  The influence of oxygen and carbon impurities on the concentrations of
defects in silicon for detector uses, in complex fields of radiation,
characteristic to high energy physics experiments, is investigated in the frame
of the quantitative phenomenological model developed previously by the authors
and extended in the present paper. Continuous irradiation conditions are
considered, simulating realistically the environments for these experiments.
The generation rate of primary defects is calculated starting from the
projectile - silicon interaction and from the recoil energy redistribution in
the lattice. The mechanisms of formation of complex defects are explicitly
analysed. Vacancy-interstitial annihilation, interstitial and vacancy migration
to sinks, divacancy, vacancy- and interstitial-impurity complex formation and
decomposition are considered. Oxygen and carbon impurities present in silicon
could monitor the concentration of all stable defects, due to their interaction
with vacancies and interstitials. Their role in the mechanisms of formation and
decomposition of the following stable defects: V_2, VO, V_2O, C_i, C_iO_i,
C_iC_s and VP, is studied. The model predictions cover a generation primary
rate of defects between 10^2 pairs/cm3/s and 10^{11} pairs/cm3/s, and could be
a useful clue in obtaining harder materials for detectors for space missions,
at the new generation of accelerators, as, e.g. LHC, Super-LHC and Eloisatron,
or for industrial applications.
