Detection of breakup fragments in inverse Coulomb dissociation experiments

In the framework of Coulomb dissociation experiments, performed to reconstruct the cross section of the inverse radiative capture process, the detection of breakup fragments is usually performed using separate detectors, which unavoidably are not sensitive to small relative angles. It is shown, by means of Monte Carlo simulations, that the phase-space constraints imposed by 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 frame. A solution to the problem of the model-dependance of the response function is proposed, making use of a single three-stage detector for the identification 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 results indicate the feasibility of measuring very low relative energies in the Coulomb dissociation approach to the solution of important problems in nuclear astrophysics via the accurate determination of reaction rates at energies far below the Coulomb barrier. (C) 1998 Elsevier Science B.V. All rights reserved.