From the neutron spectra, transmission data were obtained for pure bulk Al, 10 PPI 6101 Al foam, ‘‘foam + water” samples, and ‘‘foam + boric acid solution (1%, 2%, 3% w/v boric acid in water)” samples. The attenuation effects for the four types of samples are shown in Fig. 8 as transmission versus thickness. As seen from Fig. 8 the ‘‘foam + boric acid solution” samples show the highest attenuation, while ‘‘foam + water” samples have higher attenuation than bulk samples,