Barn Cross Section

This barn one of many on the fermilab site is located at kautz road.

Barn cross section. Values of cross sections depend on the energy of the bombarding particle and the kind of reaction. The concept of cross section is the crucial key that opens the communication between the real world of experiment and the abstract idealized world of theoretical models. Barn unit of area used to measure the reaction cross section generally different from the geometric cross section of atomic nuclei and subatomic particles in the study of their interactions with other nuclei or particles.

The fission product xenon 135 which poisons fuel rods in reactors by absorbing slow neutrons has an extraordinary cross section of 3 500 000 barns. 1fm 1e 15 m 1barn 1e 24 cm 2 scattering lengths and cross sections in parenthesis are uncertainties. A barn is approximately the cross sectional area of a uranium nucleus.

Barn absorption cross section for 2200 m s neutrons note. It is equal to 10 24 square cm. Nuclear reactions typically have cross sections in the range 0 1 to 10 barns though cross sections from 10 to 10 barns are known.

The reaction cross section is usually not the same as the geometric cross sectional area of the target nucleus or particle.