Bragg–Gray cavity theory


Bragg–Gray cavity theory relates the radiation dose in a cavity volume of material to the dose that would exist in a surrounding medium in the absence of the cavity volume. It was developed in 1936 by British scientists Louis Harold Gray, William Henry Bragg, and William Lawrence Bragg.
Most often, material is assumed to be a gas, however Bragg–Gray cavity theory applies to any cavity volume that meets the following Bragg-Gray conditions.
  1. The dimensions of the cavity containing is small with respect to the range of charged particles striking the cavity so that the cavity does not perturb the charged particle field. That is, the cavity does not change the number, energy, or direction of the charged particles that would exist in in the absence of the cavity.
  2. The absorbed dose in the cavity containing is deposited entirely by charged particles crossing it.
When the Bragg-Gray conditions are met, then
where
In an ionization chamber, the dose to material is
where