MULTI-2, a 4π spectrometer for total reaction cross section measurements

Abstract A detection setup for the direct measurement of the total reaction cross section with exotic nuclei is presented. The setup consists of a multi-detector telescope for beam-particle identification and a 4 π gamma-ray spectrometer for the detection of prompt photons and neutrons accompanying the nuclear reactions. Measurements are based on the modified transmission method and gamma-ray tagging of nuclear reaction events. Registration efficiency and response characteristics of the gamma-ray spectrometer are investigated by Monte Carlo simulations and measurement with  60Co spectroscopic source. Results show strong a dependence of the registration efficiency on gamma-ray multiplicity, with minimum registration efficiency value of 70%. Evaluation of the registration efficiency for data measured in the total reaction cross section experiments is discussed.