Difference between revisions of "TF IsotopeTracers4Cracks"

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=Photon Attenuation in Shale=
 
=Photon Attenuation in Shale=
  
The attenuation length for a 1.8 MeV photon is 0.16 /cm and 0.895 is 0.22/cm through shale.
+
According to the XCOM database, the attenuation length for a 1.8 MeV photon is 0.16 /cm and 0.895 is 0.22/cm through shale.
  
 
[[File:XCOM_attenuation4Shale.pdf]]
 
[[File:XCOM_attenuation4Shale.pdf]]
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XCOM predicts an attenuation coefficient of 0.0441 cm^2/g which becomes 0.12/cm when you multiply by the shale density of 2.6 g/cm^3.
 
XCOM predicts an attenuation coefficient of 0.0441 cm^2/g which becomes 0.12/cm when you multiply by the shale density of 2.6 g/cm^3.
The fit to GEANT4's predictions above produces a value of 0.1/cm when you plot the number of photons that pass through the shale and still have an energy of 1.8 MeV.  A least squares fit gave the parameters
+
The fit to GEANT4's predictions above produces a value of 0.1/cm when you plot the number of photons that pass through the shale and still have an energy of 1.8 MeV.   
 
 
slope=-0.16725 +/- 0.0411785
 
 
 
y-intercept=13.3424 +/- 0.10361
 
 
 
but the curve from these parameters was too low to believe.  It is not worth the time right now to figure out what is wrong.  I will argue that the fit by hand which gives 0.1/cm is enough indication that GEANT4 is correctly attenuating the photons.
 
 
 
  
 
If I use a point source isotropically emitting 1800 keV photons I observe
 
If I use a point source isotropically emitting 1800 keV photons I observe
  
 
[[File:GEANT4AttShalePntSrc_322013.png| 200 px]]
 
[[File:GEANT4AttShalePntSrc_322013.png| 200 px]]
 +
 +
which gives a the value of 0.1/cm as well.
  
 
=Yittrium in Shale=
 
=Yittrium in Shale=

Revision as of 20:26, 22 March 2013

Definition of Shale

Shale was assumed to have the chemical composition of

[math]\mbox{Al}_2\mbox{Si}_2\mbox{O}_5(\mbox{OH})_4[/math]

and a density of 2.6 g/[math]\mbox{cm}^3[/math]


G4Element* O = new G4Element("Oxygen"  , "O", z=8., a= 16.00*g/mole);
G4Element* Al = new G4Element("Aluminum"  , "Al", z=13., a= 26.98*g/mole);
G4Element* Si = new G4Element("Silicon"  , "Si", z=14., a= 28.085*g/mole);
G4Element* H = new G4Element("Hydrogen"  , "H", z=1., a= 1.008*g/mole);

G4Material* Shale = new G4Material("Shale", density= 2.6*g/cm3, nel=4);
Shale->AddElement(Al, 15*perCent);
Shale->AddElement(Si, 15*perCent);
Shale->AddElement(O, 38*perCent);
Shale->AddElement(H, 32*perCent);

Photon Attenuation in Shale

According to the XCOM database, the attenuation length for a 1.8 MeV photon is 0.16 /cm and 0.895 is 0.22/cm through shale.

File:XCOM attenuation4Shale.pdf


Directing a 1.8 MeV beam of photons in GEANT4 towards various thicknesses of shale produced the graph below.

GEANT4AttShale 3212012.png

XCOM predicts an attenuation coefficient of 0.0441 cm^2/g which becomes 0.12/cm when you multiply by the shale density of 2.6 g/cm^3. The fit to GEANT4's predictions above produces a value of 0.1/cm when you plot the number of photons that pass through the shale and still have an energy of 1.8 MeV.

If I use a point source isotropically emitting 1800 keV photons I observe

GEANT4AttShalePntSrc 322013.png

which gives a the value of 0.1/cm as well.

Yittrium in Shale

A simulation of the penetration of the 0.895 and 1.8 MeV photons from Yittrium through shale.

GEANT4 create a point source or 895 keV photon and another with 1800 keV photons iostropically distributed.

A 4" thick piece of shale was placed between the source and the detector.


Two ratios were constructed.

[math]R_p = \frac{\mbox{counts under the 1800 keV peak}}{\mbox{counts under the 895 keV peak}}[/math]

[math]R_I = \frac{\mbox{number of photons from 1800 keV source penetrating shale}}{\mbox{number of photons from 895 keV source penetrating shale}}[/math]

Y88ShaleNoCrack 1.png

Insert a single crack

TF_IsotopeTracers#Tracers_for_Cracks