Detection of breakup fragments in inverse Coulomb dissociation experiments

In the framework of Coulomb dissociation experiments, performed to reconstr uct the cross section of the inverse radiative capture process, the detecti on of breakup fragments is usually performed using separate detectors, whic h unavoidably are not sensitive to small relative angles. It is shown, by m eans of Monte Carlo simulations, that the phase-space constraints imposed b y the detection geometry can bias, specially at very low relative energies, the extracted cross section, which turns out to be strongly dependent upon the assumed angular distribution of fragments in the intrinsic reference f rame. A solution to the problem of the model-dependance of the response fun ction is proposed, making use of a single three-stage detector for the iden tification and the relative energy measurement of the breakup fragments. A test measurement on the reaction Pb-208(O-16, C-12-alpha)Pb-208 at 126 MeV incident energy has been performed, using a gas-Si-CsI tritelescope. The re sults indicate the feasibility of measuring very low relative energies in t he Coulomb dissociation approach to the solution of important problems in n uclear astrophysics via the accurate determination of reaction rates at ene rgies far below the Coulomb barrier. (C) 1998 Elsevier Science B.V. All rig hts reserved.