Testo Introduzione Cross Sections

ABSORPTION AND CROSS SECTIONS

The first task achievable with our revelators deals with absorption of gamma rays in matter. In order to fulfill this goal we put a source of Thorium directly over (above?) the HPGe revalator at a constant distance, and a variable amount of material (in) between the source and the HPGe.
We know that the law of absorption is a negative exponential giving a decrease of counts with the increasing of the thickness of the material

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so we measured the counts of different lines of the spectrum of thorium with a different lenght (thickness) of material (in) between the source and the revalator (detector) , dividing it by the live time of the apparatus.
To reach a better precision we didn't only consider the counts at the energy peak but we integrated over the FWHM. We also subtracted from all measures the natural background of Thorium, given by a measure without the source in the nearby.

Due to the fact that the mu parameter is Energy dependent and related with the cross section by the law

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we were also able to give an "extimation" of the cross sections of Pb, Cu and H20 versus Energy.



di seguito mettiamo i plot di h2o, pb e cu con poche righe di commento
ho già fatto quello dell'acqua
http://terzoannolab.blogspot.com/2008/05/h20-e-fondi.html