A parallel beam of 0.25 MeV neutrons impinges on target of aluminum that is 1 cm thick. Calculate what fraction of neutrons will undergo a neutron capture event on their first collision in the last 1...

A parallel beam of 0.25 MeV neutrons impinges on target of aluminum that is 1 cm thick. Calculate what fraction of neutrons will undergo a neutron capture event on their first collision in the last 1 mm of a target (σtot (Al) = 3b and σγ(Al) = 1b).