} \mbox{Ci} \right) \left (\frac{ (3.7 \times 10^{10} \mbox{Hz}}{\mbox{Ci}} \right)= 79122.6 Hz [/math] for the 511 line

Cs-137, 661.660 line, 85.21% * 1.066micro Ci on July 1, 2008, half life 30.0 +/- 0.2 yrs, March 31, 2016 activity = 0.891micro Ci expected rate for 661 line

= [math]\left (0.8521 \right )\left ( 0.891 \times 10^{-6} \mbox{Ci} \right) \left (\frac{ (3.7 \times 10^{10} \mbox{Hz}}{\mbox{Ci}} \right)= 28091.2 Hz [/math]

Mn-54, on July 1, 2008, half life =312.20 +/- 0.07 days, 99.975% intensity on 834.826 , March 31, 2016 activity =0.02328micro Ci

= [math]\left (0.99975 \right )\left ( 0.02328 \times 10^{-6} \mbox{Ci} \right) \left (\frac{ (3.7 \times 10^{10} \mbox{Hz}}{\mbox{Ci}} \right)= 861.1 Hz [/math] for the 834 line


Co-60, 10.42micro Ci July 1, 2008, half life 5.271 +/- 0.001 years, 99.0 % for 1173.237 and 99.9824 % for 1332.501, March 31, 2016 activity=3.759micro Ci


= [math]\left (0.99 \right )\left ( 3.759 \times 10^{-6} \mbox{Ci} \right) \left (\frac{ (3.7 \times 10^{10} \mbox{Hz}}{\mbox{Ci}} \right)= 137692.17 Hz [/math] for the 1173 line


= [math]\left (0.999824 \right )\left ( 3.759 \times 10^{-6} \mbox{Ci} \right) \left (\frac{ (3.7 \times 10^{10} \mbox{Hz}}{\mbox{Ci}} \right)= 139058.52 Hz [/math] for the 1332 line

Below is a runlist for position k

Source Serial # Reference Date Activity Start Stop Live
Na-22 129743 7-01-08 9.427 microCi 14:54 15:01 434.087
Cs-137 129793 7-01-08 1.006 microCi 15:48 15:55 413.925
Mn-54 129807 7-01-08 11.77 microCi 15:28 15:40 705.186
Co-60 129740 7-01-08 10.42 microCi 15:41 15:47 346.092

Below are the theoretical decay frequencies

Na-22, 9.427micro Ci on July 1, 2008, half life 2.602 +/- 0.002 years, 99.937% for 1274.52 and 178.8 for 511 line , activity in April 14, 2016 =1.183micro Ci

= [math]\left (0.99937 \right )\left ( 1.183 \times 10^{-6} \mbox{Ci} \right) \left (\frac{ (3.7 \times 10^{10} \mbox{Hz}}{\mbox{Ci}} \right)= 43743.4 Hz [/math] for the 1274 line
= [math]\left (1.788 \right )\left ( 1.183 \times 10^{-6} \mbox{Ci} \right) \left (\frac{ (3.7 \times 10^{10} \mbox{Hz}}{\mbox{Ci}} \right)= 78262.5 Hz [/math] for the 511 line

Cs-137, 661.660 line, 85.21% * 1.066micro Ci on July 1, 2008, half life 30.0 +/- 0.2 yrs, April 14, 2016 activity =0.890 micro Ci expected rate for 661 line

= [math]\left (0.8521 \right )\left ( 0.890 \times 10^{-6} \mbox{Ci} \right) \left (\frac{ (3.7 \times 10^{10} \mbox{Hz}}{\mbox{Ci}} \right)= 28059.7 Hz [/math]

Mn-54, on July 1, 2008, half life =312.20 +/- 0.07 days, 99.975% intensity on 834.826 , April 14, 2016 activity =0.02251micro Ci

= [math]\left (0.99975 \right )\left ( 0.02251 \times 10^{-6} \mbox{Ci} \right) \left (\frac{ (3.7 \times 10^{10} \mbox{Hz}}{\mbox{Ci}} \right)= 830.79 Hz [/math] for the 834 line


Co-60, 10.42micro Ci July 1, 2008, half life 5.271 +/- 0.001 years, 99.0 % for 1173.237 and 99.9824 % for 1332.501, April 14, 2016 activity=3.74micro Ci


= [math]\left (0.99 \right )\left ( 3.74 \times 10^{-6} \mbox{Ci} \right) \left (\frac{ (3.7 \times 10^{10} \mbox{Hz}}{\mbox{Ci}} \right)= 136996.2 Hz [/math] for the 1173 line


= [math]\left (0.999824 \right )\left ( 3.74 \times 10^{-6} \mbox{Ci} \right) \left (\frac{ (3.7 \times 10^{10} \mbox{Hz}}{\mbox{Ci}} \right)= 138355.6 Hz [/math] for the 1332 line

SeRun_01-11-16

SeRun_03-07-16

References

<references/>

MSDS

Selenium shot, amorphous, 2-6 mm, Puratronic, 99.999% Alfa Aesar product # 10603 File:AlphaAesarSelenium MDSD.pdf

Informative links

http://www.deq.idaho.gov/regional-offices-issues/pocatello/southeast-idaho-phosphate-mining/southeast-idaho-selenium-investigations/

https://inldigitallibrary.inl.gov/sti/3169894.pdf

http://giscenter.isu.edu/research/Techpg/sisp/index.htm


PAA_Research

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