Projections of measured source position distributions on the x-, y- and z-axis for different shielding conditions. A total number of 1800 10-s measurements were performed for each case. Black: bare source, blue: source inside a 4-cm radial thickness HDPE cylinder, red: source inside a 1.6 cm radial thickness lead cylinder. The Cf-252 source was placed at (x, y, z)=(0, 0, 52) cm in the coordinate system indicated in Figure 4. Taken from reference [29].