"Diffusion Length" is the average distance traveled by a particle, or a thermal neutron in a nuclear reactor, from the point at which it is formed to the point at which it is absorbed.
Applicable units are those of quantitykind:Length
http://encyclopedia2.thefreedictionary.com/diffusion+length
"Diffusion Length" is the average distance traveled by a particle, or a thermal neutron in a nuclear reactor, from the point at which it is formed to the point at which it is absorbed.
$L = \sqrt{L^2}$, where $L^2$ is the diffusion area.
http://www.iso.org/iso/catalogue_detail?csnumber=31895