The three-body photodisintegration of helium-3

Abstract

The main motivation for the experiment was the determination of the onset of the quasideuteron effect in 3He. If a neutron and a proton in a nucleus are interacting and absorb an incident photon, they can break up in a marrer kinematically similar to a deuteron, hence the name quasideuteron This effect had previously been seen in 3He above 75 MeV photon energy. This kinematically complete experiment measured the three-body photodisintegration of 3He in the photon energy range of 35 to 65 MeV by means of the coincident detection of a proton and a neutron The bremsstrahlung beam used was produced by a 68.4 MeV, 0.75 J.lA beam of electrons from the 100~ duty cycle accelerator Microtron Using a SUperconductirvJ Linac (MUSL II) at the Nuclear Physics Laboratory of the University of Illinois at Urbana-Champaign. The 3He target gas was maintained at 4.3 K and 514 Torr. The proton telescope, neutron detector and associated electronics were calibrated by the use of deuterium. The quasideuteron effect could be distinguished in the data at around 45 MeV and predominates by 60 MeV. The strength of the effect was around 50 to 60 J.lb/sr2. However, this cross section was separated by a primitive procedure; the interference between this and the competing final state interactions was not taken into account. By integrating over the neutron angles, a single differential cross section was generated and found to be about 0.6 times the deuterium cross section from 50 to 65 MeV. The neutron-proton final state interaction was clearly seen in the data. It is hoped this experiment will be an inducement for a complete theoretical treatment applicable to these energies.