Neutron interaction

1.  A fluence of thermal neutrons is 6.5 x 10¹² n/ cm² in a layer of muscle-equivalent tissue 0.1 g/cm* thick. What is the absorbed dose at the middle of the layer? Given the equation. D= (σ×N×ϕ×E )/ρ

2.Assume that the above neutron fluence is approximately uniform throughout a tissue sphere 5 cm in radius, due to thermalization of a field of intermediate-energy neutrons penetrating the sphere. What is the absorbed dose at the center resulting from thermal-neutron-capture gamma rays? How does it compare with the total absorbed dose that results (directly or indirectly) from the thermal neutrons? (Assume unit-density tissue).