Performance studies of ionisation chambers for photon-induced fission experiments

Angular and mass distributions as well as total kinetic energy of fission fragments in photon-induced fission of ²³²Th were obtained using a twin Frisch-grid ionization chamber at the superconducting Darmstadt electron accelerator S-DALINAC. To improve the experimental luminosity, e.g. for future energy-resolved experiments at ELI-NP, while maintaining the overall resolution we are studying a multi-stack ionisation chamber. We present investigations on the suitability of different gas-mixtures for optimizing the electrode design of said multi-stack chamber.