  We study the evolution of the two-pion correlation function parameters with
collision energy in the context of relativistic heavy-ion collisions within the
NICA energy range. To this end, we perform UrQMD simulations in the cascade
mode to produce samples of pions from $5\times 10^6$ Bi+Bi collisions for each
of the studied energies. The effects of the quantum-statistical correlations
are introduced using the correlation afterburner code CRAB. We fit the
correlation function using Gaussian, exponential and symmetric L\'evy shapes
and show that for all collision energies the latter provides the best fit. We
separate the sample into pions coming from primary processes and pions
originating from the decay of long-lived resonances, and show that the source
size for the latter is significantly larger than for the former. The source
size for the secondaries, is similar but in general larger than the size for
the whole pion sample. To further characterize the pion source, we also
simulate the effects of a non-ideal detector introducing a momentum smearing
parameter, representing the minimum pair momentum and thus a maximum source
size that can be resolved. The values of the correlation function intercept
parameter are therefore modified from the values they attain for the perfect
detector case. Using the core-halo picture of the source, we show that the
values of the intercept parameter are influenced by the presence of a
significant fraction of core pions coming from the decay of long-lived but
slow-moving resonances. These findings serve as a benchmark to compare with
future Monte Carlo studies that consider an Equation of State and thus allow
for a phase transition within the studied energy domain.
