  In recent years the scintillation mechanism of inorganic crystals has been
extensively investigated in different studies. The main issues are the
non-proportionality mechanism of the light response versus energy and its
connection with the shaping time used for the scintillation signals. In this
study the Compton coincidence technique has been used to measure the relative
non-proportionality of three crystals: CdWO$_{4}$, BGO, and NaI(Tl). To test
the non-proportionality dependence on shaping time, the preamplified
scintillator pulses have been digitized and shaped with a digital trapezoidal
filter. Since no analogic shaping occurs the majority of the scintillation
components are digitized, thus avoiding major information losses. The obtained
results suggest the existence of a correlation between the time constant of the
scintillation emission and light yield.
