Tag Archives: cesium

Statistically Valid Detections

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The basic idea comes from z-score * sqrt(2*background)

Basic Isotope Identification (Gamma Spectroscopy)

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Please read below (Resource links, etc)

Copyright:
All materials in this video are copyright of me. I created them all. The screen captures of the software are from Spectrum Techniques.

My Equipment:

Spectrometer: UCS30 – http://www.spectrumtechniques.com/spec_systems.htm
Sources: Cs137 – http://www.spectrumtechniques.com/disc&laminated_sources.htm
Lead: rotometals.com

Gamma Energy Resources:

http://ie.lbl.gov/decay.html
http://ie.lbl.gov/toi/radSearch.asp
http://simplynuclear.com/index.php?title=Common_Gamma_Energy

Thorium Hypothesis
Isotope Energy Branching Ratio
Actinium 228 13 keV 0.38
Thorium 232 *63.81 keV 0.00267
Lead 212 *77.11 keV 0.175
Thorium 228 84.37 keV 0.01266
Thorium 228 131.61 keV 0.001355
Thorium 228 166.41 keV 0.001075
Thorium 228 215.99 keV 0.00263
Lead 212 238.63 keV 0.433
Actinium 228 *338.32 keV 0.113
Thallium 208 510.77 keV 0.226
Thallium 208 *583.19 keV 0.845
Bismuth 212 727.33 keV 0.0658
Actinium 228 911.21 keV 0.266
Actinium 228 968.97 keV 0.162

Uranium Hypothesis
Isotope Energy Branching Ratio
Uranium 238 13 keV 0.08
Uranium 235 19.59 keV 0.61
Lead 210 46.54 keV 0.0425
Lead 214 77.11 keV 0.099
Thorium 234 92.38 keV 0.028
Thorium 234 92.8 keV 0.028
Uranium 235 143.76 keV 0.1096
Uranium 235 185.71 keV 0.572
Radium 226 *186.1 keV 0.35
Thorium 227 235.97 keV 0.123
Lead 214 *241.98 keV 0.075
Lead 214 *295.21 keV 0.185
Lead 214 *351.92 keV 0.358
Bismuth 211 404.85 keV 0.0378
Bismuth 214 *609.31 keV 0.448
Bismuth 214 768.36 keV 0.048
Protactinium 234m 1001.03 keV 0.00370

Potassium 40 Hypothesis
Isotope Energy Branching Ratio
Potassium 40 *1461 keV 0.1067

Depleted Uranium Hypothesis
Isotope Energy Branching Ratio
Thorium 234 13.3 keV 0.045
Thorium 234 *63.29 keV 0.048
Thorium 234 *92.38 keV 0.028
Thorium 234 *92.8 keV 0.028
Uranium 235 19.59 keV 0.61
Uranium 235 *143.76 keV 0.1096
Uranium 235 185.71 keV 0.572
Protactinium 234m 1001.03 keV 0.00370

Spectrum Techniques Universal Computer Spectrometer UCS30 – A Review and Overview

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A nice little unit, the UCS30 comes with 512, 1024, 2048, or 4096 channels. The unit has a built-in high voltage source and a pre-amplifier.

There are many great and wonderful scientific devices which we can obtain and use to understand our world. The most important things we can do in our lives are to learn all that we can and teach as much as possible to all who will listen.

The unit can be seen at http://spectrumtechniques.com/

Oh… and no, they didn’t ask or pay me to show off their unit. Unfortunately, I had to buy the unit myself 🙂

Basic Isotope Identification!!! – Gamma Spectroscopy 101 – Full Lesson

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Where to buy isotopes:

http://spectrumtechniques.com/

Where to find lists of gamma energies:
http://simplynuclear.com/index.php?title=Common_Gamma_Energy
http://ie.lbl.gov/toipdf/eandi.pdf
http://ie.lbl.gov/decay.html
http://www.gammaspectrometry.co.uk/appendices/appendixd.pdf

Where to get a detector
http://www.gammaspectacular.com/products/scintillation_detectors
http://spectrumtechniques.com/detectors&stands.htm
http://www.ludlums.com/component/virtuemart/gamma-detector-171-detail?activetab=options

Where to get an MCA
http://www.gammaspectacular.com/products/sound_card_spectrometry_drivers
http://spectrumtechniques.com/spec_systems.htm

Where to get uranium!!! (how could you live without it?)
http://unitednuclear.com/
http://minresco.com/radioactive/radioactive01.htm

Equations (simplified for quick and dirty use!!!)

  2 * (E keV)^2
___________________ = Compton Edge
  511 keV + 2(E keV)

                  2 * (E keV)^2
E keV – ________________ = Back Scatter peak
                  511 keV + 2(E keV)

(Tom’s opinion)
Best source for calibration: Cs137
Best detecttor type: NaI(Tl) 1″ or greater!
Best free MCA software: PRA 8

Tom’s Isotope Tables!!!

http://simplynuclear.com/index.php?title=Common_Gamma_Energy

Cesium 137 Detected in my Rain! (Radioactive Rain Detected)

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As you all know, I have always maintained that there is Fukushima fallout in the rain… but that the levels (even if they are unsafe) are too low for a Geiger counter to detect.

My sensitive Gamma Spectrometer has now (I believe) detected Cs137 in a rain water collection bucket which concentrates, or so it seems, the Cs137.

Most of the radiation detected by Geiger counters from rain is from Radon Washout, a processes whereby radon in the air (decays from natural uranium around the world) is “washed” out and falls to the ground in the rain. The decay chain is sudden and very quick, providing a few hours of potent readings before falling to background.

Inspector (regular or EXP) Sensitivity to Iodine 125:

0.02 µCi = 740Bq = 44,400Bq/60seconds
(At contact for I-125)

http://seintl.com/products/inspectorplusEXP.html

Iodine -125 Electron Capture
Gamma – 35.49 keV 6.60 %
X-Ray – 27.47 keV 75.7 %

http://ie.lbl.gov/toi/nuclide.asp?iZA=530125

Best energy range for detection by LND7317 probe:
10 keV = 100 keV (max)

The range where detector efficency falls rapidly (Cs137 is also in this range):
100 keV = 1000 keV (declining)

http://seintl.com/images/InspEnResponseC137_large.jpg

A great place to find data on isotopes:
http://ie.lbl.gov/toi/

*** Update! ****

I have calculated the activity:

My original calibrated Cs137 source (cal. vs. NIST tracible source, source ID SRS:80899-854, at 95% accuracy) was 3737 Bq.

I accounted for decay of the source:
3737*e^-((ln(2)/10979)*173) = 3696.4059560683608390980241545539265887454856828520474 Bq
=3696 Bq

For an ROI of the same size for both calibrated sample and rain water sample, I ran tests and determined counts per second:

Calibrated Source 91.2633 c/s
Rain Water Sample: 0.01439814814814814814814814814815 c/s

Now, I divided the detected calibrated sample c/s into the expected c/s to determine ratio of emission vs detection for the energies around 661.66 keV. (3696Bq * 0.851 [intensity for gamma from Ba137m])/2 = 1572.648. The division by two is because I entirely detected one side of the thin sample disk. so… 91.2633 / 1572.648 = 0.05803161292291727074335769987944

My detector is only about 5.8% efficient for such energies. (lower than my 12% “ball park by half”)

Now, merely divide the counted detection from rain by the efficiency and you have about the correct result.
(311counts/21600) /0.05803142216185694446564011781403 =

=0.01439814814814814814814814814815 / 0.05803142216185694446564011781403 = 0.24810951742643665986093914169915

Or 0.248 Bq/liter

(that is zero point two four eight Becquerels per liter)

Thoughts?