for example assume that i have three equal weighted quantities each one is 1 g of radioactive U-238 and then mix them with three different matrices i.e different elemental composition but finally all matrices after mix with the 1 g U-238 is having equal densities.then measure every sample with HPGe detector.
the question : is this correct method to measure the effect of different composition matrices on measured radioactivity.?
You may put each mixture into a sample vial with the same shape before measuring with HPGe detector.
sure to neglect geometry effect on measurements and hence i can say the differences in results obtained refer to the different matrix composition??
Different geometry of samples will effect the counting efficiency of detector
yes I understand that but here I am talking about how to study the effects of different matrix composition on the measured activity concentration when using HPGe detector provided that minimizing other factors effects on measurement like geometry........etc.
Omar,
Let me see if I understood your question.
Your are talking about shielding of a matrix used to immobilize a quantity of a radioactive material, correct?
If I am right about your question, you need to determine to each material the total mass absortion coefficient (in cm2/g) of the matrix material. Then you will discover how much radiation this matrix shield based on the density and "thickness"
I hope to help you.
hi Jorge hi Gilberto thanks for interest
but let us assume that we have three different compositions solid samples with in each one the same amount of radioactive materials and finally the three samples measuring on HPGe detector with same geometry and same counting time what is the expected results due to differences in matrix compositions!?
If you measure with the HPGe samples with the same activity, same volume, same shape and same density, then indeed you should expect less counts when the average atomic number of the matrix is higher, because of more photoabsorption by the matrix. The amplitude of this effect will however strongly depend on the thickness and density of the matrix and on the energy of the gamma line used.
Omar,
Assuming all you said, only material density will impact in the results.
Look the absorber formulation:
I = I0*exp(-μ*X), where:
I0 is the counting before absorber insertion
I is the counting after absorber insertion
The half-value layer is when intensity with absorber insertion is half of without it.
So, you can determine μ in function of X. X is dependent only the thickness and density. Then, if you use same thickness, couting time and geometry, it will depend only the material density
I hope to help you.
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