Feasibility of a Gas Degrader at FRIB for Fission Studies

One major challenge when studying the kinematics of reactions with heavy nuclei is controlling the reaction energy. In a previous experiment at the National Superconducting Cyclotron Laboratory (NSCL) studying the fission of pre-actinides, a thin sheet of iron was used to degrade the beam energy. The nonuniformity of the sheet led to an uncertainty in the reaction energy. To this end, we tested the possibility of creating a gas-based energy degrader. A gas degrader would feature a tube with two thin pressure windows, one on each side, and a high-density gas on the inside. This setup would allow ions to pass through while being slowed down by the gas. Using LISE++ and SRIM simulations, we tested the viability and required pressures of different high-density gases. A small test setup was constructed and used to test the strength of potential window materials at various pressures. Our results demonstrate the feasibility of a gas degrader for use in a fusion-fission experiment at FRIB.