Development of a twin Frisch-grid ionization chamber for correlated fission fragments studies

A Twin Frisch-Grid Ionization Chamber (TFGIC) for the measurement of correlated fission fragments has been built in the Institute of Nuclear Physics and Chemistry (INPC). The design and performance testing, as well as data analysis of fission experiments, have been described in this paper. The results of performance testing experiment with a compound alpha source of ^241,243Am showed that the ratio of the electric field between the drift region and collection region should be greater than a critical value. Meanwhile, the correction of grid inefficiency (GI) and the reconstruction of emission angle were investigated in detail. These experimental results provided a solid foundation for fission experiments. Two fission experiments of ²³⁵U have been carried out both at the Chinese Mianyang research reactor (CMRR) and neutron science facility in INPC to validate the feasibility of this setup used for investigating fission. The results showed that the angular resolution achieved 12.6%, and the mass resolution was about 5 atom mass unit (AMU). Moreover, the total kinetic energy (TKE) of fission fragments for both fission experiments agreed well with those in the literature. These primary results indicated the detector could be well applied in the subsequent fission investigation.