THE ALBEDO EFFECT ON GAMMA RAY TRANSPORT IN DUCTS

F. Boutadghart, A. Elmorabiti, A. Jehouani*

Nuclear Physics and Techniques Laboratory, Department of Physics, Faculty of Sciences Semlalia,

B. P. 2390, Cadi Ayyad University, 40000 Marrakech, Morocco

* Corresponding author. E-mail: jehouani@ucam.ac.ma

Received : 25 October 2003; revised version accepted : 01 June 2004

Abstract

The gamma ray propagation in ducts is due to two phenomena : streaming inside duct and multiple reflections on duct walls : the albedo.

In the present work we calculated the double differential albedo for the gamma rays having different energies by using the Monte Carlo method. We have taken account of the photoelectric, the pair creation and the coherent and the incoherent photon scatterings.

We considered the duct wall made of iron. The Klein-Nishina theory is used to sample the scattering angles and the residual energy of photons.

The TRIPOLI code is used to validate our computational program. The results are in good agreement. Then we calculated the dose rate in tissue located at the exit of the duct and we compared the contributions of streamed and reflected photons. We have found that the reflected photons contribution decreases when the duct radius increases for a fixed length. We have found also that the albedo attains 80% of its asymptotic value after three collisions in the duct wall. The contribution of the photon coherent scattering is found not negligible for all materials.

Keywords: Double differential albedo; Gamma-Ray; Duct; Transport; Monte Carlo; Tripoli.

 

 
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