  Scintillating homogeneous detectors represent the state of the art in
electromagnetic calorimetry. Moreover, the currently neglected crystalline
nature of the most common inorganic scintillators can be exploited to achieve
an outstanding performance boost in terms of compactness and energy resolution.
In fact, it was recently demonstrated by the AXIAL/ELIOT experiments that a
strong reduction in the radiation length inside PWO, and a subsequent
enhancement in the scintillation light emitted per unit thickness, are attained
when the incident particle trajectory is aligned with a crystal axis within
$\sim 1^\circ$. A SiPM-based system has been developed to directly probe this
remarkable effect by measuring the scintillation light emitted by a PWO sample.
The same concept could be applied to full-scale detectors that would feature a
design significantly more compact than currently achievable and unparalleled
resolution in the range of interest for present and future experiments.
