PAA Selenium

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?

As shown in the Figure below, the Se-82/Se-76 ratio varies from -1.2% to +0.2% for plant materials but remains relatively constant for other materials. The variations in plant material has been described as being due to differences in the bacteria residing in the plant. The question to investigate is whether or not these variations in the concentration can be used to determine the provenance of the sample.

Below is a table listing the natural abundances of Selenium

Natural abundance of selenium

Isotope	Abundance
Se-74	0.86%
Se-76	9.23%
Se-77	7.60%
Se-78	23.69%
Se-80	49.80%
Se-82	8.82%

Below are possible PAA reactions that may be used to observe specific Se isotopes

Reaction	Half-life	Relative activity	Gamma-rays, keV (BR)
Se-74(gamma,n)Se-73	7.1 h	1.5E-1	361 (100)
Se-74(gamma,n)Se-73m	39 m	3.2	402 (4)
Se-74(gamma,np)As-72	26 h	1.0E-3	834 (100)
Se-76(gamma,n)Se-75	120 d	1.3E-2	265(29)
Se-77(gamma,p)As-76	26.4 h	4.4E-2	559(44)
Se-78(gamma,p)As-77	38.8 h	8.6E-2	239(2)
Se-80(gamma,n)Se-79m	3.9 m	5.9	96(10)
Se-80(gamma,np)As-78	1.5 h	2.2E-2	614(54)
Se-80(gamma,p)As-79	8.2 m	1.3	96(9)
Se-80(gamma,[math]a[/math]p)Ge-75	83 m	2.8E-1	265(11)

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

Se_PAA_Reactions

Experiments

PAA Selenium/Soil Experiments

LB Se PAA Horse Feed Experiment

Nickel Normalization

LB PAA Nickel Investigation

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

Below is the EMSL report for the horse feed sample. https://wiki.iac.isu.edu/index.php/File:EMSL_Report_Horse_Feed.pdf

Chlorine is a dominant signal

First, look at the peak around 146 keV

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.

Root gives a half life of 32.9508 +/- 0.01 minutes

Now do the same for the 2127 keV line

Here are the counts plotted as a function of time

Root gives a half life of 35.3962 +/- 0.2 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

Now check the half life

Root gives a half life of 8.03 +/- 0.02 minutes

Next check the 3936 peak

and check the half life

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.

MDA and Se mass Calculations

LB MDA/Se Mass Calculations

IAC Detector Efficiencies

LB PAA IAC Detector Efficiencies

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
04-26-16	4.32x10^6	Se_B	Se_B_008	10:06	10:29	87784.755	87664.070	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
05-10-16	5.5296x10^6	Sample A	Sample_A_004	11:03	15:19	15379.475	15363.017	c
05-10-16	5.5296x10^6	Sample B	Sample_B_004	15:22:04	11:43	73256.181	73220.324	c
05-16-16	6.048x10^6	Sample C	Sample_C_004	16:33	08:19	56758.980	56711.121	c
05-18-16	6.2208x10^6	Sample D	Sample_D_006	08:44:21	14:05	19271.829	19266.929	c
05-18-16	6.2208x10^6	Sample E	Sample_E_006	14:08	08:06	151108.258	150955.915	c
05-20-16	6.3936x10^6	Se_B	Se_B_014	08:08:47	08:44	261353.204	259621.655	c
05-23-16	6.6528x10^6	Sample A	Sample_A_006	08:48	13:49	18103.004	18091.523	c
05-23-16	6.6528x10^6	Sample B	Sample_B_006	13:52	13:24	84763.938	84696.083	c
05-24-16	6.7392x10^6	Sample C	Sample_C_006	13:28:28	10:28	75571.716	75502.871	c
05-31-16	7.344x10^6	Sample B	Sample_B_008	08:57:22	08:55	86282.861	86237.392	c
06-01-16	7.4304x10^6	Sample C	Sample_C_008	08:58:39	13:31	102739.504	102647.471	c
06-02-16	7.5168x10^6	Sample D	Sample_D_010	13:33	08:41	68915.044	68898.246	c

Data Analysis

Pure Se Sample

Observed lines

LB_Feb2017_Se_Investigations

Estimate of Se-79 activity

Using known efficiency to extrapolate initial activity

Use ratio with Nickel foil rate

Se spiked in Soil

Detection limit of Se in Soil

References

User_talk:Brenleyt

<references/>

File:Krouse CanJournChem 40 1962 p367.pdf

Goryachev, A. M., & Zalesnyy, G. N. (n.d.). The studying of the photoneutron reactions cross sections in the region of the giant dipole resonance in zinc, germanium, selenium, and strontium isotopes. Retrieved September 16, 2016, from http://www-nds.indcentre.org.in/exfor/servlet/X4sSearch5?EntryID=220070

Goryachev, B. I., Ishkhanov, B. S., Kapitonov, I. M., Piskarev, I. M., Piskarev, V. G., & Piskarev, O. P. (n.d.). Giant Dipole Resonance on Ni Isotopes. Retrieved October 26, 2016, from http://www-nds.indcentre.org.in/exfor/servlet/X4sGetSubent?reqx=119235&subID=220597006&plus=1

Handbook on Photonuclear data for applications, cross sections, and spectra. (2000, October). Retrieved November 4, 2016, from http://www-pub.iaea.org/MTCD/Publications/PDF/te_1178_prn.pdf

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