A long-time chopper for direct measurement of 4He(12C,16O)γ reaction cross section

Direct measurement of the 4He(12C,16O)γ reaction cross section by detecting 16O recoils is in progress at Kyushu University tandem laboratory (KUTL). A long-time chopper (LTC) has been developed to reject backgrounds from 16O recoils which have time (energy) spread. In the measurement of 4He(12C,16O)γ cross section at Ecm = 2.4 MeV, LTC was found to reduce the backgrounds by about three orders of magnitude.