Natural boron has a density of 0.128 x 1024 at/cm and cross section = 764 b and = 4 b at an energy of E 0.025 eV. 2 S == Calculate the macroscopic cross sections at 0.025 eV for absorption, scat- tering, and total interaction. b. What fractional attenuation will a 0.025-eV neutron beam experience when traveling through 1 mm of the boron? 1 cm? mming the absorption cross section is Heation O d. What thickness of boron is required to absorb 50 percent of a 100-eV neutron beam?