  Among the reactions involved in the production and destruction of deuterium
during Big Bang Nucleosynthesis, the deuterium-burning D(p,gamma)3He reaction
has the largest uncertainty and limits the precision of theoretical estimates
of primordial deuterium abundance. Here we report the results of a careful
commissioning of the experimental setup used to measure the cross-section of
the D(p,gamma)3He reaction at the Laboratory for Underground Nuclear
Astrophysics of the Gran Sasso Laboratory (Italy). The commissioning was aimed
at minimising all sources of systematic uncertainty in the measured cross
sections. The overall systematic error achieved (< 3 %) will enable improved
predictions of BBN deuterium abundance.
