Collision Length

  The mean free path of a particle before undergoing a nuclear reaction, for a given particle in a given medium. The collision length (also known as the nuclear collision length ) follows from the total nuclear cross-section by

with Avogadro's number (6.022 10²³/mole) A = atomic weight [g/mole] and density [g/cm³]. The probability density function for distances between successive collisions is given by

If one subtracts from the total cross-section the sum of elastic and quasi-elastic (diffractive) cross-sections, one obtains by the same formula the (nuclear) interaction length .

Some numerical values for and are given in the following table.

Fe 10.6 83.3 131.9

Al 26.1 70.6 106.4

Cu 9.6 85.6 134.9

Pb 10.2 116.2 193.7

Concrete 27.0 67.4 99.9

Scintil. 56.6 58.4 82.0

The numbers are from [Barnett96] where much more material can be found.