Gamma-ray energy absorption buildup factors of gaseous
mixtures; neon (95%) + argon (5%), argon (95%) + acetylene (5%),
argon (95%) + methane (5%), argon (95%) + carbon dioxide (5%), methane
(70%) + pentane (30%) and argon (90%) + methane (10%) were studied
by Geometrical Progression (G-P) fitting for the photon energy range
0.015-15 MeV. It was found that the equivalent atomic number, Zeq of
the gaseous mixtures sharply reduces after 1 MeV photon energy. The
Zeq for the mixture of methane (70%) + pentane (30%)
is the minimum, whereas the maximum is for argon (95%) + carbon
dioxide (5%) for the photon energies under investigation. The Energy
Absorption Buildup Factor (EABF) for methane (70%) + pentane (30%)
was found to be the highest among all the selected gaseous mixtures.
The chemical composition of the gaseous mixtures has an impact on
the EABF values for photon energy and penetration depth. The investigation
of the EABF is useful for selection of gaseous mixtures in design
consideration of gaseous radiation detectors for gamma radiation.