A Twin Frisch-gridded Ionization Chamber for Correlated Fragment Emission in Fission.

A new twin Frisch-gridded ionization chamber (TFGIC) has been designed and constructed for fission fragment detection. The first experimental run was performed with a ²⁵²Cf spontaneous fission source located in the middle of the chamber and an array of trans-stilbene organic scintillators surrounding the chamber. The TFGIC determines the masses, angles of emission and kinetic energy of the fragments using the 2E method with estimated resolutions of 4-5 amu, cosθ < 0.07, and < 3 MeV, respectively. The scintillator array provides neutron and gamma-ray multiplicities and spectra. The experiment aims to study neutron and gamma-ray emission for different fragment excitation energies and masses, and thus could shed light on the role of angular momentum in nuclear fission. Details of the detector assembly and first performance tests of the setup will be presented, as well as plans for a future experimental program with the Gammasphere detector at the Argonne Tandem-Linac Accelerator System (ATLAS).