The ion-optical design of the MARA recoil separator and absolute transmission measurements of the RITU gas-filled recoil separator

Abstract

In this thesis work, the use of two complementary recoil separators for studies of nuclear structure via fusion-evaporation reactions are discussed. The design and the main ion-optical properties of the vacuum-mode recoil-mass separator MARA, intended for studies of nuclei with N Z close to the proton drip-line, are presented. MARA (Mass Analysing Recoil Apparatus) consists of a magnetic quadrupole triplet followed by an electrostatic de ector and a magnetic dipole. The working principle of MARA is discussed and the reasons for the choice of the optical parameters of the elements are given. The performance of MARA for di erent kind of fusion reactions has been studied with Monte Carlo simulations. The results of a sensitivity analysis especially of the electrostatic de ector are reported. The requirements for the instrumentation are discussed. The absolute transmission values of the RITU gas- lled recoil separator have been measured for several fusion evaporation products in the mass region A = 170{190 using di erent reaction asymmetries. It was observed that the angular distribution of products after the target and the angular acceptance of RITU determine the transmission value accurately. The e ects of lling-gas pressure on the average charge state and focal plane image properties as well as on transmission values have been studied experimentally. The transmission probability for 254No synthesized in the 48Ca+208Pb reaction has been calculated and is in agreement with the experiment. Simulations of transportation of 186Hg fusion products through RITU have been carried out. The simulated behaviour of transmission and image properties agrees well with an experiment.