  We experimentally demonstrate fast separation of a two-ion crystal in a
microstructured segmented Paul trap. By the use of spectroscopic calibration
routines for the electrostatic trap potentials, we achieve the required precise
control of the ion trajectories near the \textit{critical point}, where the
harmonic confinement by the external potential vanishes. The separation
procedure can be controlled by three parameters: A static potential tilt, a
voltage offset at the critical point, and the total duration of the process. We
show how to optimize the control parameters by measurements of ion distances,
trap frequencies and the final motional excitation. At a separation duration of
$80 \mu$s, we achieve a minimum mean excitation of $\bar{n} = 4.16(0.16)$
vibrational quanta per ion, which is consistent with the adiabatic limit given
by our particular trap. We show that for fast separation times, oscillatory
motion is excited, while a predominantly thermal state is obtained for long
times. The presented technique does not rely on specific trap geometry
parameters and can therefore be adopted for different segmented traps.
