The Purpose is to find the total neutron yield or the neutron production rate per muon per g/cm2 of the muon path in a material. All neutrons produced inside the material are counted, but only those produced in the middle are included in the final neutron yield. This removes the beginning of the muon-induced cascades and escaping particles. FLUKA and GEANT4 count all neutrons produced in inelastic collisions as 'new' neutrons. This leads to the double counting of neutrons in (n,an) reactions, where a in a positive integer. Basically, all neutrons in the final state are considered as 'new', whereas in fact, one of them is an 'old' one which initiated the reaction. To avoid this double counting, the number of neutrons in the initial state should be subtracted from that in the final state. For FLUKA this is equivalent to subtracting the number of 'stars'. It is usually assumed the highest energy neutron in the final state is the one which caused the reaction.
Right circular cylinder, 20 m diameter, 30 m long Muon energies: 10, 30, 100, 280, 1000 GeV (both + and – muons) Materials: C, CH2, H2O, CaCO3, NaCl, Fe, Pb
For muon energies below 30 GeV a correction should be applied since the muon energy loss is not negligible compared to the initial energy, meaning that the neutron yield will drop as muon energy goes down. This can be corrected by looking at the distribution of neutron yield as a function of distance and extrapolating back to the origin (original muon energy).
In addition to a basic test of the total neutron yield, all processes will be identified separately to understand their contribution to the neutron production.
The processes are:
a) muon-induced spallation = direct production of neutrons in muon-induced reactions;
b) neutron production by photons (in cascades induced by muons);
c) neutron production by pion-induced spallation;
d) neutron production by pi- capture (pi capture at rest);
e) neutron production by neutrons;
f) neutron production by electrons;
g) neutron production by protons;
h) neutron production by hadrons other than pions or protons.