CR differential kinetic energy density spectrum for ¹²C after one step in a test simulation with primary ¹²C and secondary ¹¹B only. The red curve is the primary injection spectrum of ¹²C (the amplitude is changed to compare both curves), as seen in Figure 1. We observe the differences between primaries and secondaries below p/m_pc ≤ A_C, showing how the momentum-dependent spallation rate changes the slope. A power-law fitting method applied to a few bins estimates the slope of the ¹¹B spectrum (blue curve). The corresponding curves and slopes are displayed. As expected, the slopes of ¹¹B and ¹²C differ by 1 for p/m_pc ≤ A_C and are equal for p/m_pc ≥ A_C.