Punchthrough calculations for neutrons using CALOR89

Punchthrough calculations for blocks of iron, copper, depleted uranium and lead of thicknesses of 10 and 12 interaction lengths have been completed for incident negative pions of 10 GeV and 100 GeV using the CALOR89 simulation code. The most numerous particles escaping out the back of the blocks are neutrons. The simulations show that there are significantly more neutrons escaping out the back of the lead block than any of the other absorbers, despite neutron production by fission in the depleted uranium. Two effects are held to be primarily responsible for this. First, the proton and neutron shells in lead nuclei are filled, giving lead a low neutron absorption cross section relative to the other absorbers, particularly uranium. Second, the number density of lead is lower than the other absorbers, particularly copper and iron