  We report on a concerted effort aimed at understanding the nucleosynthesis
origin of Xe-H in presolar nanodiamonds. Previously explored possible
explanations have included a secondary neutron-burst process occurring in the
He-shell of a type II supernova (SN), as well as a rapid separation, between
unstable precursor isobars of a primary r-process, and stable Xe isotopes. Here
we present results from the investigation of a rapid neutron-capture scenario
in core-collapse SNe with different non-standard r-process variants. Our
calculations are performed in the framework of the high-entropy-wind (HEW)
scenario using updated nuclear-physics input. We explore the consequences of
varying the wind expansion velocity (Vexp) for selected electron fractions (Ye)
with their correlated entropy ranges (S), and neutron-freezeout temperatures
(T9(freeze)) and timescales (tau-r(freeze). We draw several conclusions: For
Xe-H a "cold" r-process with a fast freezeout seems to be the favored scenario.
Furthermore, eliminating the low-S range (i.e. the "weak" r-process component)
and maintaining a pure "main" or even "strong" r-process leads to an optimum
overall agreement with the measured iXe/136Xe abundance ratios. Our results can
provide valuable additional insight into overall astrophysical conditions of
producing the r-process part of the total SS heavy elements in explosive
nucleosynthesis scenarios.
