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 2127 keV halflife.png

Root gives b = 3.26947x10^-4, which yields a half life of 35.3 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


2167 keV halflife.png

Root gives a value for b = -1.44218x10^(-3), which in turn gives a half life of 8 minutes

Next check the 3936 peak

3937 Peak.png

and check the half life

3936 keV halflife.png

Root gives a value for b = - 1.14372x10^(-3), which in turn gives a half life of 10.1 minutes

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

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, 11.77 microCi 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 table where the actual efficiency will be calculated for position R (farthest position).

Run Source Energy (keV) Expected Rate (Hz) HpGe Rate (Hz) HpGe Det D Efficiency (%)
Eff_003 Na-22 511 79122.6 (506:516) (4.309-0.065=4.244) 0.005
Eff_005 Cs-137 661.657 28091.2 (657:666)(1.105-0.02281=1.0821) 0.004
Eff_006 Mn-54 834.848 861.1 (830:839)(0.04037-0.009123=0.031247) 0.004
Eff_007 Co-60 1173.228 137692 (1164:1182)(3.686-0.01939=3.67) 0.003
Eff_003 Na-22 1274.537 44224 (1270:1279) (1.073-0.0057=1.0673) 0.002
Eff_007 Co-60 1332.492 139058.52 (1328:1337)(3.283-0.05702=3.22598) 0.002

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, 11.77 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

Below are the actual efficiencies for position k

Run Source Energy (keV) Expected Rate (Hz) HpGe Rate (Hz) HpGe Det D Efficiency (%)
Eff_k_002 Na-22 511 79122.6 (506:516)(49.21-0.6272=48.58) 0.06
Eff_k_006 Cs-137 661.657 28091.2 (657:666)(12.86-0.02281=12.837) 0.05
Eff_k_004 Mn-54 834.848 861.1 (830:839)(0.3204-0.009123=0.311) 0.04
Eff_k_005 Co-60 1173.228 137692 (1164:1182)(42.39-0.02053=42.369) 0.03
Eff_k_002 Na-22 1274.537 44224 (1270:1279) (12.53-0.005702)=12.52 0.03
Eff_k_005 Co-60 1332.492 139058.52 (1328:1337)(35.94-0.005072) 0.03

Below is a runlist for position C

Source Serial # Reference Date Activity Start Stop Live
Na-22 129742 7-01-08 1.146 microCi 12:55 12:57 129.782
Cs-137 129793 7-01-08 1.006 microCi 13:02 13:04 123.818
Mn-54 129806 7-01-08 1.226 microCi 13:11 13:21 613.754
Co-60 129739 7-01-08 1.082 microCi 13:08 13:09 103.599

Below are the calculations for the theoretical 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 May 5, 2016 =1.196micro Ci

= [math]\left (0.99937 \right )\left ( 0.14 \times 10^{-6} \mbox{Ci} \right) \left (\frac{ (3.7 \times 10^{10} \mbox{Hz}}{\mbox{Ci}} \right)= 5176.7 Hz [/math] for the 1274 line
= [math]\left (1.788 \right )\left ( 0.14 \times 10^{-6} \mbox{Ci} \right) \left (\frac{ (3.7 \times 10^{10} \mbox{Hz}}{\mbox{Ci}} \right)= 9261.8 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, May 5, 2016 activity = 0.89micro 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)= 28059.7 Hz [/math]

Mn-54, 1.226 microCi on July 1, 2008, half life =312.20 +/- 0.07 days, 99.975% intensity on 834.826 , May 5, 2016 activity =0.002micro Ci

= [math]\left (0.99975 \right )\left ( 0.002 \times 10^{-6} \mbox{Ci} \right) \left (\frac{ (3.7 \times 10^{10} \mbox{Hz}}{\mbox{Ci}} \right)= 73.98 Hz [/math] for the 834 line


Co-60, 1.082micro Ci July 1, 2008, half life 5.271 +/- 0.001 years, 99.0 % for 1173.237 and 99.9824 % for 1332.501, May 5, 2016 activity=0.39micro Ci


= [math]\left (0.99 \right )\left ( 0.39 \times 10^{-6} \mbox{Ci} \right) \left (\frac{ (3.7 \times 10^{10} \mbox{Hz}}{\mbox{Ci}} \right)= 14285.7 Hz [/math] for the 1173 line


= [math]\left (0.999824 \right )\left ( 0.39 \times 10^{-6} \mbox{Ci} \right) \left (\frac{ (3.7 \times 10^{10} \mbox{Hz}}{\mbox{Ci}} \right)= 14427.5 Hz [/math] for the 1332 line

Below is a table with the calculated efficiencies

Run Source Energy (keV) Expected Rate (Hz) HpGe Rate (Hz) HpGe Det D Efficiency (%)
Eff_C_001 Na-22 511 9261.8 (506:516) (45.65-0.065=45.585) 0.5
Eff_C_002 Cs-137 661.657 28059.7 (657:666)(101.7-0.02281=101.67) 0.4
Eff_C_004 Mn-54 834.848 73.98 (830:839)(0.2704-0.009123=0.2612) 0.4
Eff_C_003 Co-60 1173 14285.7 (1164:1182)(34.24-0.01939=34.22) 0.2
Eff_C_001 Na-22 1274.537 5176.7 (1270:1279) (11.15-0.0057=11.14) 0.2
Eff_C_003 Co-60 1332.492 14427.5 (1328:1337)(28.05-0.05702=27.99) 0.2

Run List

Date Time elapsed (Seconds) Sample Document Title Start Stop Real Live Position
04-01-16 2.16x10^6 Se_B Se_B_002 15:55 09:15 235989.882 235687.660 k
04-06-16 2.592x10^6 Se_B Se_B_003 12:57 Interrupted computer crash k
04-14-16 3.283x10^6 Se_B Se_B_005 15:57 09:37 63581.784 63509.895 k
04-15-16 3.37x10^6 Sample D Sample_D_001 14:47 08:23 236172.264 236173.271 k
04-19-16 3.715x10^6 Sample B Sample_B_001 15:31 15:18 85634.862 85624.090 k
4-20-16 3.802x10^6 Sample C Sample_C_001 15:22 10:19 68253.774 68232.238 k
04-21-16 3.888x10^6 Sample A Sample_A_001 10:22 10:37 87292.409 87268.114 k
04-25-16 4.234x10^6 Sample E Sample_E_001 11:36 10:03 80822.406 80795.679 k
05-05-16 5.098x10^6 Sample A Sample_A_002 13:31 14:30 3605.507 3602.925 c
05-05-16 5.098x10^6 Sample B Sample_B_002 14:34 15:26 3114.244 3112.620 c
05-05-16 5.098x10^6 Sample C Sample_C_002 15:28 10:57 70124.788 70044.470 c
05-06-16 5.184x10^6 Sample D Sample_D_002 10:59 15:34 16516.898 16512.570 c
05-06-16 5.184x10^6 Sample E Sample_E_004 15:37 16:18 261654.225 261344.308 c
05-09-16 5.443x10^6 Se B Se_B_012 16:20 11:08 67157.101 66660.298 c

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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