Development of a high resolution isobar separator for study of exotic decays

A compact isobar spectrometer and separator, based on the multi-pass-time-of-flight (MTOF) principle, is being developed by the University radioactive ion beam (UNIRIB) Consortium. It consists of two coaxial, grid-free electrostatic mirrors with auxiliary injection, focusing and extraction elements. Ions of different mass are reflected multiple times between the mirrors and separated longitudinally. Using an electron beam impact ion source and N2 as a sample gas, a mass resolving power of 110,000 (FWHM) has been achieved. In the near future, MTOF will be coupled to the on-line isotope separator UNISOR (University Isotope Separator - Oak Ridge) at Holifield radioactive ion beam facility using electrostatic beam deceleration, a radiofrequency beam cooler and a fast buncher. It will serve as a high resolution mass separator with a Bradbury-Nielsen gate, providing isotopically pure samples of exotic species in the 100Sn region and later, of neutron rich nuclei, for use in decay studies.