1. Applied Physics and Engineering Mathematics Department, University of Johannesburg, P.O Box 17011, Doornfontein, 2028, South Africa
2. Radiation Protection Training Centre African Nuclear Energy Corporation (Necsa), PO Box 582, 0001, South Africa
3. Department of Subatomic Physics, iThemba LABS, National Research Foundation, P.O. Box 722, Somerset West, 7129, South Africa
4. Department of Physics, University of Johannesburg, Auckland Park, 2006, South Africa