Water equivalence of some 3D dosimeters: a theoretical study based on the effective atomic number and effective fast neutron removal cross section

Effective atomic numbers for photon energy absorption (Z(PEAeff)) and their corresponding electron numbers (N-PEAeff), and effective macroscopic removal cross sections of fast neutrons (Sigma(R)) were calculated for 27 different types of three-dimensional dosimeters, four types of phantom materials, and water. The values of Z(PEAeff) and N-PEAeff were obtained using the direct method for energies ranging from 10 keV to 20 MeV. Results are presented relative to water, for direct comparison over the range of examined energies. The effect of monomers that are used in polymer gel dosimeters on the water equivalence is discussed. The relation between Sigma(R) and hydrogen content was studied. Micelle gel dosimeters are highly promising because our results demonstrate perfect matching between the effective atomic number, electron density number, and fast neutron attenuation coefficient of water.