Doughnut-shaped gas cell for KEK Isotope Separation System

We have developed a doughnut-shaped argon gas cell with a rotating target for the KEK Isotope Separation System (KISS). The new gas cell increased extraction yields for target-like fragments (TLFs) produced in multi-nucleon transfer (MNT) reactions. KISS is an on-line isotope separator, which makes use of a laser ion source combined with an argon gas cell as a gas catcher for TLFs. This system has been implemented for nuclear spectroscopy of neutron-rich isotopes in the region of N=126. A gas flow simulation was performed to optimize the design of the gas cell for efficient and fast transport of TLFs. To confirm the performance expected at the design stage, we performed off- and on-line experiments by using iridium atoms evaporated from a filament in the gas cell and TLFs produced by a 136Xe beam and 198Pt target system respectively. We could increase the extraction yield by more than an order of magnitude by applying a doughnut-shaped gas cell with a rotating target. Thus, we could perform nuclear spectroscopy in this heavy region with the use of KISS.