Kippenhahn diagram showing the early AGB phase (first and second thermal pulses) of a 2 M_⊙, [Fe/H] = −1.0 star (M2.0z1.0_f10 model). Convective regions are shaded gray. The dashed green and blue lines delineate the hydrogen and helium-burning zones, respectively (where the nuclear energy production by H and He burning exceeds 10 erg g⁻¹ s⁻¹). The red area shows the extent of overshooting. The magenta (cyan) line indicates the region zones where the i-process (s-process) nucleosynthesis occurs. The bottom panel shows the maximal neutron density as a function of the model number, or equivalently time as indicated in the upper x-axis.