Neutron lethargy

Neutron lethargy, or logarithmic energy decrement, u, is a dimensionless logarithm of the ratio of the energy of source neutrons to the energy of neutrons after a collision:

eq1

With that definition, the neutron lethargy increases as the neutron slows down, the gain in lethargy after a collision is:

eq2

End of story!

Read more about neutron basics here (PDF)

Leave a Reply