  We explore the perspectives of studying vacuum birefringence at the Gamma
Factory. To this end, we assess in detail the parameter regime which can be
reliably analyzed resorting to the leading contribution to the Heisenberg-Euler
effective Lagrangian. We explicitly show that -- contrarily to naive
expectations -- this approach allows for the accurate theoretical study of
quantum vacuum signatures up to fairly large photon energies. The big advantage
of this parameter regime is the possibility of studying the phenomenon in
experimentally realistic, manifestly inhomogeneous pump and probe field
configurations. Thereafter, we focus on two specific scenarios giving rise to a
vacuum birefringence effect for traversing gamma probe photons. In the first
scenario the birefringence phenomenon is induced by a quasi-constant static
magnetic field. In the second case it is driven by a counter-propagating
high-intensity laser field.
