Graphical presentation of the results discussed in Sect. 3.3. Particle acceleration starts at the beginning of the ST phase, located at mass coordinate A₁ = M_Exp+ M_Ej, i.e. when the forward shock (FS, arrows), launched at M_Exp, has swept up a mass M_S1 = M_Ej. Acceleration stops at mass coordinate A₂, corresponding in the case dicussed here to a shock velocity of 1900 km s^-1. The mass sampled by the FS between those two regions is M_Acc = A₂ − A₁. For rotating stars with mass M > 30 M_⊙, an increasing part of M_Acc includes nuclearly processed material (shaded aerea), while for rotating stars with M < 18 M_⊙, M_ACcc contains only material of ISM (=solar) “composition”.