About how calculate ambient dose equivalent rate in geant4?

Hello everyone, I would like to calculate the ambient dose equivalent rate from a fast neutron source, what tools do I need in geant4?
And what’s the difference between abrosb and gap?

TY for help.

you can set dummy spheres in your geometry. Whenever a neutron or a gamma ray traverses the sphere, retrieve and store the energy. Then you convolve the energy spectra with H*(10) to calculate the ambient dose equivalent.

Susanna