Method for High-Resolution in-Beam Studies of Internal Pair Transitions

摘要

A combination intermediate-image magnetic plus Si(Li) electron spectrometer has been adapted to internal pair formation measurements of cyclotron-induced reactions. The system is especially intended for the study of E0 transitions in the energy range from 1.5 to 8.6 MeV and to measurements of coincidences between internal pairs and heavy particles. The method is based on the fact that the electron and the positron spiral from the target to the detector simultaneously, the sense of rotation being of opposite sign. The energies of the particles are summed in a high-resolution cooled Si(Li) detector. Calculations of the spectrometer pair-line efficiency for E0 transitions versus transition energy are made in the zero-orderBorn approximation. An experimental pair-line efficiency of 1.2x10 exp -3 and a sum-peak energy resolution of 3.2 keV for the 1752 keV E0 pair-line in exp 90 Zr are achieved with a momentum band width of 22 %. (Atomindex citation 09:399117)