C-12(C-12; alpha)Ne-20 and C-12(C-12;p)Na-23 are the most important reactions during the carbon burning phase in stars. Direct measurements at the relevant astrophysical energy (E=1.5 +/- 0.3MeV) are very challenging because of the extremely small cross sections involved and of the high beam-induced background originating from impurities in the targets. In addition, persistent resonant structures at low energies are not well understood and make the extrapolation of the cross section from high energy data very uncertain. As a preliminary step towards the measurements of the C-12(C-12;alpha)Ne-20 and C-12(C-12;p)Na-23 reactions we intend to investigate the behaviour of targets under beam bombardment, specifically the quantitative measurement of hydrogen and deuterium content of highly pure stable carbon targets in relation to target temperature. Experiments are taking place at the CIRCE accelerator in Caserta, Italy and preliminary results are presented here.