Time evolution of neutron exposure. Solid lines represent the neutron exposure at the position of maximum neutron density (i.e., near the bottom of the HeCZ) and dashed lines represent the average neutron exposure in the convective zone. Red line: standard Z = 10^-8 model (M2); black line: reduced convection efficiency (M3); blue line: model including overshooting (f = 0.016 – M4); and green line: model including overshooting (f = 0.07 – M5).