[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Scattering cross sections
One measure for the scattered component of radiation
that passed through an absorber is the Buildup Factor B.
A definition of B can be found at
The Buildup Factor for lead shields of different
thicknesses can be derived by taking the ratio of the
Shielding Functions of Lead,
to the Transmission Functions of Lead,
Finally, most of the scattering at common energies is
caused by the Compton Effect. Graphs and Tables of
Compton Scattering (and other) coefficients can be
AIC SOFTWARE, Inc.
At 01:42 AM 4/14/98 -0500, you wrote:
>I am posting this message for a friend who does not have an email account.
>Please respond to me personally. She writes ....
>I completing a physics Masters by research. (I absolutely have to be
>finished by the end of June)
>The project is looking at contrast modelling of photon imaging of dense
>objects with particular emphasis on computed tomography (x- and gamma-ray)
>of industrial objects such as rock cores. It is a simplistic model comparing
>the intensity transmission through two areas of an object, one an
>homogeneous area and the other with a small inclusion (for example quartz
>with an air inclusion). The aim of the modelling is to predict the
>theoretical minimum visible inclusion size given sufficient spatial
>resolution of the detectors. There are four scenarios: monochromatic narrow
>and broad beams and polychromatic narrow and broad beams.
>I've completed the first three of the scenarios and m now faced with
>polychromatic broad beam.
>I have divided each beam into ten energies (so I have a setting of 100keV
>and according to Kramers Law have a particular spectrum over the energy
>range of 0-100keV). The amount of scatter will vary for each of those 10
>energy ranges. Where I am stuck is trying to calculate the amount of scatter
>for each of the energy ranges. I am led to believe that the mass attenuation
>coefficient is related to the scattering cross sections and that somehow
>this will enable me to calculate the scatter factor for each of the energy
>For a start is it the mass attenuation or absorption coefficient?
>What exactly is a scattering cross section?
>How does all of this enable me to calculate the scatter factor?
>And finally (and prosaically), why does scattered radiation decrease